The Role of the Endothelium in the Short-Term Complications of Hematopoietic SCT
Total Page:16
File Type:pdf, Size:1020Kb
Bone Marrow Transplantation (2011) 46, 1495–1502 & 2011 Macmillan Publishers Limited All rights reserved 0268-3369/11 www.nature.com/bmt REVIEW The role of the endothelium in the short-term complications of hematopoietic SCT E Carreras1,3 and M Diaz-Ricart2 1Hematology Department, Hospital Clinic, Institut d’Investigacions Biome`diques Augustı´ Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Spain; 2Hemotherapy-Hemostasis Department, Hospital Clinic, Institut d’Investigacions Biome`diques Augustı´ Pi i Sunyer (IDIBAPS), University of Barcelona, Barcelona, Spain and 3Spanish Bone Marrow Donor Program (REDMO), Josep Carreras International Foundation, Barcelona, Spain In this review, we analyse the role of the endothelium Introduction in the development of several complications that appear soon after haematopoietic SCT (HSCT). Once it had been Haematopoietic SCT (HSCT) is a well-established ap- demonstrated that sinusoidal damage is the initiating proach for the treatment of several haematologic, meta- event of the sinusoidal obstruction syndrome, it was bolic and neoplastic disorders.1 However, HSCT is not an considered that other short-term complications with innocuous procedure and may be associated with several overlapping clinical manifestations, such as capillary leak early and late life-threatening complications. Those com- syndrome, engraftment syndrome, transplant-associated plications that appear early after HSCT are usually caused microangiopathy, diffuse alveolar haemorrhage and idio- by the toxicity of the conditioning regimen, infections or pathic pneumonia syndrome, could have an endothelial immune reactions (mainly GVHD). In addition, in this origin. During HSCT, endothelial cells (ECs) are initial phase, there is an interesting group of complications activated and damaged by several factors, including that do not have well-established origins. The most relevant conditioning, cytokines released by damaged tissues, are sinusoidal obstruction syndrome, capillary leak syn- endotoxins translocated through damaged mucosa, drugs drome, engraftment syndrome, transplant-associated mi- used in the procedure, the engraftment, and—in the croangiopathy (TAM), diffuse alveolar haemorrhage, and allogeneic setting—immunological reactions. The differ- idiopathic pneumonia syndrome. All these complications ent clinical syndromes that occur could be determined by share the following characteristics: they have an early onset the predominant phenotypic change in the ECs and the after HSCT, overlapping clinical manifestations, the location of this change (organ dependant or systemic). absence of well-defined clinical criteria for diagnosis (and Several translational studies have provided evidence of this consequently an unknown true incidence), the absence of endothelial dysfunction on the basis of analysis of soluble well-established treatments, and the tendency to evolve to markers, soluble forms of adhesion molecules, the an irreversible multiorgan dysfunction syndrome. enumeration of circulating ECs and microparticles, and morphologic and functional changes induced in cultured ECs. This increased knowledge has opened up a wide What is known about the pathogenesis of these syndromes? range of potential pharmacologic interventions to prevent or treat endothelial damage and, consequently, to improve Sinusoidal obstruction syndrome, commonly called hepatic the outcome of patients receiving HSCT. veno-occlusive disease (VOD), is the most frequent and well Bone Marrow Transplantation (2011) 46, 1495–1502; studied of these complications and the only one with well- doi:10.1038/bmt.2011.65; published online 4 April 2011 established clinical criteria for diagnosis.2,3 Its frequency Keywords: endothelial cells; endothelial damage; veno- ranges from 3% in autologous HSCT (auto-HSCT) to occlusive disease; haematopoietic SCT; microvasculature 50–60% in the allogeneic setting.2,4 In vivo studies conducted in rats that received monocrotaline show that the first morphologic change noted by EM is the loss of sinusoidal endothelial cell (EC) fenestration and the appearance of gaps in the sinusoidal EC barrier (Figure 1b). These studies also show that the sinusoidal ECs round up, and the RBC begin to penetrate into Correspondence: Dr E Carreras, Spanish Bone Marrow Donor Program the space of Disse beneath the ECs and dissect off the (REDMO), Josep Carreras International Foundation, Muntaner 383 endothelial lining (Figure 1c). Finally, the sloughed 2-2, 08021-Barcelona, Spain. E-mail: [email protected] sinusoidal lining cells embolize downstream and obstruct Received 31 January 2011; revised and accepted 17 February 2011; sinusoidal flow (Figure 1d). In these early stages, histolo- published online 4 April 2011 gical examinations show thickening of the subintimal Endothelial syndromes after HSCT E Carreras and M Diaz-Ricart 1496 ab cd Figure 1 Veno-oclusive disease pathogenesis. (a) Normal hepatic sinusoid; (b) Sinusoidal ECs damaged during conditioning round up favouring the appearance of gaps in the sinusoidal barrier; (c) RBC begin to penetrate into the space of Disse detaching the endothelial lining; (d) The sloughed sinusoidal lining cells embolize downstream and obstruct the sinusoidal flow (sinusoidal obstruction syndrome). Images provided by Jordi Bozo. zone that leads to the narrowing of the venular lumen and Table 1 Suspected pathogenesis of vascular endothelial syndromes an increased resistance to blood flow, which contribute after HSCT to the haemodynamic changes seen in this disease. Thus, Syndrome Supposed pathogenesis despite the possibility that other factors can contribute to VOD development, endothelial injury seems to be the VOD See text initiating event in the cascade of events leading to clinical CLS Diffusely injured capillary endothelium leads to the 5–7 leakage of intravascular fluids into interstitial space manifestation of this complication. ES Massive release of pro-inflammatory cytokines when new These observations of VOD, the fact that the pathogen- neutrophils cross the endothelial barrier when moving esis of the remaining early complication seems to have a from marrow niches to blood flow close relationship with the microvascular tree (Table 1), DAH Lung capillary endothelium damaged by conditioning and their overlapping clinical manifestations (Table 2), are plus engrafted neutrophils and silent infections, among other factors, allowing the leakage of RBC into the the main reasons these syndromes have been grouped under pulmonary alveoli the denomination of vascular syndromes or vascular TAM Generalized endothelial dysfunction with intravascular endothelial syndromes after HSCT. platelet activation and formation of platelet-rich thrombi within the microcirculation IPS Clinical and experimental IPS is associated with vascular EC injury in the lungs and increased permeability Why does HSCT lead to endothelial damage? produced by TNF, neutrophils and immune reactions The endothelium is an active biologic interface between the Abbreviations: CLS ¼ capillary leak syndrome; DAH ¼ diffuse alveolar blood and all other tissues, and it mediates vaso-motor haemorrhage; EC ¼ endothelial cell; ES ¼ engraftment syndrome; tone, haemostatic balance and inflammatory reactions, IPS ¼ idiopathic pneumonia syndrome; TAM ¼ transplant-associated mi- croangiopathy; TNF ¼ tumour necrosis factor; VOD ¼ veno-occlusive among other functions, throughout the circulatory system. disease. Several input stimuli can produce a local or systemic physiological endothelial activation. The term EC activa- tion includes a wider spectrum of phenotypic changes in The proposed hypothesis is that, during HSCT, ECs the endothelium. This activation takes place in a graded can be activated and damaged by factors such as the manner rather than an ‘all or nothing’ response and differs chemoradiotherapy included in the conditioning regimen, according to several physiological variables, including the cytokines produced by the injured tissues, endogenous location of the vascular bed. When the activating stimulus microbial products translocated through damaged mucosal is too intense or persistent, it can produce a localized barriers,9 drugs used during the procedure (such as G-CSF or systemic endothelial dysfunction. Currently, the term or calcineurin inhibitors),10,11 and the complex process of dysfunction is broadly applied to states in which the EC engraftment. All these factors produce a physiological phenotype poses a net liability to the host.8 activation of the EC; however, if they are intense and Bone Marrow Transplantation Endothelial syndromes after HSCT E Carreras and M Diaz-Ricart 1497 sustained, the EC activation can evolve into endothelial Moreover, there is clinical evidence suggesting that, damage. The different syndromes are determined by in the allogeneic setting, alloreactivity also has a role in the predominant phenotypic change (pro-inflammatory, the pathogenesis of these endothelial complications.12,13 pro-thrombotic, pro-apoptotic) and its localisation This could explain why these complications are more (systemic or organ dependant) (Figure 2). frequent in allogeneic rather than auto-HSCT, despite identical conditionings being used. In addition, they are more frequent among patients receiving HSCT from unrelated donors, especially if they are mismatched, Table 2 Clinical manifestations of the vascular endothelial and the procedures reducing the allogenicity of the graft syndromes after HSCT (such as T-cell depletion) reduce their