Single intra-arterial injection of mesenchymal stromal cells for treatment of steroid-refractory acute graft-versus-host disease: a pilot study

Two-year safety outcomes of iPS cell-derived mesenchymal stromal cells in acute steroid-resistant graft-versus-host disease

The first completed clinical trial of induced pluripotent stem cell (iPS cell)-derived cells was conducted in 15 participants with steroid-resistant acute graft-versus-host disease. After intravenous infusion of mesenchymal stromal cells (CYP-001 derived from a clone of human iPS cells), we reported the safety, tolerability and efficacy within the primary evaluation period at day 100. We now report results at the 2-year follow-up: 9 of 15 (60%) participants survived, which compares favorably with previously reported outcomes in studies of steroid-resistant acute graft-versus-host disease. Causes of death were complications commonly observed in recipients of allogeneic hematopoietic stem cell transplantation, and not considered by the investigators to be related to CYP-001 treatment. There were no serious adverse events, tumors or other safety concerns related to CYP-001. In conclusion, systemic delivery of iPS cell-derived cells was safe and well tolerated over 2 years of follow-up, with sustained outcomes up to 2 years after the first infusion. ClinicalTrials.gov registration: NCT02923375 .

Hepatic graft-versus-host disease: what we know, when to biopsy, and how to diagnose

Graft-versus-host disease (GVHD) is one of the serious complications that may develop after hematopoietic cell transplantation (HCT), for hematologic malignancies, solid organ transplantation, and other hematologic disorders. GVHD develops due to T lymphocytes present in the graft attacking the host antigens, which results in tissue damage. A significant number of HCT patients develop acute or chronic GVHD, which may affect multiple organs including the liver. The diagnosis of hepatic GVHD (hGVHD) is challenging as many other conditions in HCT patients may lead to liver dysfunction. Particularly challenging among the various conditions that give rise to liver dysfunction is differentiating sinusoidal obstruction syndrome and drug-induced liver injury (DILI) from hGVHD on clinical grounds and laboratory tests. Despite the minimal risks involved in performing a liver biopsy, the information gleaned from the histopathologic changes may help in the management of these very complex patients. There is a spectrum of histologic features found in hGVHD, and most involve histopathologic changes affecting the interlobular bile ducts. These include nuclear and cytoplasmic abnormalities including dysmorphic bile ducts, apoptosis, and cholangiocyte necrosis, among others. The hepatitic form of hGVHD typically shows severe acute hepatitis. With chronic hGVHD, there is progressive bile duct loss and eventually fibrosis. Accurate diagnosis of hGVHD is paramount so that timely treatment and management can be initiated. Techniques to prevent and lower the risk of GVHD from developing have recently evolved. If a diagnosis of acute GVHD is made, the first-line of treatment is steroids. Recurrence is common and steroid resistance or dependency is not unusual in this setting. Second-line therapies differ among institutions and have not been uniformly established. The development of GVHD, particularly hGVHD, is associated with increased morbidity and mortality.

Mesenchymal Stromal Cells for the Treatment of Graft Versus Host Disease

Graft versus host disease (GvHD) is a life-threating complication of allogeneic hematopoietic stem cell transplantation, which is initially treated with high dose corticosteroids. Approximately 50% of acute GvHD cases are resistant to steroid treatment, and two-year mortality rates in those steroid-resistant patients exceed 80%. Chronic GvHD necessitates prolonged corticosteroid use, which is typically associated with limited efficacy and troublesome adverse effects. No agent has yet been established as an optimal second line therapy for either acute or chronic GvHD, but mesenchymal stromal cells (MSCs) have shown substantial promise. MSCs promote an immunosuppressive and immunoregulatory environment via multifactorial mechanisms, including: secretion of proteins/peptides/hormones; transfer of mitochondria; and transfer of exosomes or microvesicles containing RNA and other molecules. A large number of clinical studies have investigated MSCs from various sources as a treatment for acute and/or chronic GvHD. MSCs are generally safe and well tolerated, and most clinical studies have generated encouraging efficacy results, but response rates have varied. Confounding factors include variability in MSC donor types, production methodology and dose regimens, as well as variations in study design. It is well-established that extensive culture expansion of primary donor-derived MSCs leads to marked changes in functionality, and that there is a high level of inter-donor variability in MSC properties. However, recent manufacturing innovations may be capable of overcoming these problems. Further adequately powered prospective studies are required to confirm efficacy and establish the place of MSC therapy in the treatment of this condition.

A systematic review of intracavernosal injection of mesenchymal stem cells for diabetic erectile dysfunction

BACKGROUND As current erectile dysfunction (ED) treatments are limited, other treatment such as stem cells should be explored. Hence, this study aimed to review the sources, method of administration, and therapeutic effect of mesenchymal stem cells (MSCs) for diabetic ED treatment. METHODS All relevant articles regarding the use of MSCs for diabetic ED were searched in PubMed and Google Scholar databases from December 15, 2019 to January 1, 2020 published in the past 10 years. The keywords were “mesenchymal stem cells” and “diabetic ED”. The selection and critical appraisal of the studies were discussed. Diabetic ED was evaluated for functional and structural outcome. Functional outcome in animal studies was assessed by intracavernosal pressure/mean arterial pressure (ICP/MAP) ratio, meanwhile the structural outcome was done microscopically. In human study, the assessments were done using international index of erectile function score (IIEF-5) to erection hardness score and penile Doppler ultrasonography. RESULTS There were 10 animal studies and 3 human studies. The studies used MSCs from adipose (n = 6), bone marrow (n = 4), placenta (n = 1), umbilical cord (n = 1), and muscle tissue (n = 1). The MSCs were administrated through intracavernosal injection in all studies. In all animal studies, functional outcome was improved, shown in higher ICP/MAP ratio. Microscopically, there were an increase of cavernosal endothelial cells, vascular endothelial growth factor, nitric oxide synthase, and smooth muscle cells. In human studies, IIEF-5 and erection hardness score were improved. Peak systolic velocity was also higher. CONCLUSIONS MSCs may be a promising therapy for diabetic ED; however, long-term safety concerns still need further investigations.

Erectile Dysfunction Treatment Using Stem Cells: A Review

Erectile dysfunction (ED) is a disorder that affects the quality of life and the sexual relations of more than half of the male population aged over 40 years. The prediction regarding the incidence of ED is devastating as it is expected that this disorder will affect more than 300 million men in the next five years. Several studies have suggested the use of stem cells for the treatment of ED and showed that this type of treatment is promising in terms of damaged tissue repair as well as of clinical efficacy; however, there are several gaps in the knowledge and evidence is lacking. In order to highlight a few of them in this review, we performed a research of the literature focusing on currently available clinical studies regarding the clinical efficacy of stem cell administration for the treatment of ED. We reviewed the methods of administration, the cell types used in the performed clinical trials and the safety and efficiency of such procedures. We conclude that there are rapidly expanding and promising results from the reported clinical studies indicating that stem cells could indeed be a potential treatment for patients with ED although more studies are necessary.

A Phase I Study to Evaluate Two Doses of Wharton's Jelly-Derived Mesenchymal Stromal Cells for the Treatment of De Novo High-Risk or Steroid-Refractory Acute Graft Versus Host Disease

BACKGROUND

Because of their well-described immunosuppressive properties, allogeneic adult human mesenchymal stromal cells (MSC) derived from bone marrow have demonstrated safety and efficacy in steroid refractory acute graft versus host disease (SR aGVHD). Clinical trials have resulted in variable success and an optimal source of MSC has yet to be defined. Based on the importance of maternal-fetal interface immune tolerance, extraembryonic fetal tissues, such as the umbilical cord, may provide an superior tissue source of MSC to mediate immunomodulation in aGVHD.

METHODS

A two-dose cohort trial allogeneic Wharton's Jelly-derived mesenchymal stromal cells (WJMSC, referred to as MSCTC-0010, here) were tested in 10 patients with de novo high risk (HR) or SR aGVHD post allogeneic hematopoietic stem cell transplantation (allo-HCT). Following Good Manufacturing Practices isolation, expansion and cryostorage, WJMSC were thawed and administered via intravenous infusions on days 0 and 7 at one of two doses (low dose cohort, 2 × 106/kg, n = 5; high dose cohort, 10 × 106/kg, n = 5). To evaluate safety, patients were monitored for infusion related toxicity, Treatment Related Adverse Events (TRAE) til day 42, or ectopic tissue formation at day 90. Clinical responses were monitored at time points up to 180 days post infusion. Serum biomarkers ST2 and REG3α were acquired 1 day prior to first MSCTC-0010 infusion and on day 14.

RESULTS

Safety was indicated, e.g., no infusion-related toxicity, no development of TRAE, nor ectopic tissue formation in either low or high dose cohort was observed. Clinical response was suggested at day 28: the overall response rate (ORR) was 70%, 4 of 10 patients had a complete response (CR) and 3 had a partial response (PR). By study day 90, the addition of escalated immunosuppressive therapy was necessary in 2 of 9 surviving patients. Day 100 and 180 post infusion survival was 90% and 60%, respectively. Serum biomarker REG3α decreased, particularly in the high dose cohort, and with REG3α decrease correlated with clinical response.

CONCLUSIONS

Treatment of patients with de novo HR or SR aGVHD with low or high dose MSCTC-0010 was safe: the infusion was well-tolerated, and no TRAEs or ectopic tissue formation was observed. A clinical improvement was seen in about 70% patients, with 4 of 10 showing a complete response that may have been attributable to MSCTC-0010 infusions. These observations indicate safety of two different doses of MSCTC-0010, and suggest that the 10 × 106 cells/ kg dose be tested in an expanded randomized, controlled Phase 2 trial. Graphical abstract.

The Role of Bone Marrow Mesenchymal Stem Cell Derived Extracellular Vesicles (MSC-EVs) in Normal and Abnormal Hematopoiesis and Their Therapeutic Potential

Mesenchymal stem cells (MSCs) represent a heterogeneous cellular population responsible for the support, maintenance, and regulation of normal hematopoietic stem cells (HSCs). In many hematological malignancies, however, MSCs are deregulated and may create an inhibitory microenvironment able to induce the disease initiation and/or progression. MSCs secrete soluble factors including extracellular vesicles (EVs), which may influence the bone marrow (BM) microenvironment via paracrine mechanisms. MSC-derived EVs (MSC-EVs) may even mimic the effects of MSCs from which they originate. Therefore, MSC-EVs contribute to the BM homeostasis but may also display multiple roles in the induction and maintenance of abnormal hematopoiesis. Compared to MSCs, MSC-EVs have been considered a more promising tool for therapeutic purposes including the prevention and treatment of Graft Versus Host Disease (GVHD) following allogenic HSC transplantation (HSCT). There are, however, still unanswered questions such as the molecular and cellular mechanisms associated with the supportive effect of MSC-EVs, the impact of the isolation, purification, large-scale production, storage conditions, MSC source, and donor characteristics on MSC-EV biological effects as well as the optimal dose and safety for clinical usage. This review summarizes the role of MSC-EVs in normal and malignant hematopoiesis and their potential contribution in treating GVHD.

Assessment of Enrichment of Human Mesenchymal Stem Cells Based on Plasma and Mitochondrial Membrane Potentials

Background: Human mesenchymal stem cells (hMSCs) are utilized preclinically and clinically as a candidate cell therapy for a wide range of inflammatory and degenerative diseases. Despite promising results in early clinical trials, consistent outcomes with hMSC-based therapies have proven elusive in many of these applications. In this work, we attempt to address this limitation through the design of a stem cell therapy to enrich hMSCs for desired electrical and ionic properties with enhanced stemness and immunomodulatory/regenerative capacity. Materials and Methods: In this study, we sought to develop initial protocols to achieve electrically enriched hMSCs (EE-hMSCs) with distinct electrical states and assess the potential relationship with respect to hMSC state and function. We sorted hMSCs based on fluorescence intensity of tetramethylrhodamine ethyl ester (TMRE) and investigated phenotypic differences between the sorted populations. Results: Subpopulations of EE-hMSCs exhibit differential expression of genes associated with senescence, stemness, immunomodulation, and autophagy. EE-hMSCs with low levels of TMRE, indicative of depolarized membrane potential, have reduced mRNA expression of senescence-associated markers, and increased mRNA expression of autophagy and immunomodulatory markers relative to EE-hMSCs with high levels of TMRE (hyperpolarized). Conclusions : This work suggests that the utilization of EE-hMSCs may provide a novel strategy for cell therapies, enabling live cell enrichment for distinct phenotypes that can be exploited for different therapeutic outcomes.

Comparison of the immunomodulatory effect of single MSC batches versus pooled MSC products

Severe corticosteroid-refractory graft-versus-host-disease (GVHD) is a major non-relapse cause of mortality and morbidity after an allogeneic hematopoietic stem cell transplantation (allo-HSCT). One of the most promising treatment options is using advanced therapy medicinal products based on mesenchymal stem cells (MSCs) immunomodulation ability. The protocols of MSC application differ in many parameters including a source of MSC, a dose, a number of doses or way of preparation of the medicinal product. The process is limited by the need for laborious and expensive manufacturing processes fraught with batch-to-batch variability. In our study, we compared the immunomodulatory effects of different MSC batches versus pooled MSC, specifically the influence on lymphocyte proliferation, the metabolic activity, and the expression of activation markers on T cells. Our goal was to determine whether the effect depends on donor-to-donor heterogeneity and if pooling of MSCs could increase their immunomodulatory ability. All tested batches showed an immunomodulatory effect, with no significant differences between the groups. Our study suggests that immunosuppressive potential is comparable in single batches and pooled products, and the use of products got from individual donors is suitable to treat corticosteroid-refractory GVHD.

Long-Term Results of Intracardiac Mesenchymal Stem Cell Transplantation in Patients With Cardiomyopathy

BACKGROUND

Mesenchymal stem cells (MSCs), which have the potential to differentiate into cardiomyocytes or vascular endothelial cells, have been used clinically as therapy for cardiomyopathy. In this study, we aimed to evaluate the long-term follow-up results.Methods and Results:We studied 8 patients with symptomatic heart failure (HF) on guideline-directed therapy (ischemic cardiomyopathy, n=3; nonischemic cardiomyopathy, n=5) who underwent intracardiac MSC transplantation using a catheter-based injection method between May 2004 and April 2006. Major adverse events and hospitalizations were investigated up to 10 years afterward. Compared with baseline, there were no significant differences in B-type natriuretic peptide (BNP) (from 211 to 173 pg/mL), left ventricular ejection fraction (LVEF) (from 24% to 26%), and peak oxygen uptake (from 16.5 to 19.2 mL/min/kg) at 2 months. During the follow-up period, no patients experienced serious adverse events such as arrhythmias. Three patients died of pneumonia in the 1st year, liver cancer in the 6th year, and HF in the 7th year. Of the remaining 5 patients, 3 patients were hospitalized for exacerbated HF, 1 of whom required heart transplantation in the 2nd year; 2 patients survived for 10 years without worsening HF.

CONCLUSIONS

The results of this exploratory study of intracardiac MSCs administration suggest further research regarding the feasibility and efficacy is warranted.

Conditioned medium from human palatine tonsil mesenchymal stem cells attenuates acute graft‑vs.‑host disease in mice

Graft-vs.-host disease (GVHD) is a severe and potentially life-threatening complication of hematopoietic stem cell transplantation. Approximately 50% of patients exhibiting GVHD will not benefit from conventional steroid treatment. Although several second‑line treatments are available for these patients, their prognoses remain poor due to the increased risk of infection, immunosuppression-mediated toxicity and incomplete GVHD remission, which occurs in the majority of cases. Mesenchymal stem cells (MSCs), a multipotent cell population, possess broad immunosuppressive activity and are a reportedly effective treatment of GVHD. However, the therapeutic effects of conditioned medium from MSCs on GVHD have not been demonstrated. In the present study, the efficacy of conditioned medium from human palatine tonsil‑derived MSCs (T‑MSC‑CM) was validated against GVHD in mice. The suppressive function of T‑MSC‑CM on immune cell chemotaxis was confirmed in vitro. A systemic infusion of T‑MSC‑CM in mice with GVHD resulted in prolonged survival, rapid recovery from weight loss and reduced pathological damage in numerous GVHD‑targeted organs. Furthermore, lymphocyte gene expression was significantly downregulated in GVHD mice administered T‑MSC‑CM. These results indicate that T‑MSC‑CM is a promising cellular agent to prevent or treat transplantation‑associated complications such as GVHD.

A Cell-Based Approach to the Treatment of Inflammatory Bowel Disease-Entering an Era of Regenerative Medicine

Corticosteroids, and more recently biologics, have been the mainstay of therapy for patients with inflammatory bowel disease. Unfortunately, both are fraught with side effects and limited by lack of efficacy or loss of response. Many patients ultimately succumb to medically refractory disease and require an operation. As we enter an era of regenerative medicine, a new genre of cell-based therapeutics offers significant promise for both an improved safety profile and improved efficacy compared with conventional treatment approaches. The ability to restore and rebuild health with autologous products rather than react to disease with pharmaceuticals gives hope to those who treat inflammatory bowel disease. The rationale and ongoing trials in an emerging field of medicine-regenerative medicine-is herein discussed.

Mesenchymal Stem Cells as Endogenous Regulators of Inflammation

This chapter discusses the regulatory role of endogenous mesenchymal stem cells (MSC) during an inflammatory response. MSC are a heterogeneous population of multipotent cells that normally contribute towards tissue maintenance and repair but have garnered significant scientific interest for their potent immunomodulatory potential. It is through these physicochemical interactions that MSC are able to exert an anti-inflammatory response on neighbouring stromal and haematopoietic cells. However, the impact of the chronic inflammatory environment on MSC function remains to be determined. Understanding the relationship of MSC between resolution of inflammation and autoimmunity will both offer new insights in the use of MSC as a therapeutic, and also their involvement in the pathogenesis of inflammatory disorders.

Graft-Versus-Host Disease Amelioration by Human Bone Marrow Mesenchymal Stromal/Stem Cell-Derived Extracellular Vesicles Is Associated with Peripheral Preservation of Naive T Cell Populations

A substantial proportion of patients with acute graft-versus-host disease (aGVHD) respond to cell therapy with culture-expanded human bone marrow mesenchymal stromal/stem cells (BM-MSCs). However, the mechanisms by which these cells can ameliorate aGVHD-associated complications remain to be clarified. We show here that BM-MSC-derived extracellular vesicles (EVs) recapitulated the therapeutic effects of BM-MSCs against aGVHD. Systemic infusion of human BM-MSC-derived EVs prolonged the survival of mice with aGVHD and reduced the pathologic damage in multiple GVHD-targeted organs. In EV-treated GVHD mice, CD4+ and CD8+ T cells were suppressed. Importantly, the ratio of CD62L-CD44+ to CD62L + CD44- T cells was decreased, suggesting that BM-MSC-derived EVs suppressed the functional differentiation of T cells from a naive to an effector phenotype. BM-MSC-derived EVs also preserved CD4 + CD25 + Foxp3+ regulatory T cell populations. In a culture of CD3/CD28-stimulated human peripheral blood mononuclear cells with BM-MSC-derived EVs, CD3+ T cell activation was suppressed. However, these cells were not suppressed in cultures with EVs derived from normal human dermal fibroblasts (NHDFs). NHDF-derived EVs did not ameliorate the clinical or pathological characteristics of aGVHD in mice, suggesting an immunoregulatory function unique to BM-MSC-derived EVs. Microarray analysis of microRNAs in BM-MSC-derived EVs versus NHDF-derived EVs showed upregulation of miR-125a-3p and downregulation of cell proliferative processes, as identified by Gene Ontology enrichment analysis. Collectively, our findings provide the first evidence that amelioration of aGVHD by therapeutic infusion of BM-MSC-derived EVs is associated with the preservation of circulating naive T cells, possibly due to the unique microRNA profiles of BM-MSC-derived EVs. Stem Cells 2018;36:434-445.

Cryopreserved or Fresh Mesenchymal Stromal Cells: Only a Matter of Taste or Key to Unleash the Full Clinical Potential of MSC Therapy?

Mesenchymal stromal cells (MSCs) harbor great therapeutic potential for numerous diseases. From early clinical trials, success and failure analysis, bench-to-bedside and back-to-bench approaches, there has been a great gain in knowledge, still leaving a number of questions to be answered regarding optimal manufacturing and quality of MSCs for clinical application. For treatment of many acute indications, cryobanking may remain a prerequisite, but great uncertainty exists considering the therapeutic value of freshly thawed (thawed) and continuously cultured (fresh) MSCs. The field has seen an explosion of new literature lately, outlining the relevance of the topic. MSCs appear to have compromised immunomodulatory activity directly after thawing for clinical application. This may provide a possible explanation for failure of early clinical trials. It is not clear if and how quickly MSCs recover their full therapeutic activity, and if the "cryo stun effect" is relevant for clinical success. Here, we will share our latest insights into the relevance of these observations for clinical practice that will be discussed in the context of the published literature. We argue that the differences of fresh and thawed MSCs are limited but significant. A key issue in evaluating potency differences is the time point of analysis after thawing. To date, prospective double-blinded randomized clinical studies to evaluate potency of both products are lacking, although recent progress was made with preclinical assessment. We suggest refocusing therapeutic MSC development on potency and safety assays with close resemblance of the clinical reality.

Regional intra-arterial steroid treatment in 120 patients with steroid-resistant or -dependent GvHD

GvHD results in death in the majority of steroid-resistant patients. This report assesses the safety and efficacy of two regional intra-arterial steroid (IAS) treatment protocols in the largest published cohort of patients with resistant/dependent hepatic and/or gastrointestinal GvHD, as well as identification of predictors of response to IAS and survival. One hundred and twenty patients with hepatic, gastrointestinal GvHD or both were given IAS. Gastrointestinal initial response (IR) and complete response (CR) were documented in 67.9% and 47.6%, respectively, whereas hepatic IR/CR in 54.9% and 33.3%, respectively. The predictors of gastrointestinal CR were lower peak GvHD and steroid-dependent (SD) GvHD. The predictors for hepatic CR were male patient, reduced intensity conditioning and SD GvHD. Twenty-six of the 120 patients (21.6%) are currently alive (median follow-up for the survivors 91.5 months). The 12 months' overall survival is 30% with no treatment-associated deaths. Predictors of 12 months' survival were as follows: first transplant, age<20 years, non-TBI regimen and GvHD CR. Shorter time to gastrointestinal IR but not time to hepatic IR was associated with improved 12 months' survival. IAS appears to be safe and effective. Gastrointestinal treatment is more effective than hepatic treatment. In our study, we conclude our current recommendations for IAS treatment.

Mesenchymal Stem Cell Derived Extracellular Vesicles: A Role in Hematopoietic Transplantation?

Mesenchymal stem cells (MSCs) are a heterogeneous cellular population containing different progenitors able to repair tissues, support hematopoiesis, and modulate immune and inflammatory responses. Several clinical trials have used MSCs in allogeneic hematopoietic stem cell transplantation (allo-HSCT) to prevent hematopoietic stem cell (HSC) engraftment failure, reduce aplasia post chemotherapy, and to control graft versus host disease (GvHD). The efficacy of MSCs is linked to their immune suppressive and anti-inflammatory properties primarily due to the release of soluble factors. Recent studies indicate that most of these effects are mediated by extracellular vesicles (EVs). MSC-EVs have therefore therapeutic effects in regenerative medicine, tumor inhibition, and immune-regulation. MSC-EVs may offer specific advantages for patient safety, such as lower propensity to trigger innate and adaptive immune responses. It has been also shown that MSC-EVs can prevent or treat acute-GvHD by modulating the immune-response and, combined with HSCs, may contribute to the hematopoietic microenvironment reconstitution. Finally, MSC-EVs may provide a new potential therapeutic option (e.g., transplantation, gene therapy) for different diseases, particularly hematological malignancies. In this review, we will describe MSC and MSC-EVs role in improving allo-HSCT procedures and in treating GvHD.

The Current Status of Stem-Cell Therapy in Erectile Dysfunction: A Review

Stem cells are undifferentiated cells that are capable of renewal and repair of tissue due to their capacity for division and differentiation. The purpose of this review is to describe recent advances in the use of stem cell (SC) therapy for male erectile dysfunction (ED). We performed a MEDLINE database search of all relevant articles regarding the use of SCs for ED. We present a concise summary of the scientific principles behind the usage of SC for ED. We discuss the different types of SCs, delivery methods, current pre-clinical literature, and published clinical trials. Four clinical trials employing SC for ED have been published. These articles are summarized in this review. All four report improvements in ED after SC therapy. SC therapy remains under investigation for the treatment of ED. It is reassuring that clinical trials thus far have reported positive effects on erectile function and few adverse events. Safety and methodical concerns about SC acquisition, preparation and delivery remain and require continued investigation prior to wide-spread application of these methods.

The clinical application of mesenchymal stromal cells in hematopoietic stem cell transplantation

Mesenchymal stromal cells (MSCs) are multipotent stem cells well known for repairing tissue, supporting hematopoiesis, and modulating immune and inflammation response. These outstanding properties make MSCs as an attractive candidate for cellular therapy in immune-based disorders, especially hematopoietic stem cell transplantation (HSCT). In this review, we outline the progress of MSCs in preventing and treating engraftment failure (EF), graft-versus-host disease (GVHD) following HSCT and critically discuss unsolved issues in clinical applications.

Mesenchymal stem cells and immunomodulation: current status and future prospects

The unique immunomodulatory properties of mesenchymal stem cells (MSCs) make them an invaluable cell type for the repair of tissue/ organ damage caused by chronic inflammation or autoimmune disorders. Although they hold great promise in the treatment of immune disorders such as graft versus host disease (GvHD) and allergic disorders, there remain many challenges to overcome before their widespread clinical application. An understanding of the biological properties of MSCs will clarify the mechanisms of MSC-based transplantation for immunomodulation. In this review, we summarize the preclinical and clinical studies of MSCs from different adult tissues, discuss the current hurdles to their use and propose the future development of pluripotent stem cell-derived MSCs as an approach to immunomodulation therapy.

Insurance approval of mesenchymal stem cell for acute GVHD in Japan: need of follow up for some remaining concerns

Acute graft-versus-host disease (aGVHD) is a major obstacle following allogeneic hematopoietic stem cell transplantation. Steroid is the standard treatment for aGVHD grade II-IV; however, nearly half of patients do not respond to the therapy. Many drugs have been proposed, but no standard therapy has been determined. This is because of the resistance to these drugs and of infections due to prolonged immunosuppressive states. Over the past decade a new approach using mesenchymal stem cells (MSCs) has been emerging in Japan and western countries. MSCs have unique characteristics such as specific immunosuppressive properties, no immunogenicity on their own and supportive activity for hematopoiesis. Most of the published trials have reported a favorable effect in acute GVHD, but a phase III trial failed to reach the primary endpoint, although, subgroup analyses found significant effects on gut and liver GVHD in the patients with MSCs infusion. In Japan several institutes are trying to develop MSC for clinical use in post HSCT patients. However, several limitations make it difficult to use MSC in clinical practice. Recently we conducted a phase II/III study using MSC (JR-031) for patients with steroid-refractory grade III or IV aGVHD. From the feasible clinical results, JR-031 was approved by PMDA as the first product which meets the Act to Revise the Pharmaceutical Affairs Act and the Act to Ensure the Safety of Regenerative Medicine. The cost of one series of the treatment is more than ten million yen. Now we encounter new issues such as cost, indication, safety and efficacy. The mechanism of MSC is still unclear and potential concerns about ectopic tissue formation and MSC related malignancy in vivo remain. In conclusion, MSC infusions are well tolerated and show benefit in some patients without adverse safety effects; however, long-term follow-up is needed to be more certain of this.

Optimization of adipose tissue-derived mesenchymal stem cells by rapamycin in a murine model of acute graft-versus-host disease

Introduction

Mesenchymal stem cells (MSCs) can protect bone marrow transplantation (BMT) recipients from the lethal acute graft-versus-host disease (aGVHD) development. However, the mechanisms underlying the anti-inflammatory properties of MSCs in aGVHD remain to be elucidated. The immunoregulatory properties of MSCs are mediated by their production of anti-inflammatory molecules, including IL-10 and TGF-β. On the other hand, MSCs can also produce proinflammatory cytokines during their normal growth, such as IL-1β and IL-6. These opposite actions may limit their therapeutic application in aGVHD. Therefore, optimization of the functional properties of MSCs can increase their benefits.

Methods

The expressions of mRNA and protein were analyzed by real-time PCR and western blotting, respectively. Expression of MSC markers was assessed by flow cytometry. An animal model of aGVHD was established by transplanting C57BL/6 donor bone marrow cells and spleen cells into lethally irradiated BALB/c recipient mice. The recipient mice were divided into the control group and the therapy [adipose tissue-derived human MSCs (Ad-hMSCs) or rapamycin-treated Ad-hMSCs] groups. The survival, body weight and clinical score of aGVHD in transplanted mice were monitored.

Results

Rapamycin pre-treatment of Ad-hMSCs increased mRNA synthesis of IL-10, indoleamine 2,3-dioxygenase, and TGF-β compared with untreated Ad-hMSCs. Rapamycin-treated Ad-hMSCs suppressed clonal expansion of interleukin-17-producing CD4⁺ T (Th17) cells more effectively than untreated cells. mRNA expression of autophagy markers such as ATG5, LC3A and LC3B was significantly increased in the rapamycin-treated Ad-hMSCs compared with untreated Ad-hMSCs. Transmission electron microscopy revealed that Ad-hMSCs exposure to rapamycin resulted in the appearance of autophagic vacuoles. Interestingly, in vitro migration efficiency of rapamycin-treated Ad-hMSCs toward the CD4⁺ T cells was increased significantly compared with the untreated cells. And, these effects were associated with autophagy induction capacity of rapamycin. In vivo, the inhibiting properties of MSCs on the clinical severities of aGVHD were greater in the mice receiving rapamycin-treated Ad-hMSCs compared with untreated Ad-hMSCs. The beneficial effects of rapamycin treatment in Ad-hMSCs shown in vivo were associated with a reduction of Th17 cells and an increase in regulatory T cells.

Conclusions

Rapamycin can optimize the immunomodulatory potential of Ad-hMSCs, suggesting a promising strategy of MSC use in aGVHD treatment.

Mesenchymal Stromal Cell Therapy in Hematology: From Laboratory to Clinic and Back Again

There is currently major interest to use mesenchymal stromal cells (MSCs) for a very diverse range of therapeutic applications. This stems mainly from the immunosuppressive qualities and differentiation capacity of these cells. In this review, we focus on cell therapy applications for MSCs in hematology. In this domain, MSCs are used for the treatment or prevention of graft-versus-host disease, support of hematopoiesis, or repair of tissue toxicities after hematopoietic cell transplantation. We critically review the accumulating clinical data and elaborate on complications that might arise from treatment with MSCs. In addition, we assume that the real clinical benefit of using MSCs for these purposes can only be estimated by a better understanding of the influence of in vitro expansion on the biological properties of these cells as well as by more harmonization of the currently used expansion protocols.

Intra-arterial Administration of Placenta-Derived Decidual Stromal Cells to the Superior Mesenteric Artery in the Rabbit: Distribution of Cells, Feasibility, and Safety

Selective administration of mesenchymal stromal cells to the mesenteric arteries is a potential technique to overcome pulmonary trapping and increase the density of transplanted cells in extensive mural inflammation of the intestine, such as in inflammatory bowel disease and graft-versus-host disease. We injected 5 × 10(6) (111)In-oxine-labeled human decidual stromal cells (DSCs) to the rabbit superior mesenteric artery (SMA) using clinical routine catheters guided by an angiographical system under sterile conditions. We used longitudinal single-photon emission tomography at 6 h and at 1, 2, and 5 days to assess trafficking and distribution of DSCs. We used digital subtraction angiography, computed tomography, and hematoxylin and eosin stainings to determine biodistribution of cells and to assess safety end points. We found that selective injection of human DSCs to the rabbit SMA does not result in acute embolic complications. Furthermore, we found that IV administration resulted in extensive retention of the radiolabeled DSCs in the lungs, corroborating previous studies on pulmonary trapping. In sharp contrast, selective injections to the SMA resulted in uptake distributed in the intestine supplied by the SMA and in the liver, indicating that this approach could significantly increase the fraction of injected DSCs reaching the target tissue.

[Safety of mesenchymal stromal cell therapy for inflammatory bowel diseases: results of a 5-year follow-up]

AIM

To compare the safety of therapy in patients with ulcerative colitis (UC) and Crohn's disease (CD) who have received combination anti-inflammatory therapy using bone marrow mesenchymal stromal cells (MSC) and standard therapy with 5-aminosalicylic acid, glucocorticosteroids, and immunosuppressive agents.

SUBJECTS AND METHODS

Unfavorable consequences were analyzed in 103 patients (56 with UC and 47 with CD) with inflammatory bowel disease (IBD) after MSC administration. The findings were compared with data obtained in 208 patients with UC and CD on standard anti-inflammatory therapy. All the patients were similar in demographic parameters, the duration of disease, the extent of intestinal injury, the nature of a course, the type and degree of disease. The analyzed groups did not include patients who had received therapy with anti-TNF-α drugs. The safety of therapy was evaluated from the presence of complications occurring during the follow-up.

RESULTS

By analyzing the unfavorable consequences in 103 patients with IBD and comparing them with treatment results in 208 patients with UC and CD on standard anti-inflammatory therapy, the authors revealed no differences in the development of acute posttransfusion reactions, infectious complications, exacerbations of chronic inflammatory diseases, severe infectious complications, malignant transformation, and fatal cases in patients with UC and CD, except for those with transient fever.

CONCLUSION

The results of this study demonstrate that the innovative method of cell therapy is clinically safe.

Wharton's Jelly-Derived Mesenchymal Stromal Cells as a Promising Cellular Therapeutic Strategy for the Management of Graft-versus-Host Disease

Allogeneic hematopoietic cell transplantation (allo-HCT), a treatment option in hematologic malignancies and bone marrow failure syndromes, is frequently complicated by Graft-versus-host disease (GVHD). The primary treatment for GVHD involves immune suppression by glucocorticoids. However, patients are often refractory to the steroid therapy, and this results in a poor prognosis. Therefore alternative therapies are needed to treat GVHD. Here, we review data supporting the clinical investigation of a novel cellular therapy using Wharton’s jelly (WJ)-derived mesenchymal stromal cells (MSCs) as a potentially safe and effective therapeutic strategy in the management of GVHD. Adult-derived sources of MSCs have demonstrated signals of efficacy in the management of GVHD. However, there are limitations, including: limited proliferation capacity; heterogeneity of cell sources; lengthy expansion time to clinical dose; expansion failure in vitro; and a painful, invasive, isolation procedure for the donor. Therefore, alternative MSC sources for cellular therapy are sought. The reviewed data suggests MSCs derived from WJ may be a safe and effective cellular therapy for GVHD. Laboratories investigated and defined the immune properties of WJ-MSCs for potential use in cellular therapy. These cells represent a more uniform cell population than bone marrow-derived MSCs, displaying robust immunosuppressive properties and lacking significant immunogenicity. They can be collected safely and painlessly from individuals at birth, rapidly expanded and stored cryogenically for later clinical use. Additionally, data we reviewed suggested licensing MSCs (activating MSCs by exposure to cytokines) to enhance effectiveness in treating GVHD. Therefore, WJCs should be tested as a second generation, relatively homogeneous allogeneic cell therapy for the treatment of GVHD.

Bone marrow stromal cells as immunomodulators. A primer for dermatologists

Bone marrow stromal cells (BMSCs, also known as mesenchymal stem cells or MSCs) represent a unique cell population in the bone marrow with a long-known function to support hematopoiesis and replace skeletal tissues. The recent discovery that BMSCs also possess potent immunoregulatory features attracted a great deal of attention from stem cell biologists, immunologists and clinicians of different specialties worldwide. Initial clinical experience along with several animal models suggested that intravenously delivered BMSCs are able to regulate a wide variety of host immune cells and act in a way that is beneficial for the recipient in a variety of diseases. The role of the present review is to give a short introduction to the biology of BMSCs and to summarize our current understanding of how BMSCs modulate the immune system with special emphasis on available clinical data. Considering the audience of this journal we will also attempt to guide dermatologists in choosing the right skin conditions where BMSCs might be considered as a therapeutic alternative.

Mesenchymal stem cell therapy and acute graft-versus-host disease: a review

Mesenchymal stem cells (MSCs) are being widely studied as potential cell therapy agents due to their immunomodulatory properties, which have been established by in vitro studies and in several clinical trials. Within this context, mesenchymal stem cell therapy appears to hold substantial promise, particularly in the treatment of conditions involving autoimmune and inflammatory components. Nevertheless, many research findings are still contradictory, mostly due to difficulties in characterization of the effects of MSCs in vivo. The purpose of this review is to report the mechanisms underlying mesenchymal stem cell therapy for acute graft-versus-host disease, particularly with respect to immunomodulation, migration, and homing, as well as report clinical applications described in the literature.

Inhibition of mesenchymal stromal cells by pre-activated lymphocytes and their culture media

Introduction

Despite having a proven immunosuppressive potential in vitro, human mesenchymal stromal cells (MSCs) are reported to display variable efficacy in vivo and, in fact, their proven benefit in the clinical practice is still limited and controversial.

Methods

The interplay between clinical grade MSCs and pre-activated donor lymphocytes or selected lymphocyte subsets was studied in vitro. The kinetics of MSC growth and viability was evaluated by adhesion-dependent changes of culture plate impedance and biochemically by a colorimetric assay. Activation of natural killer (NK) cells was assessed as well, using a flow cytometry assay.

Results

A strong inhibition of MSC growth was rapidly induced by the addition of pre-activated lymphocytes but not of resting lymphocytes. Inhibition seems not to be attributable to a single cell population, as similar results can be obtained by depleting NK cells or by using either selected CD4⁺ or CD8⁺ lymphocytes. In addition, conditioned medium (CM) from activated lymphocytes was able to inhibit MSC growth in a dose-dependent manner. Furthermore, licensing with IFN-γ partially protected MSCs from pre-activated lymphocytes but not from their CM. These results suggest an inhibitory role of lymphocyte-activation-derived substances. However, the identification of a single molecule responsible for MSC inhibition remained elusive, even if preliminary experiments showed that ATP and, to a lesser extent, TNF-α might play a role.

Conclusions

These results suggest that survival of MSCs can be affected by soluble mediators released by activated lymphocytes. Thus it can be hypothesized that MSC immunosuppressive action in vivo could be impaired by ongoing immune activation through the release of inflammatory mediators.

Immunomodulatory nature and site specific affinity of mesenchymal stem cells: a hope in cell therapy

Immunosuppressive ability of mesenchymal stem cells (MSCs), their differentiation properties to various specialized tissue types, ease of in vitro and in vivo expansion and specific migration capacity, make them to be tested in different clinical trials for the treatment of various diseases. The immunomodulatory effects of MSCs are less identified which probably has high clinically significance. The clinical trials based on primary research will cause better understanding the ability of MSCs in immunomodulatory applications and site specific migration in the optimization of therapy. So, this review focus on MSCs functional role in modulating immune responses, their ability in homing to tumor, their potency as delivery vehicle and their medical importance.

Mesenchymal stem or stromal cells: a review of clinical applications and manufacturing practices

Mesenchymal stem cells (MSCs) have recently generated great interest in the fields of regenerative medicine and immunotherapy due to their unique biologic properties. In this review we attempt to provide an overview of the current clinical status of MSC therapy, primarily focusing on immunomodulatory and regenerative or tissue repair applications of MSCs. In addition, current manufacturing is reviewed with attention to variation in practices (e.g., starting material, approach to culture and product testing). There is considerable variation among the 218 clinical trials assessed here; variations include proposed mechanisms of action, optimal dosing strategy, and route of administration. To ensure the greatest likelihood of success in clinical trials as the field progresses, attention must be given to the optimization of MSC culture.

Mesenchymal stem cells in tissue repair

The advent of mesenchymal stem cell (MSC)-based therapies for clinical therapeutics has been an exciting and new innovation for the treatment of a variety of diseases associated with inflammation, tissue damage, and subsequent regeneration and repair. Application-based ability to measure MSC potency and fate of the cells post-MSC therapy are the variables that confound the use of MSCs therapeutics in human diseases. An evaluation of MSC function and applications with attention to detail in the preparation as well as quality control and quality assurance are only as good as the assays that are developed. In vivo measures of efficacy and potency require an appreciation of the overall pathophysiology of the model and standardization of outcome measures. The new concepts of how MSC’s participate in the tissue regeneration and wound repair process and further, how this is impacted by estimates of efficacy and potency are important new topics. In this regard, this chapter will review some of the in vitro and in vivo assays for MSC function and activity and their application to the clinical arena.

Unrelated allogeneic bone marrow-derived mesenchymal stem cells for steroid-refractory acute graft-versus-host disease: a phase I/II study

We conducted a multicenter phase I/II study using mesenchymal stem cells (MSCs) manufactured from the bone marrow of healthy unrelated volunteers to treat steroid-refractory acute graft-versus-host disease (aGVHD). Fourteen patients with hematological malignancies who suffered from grade II (9 patients) or III aGVHD (5) were treated. Affected organs were gut (10 patients), skin (9 patients), and liver (3 patients). Seven patients had two involved organs. The median age was 52. No other second-line agents were given. MSCs were given at a dose of 2 × 10(6) cells/kg for each infusion twice a week for 4 weeks. If needed, patients were continuously given MSCs weekly for an additional 4 weeks. By week 4, 13 of 14 patients (92.9 %) had responded to MSC therapy with a complete response (CR; n = 8) or partial response (PR; n = 5). At 24 weeks, 11 patients (10 with CR and 1 with PR) were alive. At 96 weeks, 8 patients were alive in CR. A total of 6 patients died, attributable to the following: underlying disease relapse (2 patients), breast cancer relapse (1), veno-occlusive disease (1), ischemic cholangiopathy (1), and pneumonia (1). No clear adverse effects associated with MSC infusion were observed. Third party-derived bone marrow MSCs may be safe and effective for patients with steroid-refractory aGVHD.

Multipotent mesenchymal stromal cell therapy and risk of malignancies

Cell therapy with Multipotent Mesenchymal Stromal Cells (MSC) holds enormous promise for the treatment of a large number of degenerative and immune/inflammatory diseases. Their multilineage differentiation potential, immunoprivilege and capacity of promoting recovery of damaged tissues coupled with anti-inflammatory and immunosuppressive properties are the focus of a multitude of clinical studies currently underway. The recognized clinical potential of MSC repairing/immunomodulatory effects now encompasses graft-versus-host disease, hematologic malignancies, cardiovascular diseases, neurologic and inherited diseases, autoimmune diseases, organ transplantation, refractory wounds, and bone/cartilage defects among others. However, it has been suggested that both the need of extensive ex vivo culture for MSC clinical use, and their proangiogenic, anti-apoptotic and immunomodulatory properties may act together as tumor promoters, raising significant safety concerns. This paper will review the available data on in vitro MSC maldifferentiation and the ability of MSC to sustain tumor growth in vivo, with the aim to clarify whether MSC-based therapeutic approaches may carry actual risk of malignancies.

Uncovering the secretes of mesenchymal stem cells

Mesenchymal stem cells (MSC) show great promise in a wide array of therapeutic applications due mainly to their capacity to suppress immune and inflammatory reactions and instigate normal tissue repair processes. The secretion of bioactive factors is thought to play a predominant role in the mechanisms of action for these clinically relevant functions. As such, a large body of MSC research has focussed on characterization of the MSC secretome; including both soluble factors and factors released in extracellular vesicles (e.g., exosomes and microvesicles). This review provides an overview of our current knowledge of the MSC secretome in the context of determining the clinical relevance of these cells. In addition, the review summarizes various approaches that have been utilized to identify proteins secreted by MSC and discusses the advantages and limitations of different proteomic methods. Finally, we discuss issues that must be addressed before the clinical relevance of research into the MSC secretome can be realized.

Combination cell therapy using mesenchymal stem cells and regulatory T-cells provides a synergistic immunomodulatory effect associated with reciprocal regulation of TH1/TH2 and th17/treg cells in a murine acute graft-versus-host disease model

Mesenchymal stem cells (MSCs) have been considered to be an ideal cellular source for graft-versus-host disease (GVHD) treatment due to their unique properties, including tissue repair and major histocompatibility complex (MHC)-unmatched immunosuppression. However, preclinical and clinical data have suggested that the immunomodulatory activity of MSCs is not as effective as previously expected. This study was performed to investigate whether the immunomodulatory capacity of MSCs could be enhanced by combination infusion of regulatory T (Treg) cells to prevent acute GVHD (aGVHD) following MHC-mismatched bone marrow transplantation (BMT). For GVHD induction, lethally irradiated BALB/c (H-2(d)) mice were transplanted with bone marrow cells (BMCs) and spleen cells of C57BL/6 (H-2(b)) mice. Recipients were injected with cultured recipient-derived MSCs, Treg cells, or MSCs plus Treg cells (BMT + day 0, 4). Systemic infusion of MSCs plus Treg cells improved clinicopathological manifestations and survival in the aGVHD model. Culture of MSCs plus Treg cells increased the population of Foxp3(+) Treg cells and suppressed alloreactive T-cell proliferation in vitro. These therapeutic effects were associated with more rapid expansion of donor-type CD4(+)CD25(+)Foxp3(+) Treg cells and CD4(+)IL-4(+) type 2 T-helper (Th2) cells in the early posttransplant period. Furthermore, MSCs plus Treg cells regulated CD4(+)IL-17(+) Th17 cells, as well as CD4(+)IFN-γ(+) Th1 cells. These data suggest that the combination therapy with MSCs plus Treg cells may have cooperative effects in enhancing the immunomodulatory activity of MSCs and Treg cells in aGVHD. This may lead to development of new therapeutic approaches to clinical allogeneic hematopoietic cell transplantation.

Mesenchymal stem cells as immunomodulators in a vascularized composite allotransplantation

Vascularized composite allotransplantations (VCAs) are not routinely performed for tissue reconstruction because of the potentially harmful adverse effects associated with lifelong administration of immunosuppressive agents. Researchers have been eagerly seeking alternative methods that circumvent the long-term use of immunosuppressants. Mesenchymal stem cells (MSCs) show promise as an immunomodulatory therapeutic agent and are currently being tested in preclinical and clinical settings as therapies for autoimmune disorders or transplant rejection. The mechanisms by which MSCs modulate the immune response are still under thorough investigation, but these most likely involve expression of local factors influencing T-cell regulation, modulation of cytokine expression (e.g., IL-10, TGF-β, TNF-α, INF-γ, etc.), and interactions with dendritic or antigen presenting cells. In this paper, we summarize the current understanding of immunomodulation achieved by MSC therapies and introduce a possible outline for future clinical applications in VCA.

Safety of cell therapy with mesenchymal stromal cells (SafeCell): a systematic review and meta-analysis of clinical trials

Background

Mesenchymal stromal cells (MSCs, “adult stem cells”) have been widely used experimentally in a variety of clinical contexts. There is interest in using these cells in critical illness, however, the safety profile of these cells is not well known. We thus conducted a systematic review of clinical trials that examined the use MSCs to evaluate their safety.

Methods and Findings

MEDLINE, EMBASE, and the Cochrane Central Register of Controlled Trials (to June 2011), were searched. Prospective clinical trials that used intravascular delivery of MSCs (intravenously or intra-arterially) in adult populations or mixed adult and pediatric populations were identified. Studies using differentiated MSCs or additional cell types were excluded. The primary outcome adverse events were grouped according to immediate events (acute infusional toxicity, fever), organ system complications, infection, and longer term adverse events (death, malignancy). 2347 citations were reviewed and 36 studies met inclusion criteria. A total of 1012 participants with clinical conditions of ischemic stroke, Crohn's disease, cardiomyopathy, myocardial infarction, graft versus host disease, and healthy volunteers were included. Eight studies were randomized control trials (RCTs) and enrolled 321 participants. Meta-analysis of the RCTs did not detect an association between acute infusional toxicity, organ system complications, infection, death or malignancy. There was a significant association between MSCs and transient fever.

Conclusions

Based on the current clinical trials, MSC therapy appears safe. However, further larger scale controlled clinical trials with rigorous reporting of adverse events are required to further define the safety profile of MSCs.

Clinical Application of Mesenchymal Stem Cells in the Treatment and Prevention of Graft-versus-Host Disease

Mesenchymal stem cells (MSCs) represent a heterogeneous population of stromal cells with pluripotent mesenchymal differentiation potential. They have been found to have immunosuppressive properties and the ability to modulate angiogenesis and endogenous tissue repair by in vitro and animal studies. Clinical trials have examined the utility of these cells in autoimmune and inflammatory conditions. In particular, in allogeneic hematopoietic stem cell transplant (HSCT), multiple studies have been conducted to explore the use of MSC to treat acute and chronic graft-versus-host disease (GVHD) and for cotransplantation with HSCT to promote HSC engraftment and prevent GVHD. We review here the results of these studies and discuss some challenges of this treatment modality in this disease setting.

Promising cellular therapeutics for prevention or management of graft-versus-host disease (a review)

Graft-versus-host disease (GVHD) frequently occurs following allogeneic hematopoietic stem cell transplantation. The primary treatment for GVHD involves immune suppression by glucocorticoids. If patients become refractory to steroids, they have a poor prognosis. Therefore, there is a pressing need for alternative therapies to treat GVHD. Here, we review clinical data which demonstrate that a cellular therapy using mesenchymal stromal cells (MSCs) is safe and effective for GVHD. Since MSCs derived from bone marrow present certain limitations (such as time lag for expansion to clinical dose, expansion failure in vitro, painful and invasive bone marrow MSC isolation procedures), alternative sources of MSCs for cellular therapy are being sought. Here, we review data which support the notion that MSCs derived from Wharton's jelly (WJ) may be a safe and effective cellular therapy for GVHD. Many laboratories have investigated the immune properties of these discarded MSCs with an eye towards their potential use in cellular therapy. We also review data which support the notion that the licensing of MSCs (meaning the activation of MSCs by prior exposure to cytokines such as interferon-γ) may enhance their effectiveness for treatment of GVHD. In conclusion, WJCs can be collected safely and painlessly from individuals at birth, similar to the collection of cord blood, and stored cryogenically for later clinical use. Therefore, WJCs should be tested as a second generation, off-the-shelf cell therapy for the prevention or treatment of immune disorders such as GVHD.

Mesenchymal stromal cells for treatment of steroid-refractory GvHD: a review of the literature and two pediatric cases

Severe acute graft versus host disease (GvHD) is a life-threatening complication after allogeneic hematopoietic stem cell transplantation. Human mesenchymal stromal cells (MSCs) play an important role in endogenous tissue repair and possess strong immune-modulatory properties making them a promising tool for the treatment of steroid-refractory GvHD. To date, a few reports exist on the use of MSCs in treatment of GvHD in children indicating that children tend to respond better than adults, albeit with heterogeneous results.

We here present a review of the literature and the clinical course of two instructive pediatric patients with acute steroid-refractory GvHD after haploidentical stem cell transplantation, which exemplify the beneficial effects of third-party transplanted MSCs in treatment of acute steroid-refractory GvHD. Moreover, we provide a meta-analysis of clinical studies addressing the outcome of patients with steroid-refractory GvHD and treatment with MSCs in adults and in children (n = 183; 122 adults, 61 children). Our meta-analysis demonstrates that the overall response-rate is high (73.8%) and confirms, for the first time, that children indeed respond better to treatment of GvHD with MSCs than adults (complete response 57.4% vs. 45.1%, respectively).

These data emphasize the significance of this therapeutic approach especially in children and indicate that future prospective studies are needed to assess the reasons for the observed differential response-rates in pediatric and adult patients.

Genetic engineering of mesenchymal stem cells and its application in human disease therapy

The use of stem cells for tissue regeneration and repair is advancing both at the bench and bedside. Stem cells isolated from bone marrow are currently being tested for their therapeutic potential in a variety of clinical conditions including cardiovascular injury, kidney failure, cancer, and neurological and bone disorders. Despite the advantages, stem cell therapy is still limited by low survival, engraftment, and homing to damage area as well as inefficiencies in differentiating into fully functional tissues. Genetic engineering of mesenchymal stem cells is being explored as a means to circumvent some of these problems. This review presents the current understanding of the use of genetically engineered mesenchymal stem cells in human disease therapy with emphasis on genetic modifications aimed to improve survival, homing, angiogenesis, and heart function after myocardial infarction. Advancements in other disease areas are also discussed.