Hamdan Medical Journal 2012; 5:333–343 (http://dx.doi.org/10.7707/hmj.v5i3.189)

REVIEW FOR THE SHEIKH HAMDAN BIN RASHID AL MAKTOUM AWARD FOR MEDICAL SCIENCES

In utero haematopoietic stem cell transplantation – experimental progress towards clinical application

Alan W Flake

Centre for Fetal Diagnosis and Treatment, Centre for Fetal Research, Children’s Hospital of Philadelphia, and Department of Surgery, University of Pennsylvania School of Medicine, Philadelphia, PA, USA

Abstract structural anomalies, prenatal stem cell therapy is a potential therapeutic approach for a large number of In utero haematopoietic stem cell transplantation (IUHCT) is a potential therapeutic alternative to postnatal allogeneic transplantation genetic disorders. Realization of this potential would (BMT) for congenital haematologic disorders that can be diagnosed early expand fetal therapy far beyond its current focus of in gestation and can be cured by BMT. The rationale is to take advantage treating the compromised fetus. If there are biological of normal events during haematopoietic and immunologic ontogeny to advantages that favour prenatal over post-natal facilitate allogeneic haematopoietic engraftment. The most important of therapy, fetal therapy may become the preferred these is the normal process of thymic processing of self- to create strategy for the treatment of many anticipated a state of self-tolerance. Introduction of allogeneic antigen in the form of paediatric and adult diseases. This review will cover haematopoietic stem cells results in a state of permanent donor speci!c the rationale, current status and potential future tolerance, eliminating the need for immunosuppression. Although the applications of prenatal stem cell therapy. rationale remains compelling, IUHCT has only been clinically successful in X-linked severe combined immunode!ciency syndrome, a disease in which a competitive advantage exists for donor lymphoid cells. In other disorders, Rationale for in utero stem cell such as the haemoglobinopathies, where host-cell competition is a major transplantation barrier, IUHCT has not yet succeeded. However, great experimental progress has recently been made in pre-clinical animal models. Strategies based A stem cell can be de#ned as ‘a cell that can self- on prenatal tolerance induction to facilitate post-natal non-toxic cellular replicate and can give rise to more than one type transplantation appear promising and clinical application is likely imminent. of mature daughter cell’. In recent years, there Because donor speci!c tolerance induction requires relatively minimal have been many cell populations characterized as engraftment, this strategy may hold the key to broad clinical application of ‘stem cells’, many of which may ultimately be useful IUHCT in the near future. in fetal therapy. However, the best characterized Introduction stem cell and the #rst that will be applicable to fetal therapy is the haematopoietic stem cell (HSC). In the future, prenatal stem cell therapy will probably The HSC is a multipotent stem cell that maintains 1 occupy a prominent role in fetal therapy. Whereas functional by generation of all fetal surgical intervention remains limited to a few haematopoietic lineages throughout fetal and adult life. It can therefore be used to treat a broad range of haematopoietic disorders as has been demonstrated Correspondence: Alan W Flake, MD, Centre for Fetal Diagnosis by the success of post-natal HSC transplantation and Treatment, Centre for Fetal Research, Children’s Hospital of (HSCT). However, in the absence of a matched donor, Philadelphia and Department of Surgery, University of Pennsylvania standard protocols for HSCT entail considerable School of Medicine, Philadelphia, PA 19104–4318, USA. morbidity and mortality. In utero haematopoietic 333 Email: %[email protected] © 2012 The Author(s) 333 Journal Compilation © 2012 Sheikh Hamdan Bin Rashid Al Maktoum Award for Medical Sciences Hamdan Medical Journal 2012; 5:333–343 (http://dx.doi.org/10.7707/hmj.v5i3.189) REVIEW FOR THE SHEIKH HAMDAN BIN RASHID AL MAKTOUM AWARD FOR MEDICAL SCIENCES stem cell transplantation (IUHCT) is a potential with its associated morbidity. The potential clinical non-myeloablative alternative to HSCT for congenital impact of IUHCT is enormous when we consider the haematological disorders that can be diagnosed early possibility that any disorder that can be prenatally in gestation. Through advances in prenatal screening diagnosed and can be treated by HSCT might be and molecular-based diagnostics, the opportunity for optimally treated by IUHCT. fetal intervention is greater than ever before and will undoubtedly continue to increase. Experimental results supporting the e%cacy of in utero haematopoietic stem The rationale for IUHCT is based on unique events cell transplantation that occur during normal haematological and immunological development that favour the The potential for fetal tolerance to facilitate clinical successful engraftment of transplanted allogeneic transplantation has been recognized since Billingham HSCs. The phenomenon of fetal immunological et al.’s original description of ‘actively acquired tolerance, #rst described by Billingham et al.,2 is tolerance’ in 1953.2 Additional support for the concept perhaps the most important advantage of IUHCT was provided by observations in several species of over post-natal stem cell transplantation. The fetal haematopoietic chimerism and associated tolerance thymic microenvironment plays a primary role in dizygotic twins who share placental circulation. in the determination of self-recognition and the Finally, mechanistic insight into tolerance for self repertoire of responses to foreign . Pre-T antigens (and by inference foreign antigen), and the cells undergo positive and negative selection during central role of the in this process, has been a series of maturational steps in the fetal thymus elucidated over the past two decades.3,8 Given these that are controlled by thymic stromal and dendritic observations, the administration of allogeneic HSCs cells.3 The end result is the deletion of T-cell clones with appropriate timing to the pre-immune fetus with high-a"nity recognition of self antigen, and should theoretically result in engraftment of donor preservation of a T-cell repertoire against foreign cells and consistent donor-speci#c tolerance. In the antigen. Therefore, introduction of allogeneic HSC ovine model, this appeared to be the case and this prior to thymic processing should, in theory, result was the #rst model in which the potential therapeutic in presentation of donor antigen in the thymus with e"cacy of IUHCT was investigated. Early gestational resultant life-long donor-speci#c tolerance. transplantation of allogeneic HSCs into normal sheep fetuses results in sustained multilineage Another biological opportunity unique to the fetus haematopoietic chimerism.9 The fetal sheep model is the normal developmental migrations of HSCs to is also permissive to xenogeneic engraftment, as form haematopoietic compartments. Haematopoiesis persistent, multilineage haematopoietic chimerism starts in the yolk sac and aorto-gonado-mesonephric has been documented after transplantation of region, migrates to the fetal liver and #nally resides human-derived HSCs.10–12 In contrast to the ovine in the bone marrow.4 Although the original theory model, other normal animal models such as the was that development of new niches would facilitate primate, goat, canine and rat have shown much engraftment of donor cells after IUHCT without the greater resistance to engraftment with signi#cantly need for myeloablation, it is now recognized, as will lower levels of chimerism (microchimerism) or a be discussed below, that the fetal haematopoietic complete lack of engraftment. These less encouraging system is highly competitive with a relative excess of results, along with clinical failures by other groups,13 circulating HSCs.5,6 However, if the regulatory signals led us to develop the murine model of allogeneic controlling the migrations of HSCs can be understood, IUHCT, and systematically analyse the requirements it may be possible to manipulate them to favour the for engraftment and tolerance and to identify and engraftment of donor cells.7 Finally, the very small overcome the barriers to engraftment after IUHCT. size of a fetus allows the transplantation of much larger cell doses on a per kilogram basis than can be Barriers to prenatal engraftment delivered after birth. In combination, these biological advantages that exist only in the fetus may provide It is clear from the preceding discussion that despite the opportunity for engraftment and induction of the unique opportunities o$ered by the fetal associated donor-speci#c tolerance to allogeneic cells. microenvironment, there are also unique challenges The phenomenon of fetal tolerance can potentially to overcome. These barriers to engraftment after eliminate the requirement for immunosuppression IUHCT can best be understood in the context of

334 © 2012 The Author(s) Journal Compilation © 2012 Sheikh Hamdan Bin Rashid Al Maktoum Award for Medical Sciences Hamdan Medical Journal 2012; 5:333–343 (http://dx.doi.org/10.7707/hmj.v5i3.189) REVIEW FOR THE SHEIKH HAMDAN BIN RASHID AL MAKTOUM AWARD FOR MEDICAL SCIENCES two broad categories: (1) receptivity or competition donor-speci#c tolerance does not require high levels of the host haematopoietic compartment; and ( 2) of chimerism. immunological barriers to engraftment.14 Our studies suggest that the threshold for consistent induction of donor-speci#c tolerance is between Host haematopoietic receptivity or competition 1% and 2% in the murine model, a clinically Perhaps the most important barrier to engraftment achievable range.20 However, that was not always after IUHCT is host cell competition. In contrast to the case. For many years the murine model of IUHCT post-natal bone marrow transplantation in which was extremely di"cult to engraft with donor cell myeloablation is used to condition the recipient engraftment of 0% to 1% at best (referred to as prior to transplantation, IUHCT at the present time microchimerism).21,22 However, mixed haematopoietic must be performed without any myeloablative chimerism across full MHC barriers with associated preconditioning. Because of the developmental status donor-speci#c tolerance is now observed in 100% of of the fetus and the potential repercussions of any transplanted animals in our laboratory. This is partially pharmacological toxicity on the fetus and mother, attributable to overcoming the competitive barrier standard conditioning agents cannot be utilized. by transplantation of extremely high doses of donor Therefore, the fetus has an intact and vigorous HSC by the intravascular route and partially due to haematopoietic compartment to compete with the overcoming the immunological barrier described donor cells and the success of IUHCT will depend below. With the intravascular approach we can deliver on the ability of donor HSCs to e$ectively engraft approximately six times the number of HSCs that and then compete with host haematopoiesis. The was possible with intraperitoneal transplantation concepts of receptivity (available space) and host directly into the intravascular compartment.23 This cell competition are interlinked and therefore will be has resulted in average levels of chimerism in the discussed together. allogeneic IUHCT model of over 25%. This progress and data discussed below from the preclinical There is abundant experimental evidence that canine model clearly demonstrate the ability to at competition from the host haematopoietic least partially overcome the competitive barrier to compartment is a formidable barrier to successful IUHCT by intravascular delivery of very large doses of engraftment. When donor cells have a competitive donor cells. advantage, even the engraftment of a relatively limited number of cells can ultimately reconstitute Other methods to achieve a competitive advantage the recipient. The high level of donor haematopoiesis for donor cells have also been investigated. For achieved in c-kit-de#cient mouse strains, in which instance, we have investigated the use of CD26/ there is a proliferative defect in host HSCs, is an dipeptidylpeptidase IV (CD26) blockade by pre- extreme example. In this model, as few as one or incubation of donor cells with Diprotin A (a CD26 two normal HSCs were shown to fully reconstitute blocker) to selectively improve homing of donor the haematopoietic compartment after IUHCT.15,16 cells.7 CD26 cleaves dipeptides from the N-terminus Studies of IUHCT performed in the mouse severe of polypeptide chains that contain the N-terminal combined immunode#ciency (SCID) model also X-Pro or X-Ala motif.24,25 Among its many substrates, illustrate the importance of host cell competition.17,18 CD26 has been shown to have selectivity for stromal In this model, donor lymphoid cells have a survival cell-derived factor 1F(SDF-1F)/CXCL12, a primary and proliferative advantage. IUHCT results in chemokine interaction involved in homing of HSCs to complete reconstitution of the competitively de#cient the fetal liver.26 We demonstrated that CD26 blockade lymphoid compartment with minimal engraftment of increases the availability of homing receptors on other lineages, where the non-lymphoid progenitors HSCs and progenitors, and markedly improves maintain their competitive capacity. The converse homing and subsequent donor cell engraftment in is also true, i.e. when host cells are competitively the murine model of IUHCT. This represents only one superior, very minimal engraftment will be achieved. strategy that would provide a selective advantage for Although a relationship between donor cell dose and donor cells. We have investigated other approaches levels of engraftment clearly exists, transplantation including up-regulation of homing receptors by pre- of even massive doses of donor cells (2 × 1011 incubation of donor cells in haematopoietic growth cells/kg) in a congenic strain combination (where factors,27 and immunologically based methods that the immune barrier is not a factor) results in average attempt to induce a graft-versus-host haematopoiesis levels of chimerism of around 10%.19 Fortunately, e$ect without systemic graft-versus-host disease.28

© 2012 The Author(s) 335 Journal Compilation © 2012 Sheikh Hamdan Bin Rashid Al Maktoum Award for Medical Sciences Hamdan Medical Journal 2012; 5:333–343 (http://dx.doi.org/10.7707/hmj.v5i3.189) REVIEW FOR THE SHEIKH HAMDAN BIN RASHID AL MAKTOUM AWARD FOR MEDICAL SCIENCES

Of course, the ultimate method to provide a donor a maternal immune response that is transferred to cell advantage over host cells would be a highly the neonate via maternal breastmilk.29 The proof of selective and non-toxic approach to myeloablation this was that if pups after IUHCT are fostered with in the fetus, but this ‘holy grail’ of IUHCT has not yet a surrogate mother who has not been exposed to been developed. donor antigen, the frequency of chimerism remains 100%. We demonstrated unequivocally that the transfer of allospeci#c via maternal Immunological barriers to engraftment breastmilk leads to activation of an adaptive immune Although the theoretical basis for fetal tolerance response in the pup with subsequent loss of donor appeared sound, experimental results from various chimerism. We also investigated why pups within the laboratories were mixed on the ability of IUHCT same litter could be chimeric or non-chimeric. The to induce donor-speci#c tolerance. Our early explanation relates to the self-reactive T cells that mechanistic analysis of tolerance in chimeric mice are known to escape thymic deletion in signi#cant supported a primary mechanism of deletion of numbers as a result of inadequate or late presentation donor-reactive , although deletion of antigen in the thymus, and to be controlled by was not complete, implicating the presence of regulatory mechanisms, including T-regulatory (T-reg) mechanisms as well.21,22 Thus, cell populations, which are essential for prevention IUHCT appeared to result in ‘normal’ immunological of autoimmune disease.30,31 It is also known that processing of donor cells with high-level deletion maternal–fetal cell tra"cking in humans results in of donor-reactive lymphocytes in the thymus. the generation of tolerogenic fetal T-reg cells.32 This However, despite the accomplishment of easily suggests that donor cells would induce T-reg cells in measurable levels of engraftment in some animals our chimeric pups and that these could potentially and associated donor-speci#c tolerance by the counteract a low-level alloimmune response. documented mechanisms of , there Therefore, we examined the level and suppressive were unexplained observations that suggested capacity of CD4+CD25+ T-reg cells in chimeric an additional barrier to engraftment beyond host compared with non-chimeric pups, and found that cell competition. First, despite what appeared to there does appear to be a more prominent T-reg be consistent delivery of donor cells, long-term response in the non-fostered chimeric pups.28,29 We donor chimerism occurred in only approximately speculate that in the absence of an overwhelming one-third of recipients. Second, engraftment di$ered maternal response, it is the balance of immune- signi#cantly between strain combinations. By activating and regulatory response that determines performing early tracking of donor cells and long- whether or not a pup remains chimeric. Thus, the term assessment of donor chimerism, we were able mechanisms of tolerance after IUHCT do appear to to document that 100% of allogeneic and congenic recapitulate the normal mechanisms of self-tolerance. recipients maintained high levels of engraftment The most important and central component is high up to 3 weeks after IUHCT. However, between three level, but not complete, deletion of donor-reactive and 5 weeks, 70% of allogeneic animals lost their T-cells orchestrated by the fetal thymus. However, it engraftment, whereas 100% of congenic animals is also essential that cells that escape thymic deletion remained chimeric. The di$erence in the incidence and are donor cell reactive are suppressed in the of chimerism between congenic and allogeneic periphery by an adequate T-reg response. donors clearly supported the presence of an adaptive immune barrier to engraftment after IUHCT.19 We have We feel that the most important #nding in these now con#rmed that there is an allospeci#c cellular studies is not the identi#cation of the maternal and humoral response that is quantitatively higher in immune response as the key factor in loss of non-chimeric than in chimeric animals. This #nding chimerism, but rather the observation that in was inconsistent with our previous demonstration the absence of maternal in%uence allogeneic of long-term chimerism in some animals and the engraftment and long-term chimerism uniformly presence of deletional tolerance, and cast doubt on occur. This con#rms the absence of an adaptive the validity of the primary rationale of IUHCT. immune barrier in the preimmune fetus and validates the potential for practical application of ‘actively The pivotal observation that explains this acquired tolerance’ to facilitate allogeneic cellular contradiction, and should be considered in and/or organ transplantation. It raises the question all subsequent studies of IUHCT, is our recent of whether or not maternal immunization is an issue observation that the immune response is in reality in large-animal models and clinical circumstances,

336 © 2012 The Author(s) Journal Compilation © 2012 Sheikh Hamdan Bin Rashid Al Maktoum Award for Medical Sciences Hamdan Medical Journal 2012; 5:333–343 (http://dx.doi.org/10.7707/hmj.v5i3.189) REVIEW FOR THE SHEIKH HAMDAN BIN RASHID AL MAKTOUM AWARD FOR MEDICAL SCIENCES and whether or not it is a limitation to engraftment exception of sheep, there has been very limited after clinical IUHCT. It also raises the question of the success after IUHCT in large-animal models, although importance of the innate as a barrier recently that has begun to change. Successful to engraftment. Although natural killer (NK) cells achievement of measurable multilineage chimerism have recently been implicated in loss of low-level after IUHCT with associated donor-speci#c tolerance engraftment after IUHCT,33 their e$ect appears to for swine leucocyte antigen (SLA)-matched kidney be lost in circumstances of absence of maternal transplants has been demonstrated in limited in%uence. It is possible that the presence of maternal experiments in the SLA inbred pig model.38,39 In order allospeci#c can directly activate NK cells via to validate our success in the murine model, we have the mechanism of antibody-dependent cell-mediated developed the canine model of IUHCT. The canine cytotoxicity. These are important questions but, in model has been used extensively in the preclinical any case, an obvious strategy to avoid any potential testing of post-natal HSCT regimens and has been a maternally derived immune barrier would be the use reliable predictor of clinical results40,41 For instance, of maternal donor cells when appropriate. many strategies to prevent or treat GVHD were #rst evaluated in the canine model prior to their use in humans.40–46 The canine model also o$ers biological The virtues of tolerance and practical advantages speci#c to the evaluation of The achievement of donor-speci#c tolerance IUHCT. The ontogeny of the canine immune system allowed us to perform proof-in-principle studies appears relatively similar to that of humans,47 and of the promising clinical strategy of prenatal from a technical perspective, the canine pregnancy tolerance induction by IUHCT followed by post-natal allows ultrasound-guided injection of pups prior to non-toxic bone marrow transplantation (BMT) immune maturation. Finally, the canine model o$ers to increase low levels of chimerism to levels that the advantage of the availability of disease models would be therapeutic for diseases such as the that are analogous to human disorders. haemoglobinopathies. The value of this strategy is that it lowers the threshold of chimerism that We initiated our canine studies using dogs that must be obtained by IUHCT to proceed with have the canine analogue of human leucocyte clinical application. It is well established that adhesion de#ciency [canine leucocyte adhesion HSCT from a syngeneic or identical twin donor de#ciency (CLAD)]. CLAD-a$ected dogs have a requires a very minimal conditioning regimen (no severe immunode#ciency that results in death immunosuppression and minimal myelosuppression) prior to 6 months of age, whereas the CLAD carrier to achieve engraftment.34,35 As IUHCT theoretically is phenotypically normal. Neither the a$ected produces, from the perspective of the immune nor carrier dogs have a signi#cant competitive system, a perfectly matched donor, this strategy defect in the HSC compartment or in any of the should provide high-level engraftment with very haematopoietic lineages.48 Therefore, the CLAD minimal or no toxicity. We have demonstrated model should be representative of the degree of host three di$erent non-toxic post-natal strategies to cell competition expected for most target diseases. be e$ective in the murine model after IUHCT: (1) Historically, the canine model has been di"cult preparative low-dose total-body irradiation followed to engraft by IUHCT, supporting the competitive by T-cell-depleted BMT;36 (2) post-natal donor-speci#c capacity of the fetal haematopoietic system.49 In our infusion (DLI) without BMT37; and (3) initial studies in the canine model, we demonstrated low-dose busulfan as a single-agent preparative that low-level chimerism can be achieved by IUHCT regimen, followed by T-cell-depleted BMT.20 In each and that these levels of chimerism can (1) ameliorate study, complete or near-complete replacement of or cure the clinical phenotype of CLAD and (2) result host haematopoiesis by donor cells was achieved, in associated donor-speci#c tolerance in some essentially without toxicity or graft-versus-host animals that is adequate to facilitate post-natal disease (GVHD). These studies form the basis for enhancement of chimerism to potentially therapeutic what we believe will be the #rst successful clinical levels using the single-agent, low-dose busulfan- strategy for application of IUHCT to competitive conditioning regimen, followed by transplantation of haematological disorders. T-cell-depleted bone marrow from the same donor.50 In this study, we saw no signi#cant toxicity and no Of course, the murine model may not be GVHD. We have recently developed techniques representative of what will occur clinically and that result in engraftment of > 2% in over 90% of a better preclinical model was needed. With the recipient dogs after IUHCT with an average level

© 2012 The Author(s) 337 Journal Compilation © 2012 Sheikh Hamdan Bin Rashid Al Maktoum Award for Medical Sciences Hamdan Medical Journal 2012; 5:333–343 (http://dx.doi.org/10.7707/hmj.v5i3.189) REVIEW FOR THE SHEIKH HAMDAN BIN RASHID AL MAKTOUM AWARD FOR MEDICAL SCIENCES of engraftment of around 8%. These levels are well which led to no clinical improvement and the other within the range of chimerism required to induce resulted in prenatal death, probably because of GVHD. donor-speci#c tolerance and con#rm that the barriers Given this history, few recent attempts at IUHCT to engraftment can be overcome in a large-animal, have been reported and many investigators have clinically relevant model (Flake AW, manuscript in been discouraged. However, the rationale remains preparation). We are encouraged that the results of compelling and there are lessons to be learned IUHCT in the canine model appear remarkably similar from this experience that may help guide future to our results in the murine model, suggesting that e$orts. Many of the historic attempts were ill-advised our results in the murine model can be translated to for reasons that are now recognized. Many of the clinical application. transplants were performed too late in gestation, or with donor cell sources that would not be expected to succeed. For instance, the use of highly enriched HSCs Experience with clinical application as a donor source has been unsuccessful in allogeneic of in utero haematopoietic stem cell experimental systems and has also been clinically transplantation unsuccessful. In addition, the expectation that one There have been approximately 50 reported cases of could achieve therapeutic levels of engraftment IUHCT in humans over the past 20 years.51 Drawing after conventional IUHCT alone for diseases such conclusions based on clinical experience in humans as the haemoglobinopathies was somewhat naive has been di"cult because of a large variety of target given what we now understand about the barriers diseases, donor cell sources and transplantation to engraftment. However, given the experimental protocols. Not surprisingly, success has largely been progress described above we feel that it is now time limited to cases of immunode#ciency syndromes in to revisit clinical application of IUHCT. which donor cells have a clear selective advantage over host cells, i.e. X-linked SCID (XSCID). In utero Considerations for future clinical therapy for XSCID has been successful, with at least application of in utero haematopoietic 10 documented cases of cellular reconstitution with stem cell transplantation functional T cells.52–57 However, recipients manifest split chimerism, with only the T-cell compartment Based on data from the combined murine and engrafted, similar to the results of non-myeloablative preclinical canine models of IUHCT we now have the post-natal HSCT. Thus far, there is no proven expectation that clinical application of IUHCT can advantage for prenatal treatment of XSCID over be successful either alone or in combination with neonatal transplantation but not enough cases have a post-natal minimally conditioned same-donor been performed to enable meaningful comparisons.58 transplant. However, it is essential that future trials Attempts to treat other immunode#ciency of IUHCT be performed in centres with a vested disorders, such as chronic granulomatous disease interest in this therapy and preferably proven success (CGD) or Chediak–Higashi syndrome, have been in a preclinical animal model. Our data support an unsuccessful thus far as all subjects were born optimized protocol that includes the use of maternal without detectable engraftment.59–61 The use of IUHCT cells and intravascular administration. Based on for haemoglobinopathies has also been attempted, our current understanding of human immune and but has thus far been largely unsuccessful. There haematopoietic ontogeny, the ideal timing of at have been 12 attempts to treat G-thalassaemia least the #rst IUHCT would be at 13 to 14 weeks’ in utero, with only two investigators reporting gestation. During this time the fetal liver is the detectable post-natal engraftment,62–64 at least primary haematopoietic organ and thymic selection one of whom subsequently lost engraftment.54 is ongoing with very few mature lymphocytes present There have been three reported attempts to treat in the thymus or peripheral circulation. Also, at this F-thalassaemia by IUHCT, with one patient exhibiting time the fetus is very small, < 35 g in weight, allowing microchimerism and tolerance to donor antigen the opportunity to maximize the dose of donor by mixed lymphocyte reaction;65 however, all three cells. At the present time, the only disorders that patients remained transfusion dependent. There have this strategy can be contemplated for are disorders also been three reported attempts to treat sickle cell that o$er either a competitive advantage for donor anaemia; however, none has resulted in detectable cells, or perhaps disorders that require only minimal engraftment.66,67 There have been seven reported levels of engraftment for therapeutic success. At the attempts to treat metabolic storage diseases by present time, there are two clinical strategies that IUHCT, with two reports of engraftment,53,68 one of may be successful in clinical application. The #rst is

338 © 2012 The Author(s) Journal Compilation © 2012 Sheikh Hamdan Bin Rashid Al Maktoum Award for Medical Sciences Hamdan Medical Journal 2012; 5:333–343 (http://dx.doi.org/10.7707/hmj.v5i3.189) REVIEW FOR THE SHEIKH HAMDAN BIN RASHID AL MAKTOUM AWARD FOR MEDICAL SCIENCES

IUHCT alone, which may be successful for selected reconstitution alone. Other diseases that are known biologically favourable target disorders. The second to be treatable with low levels of chimerism include is IUHCT for donor-speci#c tolerance induction CGD, hyper-IgM syndrome and LAD. It has been well followed by post-natal minimally conditioned HSCT documented that CGD can be corrected by as few as from the same donor. The latter approach holds the 5% normal ,74 and in X-linked hyper-IgM most immediate promise for broad clinical application syndrome, phenotypically normal carriers have of IUHCT because it requires only a minimal level been identi#ed in whom the normal gene has been of chimerism to be successful, and as it would be predominantly silenced.75 LAD results from mutations applicable to the majority of disorders that can be in the leucocyte integrin CD18, which inhibits the prenatally diagnosed and treated by post-natal IUHCT. expression of the CD18/CD11 complex on the cell surface and thus the ability of leucocytes to adhere to the vessel wall and migrate to sites of infection.76 Favourable disease targets for in utero Recent studies in the analogous CLAD model have haematopoietic stem cell transplantation demonstrated that even low levels of donor CD18+ alone cell engraftment following non-myeloablative Clearly, the most biologically favourable disease for matched littermate BMT can reverse the lethal treatment by IUHCT alone remains XSCID. Other disease phenotype in CLAD.48,77 We have recently characterized mutations in receptor demonstrated correction of the CLAD phenotype signalling pathways [i.e. Janus kinase 3 (Jak3) or by IUHCT of haploidentical adult BM-derived cells zeta-associated protein 70 (ZAP-70)] resulting in the canine model.50 Speci#c non-haematopoietic in SCID should also be favourable candidate disorders of bone metabolism may also be attractive diseases for IUHCT. Based on the available clinical target disorders for IUHCT. A recent report of rescue and experimental evidence, it is likely that any of osteopetrotic mice with the same mutation as member of this group of disorders can be e$ectively approximately half of human patients with the treated by IUHCT alone as even minimal levels of autosomal recessive disease by IUHCT is intriguing.78 engraftment should provide adequate T- and B-cell In this study, complete phenotypic correction function to provide immune protection. If B-cell associated with osteoclast engraftment was achieved, engraftment occurs, then there would be a strong despite the fact that an abundance of host osteoclasts rationale favouring IUHCT over the current standard remained present that were not functional. There is for comparison of neonatal non-myeloablative also interest in treatment of osteogenesis imperfecta haploidentical transplantation in which only T-cell by prenatal replacement of mesenchymal stem engraftment occurs and the children must be cells or stromal progenitor cells79 and clinical cases supported with supplemental IgG.69 Another group have been reported with somewhat promising of diseases that could bene#t from IUHCT alone results.80 The experimental basis for application of are those in which somatic mosaicism and in vivo IUHCT towards this disease, however, needs further selection have been documented to occur. In these development. For all of these disorders, even if diseases there is presumably a survival advantage for curative levels of engraftment are not achieved, levels the spontaneously corrected cells.70 Such correction adequate for donor-speci#c tolerance induction has been noted in adenosine deaminase SCID,71 would allow conversion of the patient to the second Fanconi anaemia72 and Bloom syndrome,73 the last strategy described below. two of which are chromosomal breakage syndromes. In both Fanconi anaemia and Bloom syndrome In utero haematopoietic stem cell mitotic recombination was documented as the transplantation for donor-speci!c tolerance molecular mechanism of somatic reversion. This induction followed by post-natal minimal represents an experiment of nature documenting conditioning same-donor haematopoietic the improvement in a disease by clonal expansion of stem cell transplantation a single spontaneously corrected HSC and suggests that even low-level engraftment achieved by IUHCT As discussed earlier, low levels of mixed could eventually replace host haematopoiesis as haematopoietic chimerism after IUHCT are associated progressive bone marrow failure occurred. True with donor-speci#c tolerance. The exact level of clinical cure of either disease is unlikely, as they are chimerism required may vary slightly with species, but associated with other pleiotropic manifestations, is in the 1–2% range. In the murine system, we have such as an increased rate of malignancy, that observed that in the presence of microchimerism are unlikely to be reversed by haematopoietic (< 0.5%, donor cells detectable only by ampli#cation

© 2012 The Author(s) 339 Journal Compilation © 2012 Sheikh Hamdan Bin Rashid Al Maktoum Award for Medical Sciences Hamdan Medical Journal 2012; 5:333–343 (http://dx.doi.org/10.7707/hmj.v5i3.189) REVIEW FOR THE SHEIKH HAMDAN BIN RASHID AL MAKTOUM AWARD FOR MEDICAL SCIENCES by polymerase chain reaction) approximately one- transplantation. Blood 2006; 108:4268–74. third of animals are tolerant of donor skin grafts http://dx.doi.org/10.1182/blood-2006-04-018986 and non-reactive by mixed lymphocyte reaction.21,22 8 Sprent J. Central tolerance of T cells. Int Rev Immunol 1995; 13:95–105. In a separate study, using the ability to enhance http://dx.doi.org/10.3109/08830189509061740 chimerism after IUHCT by minimal conditioning 9 Flake AW, Harrison MR, Adzick NS, et al. Transplantation post-natal IUHCT from the same donor strain as the of fetal haematopoietic stem cells In utero: the creation de#nition of tolerance, only 60% of animals with %ow of haematopoietic chimeras. Science 1986; 233:776–8. cytometrically detectable chimerism of < 1% were http://dx.doi.org/10.1126/science.2874611 10 Flake AW, Hedrick MH, Rice HE, et al. Enhancement tolerant, whereas I00% of animals with chimerism of of human hematopoiesis by mast cell growth factor > 1% were tolerant.20 Given the relatively high levels in human–sheep chimeras created by the In utero of chimerism achieved in the canine model, we feel transplantation of human fetal haematopoietic cells. that there is a very high likelihood that this strategy Exp Haematol 1995; 23:252–7. can be successful. If so, it would be applicable to all 11 Zanjani ED, Flake AW, Rice H, et al. Long-term repopulating ability of xenogeneic transplanted human disorders that are currently treatable by HSCT and fetal liver haematopoietic stem cells in sheep. J Clin that can be diagnosed prenatally. The most important Invest 1994; 93:1051–5. of these are the haemoglobinopathies, i.e. sickle cell http://dx.doi.org/10.1172/JCI117054 disease and β-thalassaemia. These are two of the most 12 Zanjani ED, Pallavicini MG, Flake AW, et al. Engraftment common genetic disorders in the world and there and long-term expression of human fetal hemopoietic stem cells in sheep following transplantation in utero. is at present no satisfactory post-natal treatment. J Clin Invest 1992; 89:1178–88. They are favourable disorders to treat by IUHCT http://dx.doi.org/10.1172/JCI115701 from the perspective of their post-natal biology, 13 Flake AW. In utero stem cell transplantation. Best Pract in that levels of mixed haematopoietic chimerism Res Clin Obstet Gynaecol 2004; 18:941–58. of 15–25% phenotypically correct the disease. The http://dx.doi.org/10.1016/j.bpobgyn.2004.06.006 14 Flake AW, Zanjani ED. In utero haematopoietic stem cell short half-life of diseased red cells in both disorders transplantation: ontogenic opportunities and biologic allows ampli#cation of myelolymphoid engraftment barriers. Blood 1999; 94:2179–91. in the bone marrow in the circulating red cell 15 Fleischman R, Mintz B. Prevention of genetic anemias in compartment.81 However, both disorders have normal mice by microinjection of normal haematopoietic cells prenatal haematopoiesis and are highly competitive into the fetal placenta. Proc Natl Acad Sci U S A 1979; 76:5736–40. http://dx.doi.org/10.1073/pnas.76.11.5736 targets for IUHCT. Thus it is likely that a two-step 16 Mintz B, Anthony K, Litwin S. Monoclonal derivation of approach will be required. We plan to initiate a clinical mouse myeloid and lymphoid lineages from totipotent trial for SCD at our centre in the near future. haematopoietic stem cells experimentally engrafted in fetal hosts. Proc Natl Acad Sci U S A 1984; 81:7835–9. http://dx.doi.org/10.1073/pnas.81.24.7835 References 17 Blazar BR, Taylor PA, Vallera DA. In utero transfer of adult bone marrow cells into recipients with severe combined 1 Flake AW. Surgery in the human fetus: the future. immunode#ciency disorder yields lymphoid progeny J Physiol 2003; 547:45–51. with T- and B-cell functional capabilities. Blood 1995; http://dx.doi.org/10.1113/jphysiol.2002.022327 86:4353–66. 2 Billingham R, Brent L, Medawar PB. Actively acquired 18 Waldschmidt TJ, Panoskaltsis-Mortari A, McElmurry RT, tolerance of foreign cells. Nature 1953; 172:603–7. et al. Abnormal -dependent B-cell responses in http://dx.doi.org/10.1038/172603a0 SCID mice receiving allogeneic bone marrow in utero. 3 Takahama Y. Journey through the thymus: stromal Severe combined immune de#ciency. Blood 2002; guides for T-cell development and selection. Nat Rev 100:4557–64. 2006; 6:127–35. http://dx.doi.org/10.1038/nri1781 http://dx.doi.org/10.1182/blood-2002-04-1232 4 Christensen JL, Wright DE, Wagers AJ, et al. Circulation 19 Peranteau WH, Endo M, Adibe OO, et al. Evidence for and chemotaxis of fetal haematopoietic stem cells. PLoS an immune barrier after in utero haematopoietic-cell Biol 2004; 2:E75. B transplantation. Blood 2007; 109:1331–3. http://dx.doi.org/10.1371/journal.pbio.0020075 http://dx.doi.org/10.1182/blood-2006-04-018606 5 Harrison DE, Zhong RK, Jordan CT, et al. Relative to adult 20 Ashizuka S, Peranteau WH, Hayashi S, et al. Busulfan- marrow, fetal liver repopulates nearly #ve times more conditioned bone marrow transplantation results in e$ectively long-term than short-term. Exp Haematol high-level allogeneic chimerism in mice made tolerant 1997; 25:293–7. by in utero haematopoietic cell transplantation. 6 Shaaban AF, Kim HB, Milner R, et al. A kinetic model Exp Hematol 2006; 34:359–68. for homing and migration of prenatally transplanted http://dx.doi.org/10.1016/j.exphem.2005.11.011 marrow. Blood 1999; 94:3251–7. 21 Kim HB, Shaaban AF, Milner R, et al. In utero bone 7 Peranteau WH, Endo M, Adibe OO, et al. CD26 marrow transplantation induces tolerance by a inhibition enhances allogeneic donor-cell homing combination of clonal deletion and anergy. J Pediatr and engraftment after in utero haematopoietic-cell Surg 1999; 34:726–30. http://dx.doi.org/10.1016/S0022-3468(99)90364-0

340 © 2012 The Author(s) Journal Compilation © 2012 Sheikh Hamdan Bin Rashid Al Maktoum Award for Medical Sciences Hamdan Medical Journal 2012; 5:333–343 (http://dx.doi.org/10.7707/hmj.v5i3.189) REVIEW FOR THE SHEIKH HAMDAN BIN RASHID AL MAKTOUM AWARD FOR MEDICAL SCIENCES

22 Kim HB, Shaaban AF, Yang EY, et al. Microchimerism and 35 Stewart FM, Zhong S, Wuu J, et al. tolerance after in utero bone marrow transplantation in Lymphohematopoietic engraftment in minimally mice. J Surg Res 1998; 77:1–5. myeloablated hosts. Blood 1998; 91:3681–7. http://dx.doi.org/10.1006/jsre.1997.5255 36 Peranteau WH, Hayashi S, Hsieh M, et al. High-level 23 Javazon EH, Merchant AM, Danzer E, et al . allogeneic chimerism achieved by prenatal tolerance Reconstitution of hematopoiesis following intrauterine induction and postnatal nonmyeloablative bone transplantation of stem cells. Methods Mol Med 2005; marrow transplantation. Blood 2002; 100:2225–34. 105:81–94. http://dx.doi.org/10.1182/blood-2002-01-0166 24 Christopherson KW II, Hangoc G, Broxmeyer HE. 37 Hayashi S, Peranteau WH, Shaaban AF, et al. Complete Cell surface peptidase CD26/dipeptidylpeptidase IV allogeneic haematopoietic chimerism achieved by a regulates CXCL12/stromal cell-derived factor-1 alpha- combined strategy of in utero haematopoietic stem mediated chemotaxis of human cord blood CD34+ cell transplantation and postnatal donor lymphocyte progenitor cells. J Immunol 2002; 169:7000–8. infusion. Blood 2002; 100:804–12. 25 Christopherson KW II, Hangoc G, Mantel CR, et al. http://dx.doi.org/10.1182/blood-2002-01-0016 Modulation of haematopoietic stem cell homing and 38 Lee PW, Cina RA, Randolph MA, et al. In utero bone engraftment by CD26. Science 2004; 305:1000–3. marrow transplantation induces kidney allograft http://dx.doi.org/10.1126/science.1097071 tolerance across a full major histocompatibility complex 26 Lambeir AM, Proost P, Durinx C, et al. Kinetic barrier in swine. Transplantation 2005; 79:1084–90. investigation of chemokine truncation by CD26/ http://dx.doi.org/10.1097/01.TP.0000161247.61727.67 dipeptidyl peptidase IV reveals a striking selectivity 39 Lee PW, Cina RA, Randolph MA, et al. Stable multilineage within the chemokine family. J Biol Chem 2001; chimerism across full MHC barriers without graft- 276:29839–45. versus-host disease following in utero bone marrow http://dx.doi.org/10.1074/jbc.M103106200 transplantation in pigs. Exp Hematol 2005; 33:371–9. 27 Shaaban AF, Kim HB, Gaur L, et al. Prenatal http://dx.doi.org/10.1016/j.exphem.2004.12.002 transplantation of cytokine-stimulated marrow 40 Diaconescu R, Storb R. Allogeneic haematopoietic cell improves early chimerism in a resistant strain transplantation: from experimental biology to clinical combination but results in poor long-term engraftment. care. J Cancer Res Clin Oncol 2005; 131:1–13. Exp Hematol 2006; 34:1278–87. http://dx.doi.org/10.1007/s00432-004-0611-6 http://dx.doi.org/10.1016/j.exphem.2006.05.007 41 Storb R. Allogeneic haematopoietic stem cell 28 Hayashi S, Hsieh M, Peranteau WH, et al. Complete transplantation – yesterday, today, and tomorrow. Exp allogeneic haematopoietic chimerism achieved by Hematol 2003; 31:1–10. in utero haematopoietic cell transplantation and http://dx.doi.org/10.1016/S0301-472X(02)01020-2 cotransplantation of LLME-treated, MHC-sensitized 42 Kuhr CS, Lupu M, Little MT, et al. RDP58 does not donor lymphocytes. Exp Hematol 2004; 32:290–9. prevent graft-versus-host disease after dog leucocyte http://dx.doi.org/10.1016/j.exphem.2003.12.008 antigen-nonidentical canine haematopoietic cell 29 Merianos DJ, Tiblad E, Santore MT, et al. Maternal transplantation. Transplantation 2006; 81:1460–2. alloantibodies induce a postnatal immune http://dx.doi.org/10.1097/01.tp.0000203323.82681.7d response that limits engraftment following in utero 43 Mielcarek M, Georges GE, Storb R. Denileukin diftitox haematopoietic cell transplantation in mice. J Clin Invest as prophylaxis against graft-versus-host disease in the 2009; 119:2590–600. canine haematopoietic cell transplantation model. Biol 30 Sakaguchi S, Sakaguchi N, Asano M, et al. Immunologic Blood Marrow Transplant 2006; 12:899–904. self-tolerance maintained by activated T cells expressing http://dx.doi.org/10.1016/j.bbmt.2006.05.005 IL-2 receptor alpha-chains (CD25). Breakdown of a 44 Storb R, Deeg HJ, Ra$ R, et al. Prevention of graft-versus- single mechanism of self-tolerance causes various host disease. Studies in a canine model. Ann N Y Acad Sci autoimmune diseases. J Immunol 1995; 155:1151–64. 1995; 770:149–64. 31 Takahashi T, Tagami T, Yamazaki S, et al. Immunologic http://dx.doi.org/10.1111/j.1749-6632.1995.tb31052.x self-tolerance maintained by CD25(+)CD4(+) regulatory 45 Storb R, Kolb HJ, Deeg HJ, et al. Prevention of graft- T cells constitutively expressing cytotoxic T lymphocyte- versus-host disease by immunosuppressive agents after associated antigen 4. J Exp Med 2000; 192:303–10. transplantation of DLA-nonidentical canine marrow. http://dx.doi.org/10.1084/jem.192.2.303 Bone Marrow Transplant 1986; 1:167–77. 32 Mould JE, Michaelsson J, Burt TD, et al. Maternal 46 Storb R, Ra$ RF, Appelbaum FR, et al. FK-506 and alloantigens promote the development of tolerogenic methotrexate prevent graft-versus-host disease in dogs fetal regulatory T cells in utero. Science 2008; given 9.2 Gy total body irradiation and marrow grafts 322:1562–5. http://dx.doi.org/10.1126/science.1164511 from unrelated dog leucocyte antigen-nonidentical 33 Durkin ET, Jones KA, Rajesh D, et al. Early chimerism donors. Transplantation 19936; 56:800–7. threshold predicts sustained engraftment and NK-cell http://dx.doi.org/10.1097/00007890-199310000-00005 tolerance in prenatal allogeneic chimeras. Blood 2008; 47 Felsburg PJ. Overview of immune system development 112:5245–53. in the dog: comparison with humans. Hum Exp Toxicol http://dx.doi.org/10.1182/blood-2007-12-128116 2002; 21:487–92. 34 Ramshaw HS, Crittenden RB, Dooner M, et al. High levels http://dx.doi.org/10.1191/0960327102ht286oa of engraftment with a single infusion of bone marrow 48 Bauer TR Jr, Creevy KE, Gu YC, et al. Very low levels cells into normal unprepared mice. Biol Blood Marrow of donor CD18+ neutrophils following allogeneic Transplant 1995; 1:74–80. haematopoietic stem cell transplantation reverse the disease phenotype in canine leucocyte adhesion

© 2012 The Author(s) 341 Journal Compilation © 2012 Sheikh Hamdan Bin Rashid Al Maktoum Award for Medical Sciences Hamdan Medical Journal 2012; 5:333–343 (http://dx.doi.org/10.7707/hmj.v5i3.189) REVIEW FOR THE SHEIKH HAMDAN BIN RASHID AL MAKTOUM AWARD FOR MEDICAL SCIENCES

de#ciency. Blood 2004; 103:3582–9. 63 Orlandi F, Giambona A, Messana F, et al. Evidence of http://dx.doi.org/10.1182/blood-2003-11-4008 induced non-tolerance in HLA-identical twins with 49 Blakemore K, Hattenburg C, Stetten G, et al. In utero hemoglobinopathy after in utero fetal transplantation. haematopoietic stem cell transplantation with Bone Marrow Transplant 1996; 18:637–9. haploidentical donor adult bone marrow in a canine 64 Touraine J. Treatment of human fetuses and induction model. Am J Obstet Gynecol 2004; 190:960–73. of immunological tolerance in humans by in utero http://dx.doi.org/10.1016/j.ajog.2004.01.014 transplantation of stem cells into fetal recipients. Acta 50 Peranteau WH, Heaton TE, Gu YC, et al. Haploidentical Haematol 1996; 96:115–19. in utero haematopoietic cell transplantation improves http://dx.doi.org/10.1159/000203741 phenotype and can induce tolerance for postnatal 65 Hayward A, Ambruso D, Battaglia F, et al. same-donor transplants in the canine leucocyte Microchimerism and tolerance following intrauterine adhesion de#ciency model. Biol Blood Marrow Transplant transplantation and transfusion for F-thalassemia-1. 2009; 15:293–305. Fetal Diagn Ther 1998; 13:8–14. http://dx.doi.org/10.1016/j.bbmt.2008.11.034 http://dx.doi.org/10.1159/000020793 51 Merianos D, Heaton T, et al. In utero haematopoietic 66 Westgren M. In utero stem cell transplantation. Semin stem cell transplantation: progress towards clinical Reprod Med 2006; 24:348–57. application. Biol Blood Marrow Transplant 2008; 14:729– http://dx.doi.org/10.1055/s-2006-952156 40. http://dx.doi.org/10.1016/j.bbmt.2008.02.012 67 Westgren M, Ringden O, Sturla E-N, et al. Lack 52 Flake A, Roncarolo M-G, Puck J, et al. Treatment of of evidence of permanent engraftment after In X-linked severe combined immunode#ciency by in utero utero fetal stem cell transplantation in congenital transplantation of paternal bone marrow. N Engl J Med hemoglobinopathies. Transplantation 1996; 61:1176–9. 1996; 335:1806–10. http://dx.doi.org/10.1097/00007890-199604270-00010 http://dx.doi.org/10.1056/NEJM199612123352404 68 Bambach BJ, Moser HW, Blakemore K, et al. Engraftment 53 Touraine JL, Raudrant D, Gol#er F, et al. Reappraisal of following In utero bone marrow transplantation in utero stem cell transplantation based on long-term for globoid cell leukodystrophy. Bone Marrow results. Fetal Diagn Ther 2004; 19:305–12. Transplantation 1997; 19:399–402. http://dx.doi.org/10.1159/000077957 http://dx.doi.org/10.1038/sj.bmt.1700665 54 Touraine JL, Raudrant D, Rebaud A, et al. In utero 69 Buckley RH, Schi$ SE, Schi$ RI, et al. Haematopoietic transplantation of stem cells in humans: immunological stem-cell transplantation for the treatment of severe aspects and clinical follow-up of patients. Bone Marrow combined immunode#ciency. N Engl J Med 1999; Transplant 1992; 1:121–6. 340:508–16. 55 Touraine JL, Raudrant D, Royo C, et al. In-utero http://dx.doi.org/10.1056/NEJM199902183400703 transplantation of stem cells in bare lymphocyte 70 Kvittengen EA, Rootwelt H, Brandtzaeg P, et al. syndrome [letter]. Lancet 1989; 1:1382. Hereditary tyrosinemia type I. Self induced correction http://dx.doi.org/10.1016/S0140-6736(89)92819-5 of the fumarylacetoacetase defect. J Clin Invest 1993; 56 Wengler G, Lanfranchi A, Frusca T, et al. In utero 91:1816–23. http://dx.doi.org/10.1172/JCI116393 transplantation of parental CD34 haematopoietic 71 Hirschhorn R, Yang DR, Puck JM, et al. Spontaneous in progenitor cells in a patient with X-linked severe vivo reversion to normal of an inherited mutation in a combined immunode#ciency (SCIDX1). Lancet 1996; patient with adenosine deaminase de#ciency. Nat Genet 348:1484–7. 1996; 13:290–6. http://dx.doi.org/10.1038/ng0796-290 http://dx.doi.org/10.1016/S0140-6736(96)09392-0 72 D’Andrea AD, Grompe M. Molecular biology of Fanconi 57 Westgren M, Ringden O, Bartmann P, et al. Prenatal anaemia: implications for diagnosis and therapy. Blood T-cell reconstitution after in utero transplantation 1997; 90:1725–36. with fetal liver cells in a patient with X-linked severe 73 Ellis NA, Lennon DJ, Proytcheva M, et al. Somatic combined immunode#ciency. Am J Obstet Gynecol 2002; intragenic recombination within the mutated locus 187:475–82. BLM can correct the high sister-chromatid exchange http://dx.doi.org/10.1067/mob.2002.123602 phenotype of Bloom Syndrome cells. Am. J Hum Genet 58 Flake AW, Zanjani ED. Treatment of severe combined 1995; 57:1019–27. immunode#ciency. Letter to the Editor. N Engl J Med 74 Bjorgvinsdottir H, Ding C, Pech N, et al. Retroviral- 1999; 341:291. mediated gene transfer of gp91phox into bone marrow 59 Flake AW, Zanjani ED. In utero haematopoietic stem cell cells rescues defect in host defence against Aspergillus transplantation. A status report. JAMA 1997; 278:932–7. fumigatus in murine X-linked chronic granulomatous http://dx.doi.org/10.1001/jama.1997.03550110070039 disease. Blood 1997; 89:41–8. 60 Jones DR, Bui TH, Anderson EM, et al. In utero 75 Hollenbaugh D, Wu LH, Ochs HD, et al. The random haematopoietic stem cell transplantation: current inactivation of the X chromosome carrying the defective perspectives and future potential. Bone Marrow gene responsible for X-linked hyper IgM syndrome Transplant 1996; 18:831–7. (X-HIM) in female carriers of HIGM1. J Clin Invest 1994; 61 Muench MO, Rae J, Barcena A, et al. Transplantation of 94:616–22. http://dx.doi.org/10.1172/JCI117377 a fetus with paternal Thy-1(+)CD34(+)cells for chronic 76 Kishimoto TK, Hollander N, Roberts TM, et al. granulomatous disease. Bone Marrow Transplant 2001; Heterogeneous mutations in the beta subunit common 27:355–64. http://dx.doi.org/10.1038/sj.bmt.1702798 to the LFA-1, Mac-1, and p150,95 glycoproteins cause 62 Monni G, Ibba RM, Zoppi MA, et al. In utero stem cell leucocyte adhesion de#ciency. Cell 1987; 50:193–202. transplantation. Croat Med J 1998; 39:220–3. http://dx.doi.org/10.1016/0092-8674(87)90215-7

342 © 2012 The Author(s) Journal Compilation © 2012 Sheikh Hamdan Bin Rashid Al Maktoum Award for Medical Sciences Hamdan Medical Journal 2012; 5:333–343 (http://dx.doi.org/10.7707/hmj.v5i3.189) REVIEW FOR THE SHEIKH HAMDAN BIN RASHID AL MAKTOUM AWARD FOR MEDICAL SCIENCES

77 Bauer TR Jr, Gu YC, Tuschong LM, et al. Nonmyeloablative sheep. Nat Med 2000; 6:1282–6. haematopoietic stem cell transplantation corrects the http://dx.doi.org/10.1038/81395 disease phenotype in the canine model of leucocyte 80 Le Blanc K, Gotherstrom C, Ringden O, et al. Fetal adhesion de#ciency. Exp Hematol 2005; 33:706–12. mesenchymal stem-cell engraftment in bone after http://dx.doi.org/10.1016/j.exphem.2005.03.010 In utero transplantation in a patient with severe 78 Frattini A, Blair HC, Sacco MG, et al. Rescue of osteogenesis imperfecta. Transplantation 2005; ATPa3-de#cient murine malignant osteopetrosis by 79:1607–14. haematopoietic stem cell transplantation In utero. Proc http://dx.doi.org/10.1097/01.TP.0000159029.48678.93 Natl Acad Sci U S A 2005; 102:14629–34. 81 Hayashi S, Abdulmalik O, Peranteau WH, et al. Mixed http://dx.doi.org/10.1073/pnas.0507637102 chimerism following In utero haematopoietic stem cell 79 Liechty KW, MacKenzie TC, Shaaban AF, et al. Human transplantation in murine models of hemoglobinopathy. mesenchymal stem cells engraft and demonstrate site- Exp Hematol 2003; 31:176–84. speci#c di$erentiation after In utero transplantation in http://dx.doi.org/10.1016/S0301-472X(02)01024-X

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