Interleukin (IL)-10 induced by CD11b(+) cells and IL-10-activated regulatory T cells play a role in immune modulation of mesenchymal stem cells in rat islet allografts

Immunoprotection Strategies in β-Cell Replacement Therapy: A Closer Look at Porcine Islet Xenotransplantation

Type 1 diabetes mellitus (T1DM) is characterized by absolute insulin deficiency primarily due to autoimmune destruction of pancreatic β-cells. The prevailing treatment for T1DM involves daily subcutaneous insulin injections, but a substantial proportion of patients face challenges such as severe hypoglycemic episodes and poorly controlled hyperglycemia. For T1DM patients, a more effective therapeutic option involves the replacement of β-cells through allogeneic transplantation of either the entire pancreas or isolated pancreatic islets. Unfortunately, the scarcity of transplantable human organs has led to a growing list of patients waiting for an islet transplant. One potential alternative is xenotransplantation of porcine pancreatic islets. However, due to inter-species molecular incompatibilities, porcine tissues trigger a robust immune response in humans, leading to xenograft rejection. Several promising strategies aim to overcome this challenge and enhance the long-term survival and functionality of xenogeneic islet grafts. These strategies include the use of islets derived from genetically modified pigs, immunoisolation of islets by encapsulation in biocompatible materials, and the creation of an immunomodulatory microenvironment by co-transplanting islets with accessory cells or utilizing immunomodulatory biomaterials. This review concentrates on delineating the primary obstacles in islet xenotransplantation and elucidates the fundamental principles and recent breakthroughs aimed at addressing these challenges.

miRNA-148a-containing GMSC-derived EVs modulate Treg/Th17 balance via IKKB/NF-κB pathway and treat a rheumatoid arthritis model

Mesenchymal stem cells (MSCs) have demonstrated potent immunomodulatory properties that have shown promise in the treatment of autoimmune diseases, including rheumatoid arthritis (RA). However, the inherent heterogeneity of MSCs triggered conflicting therapeutic outcomes, raising safety concerns and limiting their clinical application. This study aimed to investigate the potential of extracellular vesicles derived from human gingival mesenchymal stem cells (GMSC-EVs) as a therapeutic strategy for RA. Through in vivo experiments using an experimental RA model, our results demonstrate that GMSC-EVs selectively homed to inflamed joints and recovered Treg and Th17 cell balance, resulting in the reduction of arthritis progression. Our investigations also uncovered miR-148a-3p as a critical contributor to the Treg/Th17 balance modulation via IKKB/NF-κB signaling orchestrated by GMSC-EVs, which was subsequently validated in a model of human xenograft versus host disease (xGvHD). Furthermore, we successfully developed a humanized animal model by utilizing synovial fibroblasts obtained from patients with RA (RASFs). We found that GMSC-EVs impeded the invasiveness of RASFs and minimized cartilage destruction, indicating their potential therapeutic efficacy in the context of patients with RA. Overall, the unique characteristics - including reduced immunogenicity, simplified administration, and inherent ability to target inflamed tissues - position GMSC-EVs as a viable alternative for RA and other autoimmune diseases.

Timing of Mesenchymal Stromal Cell Therapy Defines its Immunosuppressive Effects in a Rat Lung Transplantation Model

Cell therapy using mesenchymal stromal cells (MSCs) is being studied for its immunosuppressive effects. In organ transplantation, the amount of MSCs that accumulate in transplanted organs and other organs may differ depending on administration timing, which may impact their immunosuppressive effects. In vitro, adipose-derived mesenchymal stem cells (ADMSCs) suppress lymphocyte activation under cell-to-cell contact conditions. However, in vivo, it is controversial whether ADMSCs are more effective in accumulating in transplanted organs or in secondary lymphoid organs. Herein, we aimed to investigate whether the timing of ADMSC administration affects its immunosuppression ability in a rat lung transplantation model. In the transplantation study, rats were intramuscularly administered half the usual dose of tacrolimus (0.5 mg/kg) every 24 h after lung transplantation. ADMSCs (1 × 106) were administered via the jugular vein before (PreTx) or after (PostTx) transplantation. Cell tracking using quantum dots was performed. ADMSCs accumulated predominantly in the lung and liver; fewer ADMSCs were distributed in the grafted lung in the PreTx group than in the PostTx group. The rejection rate was remarkably low in the ADMSC-administered groups, particularly in the PostTx group. Serum tumor necrosis factor-α (TNF-α), interferon-γ, and interleukin (IL)-6 levels showed a greater tendency to decrease in the PreTx group than in the PostTx group. The proportion of regulatory T cells in the grafted lung 10 days after transplantation was higher in the PostTx group than in the PreTx group. PostTx administration suppresses rejection better than PreTx administration, possibly due to regulatory T cell induction by ADMSCs accumulated in the transplanted lungs, suggesting a mechanism different from that in heart or kidney transplantation that PreTx administration is more effective than PostTx administration. These results could help establish cell therapy using MSCs in lung transplantation.

Local Immunomodulatory Strategies to Prevent Allo-Rejection in Transplantation of Insulin-Producing Cells

Islet transplantation has shown promise as a curative therapy for type 1 diabetes (T1D). However, the side effects of systemic immunosuppression and limited long-term viability of engrafted islets, together with the scarcity of donor organs, highlight an urgent need for the development of new, improved, and safer cell-replacement strategies. Induction of local immunotolerance to prevent allo-rejection against islets and stem cell derived β cells has the potential to improve graft function and broaden the applicability of cellular therapy while minimizing adverse effects of systemic immunosuppression. In this mini review, recent developments in non-encapsulation, local immunomodulatory approaches for T1D cell replacement therapies, including islet/β cell modification, immunomodulatory biomaterial platforms, and co-transplantation of immunomodulatory cells are discussed. Key advantages and remaining challenges in translating such technologies to clinical settings are identified. Although many of the studies discussed are preliminary, the growing interest in the field has led to the exploration of new combinatorial strategies involving cellular engineering, immunotherapy, and novel biomaterials. Such interdisciplinary research will undoubtedly accelerate the development of therapies that can benefit the whole T1D population.

Immunomodulation effect of mesenchymal stem cells in islet transplantation

Mesenchymal stem cells (MSCs) therapy has brought a great enthusiasm to the treatment of various immune disorders, tissue regeneration and transplantation therapy. MSCs are being extensively investigated for their immunomodulatory actions. MSCs can deliver immunomodulatory signals to inhibit allogeneic T cell immune responses by downregulating pro-inflammatory cytokines and increasing regulatory cytokines and growth factors. Islet transplantation is a therapeutic alternative to the insulin therapy for the treatment of type 1 diabetes mellitus (T1DM). However, the acute loss of islets due to the lack of vasculature and hypoxic milieu in the immediate post-transplantation period may lead to treatment failure. Moreover, despite the use of potent immunosuppressive drugs, graft failure persists because of immunological rejection. Many in vitro and in vivo researches have demonstrated the multipotency of MSCs as a mediator of immunomodulation and a great approach for enhancement of islet engraftment. MSCs can interact with immune cells of the innate and adaptive immune systems via direct cell-cell contact or through secretomes containing numerous soluble growth and immunomodulatory factors or mitochondrial transfer. This review highlights the interactions between MSCs and different immune cells to mediate immunomodulatory functions along with the importance of MSCs therapy for the successful islet transplantation.

Advances in mesenchymal stem cell therapy for immune and inflammatory diseases: Use of cell-free products and human pluripotent stem cell-derived mesenchymal stem cells

Mesenchymal stem cell therapy (MSCT) for immune and inflammatory diseases continues to be popular based on progressive accumulation of preclinical mechanistic evidence. This has led to further expansion in clinical indications from graft rejection, autoimmune diseases, and osteoarthritis, to inflammatory liver and pulmonary diseases including COVID‐19. A clear trend is the shift from using autologous to allogeneic MSCs, which can be immediately available as off‐the‐shelf products. In addition, new products such as cell‐free exosomes and human pluripotent stem cell (hPSC)‐derived MSCs are exciting developments to further prevalent use. Increasing numbers of trials have now published results in which safety of MSCT has been largely demonstrated. While reports of therapeutic endpoints are still emerging, efficacy can be seen for specific indications—including graft‐vs‐host‐disease, strongly Th17‐mediated autoimmune diseases, and osteoarthritis—which are more robustly supported by mechanistic preclinical evidence. In this review, we update and discuss outcomes in current MSCT clinical trials for immune and inflammatory disease, as well as new innovation and emerging trends in the field.

Cellular therapies in organ transplantation

Cellular therapy is a promising tool for improving the outcome of organ transplantation. Various cell types with different immunoregulatory and regenerative properties may find application for specific transplant rejection or injury-related indications. The current era is crucial for the development of cellular therapies. Preclinical models have demonstrated the feasibility of efficacious cell therapy in transplantation, early clinical trials have shown safety of several of these therapies, and the first steps towards efficacy studies in humans have been made. In this review, we address the current state of the art of cellular therapies in clinical transplantation and discuss monitoring tools and endpoints for these studies.

Long-term reversal of diabetes by subcutaneous transplantation of pancreatic islet cells and adipose-derived stem cell sheet using surface-immobilized heparin and engineered collagen scaffold

OBJECTIVE

Esterified collagen (EC) can be functionalized with heparin to enhance islet graft stability. Growth factors secreted by human adipose-derived stem cells (hADSCs) can bind efficiently to EC-heparin (EC-Hep), which enhances revascularization and cell protection. We investigated the therapeutic potential of a combined heparin-esterified collagen-hADSC (HCA)-islet sheet to enhance islet engraftment.

RESEARCH DESIGN AND METHODS

This study was designed to assess the efficiency of using EC-Hep as a scaffold for subcutaneous islet transplantation in diabetic athymic mice. After the hADSC-cocultured islets were seeded in the EC-Hep scaffold, islet function was measured by glucose-stimulated insulin secretion test and growth factors in the culture supernatants were detected by protein array. Islet transplantation was performed in mice, and graft function and survival were monitored by measuring the blood glucose levels. β-Cell mass and vascular densities were assessed by immunohistochemistry.

RESULTS

The EC-Hep composite allowed sustained release of growth factors. Secretion of growth factors and islet functionality in the HCA-islet sheet were significantly increased compared with the control groups of islets alone or combined with native collagen. In vivo, stable long-term glucose control by the graft was achieved after subcutaneous transplantation of HCA-islet sheet due to enhanced capillary network formation around the sheet.

CONCLUSIONS

The findings indicate the potential of the HCA-islet sheet to enhance islet revascularization and engraftment in a hADSC dose-dependent manner, following clinical islet transplantation for the treatment of diabetes mellitus.

Effect of Timing and Complement Receptor Antagonism on Intragraft Recruitment and Protolerogenic Effects of Mesenchymal Stromal Cells in Murine Kidney Transplantation

BACKGROUND

Mesenchymal stromal cells (MSCs) have protolerogenic effects in renal transplantation, but they induce long-term regulatory T cells (Treg)-dependent graft acceptance only when infused before transplantation. When given posttransplant, MSCs home to the graft where they promote engraftment syndrome and do not induce Treg. Unfortunately, pretransplant MSC administration is unfeasible in deceased-donor kidney transplantation.

METHODS

To make MSCs a therapeutic option also for deceased organ recipients, we tested whether MSC infusion at the time of transplant (day 0) or posttransplant (day 2) together with inhibition of complement receptors prevents engraftment syndrome and allows their homing to secondary lymphoid organs for promoting tolerance. We analyzed intragraft and splenic MSC localization, graft survival, and alloimmune response in mice recipients of kidney allografts and syngeneic MSCs given on day 0 or on posttransplant day 2. C3a receptor (C3aR) or C5a receptor (C5aR) antagonists were administered to mice in combination with the cells or were used together to treat MSCs before infusion.

RESULTS

Syngeneic MSCs given at day 0 homed to the spleen increased Treg numbers and induced long-term graft acceptance. Posttransplant MSC infusion, combined with a short course of C3aR or C5aR antagonist or administration of MSCs pretreated with C3aR and C5aR antagonists, prevented intragraft recruitment of MSCs and graft inflammation, inhibited antidonor T-cell reactivity, but failed to induce Treg, resulting in mild prolongation of graft survival.

CONCLUSIONS

These data support testing the safety/efficacy profile of administering MSCs on the day of transplant in deceased-donor transplant recipients and indicate that complement is crucial for MSC recruitment into the kidney allograft.

Mesenchymal stromal cells in kidney transplantation

PURPOSE OF REVIEW

Mesenchymal stromal cells (MSC) have emerged as one of the most promising candidates for immunomodulatory cell therapy in kidney transplantation. Here we describe novel insights into the MSC mechanism of action and provide an overview of initial safety and feasibility studies with MSC in kidney transplantation.

RECENT FINDINGS

Clinical studies of MSC-based cell therapy in kidney transplant recipients demonstrated the safety and feasibility of cell therapy and provide the first encouraging evidence of the efficacy of MSC in enabling the minimization of immunosuppressive drugs. In our initial experience with MSC-based therapy in kidney transplant recipients we carried out extensive clinical and immunological monitoring of MSC-treated patients and found possible biomarkers of MSC immunomodulation in some of them. Based on these biomarkers we identified a patient in whom complete discontinuation of immunosuppression has been achieved safely and successfully.

SUMMARY

Many issues should be addressed before MSC-based therapy becomes a standard treatment protocol for kidney transplantation. A better understanding of the MSC mechanism of action and the identification of biomarkers of response to therapy will inform the rational design of the most effective clinical protocol and the selection of patients amenable to safe immunosuppressive drug withdrawal.

Bone marrow stem cells modified with human interleukin 10 attenuate acute rejection in rat lung allotransplantation

OBJECTIVES

The aim of this study was to investigate new therapeutic options to attenuate acute rejection in a rat lung allograft model. Cell-based gene therapies have recently been reported as a novel curative option in acute and chronic diseases for which conventional treatments are not available. We studied the effect of human interleukin 10 (hIL-10) on expressing bone marrow-derived mesenchymal stem cells (BMSCs) in combination with cyclosporine A (CsA) on acute rejection of lung allografts in the rat.

METHODS

Lung allotransplantation was performed from male Brown Norway donor to male Fisher (F344) rats. Rat BMSCs were transfected with hIL-10 in vitro and introduced in the graft prior to implantation. Group A (n = 5) received CsA intraperitoneally (2.5 mg/kg body weight) for 5 days post-transplant; Group B (n = 5) received BMSC and CsA and Group C (n = 5) received hIL-10-BMSC before implantation and CsA. Graft function was assessed by blood gas levels only from the graft on day 5; tissue was sampled for histological grading of rejection and measurement of the wet-to-dry ratio.

RESULTS

All Group A control animals showed severe signs of rejection. On Day 5, all grafts in Group C showed improved gas exchange (mean arterial partial pressure of oxygen 222.2 ± 40.38 mmHg vs 92.36 ± 20.92 mmHg in Group B and 42.72 ± 18.07 mmHg in Group A). Histological examination revealed moderate-to-severe rejection in all animals in Group A [International Society for Heart and Lung Transplantation Level III B (ISHLT)] in contrast to low-to-moderate rejection in Group B (II-IIIA) and much improved histological grade in Group C (I-IIA). Moreover, the wet-to-dry ratio was also reduced in Group C (4.8 ± 1.19 compared with 4.78 ± 0.62 in Group B and 9.36 ± 0.90 in Group A).

CONCLUSIONS

The hIL-10 BMSC represent a promising novel method for localized cell-based gene therapy for acute rejection in a rat lung allograft model.

Mesenchymal stromal cells for tolerance induction in organ transplantation

The primary challenge in organ transplantation continues to be the need to suppress the host immune system long-term to ensure prolonged allograft survival. Long-term non-specific immunosuppression can, however, result in life-threatening complications. Thus, efforts have been pursued to explore novel strategies that would allow minimization of maintenance immunosuppression, eventually leading to transplant tolerance. In this scenario, bone marrow-derived mesenchymal stromal cells (MSC), given their unique immunomodulatory properties to skew the balance between regulatory and memory T cells, have emerged as potential candidates for cell-based therapy to promote immune tolerance. Here, we review our initial clinical experience with bone marrow-derived MSC in living-donor kidney transplant recipients and provide an overview of the available results of other clinical programs with MSC in kidney and liver transplantation, highlighting hurdles and success of this innovative cell-based therapy.

Tissue regeneration: The crosstalk between mesenchymal stem cells and immune response

Mesenchymal stem cells (MSCs) exist in almost all tissues with the capability to differentiate into several different cell types and hold great promise in tissue repairs in a cell replacement manner. The study of the bidirectional regulation between MSCs and immune response has ushered an age of rethinking of tissue regeneration in the process of stem cell-based tissue repairs. By sensing damaged signals, both endogenous and exogenous MSCs migrate to the damaged site where they involve in the reconstitution of the immune microenvironment and empower tissue stem/progenitor cells and other resident cells, whereby facilitate tissue repairs. This MSC-based therapeutic manner is conferred as cell empowerment. In this process, MSCs have been found to exert extensive immunosuppression on both innate and adaptive immune response, while such regulation needs to be licensed by inflammation. More importantly, the immunoregulation of MSCs is highly plastic, especially in the context of pathological microenvironment. Understanding the immunoregulatory properties of MSCs is necessary for appropriate application of MSCs. Here we review the current studies on the crosstalk of MSCs and immune response in disease pathogenesis and therapy.

Mesenchymal stem cells to promote islet transplant survival

PURPOSE OF REVIEW

Mesenchymal stromal cells (MSCs) are adult stromal cells with therapeutic potential in allogeneic islet transplantation for type 1 diabetes patients. The process of islet isolation alone has been shown to negatively impact islet survival and function in vivo. In addition, insults mediated by the instant blood-mediated inflammatory reaction, hypoxia, ischemia and immune response significantly impact the islet allograft post transplantation. MSCs are known to exert cytoprotective and immune modulatory properties and thus are an attractive therapeutic in this context. Herein, the recent progress in the field of MSC therapy in islet transplantation is discussed.

RECENT FINDINGS

MSC can promote islet survival and function in vivo. Importantly, studies have shown that human MSC donors have differential abilities in promoting islet regeneration/survival. Recently, several biomarkers associated with MSC islet regenerative capacity have been identified. Expressions of Annexin A1, Elastin microfibril interface 1 and integrin-linked protein kinase are upregulated in MSC displaying protective effects on islet survival and function in vivo.

SUMMARY

The discovery of biomarkers associated with MSC therapeutic efficacy represents an important step forward for the utilization of MSC therapy in islet transplantation; however, much remains to be elucidated about the mechanisms utilized by MSC in protection against transplanted islet loss, autoimmune-mediated and alloimmune-mediated rejection.

Bone Marrow Mesenchymal Stem Cells Inhibit the Function of Dendritic Cells by Secreting Galectin-1

This study aimed to investigate whether bone marrow-derived mesenchymal stem cells (BM-MSCs) can inhibit function of dendritic cells (DCs) by secreting Galectin-1 (Gal-1). BM-MSCs have been shown to inhibit the maturation and function of DCs, further inhibiting the activation and proliferation of T cells. However, the detailed mechanism remains unknown. In this current study, MSCs and DCs derived from mouse bone marrow were cocultured using Transwell culture plates under different in vitro conditions. The results showed that as the ratio of MSC to DC of the coculture system increased and the coculture time of the two cells prolonged, the concentrations of Gal-1, interleukin- (IL-) 10, and IL-12 in the supernatants were increased and the protein expression of Gal-1 on and within DCs was also enhanced. The phosphorylation of extracellular signal-regulated kinase (ERK) pathway in DCs was boosted, whereas p38 mitogen-activated protein kinase (MAPK) pathway phosphorylation was weakened. Meanwhile, the expression of costimulatory molecules on the surface of DCs was decreased, and the proliferative effect of DCs on allogeneic T cells was also decreased. Therefore, this present study indicated that Gal-1 secreted from MSCs upregulated expression of Gal-1 and stimulated formation of tolerance immunophenotype on DCs, where the underlying mechanism was the regulation of the MAPK signaling pathway in DCs, thereby inhibiting the function of DCs.

Durable Control of Autoimmune Diabetes in Mice Achieved by Intraperitoneal Transplantation of "Neo-Islets," Three-Dimensional Aggregates of Allogeneic Islet and "Mesenchymal Stem Cells"

Novel interventions that reestablish endogenous insulin secretion and thereby halt progressive end-organ damage and prolong survival of patients with autoimmune Type 1 diabetes mellitus (T1DM) are urgently needed. While this is currently accomplished with allogeneic pancreas or islet transplants, their utility is significantly limited by both the scarcity of organ donors and life-long need for often-toxic antirejection drugs. Coadministering islets with bone marrow-derived mesenchymal stem cells (MSCs) that exert robust immune-modulating, anti-inflammatory, anti-apoptotic, and angiogenic actions, improves intrahepatic islet survival and function. Encapsulation of insulin-producing cells to prevent immune destruction has shown both promise and failures. Recently, stem cell-derived insulin secreting β-like cells induced euglycemia in diabetic animals, although their clinical use would still require encapsulation or anti-rejection drugs. Instead of focusing on further improvements in islet transplantation, we demonstrate here that the intraperitoneal administration of islet-sized "Neo-Islets" (NIs), generated by in vitro coaggregation of allogeneic, culture-expanded islet cells with high numbers of immuno-protective and cyto-protective MSCs, resulted in their omental engraftment in immune-competent, spontaneously diabetic nonobese diabetic (NOD) mice. This achieved long-term glycemic control without immunosuppression and without hypoglycemia. In preparation for an Food and Drug Administration-approved clinical trial in dogs with T1DM, we show that treatment of streptozotocin-diabetic NOD/severe combined immunodeficiency mice with identically formed canine NIs produced durable euglycemia, exclusively mediated by dog-specific insulin. We conclude that this novel technology has significant translational relevance for canine and potentially clinical T1DM as it effectively addresses both the organ donor scarcity (>80 therapeutic NI doses/donor pancreas can be generated) and completely eliminates the need for immunosuppression. Stem Cells Translational Medicine 2017;6:1631-1643.

In Vivo Immunogenic Response to Allogeneic Mesenchymal Stem Cells and the Role of Preactivated Mesenchymal Stem Cells Cotransplanted with Allogeneic Islets

Mesenchymal stem cells (MSCs) are multipotent cells capable of differentiating into cells from the mesenchymal lineage. The hypoimmunogenic characteristic of MSCs has encouraged studies using allogeneic MSCs for the treatment of autoimmune diseases and inflammatory conditions. Promising preclinical results and the safety of allogeneic MSC transplantation have created the possibility of “off-the-shelf” clinical application of allogeneic cells. This study has aimed to evaluate the survival of untreated and IFN-γ- and TNF-α-treated (preactivated) allogeneic MSCs transplanted under the kidney capsule of immunocompetent mice together with the role of preactivated MSCs after cotransplantation with allogeneic islets. The preactivation of MSCs upregulated the gene expression of anti-inflammatory molecules and also enhanced their immunomodulatory capacity in vitro. In vivo, allogeneic MSCs provoked an immunogenic response, with the infiltration of inflammatory cells at the transplant site and full graft rejection in both the untreated and preactivated groups. Allogeneic islets cotransplanted with preactivated MSCs prolonged graft survival for about 6 days, compared with islet alone. The present results corroborate the hypothesis that allogeneic MSCs are not immune-privileged and that after playing their therapeutic role they are rejected. Strategies that reduce allogeneic MSC immunogenicity can potentially prolong their in vivo persistence and improve the therapeutic effects.

Old game, new players: Linking classical theories to new trends in transplant immunology

The evolutionary emergence of an efficient immune system has a fundamental role in our survival against pathogenic attacks. Nevertheless, this same protective mechanism may also establish a negative consequence in the setting of disorders such as autoimmunity and transplant rejection. In light of the latter, although research has long uncovered main concepts of allogeneic recognition, immune rejection is still the main obstacle to long-term graft survival. Therefore, in order to define effective therapies that prolong graft viability, it is essential that we understand the underlying mediators and mechanisms that participate in transplant rejection. This multifaceted process is characterized by diverse cellular and humoral participants with innate and adaptive functions that can determine the type of rejection or promote graft acceptance. Although a number of mediators of graft recognition have been described in traditional immunology, recent studies indicate that defining rigid roles for certain immune cells and factors may be more complicated than originally conceived. Current research has also targeted specific cells and drugs that regulate immune activation and induce tolerance. This review will give a broad view of the most recent understanding of the allogeneic inflammatory/tolerogenic response and current insights into cellular and drug therapies that modulate immune activation that may prove to be useful in the induction of tolerance in the clinical setting.

Administration of multipotent mesenchymal stromal cells restores liver regeneration and improves liver function in obese mice with hepatic steatosis after partial hepatectomy

Background

The liver has the remarkable capacity to regenerate in order to compensate for lost or damaged hepatic tissue. However, pre-existing pathological abnormalities, such as hepatic steatosis (HS), inhibits the endogenous regenerative process, becoming an obstacle for liver surgery and living donor transplantation.

Recent evidence indicates that multipotent mesenchymal stromal cells (MSCs) administration can improve hepatic function and increase the potential for liver regeneration in patients with liver damage. Since HS is the most common form of chronic hepatic illness, in this study we evaluated the role of MSCs in liver regeneration in an animal model of severe HS with impaired liver regeneration.

Methods

C57BL/6 mice were fed with a regular diet (normal mice) or with a high-fat diet (obese mice) to induce HS. After 30 weeks of diet exposure, 70% hepatectomy (Hpx) was performed and normal and obese mice were divided into two groups that received 5 × 10⁵ MSCs or vehicle via the tail vein immediately after Hpx.

Results

We confirmed a significant inhibition of hepatic regeneration when liver steatosis was present, while the hepatic regenerative response was promoted by infusion of MSCs. Specifically, MSC administration improved the hepatocyte proliferative response, PCNA-labeling index, DNA synthesis, liver function, and also reduced the number of apoptotic hepatocytes.

These effects may be associated to the paracrine secretion of trophic factors by MSCs and the hepatic upregulation of key cytokines and growth factors relevant for cell proliferation, which ultimately improves the survival rate of the mice.

Conclusions

MSCs represent a promising therapeutic strategy to improve liver regeneration in patients with HS as well as for increasing the number of donor organs available for transplantation.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-016-0469-y) contains supplementary material, which is available to authorized users.

Facile mechanical shaking method is an improved isolation approach for islet preparation and transplantation

Successful islet isolation is crucial for islet transplantation and cell treatment for type 1 diabetes. Current isolation methods are able to obtain 500-1,000 islets per rat, which results in a waste of ≥50% of total islets. In the present study, a facile mechanical shaking method for improving islet yield (up to 1,500 per rat) was developed and summarized, which was demonstrated to be more effective than the existing well-established stationary method. The present results showed that isolated islets have a maximum yield of 1,326±152 when shaking for 15 min for the fully-cannulated pancreas. For both fully-cannulated and half-cannulated pancreas in the presence of rat DNAse inhibitor, the optimal shaking time was amended to 20 min with a further increased yield of 1,344±134 and 1,286±124 islets, respectively. Furthermore, the majority of the isolated islets were morphologically intact with a well-defined surface and almost no central necrotic zone, which suggested that the condition of islets obtained via the mechanical shaking method was consistent with the stationary method. Islet size distribution was also calculated and it was demonstrated that islets from the stationary method exhibited the same size distribution as the non-cannulated group, which had more larger islets than the fully-cannulated and half-cannulated groups isolated via the shaking method. In addition, the results of glucose challenge showed that the refraction index of each group was >2.5, which indicated the well-preserved function of isolated islets. Furthermore, the transplanted islets exhibited a therapeutic effect after 1 day of transplantation; however, they failed to control blood glucose levels after ~7 days of transplantation. In conclusion, these results demonstrated that the facile mechanical shaking method may markedly improve the yield of rat islet isolation, and in vitro and in vivo investigation demonstrated the well-preserved function of isolated islets in the control of blood glucose. Therefore, the facile mechanical shaking method may be an alternative improved procedure to obtain higher islet yield for islet preparation and transplantation in the treatment of type 1 diabetes.

Evaluation of Immunomodulatory Effects of Mesenchymal Stem Cells Soluble Factors on miR-155 and miR-23b Expression in Mice Dendritic Cells

Mesenchymal stem cells (MSCs) can modulate dendritic cells (DCs) activation and induce tolerogenic characteristics in DCs. All mechanisms involved in MSCs-induced tolerogenic DCs are not fully understood. MicroRNAs (miRs) play important role in maturation and function of DCs. In this study, we investigated the effects of MSCs culture supernatant (C.S.) on expression of miR-155 and miR-23b in mice DCs. BALB/c mice spleens were used for DCs isolation. MSCs were isolated from the mice bone marrow and cultured in DMEM media. When MSCs expanded to sixth passage, C.S. was collected after 12, 24 and 48 h. Quantitative polymerase chain reaction (QPCR) was used to determine the expression of miR-155 and miR-23b in DCs treated with C.S. after 6 and 12 h. Secretion of IL-23 and TGF- β were detected in DCs treated with C.S. by ELISA after 24 h. miR-23b expression was significantly increased in DCs treated with 12 h C.S. for 12 h compared to negative controls. miR-155 expression did not change in DCs treated with C.S. after 6 and 12 h. miR-23b expression was significantly increased in DCs treated with 12 h C.S. for 12 h, compared to those treated with C.S. for 6 h. Similarly, miR-23b expression was increased in DCs treated with 24 h C.S. for 12 h when compared to those treated for 6 h. Production of TGF-β and IL-23 were not influenced by C.S. In conclusion, miR-23b is considered to be one of the mechanisms involved in tolerogenic DCs induction by C.S. in a time-dependent manner.

TSLP Expression and High Serum TSLP Level Indicate a Poor Prognosis in Gastric Cancer Patients

BACKGROUND

Thymic stromal lymphopoietin (TSLP) plays an important role in promoting tumor survival, by manipulating the immune response and angiogenesis. However, the clinical significance of TSLP in gastric cancer is unclear.

METHODS

Immunohistochemistry was used to investigate TSLP expression in non-cancerous gastric mucosa and gastric cancer tissue from patients with gastric cancer. Serum TSLP levels were measured using an enzyme-linked immunosorbent assay.

RESULTS

Tumors with TSLP expression were significantly larger than those without TSLP expression. TSLP expression was observed more frequently in advanced (T2/T3/T4) than in early (T1) gastric cancer and in stage 3/4 than in stage 1/2. Lymph node metastasis, liver metastasis, positive peritoneal lavage cytology, lymphatic invasion, and vascular invasion occurred significantly more often in TSLP-expressing than in non-expressing tumors. The prognosis of patients with TSLP-positive tumors was significantly worse than that of patients with TSLP-negative tumors. Patients with high serum TSLP concentrations also had a significantly worse prognosis than those with low concentrations. Multivariate analysis identified serum TSLP level as an independent prognostic indicator.

CONCLUSION

TSLP is closely related to the progression of gastric cancer and may predict survival in these patients.

Immunomodulatory properties of stem cells and bioactive molecules for tissue engineering

The immune system plays a crucial role in the success of tissue engineering strategies. Failure to consider the interactions between implantable scaffolds, usually containing cells and/or bioactive molecules, and the immune system can result in rejection of the implant and devastating clinical consequences. However, recent research into mesenchymal stem cells, which are commonly used in many tissue engineering applications, indicates that they may play a beneficial role modulating the immune system. Likewise, direct delivery of bioactive molecules involved in the inflammatory process can promote the success of tissue engineering constructs. In this article, we will review the various mechanisms in which modulation of the immune system is achieved through delivered bioactive molecules and cells and contextualize this information for future strategies in tissue engineering.

A local application of mesenchymal stem cells and cyclosporine A attenuates immune response by a switch in macrophage phenotype

The immunosuppressive effects of systemically administered mesenchymal stem cells (MSCs) and immunosuppressive drugs have been well documented. We analysed the mechanisms underlying the therapeutic effect of MSCs applied locally in combination with non-specific immunosuppression in a mouse model of allogeneic skin transplantation. The MSC-seeded and cyclosporine A (CsA)-loaded nanofibre scaffolds were applied topically to skin allografts in a mouse model and the local immune response was assessed and characterized. MSCs migrated from the scaffold into the side of injury and were detected in the graft region and draining lymph nodes (DLNs). The numbers of graft-infiltrating macrophages and the production of nitric oxide (NO) were significantly decreased in recipients treated with MSCs and CsA, and this reduction correlated with impaired production of IFNγ in the graft and DLNs. In contrast, the proportion of alternatively activated macrophages (F4/80⁺ CD206⁺ cells) and the production of IL-10 by intragraft macrophages were significantly upregulated. The ability of MSCs to alter the phenotype of macrophages from the M1 type into an M2 population was confirmed in a co-culture system in vitro. We suggest that the topical application of MSCs in combination with CsA induces a switch in macrophages to a population with an alternatively activated 'healing' phenotype and producing elevated levels of IL-10. These alterations in macrophage phenotype and function could represent one of the mechanisms of immunosuppressive action of MSCs applied in combination with CsA. Copyright © 2015 John Wiley & Sons, Ltd.

Mesenchymal stem cells and adaptive immune responses

Over the past decade, our understanding of the regulatory role of mesenchymal stem cells (MSCs) in adaptive immune responses through both preclinical and clinical studies has dramatically expanded, providing great promise for treating various inflammatory diseases. Most studies are focused on the modulatory effects of these cells on the properties of T cell-mediated immune responses, including activation, proliferation, survival, and subset differentiation. Interestingly, the immunosuppressive function of MSCs was found to be licensed by IFN-γ and TNF-α produced by T cells and that can be further amplified by cytokines such as IL-17. However, the immunosuppressive function of MSCs can be reversed in certain situation, such as suboptimal levels of inflammatory cytokines, or in the presence of immunosuppressive molecules. Here we review the influence of MSCs on adaptive immune system, especially their bidirectional interaction in tuning the immune microenvironment and subsequently repairing damaged tissue. Understanding MSC-mediated regulation of T cells is expected to provide fundamental information for guiding appropriate applications of MSCs in clinical settings.

Immunological effect induced by mesenchymal stem cells in a rat liver transplantation model

The aim of the present study was to investigate the immunological effect induced by bone marrow mesenchymal stem cells (MSCs) in rats that had undergone an orthotopic liver transplantation (OLT). MSCs were isolated and cultured from the bone marrow tissue of Lewis rats. In total, 42 rat OLT models were established and equally distributed into three groups. Group A received an OLT only, group B were also intramuscularly injected with tacrolimus (FK506), while group C were not only administered FK506, but also received MSCs. On day 7 post-surgery, the blood levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and total bilirubin (TBIL) were measured. In addition, pathological changes were observed in the liver, levels of immune cytokines, including transforming growth factor (TGF)-α₁, interleukin (IL)-10 and IL-12, were determined using immunohistochemistry, MSC homing was assessed and the survival times of the patients were recorded. Liver function, as assessed by the levels of ALT, AST and TBIL, was shown to improve in group C when compared with groups B and A (both P<0.01). In addition, survival analysis revealed that the survival times in groups B (median, 44 days) and C (median, 63 days) were significantly longer compared with group A (median, 11 days; both P<0.01). The survival rate of group C was also higher compared with group B (P<0.01). Pathological examination demonstrated strong acute rejection in group A, a mild acute rejection in group B and the mildest reaction in group C. In addition, immunohistochemistry revealed that TGF-α₁ and IL-10 expression was stronger in groups C and B, with group C exhibiting more significant expression than group B. By contrast, expression levels of IL-12 in groups A, B and C were positive, weak-positive and negative, respectively. Therefore, postoperative immunosuppression induced by MSCs is important for the alleviation of immune rejection from recipient-to-graft, and may induce immune tolerance in rat OLT models.

iPSC-MSCs Combined with Low-Dose Rapamycin Induced Islet Allograft Tolerance Through Suppressing Th1 and Enhancing Regulatory T-Cell Differentiation

Mesenchymal stem cell (MSC) differentiation is dramatically reduced after long-term in vitro culture, which limits their application. MSCs derived from induced pluripotent stem cells (iPSCs-MSCs) represent a novel source of MSCs. In this study, we investigated the therapeutic effect of iPSC-MSCs on diabetic mice. Streptozocin-induced diabetic mice transplanted with 400 islets alone or with 1×10(6) iPSC-MSCs were examined following rapamycin injection (0.1 mg/kg/day, i.p., from days 0 to 9) after transplantation. Our results showed that iPSC-MSCs combined with rapamycin significantly prolonged islet allograft survival in the diabetic mice; 50% of recipients exhibited long-term survival (>100 days). Histopathological analysis revealed that iPSC-MSCs combined with rapamycin preserved the graft effectively, inhibited inflammatory cell infiltration, and resulted in substantial release of insulin. Flow cytometry results showed that the proportion of CD4(+) and CD8(+) T cells was significantly reduced, and the number of T regulatory cells increased in the spleen and lymph nodes in the iPSC-MSCs combined with the rapamycin group compared with the rapamycin-alone group. Production of the Th1 proinflammatory cytokines interleukin-2 (IL-2) and interferon-γ was reduced, and secretion of the anti-inflammatory cytokines IL-10 and transforming growth factor-β was enhanced compared with the rapamycin group, as determined using enzyme-linked immunosorbent assays. Transwell separation significantly weakened the immunosuppressive effects of iPSC-MSCs on the proliferation of Con A-treated splenic T cells, which indicated that the combined treatment exerted immunosuppressive effects through cell-cell contact and regulation of cytokine production. Taken together, these findings highlight the potential application of iPSC-MSCs in islet transplantation.

Mesenchymal stem cells in the treatment of type 1 diabetes mellitus

Diabetes mellitus type 1 is a form of diabetes mellitus that results from the autoimmune destruction of insulin-producing beta cells in the pancreas. The current gold standard therapy for pancreas transplantation has limitations because of the long list of waiting patients and the limited supply of donor pancreas. Mesenchymal stem cells (MSCs), a relatively new potential therapy in various fields, have already made their mark in the young field of regenerative medicine. Recent studies have shown that the implantation of MSCs decreases glucose levels through paracrine influences rather than through direct transdifferentiation into insulin-producing cells. Therefore, these cells may use pro-angiogenic and immunomodulatory effects to control diabetes following the cotransplantation with pancreatic islets. In this review, we present and discuss new approaches of using MSCs in the treatment of diabetes mellitus type 1.

Adipose-derived mesenchymal stem cell administration does not improve corneal graft survival outcome

The effect of local and systemic injections of mesenchymal stem cells derived from adipose tissue (AD-MSC) into rabbit models of corneal allograft rejection with either normal-risk or high-risk vascularized corneal beds was investigated. The models we present in this study are more similar to human corneal transplants than previously reported murine models. Our aim was to prevent transplant rejection and increase the length of graft survival. In the normal-risk transplant model, in contrast to our expectations, the injection of AD-MSC into the graft junction during surgery resulted in the induction of increased signs of inflammation such as corneal edema with increased thickness, and a higher level of infiltration of leukocytes. This process led to a lower survival of the graft compared with the sham-treated corneal transplants. In the high-risk transplant model, in which immune ocular privilege was undermined by the induction of neovascularization prior to graft surgery, we found the use of systemic rabbit AD-MSCs prior to surgery, during surgery, and at various time points after surgery resulted in a shorter survival of the graft compared with the non-treated corneal grafts. Based on our results, local or systemic treatment with AD-MSCs to prevent corneal rejection in rabbit corneal models at normal or high risk of rejection does not increase survival but rather can increase inflammation and neovascularization and break the innate ocular immune privilege. This result can be partially explained by the immunomarkers, lack of immunosuppressive ability and immunophenotypical secretion molecules characterization of AD-MSC used in this study. Parameters including the risk of rejection, the inflammatory/vascularization environment, the cell source, the time of injection, the immunosuppression, the number of cells, and the mode of delivery must be established before translating the possible benefits of the use of MSCs in corneal transplants to clinical practice.

Multipotent mesenchymal stromal cells synergize with costimulation blockade in the inhibition of immune responses and the induction of Foxp3+ regulatory T cells

Multipotent mesenchymal stromal cell (MSC) therapy and costimulation blockade are two immunomodulatory strategies being developed concomitantly for the treatment of immunological diseases. Both of these strategies have the capacity to inhibit immune responses and induce regulatory T cells; however, their ability to synergize remains largely unexplored. In order to study this, MSCs from C57BL/6 (H2b) mice were infused together with fully major histocompatibility complex-mismatched Balb/c (H2d) allogeneic islets into the portal vein of diabetic C57BL/6 (H2b) mice, which were subsequently treated with costimulation blockade for the first 10 days after transplantation. Mice receiving both recipient-type MSCs, CTLA4Ig, and anti-CD40L demonstrated indefinite graft acceptance, just as did most of the recipients receiving MSCs and CTLA4Ig. Recipients of MSCs only rejected their grafts, and fewer than one half of the recipients treated with costimulation blockade alone achieved permanent engraftment. The livers of the recipients treated with MSCs plus costimulation blockade contained large numbers of islets surrounded by Foxp3+ regulatory T cells. These recipients showed reduced antidonor IgG levels and a glucose tolerance similar to that of naïve nondiabetic mice. Intrahepatic lymphocytes and splenocytes from these recipients displayed reduced proliferation and interferon-γ production when re-exposed to donor antigen. MSCs in the presence of costimulation blockade prevented dendritic cell maturation, inhibited T cell proliferation, increased Foxp3+ regulatory T cell numbers, and increased indoleamine 2,3-dioxygenase activity. These results indicate that MSC infusion and costimulation blockade have complementary immune-modulating effects that can be used for a broad number of applications in transplantation, autoimmunity, and regenerative medicine.

Mesenchymal stromal cells to promote kidney transplantation tolerance

PURPOSE OF REVIEW

Cell therapy with mesenchymal stromal cells (MSC) has emerged as a promising tolerance-inducing strategy, as MSC are potent modifiers of immune cells within adaptive as well as innate arm of the immune system. Here, we review recent evidence on both the beneficial and deleterious effect of MSC in experimental models of solid organ transplantation as well as first clinical experiences of MSC therapy in kidney transplant recipients.

RECENT FINDINGS

MSC are able to reprogram macrophages toward an anti-inflammatory phenotype capable to regulate antigraft immune response. This interaction is mediated mainly by TNF-α-induced-protein-6. Conversely, MSC also take on a proinflammatory phenotype and actually could worsen graft outcome. MSC in clinical transplantation is in its infancy and nobody so far has attempted to or provided evidence that this cell-based therapy is capable to promote operational tolerance. There are, however, supporting data of the ex-vivo immunoregulatory activity of MSC in treated patients.

SUMMARY

MSC have a great potential as a tolerance-promoting cell therapy. Extensive investigations are still needed to dissect the mechanism(s) of action of MSC, particularly in the setting of a proinflammatory environment, and to establish specific assays for monitoring MSC-treated patients to define the protolerogenic potential of MSC-based therapy in kidney transplantation.

Mitigation of Lethal Radiation Syndrome in Mice by Intramuscular Injection of 3D Cultured Adherent Human Placental Stromal Cells

Exposure to high lethal dose of ionizing radiation results in acute radiation syndrome with deleterious systemic effects to different organs. A primary target is the highly sensitive bone marrow and the hematopoietic system. In the current study C3H/HeN mice were total body irradiated by 7.7 Gy. Twenty four hrs and 5 days after irradiation 2×10⁶ cells from different preparations of human derived 3D expanded adherent placental stromal cells (PLX) were injected intramuscularly. Treatment with batches consisting of pure maternal cell preparations (PLX-Mat) increased the survival of the irradiated mice from ∼27% to 68% (P<0.001), while cell preparations with a mixture of maternal and fetal derived cells (PLX-RAD) increased the survival to ∼98% (P<0.0001). The dose modifying factor of this treatment for both 50% and 37% survival (DMF₅₀ and DMF₃₇) was∼1.23. Initiation of the more effective treatment with PLX-RAD injection could be delayed for up to 48 hrs after irradiation with similar effect. A delayed treatment by 72 hrs had lower, but still significantly effect (p<0.05). A faster recovery of the BM and improved reconstitution of all blood cell lineages in the PLX-RAD treated mice during the follow-up explains the increased survival of the cells treated irradiated mice. The number of CD45+/SCA1+ hematopoietic progenitor cells within the fast recovering population of nucleated BM cells in the irradiated mice was also elevated in the PLX-RAD treated mice. Our study suggests that IM treatment with PLX-RAD cells may serve as a highly effective “off the shelf” therapy to treat BM failure following total body exposure to high doses of radiation. The results suggest that similar treatments may be beneficial also for clinical conditions associated with severe BM aplasia and pancytopenia.

Intra-osseous injection of donor mesenchymal stem cell (MSC) into the bone marrow in living donor kidney transplantation; a pilot study

Background

Mesenchymal stem cells (MSCs) are multi-potent non-hematopoietic progenitor cells possessing an immune-regulatory function, with suppression of proliferation of activated lymphocytes. In this study, adult living donor kidney transplantation (LDKT) recipients were given MSCs derived from the donor bone marrow to evaluate the safety and the feasibility of immunological changes related to the intra-osseous injection of MSC into the bone marrow.

Methods

MSCs were derived from negative HLA cross-match donors. Donor bone marrow was harvested 5 weeks prior to KT. At the time of transplantation, 1 x 10⁶ cell/kg of donor MSC was directly injected into the bone marrow of the recipient’s right iliac bone. Patients’ clinical outcomes, presence of mixed chimerism by short tandem repeat polymerase chain reaction, analysis of plasma FoxP3 mRNA and cytokine level, and mixed lymphocyte reaction (MLR) were performed.

Results

Seven patients enrolled in this study and received donor MSC injections simultaneously with LDKT. The median age of recipients was 36 years (32 ~ 48). The number of HLA mismatches was 3 or less in 5 and more than 3 in 2. No local complications or adverse events such as hypersensitivity occurred during or after the injection of donor MSC. There was no graft failure, but the biopsy-proven acute rejections were observed in 3 recipients during the follow-up period controlled well with steroid pulse therapy (SPT). The last serum creatinine was a median of 1.23 mg/dL (0.83 ~ 2.07). Mixed chimerism was not detected in the peripheral blood of the recipients at 1 and 8 week of post-transplantation. Donor-specific lymphocyte or T cell proliferation and Treg priming responses were observed in some patients. Plasma level of IL-10, a known mediator of MSC-induced immune suppression, increased in the patients with Treg induction.

Conclusion

Donor MSC injection into the iliac bone at the time of KT was feasible and safe. A possible correlation was observed between the induction of inhibitory immune responses and the clinical outcome in the MSC-kidney transplanted patients. Further research will be performed to evaluate the efficacy of MSC injection for the induction of mixed chimerism and subsequent immune tolerance in KT.

Mesenchymal stromal cells to promote solid organ transplantation tolerance

PURPOSE OF REVIEW

Mesenchymal stromal cells (MSCs) possess unique immunomodulatory features. MSCs dampen effector T-cell response while promoting the emergence of regulatory T cells. By skewing this balance, MSC could represent the ideal strategy for tolerance induction in organ transplantation. Here we review recent evidence on the efficacy of MSC-based therapy in experimental models of solid organ transplantation as well as the early clinical experiences in kidney transplantation.

RECENT FINDINGS

MSC infusion in experimental models of solid organ transplantation resulted in a Treg-mediated tolerance. MSC also synergized with low-dose or transient pharmacological immunosuppression in inducing long-term graft survival indicating that these cells could allow safe minimization of maintenance drug therapy. Early results from clinical studies in kidney transplant recipients reported encouraging results on the immunoregulatory effect of MSC, although posttransplant MSC infusion could associate with acute graft dysfunction (engraftment syndrome).

SUMMARY

Immunoregulatory functions of MSC are not fixed but rather the result of microenvironment they encounter in vivo. Further studies are needed to establish how and wherein these cells have to be administered and how they may function to safely modulate host immune response in vivo in clinical transplant setting.

Novel mechanism of inhibition of dendritic cells maturation by mesenchymal stem cells via interleukin-10 and the JAK1/STAT3 signaling pathway

Mesenchymal stem cells (MSCs) can suppress dendritic cells (DCs) maturation and function, mediated by soluble factors, such as indoleamine 2,3-dioxygenase (IDO), prostaglandin E(2) (PGE(2)), and nitric oxide (NO). Interleukin-10 (IL-10) is a common immunosuppressive cytokine, and the downstream signaling of the JAK-STAT pathway has been shown to be involved with DCs differentiation and maturation in the context of cancer. Whether IL-10 and/or the JAK-STAT pathway play a role in the inhibitory effect of MSCs on DCs maturation remains controversial. In our study, we cultured MSCs and DCs derived from rat bone marrow under different culturing conditions. Using Transwell plates, we detected by ELISA that the level of IL-10 significantly increased in the supernatants of MSC-DC co-cultures at 48 hours. The cell immunofluorescence assay suggested that the MSCs secreted more IL-10 than the DCs in the co-cultures. Adding exogenous IL-10 to the DCs monoculture or MSC-DC co-cultures stimulated IL-10 and led to a decrease in IL-12, and lower expression of the DCs surface markers CD80, CD86, OX62, MHC-II and CD11b/c. Supplementing the culture with an IL-10 neutralizing antibody (IL-10NA) showed precisely the opposite effect of adding IL-10. Moreover, we demonstrated that the JAK-STAT signaling pathway is involved in inhibiting DCs maturation. Both JAK1 and STAT3 expression and IL-10 secretion decreased markedly after adding a JAK inhibitor (AG490) to the co-culture plate. We propose that there is an IL-10 positive feedback loop, which may explain our observations of elevated IL-10 and enhanced JAK1 and STAT3 expression. Overall, we demonstrated that MSCs inhibit the maturation of DCs through the stimulation of IL-10 secretion, and by activating the JAK1 and STAT3 signaling pathway.

Mesenchymal stromal cells and regulatory T cells: the Yin and Yang of peripheral tolerance?

In recent years, mesenchymal stromal cells (MSCs) and regulatory T cells (Tregs) have both garnered significant interest from immunologists worldwide, not least because of the potential application of both cell types in the treatment of many chronic inflammatory and autoimmune diseases. Although both MSCs and Tregs can be considered immunosuppressive in their own right, the induction of Tregs by activated MSCs is now a well-publicised phenomenon; however, only recently have the mechanisms involved in this induction started to become clear. Indeed, it is becoming increasingly apparent that there exists a complex interplay between the two lineages leading to this potent inhibition of the host immune response. Cell contact, soluble mediators-including prostaglandin E(2) and transforming growth factor β-and indirect induction via manipulation of other antigen-presenting cells all appear to have vital roles in the interactions between MSCs and Tregs. Much still remains to be discovered before we have a full understanding of this important aspect of the immune response, but there have already been a multitude of clinical trials suggesting that MSC/Treg therapies could offer significant benefits in the treatment of both autoimmune disease and graft versus host disease. Although these therapies are still in their infancy, the synergy between MSCs and Tregs will undoubtedly yield future breakthroughs in the treatment of many debilitating conditions and usher in a new wave of targeted, cell-based therapeutics.

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.

Stem cells as a tool to improve outcomes of islet transplantation

The publication of the promising results of the Edmonton protocol in 2000 generated optimism for islet transplantation as a potential cure for Type 1 Diabetes Mellitus. Unfortunately, follow-up data revealed that less than 10% of patients achieved long-term insulin independence. More recent data from other large trials like the Collaborative Islet Transplant Registry show incremental improvement with 44% of islet transplant recipients maintaining insulin independence at three years of follow-up. Multiple underlying issues have been identified that contribute to islet graft failure, and newer research has attempted to address these problems. Stem cells have been utilized not only as a functional replacement for β cells, but also as companion or supportive cells to address a variety of different obstacles that prevent ideal graft viability and function. In this paper, we outline the manners in which stem cells have been applied to address barriers to the achievement of long-term insulin independence following islet transplantation.

Secreted factors of human liver-derived mesenchymal stem cells promote liver regeneration early after partial hepatectomy

Rapid liver regeneration is required after living-donor liver transplantation and oncologic liver resections to warrant sufficient liver function and prevent small-for-size syndrome. Recent evidence highlights the therapeutic potential of mesenchymal stem cells (MSC) for treatment of toxic liver injury, but whether MSC and their secreted factors stimulate liver regeneration after surgical injury remains unknown. Therefore, the aim of this study is to investigate the effect of human liver-derived MSC-secreted factors in an experimental liver resection model. C57BL/6 mice were subjected to a 70% partial hepatectomy and treated with either concentrated MSC-conditioned culture medium (MSC-CM) or vehicle control. Animals were analyzed for liver and body weight, hepatocyte proliferation, and hepatic gene expression. Effects of MSC-CM on gene expression in a human hepatocyte-like cell line (Huh7 cells) were analyzed using genome-wide gene expression arrays. Liver regeneration was significantly stimulated by MSC-CM as shown by an increase in liver to body weight ratio and hepatocyte proliferation. MSC-CM upregulated hepatic gene expression of cytokines and growth factors relevant for cell proliferation, angiogenesis, and anti-inflammatory responses. In vitro, treatment of Huh7 cells with MSC-CM significantly altered expression levels of ~3,000 genes. Functional analysis revealed strong effects on networks associated with protein synthesis, cell survival, and cell proliferation. This study shows that treatment with MSC-derived factors can promote hepatocyte proliferation and regenerative responses in the early phase after surgical resection. MSC-CM may represent a feasible new strategy to promote liver regeneration in patients undergoing extensive liver resection or after transplantation of small liver grafts.

Immunomodulatory effects of bone marrow-derived mesenchymal stem cells in a swine hemi-facial allotransplantation model

BACKGROUND

In this study, we investigated whether the infusion of bone marrow-derived mesenchymal stem cells (MSCs), combined with transient immunosuppressant treatment, could suppress allograft rejection and modulate T-cell regulation in a swine orthotopic hemi-facial composite tissue allotransplantation (CTA) model.

METHODOLOGY/PRINCIPAL FINDINGS

Outbred miniature swine underwent hemi-facial allotransplantation (day 0). Group-I (n = 5) consisted of untreated control animals. Group-II (n = 3) animals received MSCs alone (given on days -1, +1, +3, +7, +14, and +21). Group-III (n = 3) animals received CsA (days 0 to +28). Group-IV (n = 5) animals received CsA (days 0 to +28) and MSCs (days -1, +1, +3, +7, +14, and +21). The transplanted face tissue was observed daily for signs of rejection. Biopsies of donor tissues and recipient blood sample were obtained at specified predetermined times (per 2 weeks post-transplant) or at the time of clinically evident rejection. Our results indicated that the MSC-CsA group had significantly prolonged allograft survival compared to the other groups (P<0.001). Histological examination of the MSC-CsA group displayed the lowest degree of rejection in alloskin and lymphoid gland tissues. TNF-α expression in circulating blood revealed significant suppression in the MSC and MSC-CsA treatment groups, as compared to that in controls. IHC staining showed CD45 and IL-6 expression were significantly decreased in MSC-CsA treatment groups compared to controls. The number of CD4+/CD25+ regulatory T-cells and IL-10 expressions in the circulating blood significantly increased in the MSC-CsA group compared to the other groups. IHC staining of alloskin tissue biopsies revealed a significant increase in the numbers of foxp3(+)T-cells and TGF-β1 positive cells in the MSC-CsA group compared to the other groups.

CONCLUSIONS

These results demonstrate that MSCs significantly prolong hemifacial CTA survival. Our data indicate the MSCs did not only suppress inflammation and acute rejection of CTA, but also modulate T-cell regulation and related cytokines expression.

Current status of immunomodulatory and cellular therapies in preclinical and clinical islet transplantation

Clinical islet transplantation is a β-cell replacement strategy that represents a possible definitive intervention for patients with type 1 diabetes, offering substantial benefits in terms of lowering daily insulin requirements and reducing incidences of debilitating hypoglycemic episodes and unawareness. Despite impressive advances in this field, a limiting supply of islets, inadequate means for preventing islet rejection, and the deleterious diabetogenic and nephrotoxic side effects associated with chronic immunosuppressive therapy preclude its wide-spread applicability. Islet transplantation however allows a window of opportunity for attempting various therapeutic manipulations of islets prior to transplantation aimed at achieving superior transplant outcomes. In this paper, we will focus on the current status of various immunosuppressive and cellular therapies that promote graft function and survival in preclinical and clinical islet transplantation with special emphasis on the tolerance-inducing capacity of regulatory T cells as well as the β-cells regenerative capacity of stem cells.

Genetically modified mesenchymal stem cells for improved islet transplantation

The use of adult stem cells for therapeutic purposes has met with great success in recent years. Among several types of adult stem cells, mesenchymal stem cells (MSCs) derived from bone marrow (BM) and other sources have gained popularity for basic research and clinical applications because of their therapeutic potential in treating a variety of diseases. Because of their tissue regeneration potential and immune modulation effect, MSCs were recently used as cell-based therapy to promote revascularization, increase pancreatic β-cell proliferation, and avoid allograft rejection in islet transplantation. Taking advantage of the recent progress in gene therapy, genetically modified MSCs can further enhance and expand the therapeutic benefit of primary MSCs while retaining their stem-cell-like properties. This review aims to gain a thorough understanding of the current obstacles to successful islet transplantation and discusses the potential role of primary MSCs before or after genetic modification in islet transplantation.