Prolotherapy, Platelet-Rich Plasma Therapy, and Stem Cell Therapy-Theory and Evidence

Techniques in Regional Anesthesia and Pain Management (2011) 15, 74-80 Techniques in Regional Anesthesia & Pain Manas tt

ELSEVIER

Regenerative medicine in the fieLd of pain medicine: ProLotherapy, pLateLet-rich pLasma therapy, and stem cell therapy-Theory and evidence

David M. DeChellis, DO,a Megan Helen Cortazzo, MDa,b

From the "University of Pittsburgh Physical Medicine and Rehabilitation, Pittsburgh, Pennsylvania; and "Physical Medicine and Rehabilitation Outpatient Clinics; UPMC, Mercy-Southside lnterventional Spine and Pain Program; and University of Pittsburgh, Department of Physical Medicine and Rehabilitation, Pittsburgh, Pennsylvania.

The concept of "regenerative medicine" (RM) has been applied to musculoskeletal injuries dating back to the 1930s. Currently, RM is an umbrella term that has been used to encompass several therapies. namely prolotherapy, platelet-rich plasma therapy (PRP), and stem cell therapy, which are being used to treat musculoskeletal injuries. Although the specific treatments share similar concepts, the mechanism behind their reparative properties differs. Recently, treatments that possess a regenerative quality are resurfacing and expanding into the musculoskeletal field as potential therapeutic treatment modalities. RM, in the form of prolotherapy, was first used to treat tendon and ligament injuries. With the advancement of technology, RM has expanded to PRP and stem cell therapy. The expansion of different RM treatments has lead to its increase in the application for ligament and tendon injuries, muscle defects, as well as pain associated with osteoarthritis and degenerative disks. Recently, the use of ultrasound has been added to these therapies to guide the solution to the exact site of injury. We review 3 forms of RM injection: prolotherapy, PRP therapy, and stem cell therapy. © 2011 Elsevier Inc. All rights reserved.

Historically the field of interventional pain medicine has of regenerative medicine are prolotherapy, platel.et-rich focused primarily on spinal procedures. However, muscu- plasma, and mesenchymal stem cell therapies. As increasing loskeletal injuries as a whole are the most common cause of evidence on regenerative medicine is generated, more in- severe long-term pain and often affect psychosocial status, terventional pain physicians are looking to use this field for social interactions, and employment. [ With a worldwide pain-mediated peripheral sources via percutaneous means." incidence of more than 100 million musculoskeletal injuries annually, pain physicians have now begun to direct their attention to this area.2 Regenerative medicine is a develop- Prolotherapy ing field with the goal of inciting repair or replacement of pathologic tissues through the augmentation of natural pro- The term "prolotherapy" first appeared in the medical liter- cesses or bioengineered means? Included in this umbrella ature during the mid-19S0s and was described as a form of treatment for "incompetent structures through the generation of new cellular tissue. ,,5,6 Introducing an irritating. sub- Address reprint requests and correspondences Megan Helen Cor- tazzo, MD, Uni versity of Pittsburgh, Department of Physical Medicine and stance to induce healing has been used since the time of 7 Rehabilitation, 2000 Mary Street, 4th floor, Pittsburgh, PA 15203. Hippocrates ; however, the modern use of prolotherapy in E-mail address: [email protected]. musculoskeletal injuries can be traced back to the 1930s.8.9

Proliferant solutions used in this form of treatment are patients with knee osteoarthritis (OA).33 Patients with finger hypothesized to induce collagen deposition through chemo- OA also showed significant improvements in pain and range modulation, as well as the "temporary neurolysis" of pe- of motion following hyperosmolar dextrose injections com- ripheral nociceptors through chemoneuromodulation. Mod- pared to controls at 6 months. II A randomized controlled ulation in this setting is purported to be mediated by trial of the sacroiliac joint demonstrated significant im- multiple growth factors and cytokines.6,10-12 To date, the provement in pain after intra-articular RIT. Although the exact mechanism of prolotherapy remains elusive and has pain was not statistically significant in comparison with not been well defined by high-level evidence studies.P intra-articular steroid injection, the RIT group had a longer Although the exact proliferant used in prolotherapy often period of pain reliefr'" varies, all solutions, excluding chemotactic agents, have the Studies for the use of RIT in neck and back pain have universal effect of inciting local tissue irritation, which been widely investigated. Its use for cervical-mediated pain leads to an influx of inflammatory cells. Inflammation, be- has been promoted, with retrospective studies demonstrat- ing the first step in the wound-healing cascade, results in the ing improvement in pain and function following whiplash end-product of fibroblast proliferation with the subsequent injuries.35.36High-level evidence regarding nonspecific low deposition of collagen.!" The different proliferants can be back pain has been less congruent.15.16.37-41Complicated by classified into 3 classes. Osmotic agents, which include limitations in methodology and the heterogeneity of clinical hyperosmolar dextrose, zinc sulfate, and glycerin, act by protocols, studies of RIT on low back pain have been dehydrating local cells to the point of rupture in a process difficult to interpret collectively.41.42 However, the response referred to as "osmotic shock.,,14.15 Phenol, guaiacol, and of leg pain secondary to moderate-to-severe lumbar .degen- pumic acid belong to the second class known as irritants and erative disk disease appears promising in the case series by act by either directly damaging cell membranes or causing Miller and colleagues. This uncontrolled study showed sta- local cells to become antigenic.l''i'" Chemotactic agents are tistically significant pain improvements in patients treated the final class and include the commonly used sodium with 25% dextrose, suggesting RIT may have an indication morrhuate. This class is purported to be a direct chemotactic in this specific patient population.P agent to inflammatory cells, which differs from the former Despite a minimal volume of robust evidence to support classes that induce inflammation indirectly. 14The injection .its use in musculoskeletal pathologies, RIT's overall safety protocols of these proliferants lack standardization and dif- profile and strong anecdotal evidence leads many physicians fer with regard to volumes and concentration of proliferants to continue using this treatment modality for a wide array of used, frequency of injections, injection technique, and con- chronic pain entities. 13.44 current cointerventions.V''" Now more commonly referred to as "regenerative injection therapy" (RIT), prolotherapy is currently used in a wide variety of chronic pain entities. The effects on tendons and Platelet-rich plasma therapy ligaments have been widely discussed in medical literature, ranging from animal studies to randomized controlled trials In the search for better modalities in the nonsurgical treat- in humans. Animal studies have demonstrated Rl'I''s signif- ment of musculoskeletal injuries, platelet-rich plasma ther- icant advantageous effect on tendon cross-sectional area'" apy (PRP) has recently been thrust to the forefront of public and strength.F" This is in contrast to animal studies regard- attention.45.46 Initially used clinically in the fields of car- ing ligaments that have been separated by discord. While diothoracic and maxillofacial surgery in the late 1980s and Liu and colleagues found an increase in force failure, mass, early 1990s, PRP has since been adopted into the field of and fiber diameter in ligaments." a more recent study musculoskeletal medicine.47-49 The concept behind its use showed RIT had no significant effect on fiber diameter or as a nonsurgical treatment modality is to place it directly force failure.22 into areas of soft tissue pathology, via percutaneous injec- In human trials, Reeves and Hassanein showed signifi- tion, to facilitate tissue regeneration. Healing is theorized to cantly improved ligamentous stability and knee flexion in occur secondary to the PRP's ability to augment the recruit- patients with anterior cruciate ligament laxity 36 months ment, proliferation, and differentiation of cells involved in after hyperosmolar dextrose injections.P Case reports have the regeneration of injured tissue.48-51 These actions are also demonstrated magnetic resonance imaging verified re- purported to be mediated by numerous growth factors and pair of complete anterior cruciate ligament and Achilles bioactive proteins secreted by PRP's platelets following tendon tears following a series of RIT, without surgical activation, in a process known as degranulation.Y" The intervention?4,25 In addition, RIT has been documented as exact mechanism by which PRP acts to augment the endog- a favorable treatment modality in overuse syndromes such enous healing process remains elusive despite extensive as lateral epicondyle tendinopathy, Achilles tendinosis, coc- research. cygodynia, chronic groin pain, and plantar fasciitis?6-32 The PRP by its strictest definition is an autologous sample of benefits of intra-articular RIT have been assessed in multi- blood with a concentration of platelets above the physio- ple joints. Reeves and Hassanein have reported significant logical baseline.49.52 Following the extraction of autologous reduction in pain, as well as radiologic improvement, in venous blood with a large-gauge needle to prevent prema- 76 Techniques in Regional Anesthesia and Pain Management, VollS, No 2, April 2Qll

ture platelet activation,53 platelets are separated from other pelling pieces of literature to support the use of this blood components and further concentrated. 50 This occurs treatment modality in tendinopathy has been described in a through a centrifuge process, in which platelets are able to level 1 evidence study by Peerbooms and colleagues. The be isolated from the other cell components of blood based authors evaluated the response to intratendinous injections on their physiological size.50 The further concentrating of of either PRP or corticosteroids in patients with refractory platelets occurs with subsequent centrifuge cycles." Al- lateral epicondyle tendinopatby. The results showed a sig- though some authors suggest a minimal platelet concentra- nificant difference in pain control and function in favor of tion to be "therapeutic;>4&.52,55studies with lesser concen- the PRP group at 26- and 52-week follow-ups.88 trations have shown good results.52.56. Numerous PRP Much like RIT, the overlying theme that precludes strong preparation centrifuges are available for clinical use, with comparison of studies in the current medical literature is the each system producing a slightly variable end product Differ- lack of randomized controlled trials with protocol standard- ences include platelet concentration, presence of leukocytes, ization. Future studies need to address questions regarding and total amount of PRP produced.49.so.57The administration PRP, such as possible long-term side effects associated with protocol of PRP currently remains nonstandardized. Although administration, how storage of PRP affects efficacy, and historically "activated" by exogenous substances, evidence how the presence of leukocytes effects different tissue sub- may now suggest that PRP may be activated endogenously by types. Procedural standardization also needs to be addressed type I collagen in vivo.58 This degranulation method may in terms of injection technique, postinjection protocol, and reduce the loss of platelet-secreted bioactive mediators and concurrent use of nonsteroidal anti-inflammatory drugs . . also the risk of activator agent-induced complications such as coagulopathy .4.50.5J The effects of PRP have been extensively documented Stem cell therapy for a variety of tissue types, in a vast number of different laboratory and clinical settings. Despite the uncertainty of Adult tissues often have the ability to repair and regenerate its intrinsic healing mechanism and administration protocol following injury. To date, the exact mechanism of repair is

differences, the early evidence of PRP's use for musculo- poorly understood; I however, it is hypothesized to occur skeletal-mediated pain entities has been encouraging. In through the proliferation and differentiation of cells that vitro and animals studies have demonstrated positive results ultimately restore == functionality. One possible expla- in numerous types of tissue injuries that frequently plague nation is found within nonhemopoietic progenitor cells patients including muscle.i" tendon,60,61 meniscus,62 liga- found in pathologic ltissue. as well as cell reservoirs at other ment,63 cartilage,64-66 osteochondral surfaces." nerve,68.69 locations, which may help to provide this reparative capa- and intervertebral disks.70,71 Although anecdotal evidence bility.89 These regenerative-capable cells are commonly re- exists to support its percutaneous clinical administration for ferred to as mesenchymal stem cells (MSCs), or bone marrow muscle72-74 and acute ligamentous pathology,50,75 high- stromal cellS.89,9OMSCs are pmported to be multipotent.cells, level evidence is mostly void. Pain generated from connec- with the capability of replicating as undifferentiated.cells" and tive.tissue of the foot has had minimal investigation. A pilot also multilineage differentiation in response to local cell study of plantar fasciitis reported nearly 80% of patients signaling pathways.89,9O,92-95 showed improvement at 1year following ultrasound-guided Over 40 years ago, bone marrow was the first loc.ation 92 95 PRP. injections. 76 from which stem cells were isolated. • ,96 Since that time, OA occurs in up to 9.6% of men and 18% of women over stem cells have been found in a variety of tissue types 60 years of age and is expected to be the fourth leading including adipose97-99 and synovium, among others.4,97.100 cause of disability within the next 10 years. 1 Local anes- Differences in marker gene expression between marrow- thetic and corticosteroids historically used for treatment are derived MSCs and MSCs from other sources have been now being called into question, due to their purported det- demonstrated. However the effects of these differences have rimental effects on structure and inability to affect the nat- not been fully delineated.94,101 Conflicting evidence cur- ural history of OA.77-81 The use of PRP as a treatment rently exists regarding the differentiation efficacy of MSCs modality has gained recent interest and may be 1possible obtained from different stem cell reservoirs, such as marrow future candidate to treat this condition. Two recent pilot and adipose tissue.101,102In addition, there is controversy studies, including 1 involving over 100 degenerative knees, surrounding the quality of stem cells derived from bone showed data suggestive of pain reduction, improved knee marrow or adipose MSCs with respect to growth kinetics, function, and improvement in quality of life at 1 year fol- cell senescence, and multilineage differentiation poten- lowing intra-articular PRP injection.82.83 Although long- tial.10l.l02 These differences in MSCs and mesenchymaI- term follow-up demonstrated a decline in pain control, pain like cells have prompted the International Society for Cel- improvement remained above baseline." lular Therapy to create minimum criteria for MSCs based on The use of PRP for chronic tendinopathies has been surface marker expression. activity in culture, as well as investigated, with pilot studies showing advantageous ef- differentiation potential. 103 fects stemming from its percutaneous administration at var- Evidence suggests that in response to injury, MSCs are ious anatomical locations.85-87 Perhaps 1of the most com- first mobilized from perivascular niches into peripheral.cir- DeChellis and Cortazzo Regenerative Medicine in the Field of Pain Medicine 77 culation,90,I04-I06 with subsequent migration into damaged eration, following the treatment of intra-articular injected tissues,90 Although the exact reparative mechanism of MSCs suspended in hyaluronic acid. 116,17I Percutaneous MSCs is uncertain, early evidence suggested that these cells injection of bone marrow-derived MSCs in a patient with may differentiate into native cells of the injured tissue. More knee OA yielded a 95% reduction in pain and magnetic recent evidence suggests MSCs may also induce healing resonance imaging evidence of increased meniscus and car- through a paracrine-like effect. This includes the mobiliza- tilage volume." tion of MSCs to specific injured tissues, followed by the A surge of interest has been noted in recent medical ability for these reparative cells to secrete bioactive factors literature regarding the use of regenerative medicine to that induce a regenerative microenvironment known as combat intervertebral degenerative disk disease. Cells ex- "trophic activity.,,9o,lo7 pressing stem cell markers have been identified in interver- Based on their augmenting effects, physicians are now tebral disksYs MSCs have been 1 of the primary targets of harvesting these cells for clinical application. Following the cell therapy in the treatment of disk degeneration, with aspiration from autologous bone marrow, MSCs are typi- positive effects seen in animal and in vitro studies. MSCs cally isolated from other marrow cells and concentrated in a have shown a superior ability to produce extracellular ma- series of steps. The process of isolating MSCs, which are a trix compared to more terminally differentiated cells. Other small portion of marrow's nucleated cell fraction, occurs effects of MSCs include the ability to differentiate into most often through their adhesion to plastic in tissue cul- disk-like cells, prevent disk cell apoptosis, limit disk cell ture." Evidence by Hemigou and colleagues has suggested senescence, and retard the local immune system. Theoreti- that a minimum number of progenitor cells per volume is cally these effects should play a role in preventing the needed in order for percutaneous injections to be efficacious overall degenerative process of intervertebral disks. I 19 The in tissue repair.108 Since bone marrow aspiration contains clinical use of MSCs for degenerative disk disease is scant an MSC concentration well below this suggested "mini- in current literature; however, a recent case study demon- mum," the isolated MSCs are further cultured for multiple strated significant pain reduction following the percutane- passages to induce cell expansion." A passage includes the ous placement of MSCs into lumbar degenerative interver- removal of the isolated cells from culture, with replacement tebral disks.109 This evidence may suggest further clinical into culture media with new nutrients and growth factors for trials are needed to determine the role of these cells as a further cell expansion. This total process typically takes future treatment mobility for intervertebral degenerative several weeks from the time of aspiration until the final disk disease. product is administered to the patient.4,109 Although increasing data are being generated to support Literature shows acute skeletal muscle injury in humans the use of MSCs in musculoskeletal injuries, most studies to leads to the mobilization of MSCs into vascular circula- this point have been conducted using in vitro and .animal tion.IOSFurther studies have demonstrated the stepwise pro- models. As some authors have appropriately suggested, the gression of bone marrow-derived MSCs into eventual multi- effects of MSCs may differ in clinical use given the phys- nucleated muscle fibers.v'" In the use of tendons, iological differences in cellular composition and me.chanical intratendinous therapy induces histologic and biomechani- loading within species;'?" Many questions and unverified cal improvements in the early stages of tendon healing theories still remain regarding the clinical production, use, following injury. III Recent evidence by Mirsha and col- and placement of these naturally occurring regenerative leagues also suggests other regenerative medicine modali- cells. ties such as PRP may enhance the effect of MSCs. The authors of this study showed a statistically significant enhancement in MSC proliferation when exposed to PRP in vitro compared to controls. I12 Conclusions MSCs' effect on cartilage defects and OA has been well studied and reported. Their ability to differentiate into chon- Regenerative medicine is a new intriguing concept on the drocytes has been well documented, with evidence suggest- horizon in the field of pain medicine. Although continued ing that the use of dexamethasone in micro doses may direct research is greatly needed to determine efficacy and safety differentiation toward a chondrogenic lineage." Full-thick- profiles, early evidence may foreshadow its future use in ness cartilage tear repairs are purported to occur solely clinical practice. through the actions of MSCs. Il3 However, MSCs from osteoarthritic marrow are found to have reduced proliferation rates, reduced chondrogenic activity, and an increase predisposition towards osteogenic differentiation. I I4, 115 References These limitations to repair have led clinicians to search for a treatment modality to augment the healing of cartilage 1. Woolf AD, Pfleger B: Burden of major musculoskeletal conditions. Bull World Health Organization 81:646-656,2003 through percutaneous intervention. Animal studies have 2. Ljungqvist A, Schwellnus MP, Bachl N, et al: International Olympic shown evidence of both morphologic and histologic im- Committee consensus statement: molecular basis of connective tissue provements in cartilage healing, as well as meniscus regen- and muscle injuries in sport. 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