Safety and feasibility of third-party multipotent adult progenitor cells for immunomodulation therapy after liver transplantation--a phase I study (MISOT-I)

Graft infusion of adipose-derived mesenchymal stromal cells to prevent rejection in experimental intestinal transplantation: A feasibility study

BACKGROUND

Mesenchymal stromal cells (MSC) have been proposed as a promising complement to standard immunosuppression in solid organ transplantation because of their immunomodulatory properties. The present work addresses the role of adipose-derived MSC (Ad-MSC) in an experimental model of acute rejection in small bowel transplantation (SBT).

MATERIAL/METHODS

Heterotopic allogeneic SBT was performed. A single dose of 1.5x106 Ad-MSC was intra-arterially delivered just before graft reperfusion. Animals were divided into CONTROL (CTRL), CONTROL+Ad-MSC (CTRL_MSC), tacrolimus (TAC), and TAC+Ad-MSC (TAC_MSC) groups. Each Ad-MSC groups was subdivided in autologous and allogeneic third-party groups.

RESULTS

Rejection rate and severity were similar in MSC-treated and untreated animals. CTRL_MSC animals showed a decrease in macrophages, T-cell (CD4, CD8, and Foxp3 subsets) and B-cell counts in the graft compared with CTRL, this decrease was attenuated in TAC_MSC animals. Pro- and anti-inflammatory cytokines and some chemokines and growth factors increased in CTRL_MSC animals, especially in the allogeneic group, whereas milder changes were seen in the TAC groups.

CONCLUSION

Ad-MSC did not prevent rejection when administered just before reperfusion. However, they showed immunomodulatory effects that could be relevant for a longer-term outcome. Interference between tacrolimus and the MSC effects should be addressed in further studies.

Mesenchymal Stromal Cells in Solid Organ Transplantation

Over the past decade, the clinical application of mesenchymal stromal cells (MSCs) has generated growing enthusiasm as an innovative cell-based approach in solid organ transplantation (SOT). These expectations arise from a significant number of both transplant- and non-transplant-related experimental studies investigating the complex anti-inflammatory, immunomodulatory, and tissue-repair properties of MSCs. Promising preclinical results have prompted clinical trials using MSC-based therapy in SOT. In the present review, the general properties of MSCs are summarized, with a particular emphasis on MSC-mediated impact on the immune system and in the ischemic conditioning strategy. Next, we chronologically detail all clinical trials using MSCs in the field of SOT. Finally, we envision the challenges and perspectives of MSC-based cell therapy in SOT.

The Delivery of Multipotent Adult Progenitor Cells to Extended Criteria Human Donor Livers Using Normothermic Machine Perfusion

Background: Pre-clinical research with multi-potent adult progenitor cells (MAPC® cells, Multistem, Athersys Inc., Cleveland, Ohio) suggests their potential as an anti-inflammatory and immunomodulatory therapy in organ transplantation. Normothermic machine perfusion of the liver (NMP-L) has been proposed as a way of introducing therapeutic agents into the donor organ. Delivery of cellular therapy to human donor livers using this technique has not yet been described in the literature. The primary objectives of this study were to develop a technique for delivering cellular therapy to human donor livers using NMP-L and demonstrate engraftment. Methods: Six discarded human livers were perfused for 6 h at 37°C using the Liver Assist (Organ Assist, Groningen). 50 × 106 CMPTX-labeled MAPC cells were infused directly into the right lobe via the hepatic artery (HA, n = 3) or portal vein (PV, n = 3) over 20 min at different time points during the perfusion. Perfusion parameters were recorded and central and peripheral biopsies were taken at multiple time-points from both lobes and subjected to standard histological stains and confocal microscopy. Perfusate was analyzed using a 35-plex multiplex assay and proteomic analysis. Results: There was no detrimental effect on perfusion flow parameters on infusion of MAPC cells by either route. Three out of six livers met established criteria for organ viability. Confocal microscopy demonstrated engraftment of MAPC cells across vascular endothelium when perfused via the artery. 35-plex multiplex analysis of perfusate yielded 13 positive targets, 9 of which appeared to be related to the infusion of MAPC cells (including Interleukin's 1b, 4, 5, 6, 8, 10, MCP-1, GM-CSF, SDF-1a). Proteomic analysis revealed 295 unique proteins in the perfusate from time-points following the infusion of cellular therapy, many of which have strong links to MAPC cells and mesenchymal stem cells in the literature. Functional enrichment analysis demonstrated their immunomodulatory potential. Conclusion: We have demonstrated that cells can be delivered directly to the target organ, prior to host immune cell population exposure and without compromising the perfusion. Transendothelial migration occurs following arterial infusion. MAPC cells appear to secrete a host of soluble factors that would have anti-inflammatory and immunomodulatory benefits in a human model of liver transplantation.

Transplant Tolerance Induction: Insights From the Liver

A comparison of pre-clinical transplant models and of solid organs transplanted in routine clinical practice demonstrates that the liver is most amenable to the development of immunological tolerance. This phenomenon arises in the absence of stringent conditioning regimens that accompany published tolerizing protocols for other organs, particularly the kidney. The unique immunologic properties of the liver have assisted our understanding of the alloimmune response and how it can be manipulated to improve graft function and survival. This review will address important findings following liver transplantation in both animals and humans, and how these have driven the understanding and development of therapeutic immunosuppressive options. We will discuss the liver's unique system of immune and non-immune cells that regulate immunity, yet maintain effective responses to pathogens, as well as mechanisms of liver transplant tolerance in pre-clinical models and humans, including current immunosuppressive drug withdrawal trials and biomarkers of tolerance. In addition, we will address innovative therapeutic strategies, including mesenchymal stem cell, regulatory T cell, and regulatory dendritic cell therapy to promote liver allograft tolerance or minimization of immunosuppression in the clinic.

Will cell therapies provide the solution for the shortage of transplantable organs?

PURPOSE OF REVIEW

The potential to regenerate ischemically damaged kidneys while being perfused ex-vivo offers the best near-term solution to increasing kidney allografts for transplantation.

RECENT FINDINGS

There are a number of stem-cell sources including: stromal mesenchymal cells (MSC), induced adult pluripotent stem cells, fetal stem cells from placenta, membranes, amniotic fluid and umbilical cord and hematopoietic cells. MSC are increasingly the stem cell of choice and studies are primarily focused on novel induction immunosuppression to prevent rejection. Stem-cell therapies applied in vivo may be of limited benefit because the nonintegrating cells do not remain in the kidney and are not detectable in the body after several days. MSC therapies for transplantation have demonstrated early safety and feasibility. However, efficacy has not been clearly established. A more feasible application of a stem-cell therapy in transplantation is the administration of MSC to treat damaged renal allografts directly while being perfused ex vivo. Initial feasibility has been established demonstrating MSC-treatment results in statistically significant reduction of inflammatory responses, increased ATP and growth factor synthesis and mitosis.

SUMMARY

The ability to regenerate renal tissue ex-vivo sufficiently to result in immediate function could revolutionize transplantation by solving the chronic organ shortage.

N-acetylcysteine prevents oxidized low-density lipoprotein-induced reduction of MG53 and enhances MG53 protective effect on bone marrow stem cells

MG53 is an important membrane repair protein and partially protects bone marrow multipotent adult progenitor cells (MAPCs) against oxidized low‐density lipoprotein (ox‐LDL). The present study was to test the hypothesis that the limited protective effect of MG53 on MAPCs was due to ox‐LDL‐induced reduction of MG53. MAPCs were cultured with and without ox‐LDL (0‐20 μg/mL) for up to 48 hours with or without MG53 and antioxidant N‐acetylcysteine (NAC). Serum MG53 level was measured in ox‐LDL‐treated mice with or without NAC treatment. Ox‐LDL induced significant membrane damage and substantially impaired MAPC survival with selective inhibition of Akt phosphorylation. NAC treatment effectively prevented ox‐LDL‐induced reduction of Akt phosphorylation without protecting MAPCs against ox‐LDL. While having no effect on Akt phosphorylation, MG53 significantly decreased ox‐LDL‐induced membrane damage and partially improved the survival, proliferation and apoptosis of MAPCs in vitro. Ox‐LDL significantly decreased MG53 level in vitro and serum MG53 level in vivo without changing MG53 clearance. NAC treatment prevented ox‐LDL‐induced MG53 reduction both in vitro and in vivo. Combined NAC and MG53 treatment significantly improved MAPC survival against ox‐LDL. These data suggested that NAC enhanced the protective effect of MG53 on MAPCs against ox‐LDL through preventing ox‐LDL‐induced reduction of MG53.

Research Status of Mesenchymal Stem Cells in Liver Transplantation

Liver transplantation has been deemed the best choice for end-stage liver disease patients but immune rejection after surgery is still a serious problem. Patients have to take immunosuppressive drugs for a long time after liver transplantation, and this often leads to many side effects. Mesenchymal stem cells (MSCs) gradually became of interest to researchers because of their powerful immunomodulatory effects. In the past, a large number of in vitro and in vivo studies have demonstrated the great potential of MSCs for participation in posttransplant immunomodulation. In addition, MSCs also have properties that may potentially benefit patients undergoing liver transplantation. This article aims to provide an overview of the current understanding of the immunomodulation achieved by the application of MSCs in liver transplantation, to discuss the problems that may be encountered when using MSCs in clinical practice, and to describe some of the underlying capabilities of MSCs in liver transplantation. Cell–cell contact, soluble molecules, and exosomes have been suggested to be critical approaches to MSCs’ immunoregulation in vitro; however, the exact mechanism, especially in vivo, is still unclear. In recent years, the clinical safety of MSCs has been proven by a series of clinical trials. The obstacles to the clinical application of MSCs are decreasing, but large sample clinical trials involving MSCs are still needed to further study their clinical effects.

Histone Arginine Methylation-Mediated Epigenetic Regulation of Discoidin Domain Receptor 2 Controls the Senescence of Human Bone Marrow Mesenchymal Stem Cells

The application of human bone marrow mesenchymal stem cells (hBM-MSCs) in cell-based clinical therapies is hindered by the limited number of cells remaining after the initial isolation process and by cellular senescence following in vitro expansion. Understanding the process of in vitro senescence in hBM-MSCs would enable the development of strategies to maintain their vitality after cell culture. Herein, we compared the gene expression profiles of human embryonic stem cells and human BM-MSCs from donors of different ages. We first found that the expression of discoidin domain receptor 2 (DDR2) in adult donor-derived hBM-MSCs was lower than it was in the young donor-derived hBM-MSCs. Moreover, in vitro cultured late-passage hBM-MSCs showed significant downregulation of DDR2 compared to their early-passage counterparts, and siRNA inhibition of DDR2 expression recapitulated features of senescence in early-passage hBM-MSCs. Further, we found through knockdown and overexpression approaches that coactivator-associated arginine methyltransferase 1 (CARM1) regulated the expression level of DDR2 and the senescence of hBM-MSCs. Finally, chromatin immunoprecipitation analysis confirmed direct binding of CARM1 to the DDR2 promoter region with a high level of H3R17 methylation in early-passage hBM-MSCs, and inhibition of CARM1-mediated histone arginine methylation decreased DDR2 expression and led to cellular senescence. Taken together, our findings suggest that DDR2 plays a major role in regulating the in vitro senescence of hBM-MSCs and that CARM1-mediated histone H3 methylation might be the upstream regulatory mechanism controlling this function of DDR2.

The influence of the ratio of liver cells and bone marrow in the implantable cell-engineering structures of the liver on the recovery efficiency of functional and morphological parameters in chronic liver failure

Aim:to determinate the most effective liver cells and multipotent mesenchymal stromal cells of bone marrow (MMSC BM) ratio into implantable cell engineering constructions (CECs) used for chronic liver failure (CLF) correcting.

Materials and methods.For creating liver CECs it was used a biopolymer implant – a composition of a heterogeneous collagen-containing gel (BMCG) (Sphero®GEL trademark) containing viable liver cells and MMSC BM in the following ratios – 1 : 1; 5 : 1 and 10 : 1 respectively. CECs with different ratios of liver cells and MMSC BM were implanted into liver of rats in which chronic liver failure (CLF), was modeled by using CCl4. The effectiveness of the regulatory effects of CECs (with different cell ratios) on regenerative processes in livers were assessed by using biochemical, morphological and morphometric methods at different periods after their implantation.

Results.Corrective effect of CECs with different cell composition on biochemical and morphological parameters of livers at chronic liver failure was established. During studying the liver CECs with various cell ratios of liver cells and MMSC BM (1 : 1; 5 : 1 and 10 : 1 respectively), it was found that the most optimal ratio of cells into the CECs is 5 : 1, because at this ratio of cells, there were a more distinct normalization of the morphological and functional liver parameters within 365 days after modeling CLF and maintenance of the structural homeostasis into the CECs. Themselves, which allows predicting their long-term regulatory effect on the liver tissue in CLF and maintaining its normal structural and functional state.

Conclusion.The effective correction of chronic liver failure can be carried out by using the implanted liver CECs, in which donor liver cells and MMSC BM where presented in ratios – 1 : 1; 5 : 1 and 10 : 1. But analysis of prolonged correction of liver morphological and functional parameters at CECs using it was allow to recommend the preferences using of CECs with ratio 5 : 1, because prolonged preservation of structural homeostasis into these CECs makes possible to prognosticate their prolonged regulatory action on the liver tissue at CLF, especially for recipients on a waiting list for liver transplantation.

Multipotent Adult Progenitor Cells Suppress T Cell Activation in In Vivo Models of Homeostatic Proliferation in a Prostaglandin E2-Dependent Manner

Lymphodepletion strategies are used in the setting of transplantation (including bone marrow, hematopoietic cell, and solid organ) to create space or to prevent allograft rejection and graft versus host disease. Following lymphodepletion, there is an excess of IL-7 available, and T cells that escape depletion respond to this cytokine undergoing accelerated proliferation. Moreover, this environment promotes the skew of T cells to a Th1 pro-inflammatory phenotype. Existing immunosuppressive regimens fail to control this homeostatic proliferative (HP) response, and thus the development of strategies to successfully control HP while sparing T cell reconstitution (providing a functioning immune system) represents a significant unmet need in patients requiring lymphodepletion. Multipotent adult progenitor cells (MAPC^®) have the capacity to control T cell proliferation and Th1 cytokine production. Herein, this study shows that MAPC cells suppressed anti-thymocyte globulin-induced cytokine production but spared T cell reconstitution in a pre-clinical model of lymphodepletion. Importantly, MAPC cells administered intraperitoneally were efficacious in suppressing interferon-γ production and in promoting the expansion of regulatory T cells in the lymph nodes. MAPC cells administered intraperitoneally accumulated in the omentum but were not present in the spleen suggesting a role for soluble factors. MAPC cells suppressed lymphopenia-induced cytokine production in a prostaglandin E2-dependent manner. This study suggests that MAPC cell therapy may be useful as a novel strategy to target lymphopenia-induced pathogenic T cell responses in lymphodepleted patients.

Allogeneic bone marrow-derived mesenchymal stromal cells for hepatitis B virus-related acute-on-chronic liver failure: A randomized controlled trial

Mortality from hepatitis B virus (HBV)-related acute-on-chronic liver failure (ACLF) is high due to limited treatment options. Preclinical and clinical investigations have proved that treatment with mesenchymal stromal cells (MSCs) is beneficial for recovery from liver injury. We hypothesized that the outcome of HBV-related ACLF would be improved by MSC treatment. From 2010 to 2013, 110 patients with HBV-related ACLF were enrolled in this open-label, nonblinded randomized controlled study. The control group (n = 54) was treated with standard medical therapy (SMT) only. The experimental group (n = 56) was infused weekly for 4 weeks with 1.0 to 10 × 10⁵ cells/kg allogeneic bone marrow-derived MSCs and then followed for 24 weeks. The cumulated survival rate of the MSC group was 73.2% (95% confidence interval 61.6%-84.8%) versus 55.6% (95% confidence interval 42.3%-68.9%) for the SMT group (P = 0.03). There were no infusion-related side effects, but fever was more frequent in MSC compared to SMT patients during weeks 5-24 of follow-up. No carcinoma occurred in any trial patient in either group. Compared with the control group, allogeneic bone marrow-derived MSC treatment markedly improved clinical laboratory measurements, including serum total bilirubin and Model for End-Stage Liver Disease scores. The incidence of severe infection in the MSC group was much lower than that in the SMT group (16.1% versus 33.3%, P = 0.04). Mortality from multiple organ failure and severe infection was higher in the SMT group than in the MSC group (37.0% versus 17.9%, P = 0.02).

CONCLUSION

Peripheral infusion of allogeneic bone marrow-derived MSCs is safe and convenient for patients with HBV-related ACLF and significantly increases the 24-week survival rate by improving liver function and decreasing the incidence of severe infections. (Hepatology 2017;66:209-219).

Safety and Tolerance of Donor-Derived Mesenchymal Stem Cells in Pediatric Living-Donor Liver Transplantation: The MYSTEP1 Study

Background

Calcineurin inhibitors (CNI) have significantly improved patient and graft survival in pediatric liver transplantation (pLT). However, CNI toxicity leads to significant morbidity. Moreover, CNIs cannot prevent long-term allograft injury. Mesenchymal stem (stromal) cells (MSC) have potent immunomodulatory properties, which may promote allograft tolerance and ameliorate toxicity of high-dose CNI. The MYSTEP1 trial aims to investigate safety and feasibility of donor-derived MSCs in pLT.

Methods/Design

7 to 10 children undergoing living-donor pLT will be included in this open-label, prospective pilot trial. A dose of 1 × 10⁶ MSCs/kg body weight will be given at two time points: first by intraportal infusion intraoperatively and second by intravenous infusion on postoperative day 2. In addition, participants will receive standard immunosuppressive treatment. Our primary objective is to assess the safety of intraportal and intravenous MSC infusion in pLT recipients. Our secondary objective is to evaluate efficacy of MSC treatment as measured by the individual need for immunosuppression and the incidence of biopsy-proven acute rejection. We will perform detailed immune monitoring to investigate immunomodulatory effects.

Discussion

Our study will provide information on the safety of donor-derived MSCs in pediatric living-donor liver transplantation and their effect on immunomodulation and graft survival.

Emerging drugs for prevention of T-cell mediated rejection in liver and kidney transplantation

INTRODUCTION

Acute and chronic graft rejection continues to be an important problem after solid organ transplantation. With the introduction of potent immunosuppressive agents such as calcineurin inhibitors, the risk of rejection has been significantly reduced. However, the adverse effects of life-long immunosuppression remain a concern, and there exist a fine balance between over-immunosuppression and risk of rejection. Areas covered: In this review, the current standard of care in immunosuppressive therapy, including the use of steroids, calcineurin inhibitors, mycophenolate prodrugs and mammalian target of rapamycin inhibitors, will be discussed. Newer immunosuppressive agents showing promising early data after liver and kidney transplantation will also be explored. Expert Opinion: Currently, calcineurin inhibitors continue to be a vital component of immunosuppressive therapy after solid organ transplantation. Although minimization and avoidance strategies have been developed, the ultimate goal of inducing tolerance remains elusive. Newer emerging agents should have potent and specific immunosuppressive activity, with minimal associated side effects. An individualized approach should be adopted to tailor immunosuppression according to the different needs of recipients.

Biliary complications after liver transplantation; recent developments in etiology, diagnosis and endoscopic treatment

Biliary complications are considered to be the Achilles' heel of liver transplantation. The most common complications are leaks and bile duct strictures. Strictures can arise at the level of the anastomosis (anastomotic strictures; AS) or at other locations in the biliary tree (non-anastomotic strictures; NAS). Endoscopic treatment via endoscopic retrograde cholangiopancreatography (ERCP) is considered to be the preferred therapy for these complications. This review will focus on the diagnostic modalities, new insights in etiology of biliary complications and outcomes after different endoscopic therapies, in both deceased donor transplantation and living-donor liver transplantations. Advances in recent therapies, such as the use of self-expendable metal stents (SEMS) and endoscopic therapy for patients with a bilio-digestive anastomosis will be discussed.

Stem cell therapy for cardiac regeneration: hits and misses

Cardiac injury and loss of cardiomyocytes is a causative as well as a resultant condition of cardiovascular disorders, which are the leading cause of death throughout the world. This loss of cardiomyocytes cannot be completely addressed through the currently available drugs being administered, which mainly function only in relieving the symptoms. There is a huge potential being investigated for regenerative and cell replacement therapies through recruiting stem cells of various origins namely embryonic, reprogramming/induction, and adult tissue. These sources are being actively studied for translation to clinical scenarios. In this review, we attempt to discuss some of these promising scenarios, including the clinical trials and the obstacles that need to be overcome, and hope to address the direction in which stem cell therapy is heading.

Machine perfusion in liver transplantation as a tool to prevent non-anastomotic biliary strictures: Rationale, current evidence and future directions

The high incidence of non-anastomotic biliary strictures (NAS) after transplantation of livers from extended criteria donors is currently a major barrier to widespread use of these organs. This review provides an update on the most recent advances in the understanding of the etiology of NAS. These new insights give reason to believe that machine perfusion can reduce the incidence of NAS after transplantation by providing more protective effects on the biliary tree during preservation of the donor liver. An overview is presented regarding the different endpoints that have been used for assessment of biliary injury and function before and after transplantation, emphasizing on methods used during machine perfusion. The wide spectrum of different approaches to machine perfusion is discussed, including the many different combinations of techniques, temperatures and perfusates at varying time points. In addition, the current understanding of the effect of machine perfusion in relation to biliary injury is reviewed. Finally, we explore directions for future research such as the application of (pharmacological) strategies during machine perfusion to further improve preservation. We stress the great potential of machine perfusion to possibly expand the donor pool by reducing the incidence of NAS in extended criteria organs.

First-in-Human Case Study: Multipotent Adult Progenitor Cells for Immunomodulation After Liver Transplantation

Mesenchymal stem cells and multipotent adult progenitor cells (MAPCs) have been proposed as novel therapeutics for solid organ transplant recipients with the aim of reducing exposure to pharmacological immunosuppression and its side effects. In the present study, we describe the clinical course of the first patient of the phase I, dose-escalation safety and feasibility study, MiSOT-I (Mesenchymal Stem Cells in Solid Organ Transplantation Phase I). After receiving a living-related liver graft, the patient was given one intraportal injection and one intravenous infusion of third-party MAPC in a low-dose pharmacological immunosuppressive background. Cell administration was found to be technically feasible; importantly, we found no evidence of acute toxicity associated with MAPC infusions.

Single and multiple dose MultiStem (multipotent adult progenitor cell) therapy prophylaxis of acute graft-versus-host disease in myeloablative allogeneic hematopoietic cell transplantation: a phase 1 trial

We conducted a multicenter, phase 1 dose escalation study evaluating the safety of the allogeneic multipotent adult progenitor cell (MAPC, MultiStem, Athersys, Inc., Cleveland, OH) stromal product administered as an adjunct therapy to 36 patients after myeloablative allogeneic hematopoietic cell transplantation (HCT). Patients received increasing doses of MAPC (1, 5, or 10 million cells per kilogram recipient weight) as a single i.v. dose on day +2 after HCT (n = 18), or once weekly for up to 5 doses (1 or 5 million cells per kilogram; n = 18). Infusional and regimen-related toxicities were assessed for 30 days after the last MAPC dose. Of 36 allogeneic HCT donors (17 related and 19 unrelated), 35 were 6/6 HLA matched. MAPC infusions were well tolerated without associated infusional toxicity, graft failure, or increased incidence of infection. Median times to neutrophil (n = 36) and platelet (n = 31) engraftment were 15 (range, 11 to 25) and 16 (range, 11 to 41) days, respectively. The overall cumulative incidences of grades II to IV and III and IV acute graft-versus-host disease (GVHD) at day 100 were 37% and 14%, respectively (n = 36). In the group that received the highest single MAPC dose (10 million cells/kg), day 100 incidence of grade II to IV GVHD was 11.1% (1 of 9) with no observed cases of grade III and IV GVHD. We found no evidence for MHC class II allogeneic antibody induction, although some patients showed an increase in serum anticlass I titers compared with baseline. MAPC contribution to blood chimerism was negligible. These phase I data support the safety of stromal stem cell therapy and suggest that MAPC should be tested prospectively as a novel therapeutic option for GVHD prophylaxis after HCT.

Caveats of mesenchymal stem cell therapy in solid organ transplantation

In the past decade, therapeutic use of mesenchymal stem cells (MSCs) has increased dramatically. The weight of existing evidence supports that the short-term application of MSCs is safe and feasible; however, concerns remain over the possibility of unwanted long-term effects. One fundamental difference between MSCs and pharmacotherapy is that, once applied, the effects of cell products cannot be easily reversed. Therefore, a carefully considered decision process is indispensable before cell infusion. In addition to unwanted interactions of MSCs with the host immune system, there are concerns that MSCs may promote tumor progression or even give rise to cancer themselves. As animal models and first-in-man clinical studies have provided conflicting results, it is challenging to estimate the long-term risk of individual patients. In addition, most animal models, especially rodents, are ill-suited to adequately address questions over long-term side effects. Based on the available evidence, we address the potential pitfalls for the use of MSCs as a therapeutic agent to control alloimmune effects. The aim of this review was not to discourage investigators from clinical studies, but to raise awareness of the intrinsic risks of MSC therapy.

Multipotent mesenchymal stromal cells in liver cancer: implications for tumor biology and therapy

Remodeling of tumor microenvironment is a hallmark in the pathogenesis of liver cancer. Being a pivotal part of tumor stroma, multipotent mesenchymal stromal cells (MSCs), also known as mesenchymal stem cells (MSCs), are recruited and enriched in liver tumors. Owing to their tumor tropism, MSCs are now emerging as vehicles for anticancer drug/gene delivery against liver cancer. However, the exact impact of MSCs on liver cancer remains elusive, as a variety of effects of these cells that have been reported included a plethora of tumor-promoting effects and anti-oncogenic properties. This review aims to dissect the mechanistic insight regarding this observed discrepancy in different experimental settings of liver cancer. Furthermore, we call for caution using MSCs to treat liver cancer or even premalignant liver diseases, before conclusive evidence for safety and efficacy having been obtained.

Advances in the management of the explanted donor liver

Liver transplantation is the best therapy in end-stage liver disease. Donor organ shortage and efforts to expand the donor organ pool are permanent issues given that advances in perioperative management and immunosuppressive therapy have brought the procedure into widespread clinical use. The management of organ procurement, including donor preconditioning and adequate organ storage, has a key role in transplantation. However, the organ procurement process can differ substantially between transplant centres, depending on local and national preferences. Advances in the field have come from experimental and clinical research on dynamic storage systems, such as machine perfusion devices, as an alternative to static cold storage. Determination of the clinical significance of these new systems is a topic worthy of future investigations.

Mesenchymal Stem Cells in Solid Organ Transplantation (MiSOT) Fourth Meeting: lessons learned from first clinical trials

The Fourth Expert Meeting of the Mesenchymal Stem Cells in Solid Organ Transplantation (MiSOT) Consortium took place in Barcelona on October 19 and 20, 2012. This meeting focused on the translation of preclinical data into early clinical settings. This position paper highlights the main topics explored on the safety and efficacy of mesenchymal stem cells as a therapeutic agent in solid organ transplantation and emphasizes the issues (proper timing, concomitant immunossupression, source and immunogenicity of mesenchymal stem cells, and oncogenicity) that have been addressed and will be followed up by the MiSOT Consortium in future studies.

MSC-based therapies in solid organ transplantation

Immunomodulatory cell therapy as a complement to standard pharmacotherapy represents a novel approach to solid organ allograft acceptance. This methodology may allow for a reduced dose of immunosuppressive drug to be administered and thus attenuate the severe side effects associated with long-term immunosuppression such as drug-related impairment of renal function, increased risk from opportunistic infections and malignancies. Mesenchymal stem cells (MSCs) have been shown to possess both immune modulatory and regenerative properties in vitro and in preclinical models. Encouraging results have been reported from studies examining the safety and efficacy of MSCs as a treatment for acute graft-versus-host disease. MSCs represent a promising candidate cell therapy to supplement immunosuppression in recipients of solid organs, and initial reports on the clinical use of MSCs in kidney transplantation have been recently published (Tan et al. in J Am Med Assoc 307:1169-1177, 2012; Reinders et al. in Stem Cells Transl Med 2:107-111, 2013; Perico et al. in Transpl Int 26:867-878, 2013; Perico et al. in Clin J Am Soc Nephrol 6:412-422, 2011). An area of even greater interest might be the application of MSCs in clinical liver transplantation as graft survival is closely associated with overall patient survival. Here, we present preclinical findings and discuss their possible impact on clinical liver transplantation. Then we discuss clinical studies designed to investigate how MSCs may be distributed and act in solid organ transplantation.

Mesenchymal stem cells induce an inflammatory response after intravenous infusion

Mesenchymal stem cells (MSCs) have potent immunosuppressive effects in vitro and are considered as a therapeutic option for autoimmune disease and organ transplantation. While MSCs show beneficial effects on immune disease progression and transplant survival in animal models, the immunomodulatory mechanisms involved are largely unknown. In the present study, we show that intravenously infused C57BL/6- green fluorescent protein (GFP) MSCs home to the lungs in C57BL/6 recipient mice and induce an inflammatory response. This response was characterized by increased mRNA expression of monocyte chemoattractant protein-1 (MCP1), IL1-β, and TNF-α and an increase in macrophages in lung tissue 2 h after MSC infusion. Simultaneously, serum levels of proinflammatory IL6, CXCL1, and MCP1 protein increased, demonstrating systemic immune activation after MSC infusion. In liver tissue, no C57BL/6-GFP MSCs were detected, but MCP1 and TNF-α mRNA levels peaked 4 h after MSC infusion. The expression of the anti-inflammatory cytokines TGF-β, IL4, and IL10 was only marginally affected. Nevertheless, 3 days after MSC infusion, animals developed a milder inflammatory response to lipopolysaccharides. Our results suggest that the in vivo immunomodulatory effects of MSCs originate from an inflammatory response that is induced by the infusion of MSCs, which is followed by a phase of reduced immune reactivity.

Heart grafts tolerized through third-party multipotent adult progenitor cells can be retransplanted to secondary hosts with no immunosuppression

Multipotent adult progenitor cells (MAPCs) are an adherent stem cell population that belongs to the mesenchymal-type progenitor cell family. Although MAPCs are emerging as candidate agents for immunomodulation after solid organ transplantation, their value requires further validation in a clinically relevant cell therapy model using an organ donor- and organ recipient-independent, third-party cell product. We report that stable allograft survival can be achieved following third-party MAPC infusion in a rat model of fully allogeneic, heterotopic heart transplantation. Furthermore, long-term accepted heart grafts recovered from MAPC-treated animals can be successfully retransplanted to naïve animals without additional immunosuppression. This prolongation of MAPC-mediated allograft acceptance depends upon a myeloid cell population since depletion of macrophages by clodronate abrogates the tolerogenic MAPC effect. We also show that MAPC-mediated allograft acceptance differs mechanistically from drug-induced tolerance regarding marker gene expression, T regulatory cell induction, retransplantability, and macrophage dependence. MAPC-based immunomodulation represents a promising pathway for clinical immunotherapy that has led us to initiate a phase I clinical trial for testing safety and feasibility of third-party MAPC therapy after liver transplantation.

Mesenchymal stromal cells and kidney transplantation: pretransplant infusion protects from graft dysfunction while fostering immunoregulation

Bone marrow-derived mesenchymal stromal cells (MSC) have emerged as useful cell population for immunomodulation therapy in transplantation. Moving this concept towards clinical application, however, should be critically assessed by a tailor-made step-wise approach. Here, we report results of the second step of the multistep MSC-based clinical protocol in kidney transplantation. We examined in two living-related kidney transplant recipients whether: (i) pre-transplant (DAY-1) infusion of autologous MSC protected from the development of acute graft dysfunction previously reported in patients given MSC post-transplant, (ii) avoiding basiliximab in the induction regimen improved the MSC-induced Treg expansion previously reported with therapy including this anti-CD25-antibody. In patient 3, MSC treatment was uneventful and graft function remained normal during 1 year follow-up. In patient 4, acute cellular rejection occurred 2 weeks post-transplant. Both patients had excellent graft function at the last observation. Circulating memory CD8(+) T cells and donor-specific CD8(+) T-cell cytolytic response were reduced in MSC-treated patients, not in transplant controls not given MSC. CD4(+) FoxP3(+) Treg expansion was comparable in MSC-treated patients with or without basiliximab induction. Thus, pre-transplant MSC no longer negatively affect kidney graft at least to the point of impairing graft function, and maintained MSC-immunomodulatory properties. Induction therapy without basiliximab does not offer any advantage on CD4(+) FoxP3(+) Treg expansion (ClinicalTrials.gov number: NCT 00752479).

Tumor promotion through the mesenchymal stem cell compartment in human hepatocellular carcinoma

Although the infiltration of mesenchymal stem (stromal) cells (MSCs) into different tumors is widely recognized in animal models, the question whether these MSCs have a positive or negative effect on disease progression remains unanswered. The aim of this study is to investigate whether human hepatocellular carcinoma (HCC) harbors MSCs and whether these MSCs affect tumor growth. We observed that cells capable of differentiation into both adipocyte and osteocyte lineages and expressing MSC markers can be cultured from surgically resected HCC tissues. In situ staining of human HCC tissues with a STRO-1 antibody showed that the tumor and tumor-stromal region are significantly enriched with candidate MSCs compared with adjacent tissue (n = 12, P < 0.01). In mice, coengraftment of a human HCC cell line (Huh7) with MSCs resulted in substantially larger tumors compared with paired engraftment of Huh7 alone (n = 8, P < 0.01). Consistently, coculturing Huh7 with irradiated MSCs significantly increased the number and the size of colonies formed. This enhancement of Huh7 colony formation was also observed by treatment of MSC-conditioned medium (MSC-CM), suggesting that secreted trophic factors contribute to the growth-promoting effects. Genome-wide gene expression array and pathway analysis confirmed the upregulation of cell growth and proliferation-related processes and downregulation of cell death-related pathways by treatment of MSC-CM in Huh7 cells. In conclusion, these results show that MSCs are enriched in human HCC tumor compartment and could exert trophic effects on tumor cells. Thus, targeting of HCC tumor MSCs may represent a new avenue for therapeutic intervention.

Regulatory macrophages as therapeutic targets and therapeutic agents in solid organ transplantation

PURPOSE OF REVIEW

This review aims to provide a basic introduction to human macrophage biology and an appreciation of the diverse roles played by macrophage subsets in allograft damage and repair. Current and future strategies for therapeutically manipulating macrophage behaviour are discussed.

RECENT FINDINGS

Macrophages are extremely versatile effector cells that exert both immunostimulatory and immunosuppressive effects. This adaptability cannot be explained by differentiation into committed sublineages, but instead reflects the ability of macrophages to rapidly transition between states of functional polarisation. Consequently, categorisation of macrophage subpopulations is not straightforward and this, in turn, creates difficulties in studying their pathophysiology. Nevertheless, particular macrophage subpopulations have been implicated in exacerbating or attenuating ischaemia-reperfusion injury, rejection reactions and allograft fibrosis. Three general strategies for therapeutically targeting macrophages can be envisaged, namely, depletional approaches, in-situ repolarisation towards a regulatory or tissue-reparative phenotype, and ex-vivo generation of regulatory macrophages (M reg) as a cell-based therapy.

SUMMARY

As critical determinants of the local and systemic immune response to solid organ allografts, macrophage subpopulations represent attractive therapeutic targets. Rapid progress is being made in the implementation of novel macrophage-targeted therapies, particularly in the use of ex-vivo-generated M regs as a cell-based medicinal product.

Machine perfusion in organ transplantation: a tool for ex-vivo graft conditioning with mesenchymal stem cells?

PURPOSE OF REVIEW

Machine perfusion has emerged as a tool to evaluate pretransplant graft function more objectively during preservation. Machine perfusion also offers the possibility to recondition questionable organs and to 'immunomodulate' allografts ex vivo. This article aims to review the current knowledge on machine perfusion of the various solid thoracic and abdominal organs, and to discuss the new possibility of conditioning and treating grafts with mesenchymal stem cells (MSCs) during machine perfusion.

RECENT FINDINGS

Different methods of machine perfusion have been described varying among organs in temperature and composition of perfusate. Commercial devices have recently become available for machine perfusion of all organs, with the largest clinical experience acquired in kidney and lung transplantation. Clinical studies are ongoing for liver, heart, and pancreas. MSC therapy in organ transplantation is now emerging with clinical studies set up to investigate its potential to attenuate ischemia/reperfusion injury (innate immunity) and to downregulate the alloimmune response (adaptive immunity) and promote engraftment after transplantation. We hypothesize that delivery of MSCs directly into the machine perfusion circuit may provide a unique opportunity to treat and immunomodulate organs prior to transplantation. To our knowledge, no study on ex-vivo delivery of MSCs during machine perfusion has been reported.

SUMMARY

Machine perfusion of solid organs has regained much attention during the last decade. It provides a new promising tool that may allow pretransplant ex-vivo assessment, preservation, repair, and conditioning of grafts. Experimental research and clinical trials testing the administration of MSCs during machine perfusion are warranted to explore the potential benefit and mechanisms of this approach.

Generation of mesenchymal stem cells as a medicinal product in organ transplantation

PURPOSE OF REVIEW

Mesenchymal stem cells (MSCs) are emerging as an alternative treatment in solid-organ transplantation. The use of MSCs as a therapeutic product requires the translation of basic research protocols into a production process under good manufacturing practice (GMP) to obtain a safe product of high quality. This requires a different mindset from the academic setting of changing protocols into a well defined, controlled and documented process. This review describes some of the challenges faced by culturing MSCs as a medicinal product.

RECENT FINDINGS

Clinical-grade MSCs are used in the clinical trials and proved to be safe as a medicinal product. Because of the differences in the type of MSCs and in the production process, clinical outcome is not always comparable. New standardized methods in the culture condition such as the use of alternatives for fetal bovine serum (FBS), standardized plating densities or the use of bioreactors may further standardize the production process.

SUMMARY

To generate MSCs as a medicinal product in organ transplantation, regulation requires that MSCs have to be generated under GMP. During the whole production process, all critical steps should be known and described. Further steps should be taken to optimize and standardize the production process.

Human Bone Marrow- and Adipose Tissue-derived Mesenchymal Stromal Cells are Immunosuppressive In vitro and in a Humanized Allograft Rejection Model

Background

Recent studies with bone marrow (BM)-derived Mesenchymal Stromal Cells (MSC) in transplant recipients demonstrate that treatment with MSC is safe and clinically feasible. While BM is currently the preferred source of MSC, adipose tissue is emerging as an alternative. To develop efficient therapies, there is a need for preclinical efficacy studies in transplantation. We used a unique humanized transplantation model to study the in vivo immunosuppressive effect of human BM-MSC and adipose tissue-derived MSC (ASC).

Methods

Gene expression of BM-MSC and ASC and their capacity to inhibit activated PBMC proliferation was evaluated. The in vivo immunosuppressive effect of BM-MSC and ASC was studied in a humanized mouse model. SCID mice were transplanted with human skin grafts and injected with human allogeneic PBMC with or without administration of BM-MSC or ASC. The effect of MSC on skin graft rejection was studied by immunohistochemistry and PCR.

Results

BM-MSC and ASC expressed TGFβ, CXCL-10 and IDO. IDO expression and acitivity increased significantly in BM-MSC and ASC upon IFN-γ stimulation. IFN-γ stimulated BM-MSC and ASC inhibited the proliferation of activated PBMC in a significant and dose dependent manner. In our humanized mouse model, alloreactivity was marked by pronounced CD45+ T-cell infiltrates consisting of CD4+ and CD8+ T cells and increased IFN-γ expression in the skin grafts which were all significantly inhibited by both BM-MSC and ASC.

Conclusion

BM-MSC and ASC are immunosuppressive in vitro and suppress alloreactivity in a preclinical humanized transplantation model.

Application of MultiStem(®) Allogeneic Cells for Immunomodulatory Therapy: Clinical Progress and Pre-Clinical Challenges in Prophylaxis for Graft Versus Host Disease

The last decade has seen much progress in adjunctive cell therapy for immune disorders. Both corporate and institutional Phase III studies have been run using mesenchymal stromal cells (MSC) for treatment of Graft versus Host Disease (GvHD), and product approval has been achieved for treatment of pediatric GvHD in Canada and New Zealand (Prochymal(®); Osiris Therapeutics). This effectiveness has prompted the prophylactic use of adherent stem cells at the time of allogeneic hematopoietic stem cell transplantation (HSCT) to prevent occurrence of GvHD and possibly provide stromal support for hematopoietic recovery. The MultiStem(®) product is an adult adherent stem cell product derived from bone marrow which has significant clinical exposure. MultiStem cells are currently in phase II clinical studies for treatment of ischemic stroke and ulcerative colitis, with Phase I studies completed in acute myocardial infarction and for GvHD prophylaxis in allogeneic HSCT, demonstrating that MultiStem administration was well tolerated while the incidence and severity of GvHD was reduced. In advancing this clinical approach, it is important to recognize that alternate models exist based on clinical manufacturing strategies. Corporate sponsors exploit the universal donor properties of adherent stem cells and manufacture at large scale, with many products obtained from one or limited donors and used across many patients. In Europe, institutional sponsors often produce allogeneic product in a patient designated context. For this approach, disposable bioreactors producing <10 products/donor in a closed system manner are very well suited. In this review, the use of adherent stem cells for GvHD prophylaxis is summarized and the suitability of disposable bioreactors for MultiStem production is presented, with an emphasis on quality control parameters, which are critical with a multiple donor approach for manufacturing.

Treatment-emergent adverse events after infusion of adherent stem cells: the MiSOT-I score for solid organ transplantation

BACKGROUND

Cellular therapy after organ transplantation is emerging as an intriguing strategy to achieve dose reduction of classical immunosuppressive pharmacotherapy. Here, we introduce a new scoring system to assess treatment-emergent adverse events (TEAEs) of adherent stem cell therapies in the clinical setting of allogeneic liver transplantation (for example, the MiSOT-I trial Eudract CT: 2009-017795-25).

METHODS

The score consists of three independent modalities (set of parameters) that focus on clinically relevant events early after intravenous or intraportal stem cell infusion: pulmonary toxicity, intraportal-infusional toxicity and systemic toxicity. For each modality, values between 0 (no TEAE) and 3 (severe TEAE) were defined. The score was validated retrospectively on a cohort of n=187 recipients of liver allografts not receiving investigational cell therapy between July 2004 and December 2010. These patients represent a control population for further trials. Score values were calculated for days 1, 4, and 10 after liver transplantation.

RESULTS

Grade 3 events were most commonly related to the pulmonary system (3.5% of study cohort on day 4). Almost no systemic-related TEAEs were observed during the study period. The relative frequency of grade 3 events never exceeded 5% over all modalities and time points. A subgroup analysis for grade 3 patients provided no descriptors associated with severe TEAEs.

CONCLUSION

The MiSOT-I score provides an assessment tool to score specific adverse events that may occur after adherent stem cell therapy in the clinical setting of organ transplantation and is thus a helpful tool to conduct a safety study.

Mesenchymal stem cells are short-lived and do not migrate beyond the lungs after intravenous infusion

Mesenchymal stem cells (MSC) are under investigation as a therapy for a variety of disorders. Although animal models show long term regenerative and immunomodulatory effects of MSC, the fate of MSC after infusion remains to be elucidated. In the present study the localization and viability of MSC was examined by isolation and re-culture of intravenously infused MSC. C57BL/6 MSC (500,000) constitutively expressing DsRed-fluorescent protein and radioactively labeled with Cr-51 were infused via the tail vein in wild-type C57BL/6 mice. After 5 min, 1, 24, or 72 h, mice were sacrificed and blood, lungs, liver, spleen, kidneys, and bone marrow removed. One hour after MSC infusion the majority of Cr-51 was found in the lungs, whereas after 24 h Cr-51 was mainly found in the liver. Tissue cultures demonstrated that viable donor MSC were present in the lungs up to 24 h after infusion, after which they disappeared. No viable MSC were found in the other organs examined at any time. The induction of ischemia-reperfusion injury in the liver did not trigger the migration of viable MSC to the liver. These results demonstrate that MSC are short-lived after i.v. infusion and that viable MSC do not pass the lungs. Cell debris may be transported to the liver. Long term immunomodulatory and regenerative effects of infused MSC must therefore be mediated via other cell types.