Localization of mesenchymal stromal cells dictates their immune or proinflammatory effects in kidney transplantation

Stem/Stromal Cells for Treatment of Kidney Injuries With Focus on Preclinical Models

Within the last years, the use of stem cells (embryonic, induced pluripotent stem cells, or hematopoietic stem cells), Progenitor cells (e.g., endothelial progenitor cells), and most intensely mesenchymal stromal cells (MSC) has emerged as a promising cell-based therapy for several diseases including nephropathy. For patients with end-stage renal disease (ESRD), dialysis or finally organ transplantation are the only therapeutic modalities available. Since ESRD is associated with a high healthcare expenditure, MSC therapy represents an innovative approach. In a variety of preclinical and clinical studies, MSC have shown to exert renoprotective properties, mediated mainly by paracrine effects, immunomodulation, regulation of inflammation, secretion of several trophic factors, and possibly differentiation to renal precursors. However, studies are highly diverse; thus, knowledge is still limited regarding the exact mode of action, source of MSC in comparison to other stem cell types, administration route and dose, tracking of cells and documentation of therapeutic efficacy by new imaging techniques and tissue visualization. The aim of this review is to provide a summary of published studies of stem cell therapy in acute and chronic kidney injury, diabetic nephropathy, polycystic kidney disease, and kidney transplantation. Preclinical studies with allogeneic or xenogeneic cell therapy were first addressed, followed by a summary of clinical trials carried out with autologous or allogeneic hMSC. Studies were analyzed with respect to source of cell type, mechanism of action etc.

Long-Term Clinical and Immunological Profile of Kidney Transplant Patients Given Mesenchymal Stromal Cell Immunotherapy

We report here the long-term clinical and immunological results of four living-donor kidney transplant patients given autologous bone marrow-derived mesenchymal stromal cells (MSCs) as part of a phase 1 study focused on the safety and feasibility of this cell therapy. According to study protocols implemented over time, based on initial early safety findings, the patients were given MSC at day 7 posttransplant (n = 2) or at day −1 pretransplant (n = 2) and received induction therapy with basiliximab and low-dose rabbit anti-thymocyte globulin (RATG) or RATG alone, and were maintained on low-dose ciclosporin (CsA)/mycophenolate mofetil (MMF). All MSC-treated patients had stable graft function during the 5- to 7-year follow-up, without increased susceptibility to infections or neoplasm. In three MSC recipients, but not historical control patients, circulating memory CD8⁺ T cell percentages remained lower than basal, coupled with persistent reduction of ex vivo donor-specific cytotoxicity. Two patients showed a long-lasting increase in the regulatory T cell/memory CD8⁺ T cell ratio, paralleled by high circulating levels of naïve and transitional B cells. In one of these two patients, CsA was successfully discontinued, and currently the low-dose MMF monotherapy is on the tapering phase. The study shows that MSC therapy is safe in the long term and could promote a pro-tolerogenic environment in selected patients. Extensive immunomonitoring of MSC-treated kidney transplant recipients could help selection of patients for safe withdrawal of maintenance immunosuppressive drugs (NCT00752479 and NCT02012153).

The effects of local administration of mesenchymal stem cells on rat corneal allograft rejection

Background

Mesenchymal stem cells (MSCs) have been reported to promote long-term cellular and organ transplant acceptance due to their immunotherapeutic characteristics. Previous work from our lab using a rat allograft model has shown that systemic infusion of MSCs inhibited corneal allograft rejection and prolonged graft survival. Here, we further investigated the effects of local MSCs administration in the same animal model.

Methods

Donor-derived MSCs were isolated and cultured while corneal grafts obtained from Wistar rats were transplanted into Lewis rat hosts. Hosts were then randomly separated into four groups and treated with previously cultured MSCs at different times and doses. Graft survival was clinically assessed using slit-lamp biomicroscopy and the median survival time (MST) was calculated. Grafts were examined histologically using hematoxylin-eosin (H-E) staining and immunohistochemically using antibodies against CD4. A comprehensive graft analysis of IL-2, IL-4, IL-10, and IFN-γ expression was also conducted using both real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA).

Results

Postoperative MSCs injection prolonged graft survival time when compared with controls (MST 9.8 ± 1.2 days). Injection twice of MSCs (MST 12.6 ± 1.4 days) was more effective than a single injection (MST 10.8 ± 1.3 days). MSCs-treated groups also showed suppression of inflammatory cell as well as CD4 + T cell infiltration in the allograft region. IL-4 and IL-10 levels were significantly increased in grafts obtained from postoperative twice MSCs-treated rats when compared with controls. There were no significant differences in IL-2 or IFN-γ expression across groups.

Conclusions

Subconjunctival injection of MSCs in rats was effective in prolonging corneal allograft survival. This effect was mediated by inhibition of inflammatory and immune responses, indicating an anti-inflammatory shift in the balance of T helper (Th)1 to T helper(Th) 2.

Electronic supplementary material

The online version of this article (10.1186/s12886-018-0802-6) contains supplementary material, which is available to authorized users.

Allogeneic mesenchymal stem cells as induction therapy are safe and feasible in renal allografts: pilot results of a multicenter randomized controlled trial

BACKGROUND

Kidneys from deceased donors are being used to meet the growing need for grafts. However, delayed graft function (DGF) and acute rejection incidences are high, leading to adverse effects on graft outcomes. Optimal induction intervention should include both renal structure injury repair and immune response suppression. Mesenchymal stem cells (MSCs) with potent anti-inflammatory, regenerative, and immune-modulatory properties are considered a candidate to prevent DGF and acute rejection in renal transplantation. Thus, this prospective multicenter paired study aimed to assess the clinical value of allogeneic MSCs as induction therapy to prevent both DGF and acute rejection in deceased donor renal transplantation.

METHODS

Forty-two renal allograft recipients were recruited and divided into trial and control groups. The trial group (21 cases) received 2 × 10⁶/kg human umbilical-cord-derived MSCs (UC-MSCs) via the peripheral vein before renal transplantation, and 5 × 10⁶ cells via the renal artery during the surgical procedure. All recipients received standard induction therapy. Incidences of DGF and biopsy-proven acute rejection were recorded postoperatively and severe postoperative complications were assessed. Graft and recipient survivals were also evaluated.

RESULTS

Treatment with UC-MSCs achieved comparable graft and recipient survivals with non-MSC treatment (P = 0.97 and 0.15, respectively). No increase in postoperative complications, including DGF and acute rejection, were observed (incidence of DGF: 9.5% in the MSC group versus 33.3% in the non-MSC group, P = 0.13; Incidence of acute rejection: 14.3% versus 4.8%, P = 0.61). Equal postoperative estimated glomerular filtration rates were found between the two groups (P = 0.88). All patients tolerated the MSCs infusion without adverse clinical effects. Additionally, a multiprobe fluorescence in situ hybridization assay revealed that UC-MSCs administered via the renal artery were absent from the recipient's biopsy sample.

CONCLUSIONS

Umbilical-cord-derived MSCs can be used as clinically feasible and safe induction therapy. Adequate timing and frequency of UC-MSCs administration may have a significant effect on graft and recipient outcomes. Trial registration NCT02490020 . Registered on June 29 2015.

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.

Clinical Translation of Mesenchymal Stromal Cell Therapies in Nephrology

Mesenchymal stromal cells have emerged as potential candidates for cell-based therapies to modulate the immune response in organ transplantation and repair tissues after acute or chronic injury. Preclinical studies have shown convincingly in rodent models that mesenchymal stromal cells can prolong solid organ graft survival and that they can induce immune tolerance, accelerate recovery from AKI, and promote functional improvement in chronic nephropathies. Multiple complex properties of the cells, including immunomodulatory, anti-inflammatory, and proregenerative effects, seem to contribute. The promising preclinical studies have encouraged investigators to explore the safety, tolerability, and efficacy of mesenchymal stromal cell-based therapy in pilot clinical trials, including those for bone marrow and solid organ transplantation, autoimmune diseases, and tissue and organ repair. Here, we review the available data on culture-expanded mesenchymal stromal cells tested in renal transplantation, AKI, and CKD. We also briefly discuss the relevant issues that must be addressed to ensure rigorous assessment of the safety and efficacy of mesenchymal stromal cell therapies to allow the translation of this research into the practice of clinical nephrology.

Allogeneic mesenchymal stem cell as induction therapy to prevent both delayed graft function and acute rejection in deceased donor renal transplantation: study protocol for a randomized controlled trial

Background

Using kidneys from deceased donors is an available strategy to meet the growing need of grafts. However, higher incidences of delayed graft function (DGF) and acute rejection exert adverse effects on graft outcomes. Since ischemia-reperfusion injury (IRI) and ongoing process of immune response to grafts are the major causes of DGF and acute rejection, the optimal induction intervention should possess capacities of both repairing renal structure injury and suppressing immune response simultaneously. Mesenchymal stem cells (MSCs) with potent anti-inflammatory, regenerative and immune-modulatory properties are considered as a candidate to prevent both DGF and acute rejection in renal transplantation. Previous studies just focused on the safety of autologous MSCs on living-related donor renal transplants, and lack of concomitant controls and the sufficient sample size and source of MSCs. Here, we propose a prospective multicenter controlled study to assess the clinical value of allogeneic MSCs in preventing both DGF and acute rejection simultaneously as induction therapy in deceased-donor renal transplantation.

Methods/design

Renal allograft recipients (n = 100) will be recruited and divided into trial and control groups, and 50 patients in the trial group will be administered with a dose of 2 × 10⁶ per kilogram human umbilical-cord-derived MSCs (UC-MSCs) via peripheral vein injection preoperatively, and a dose of 5 × 10⁶ cells via renal arterial injection during surgery, with standard induction therapy. Incidences of postoperative DGF and biopsy-proved acute rejection (BPAR) will be recorded and analyzed. Additionally, other clinical parameters such as baseline demographics, graft and recipient survival and other severe postoperative complications, including complicated urinary tract infection, severe pneumonia, and severe bleeding, will be also assessed.

Discussion

This study will clarify the clinical value of UC-MSCs in preventing DGF and acute rejection simultaneously in deceased-donor renal transplantation, and provide evidence as to whether allogeneic MSCs can be used as clinically feasible and safe induction therapy.

Trial registration

ClinicalTrials.gov, NCT02490020. Registered on 29 June 2015.

Electronic supplementary material

The online version of this article (doi:10.1186/s13063-017-2291-y) contains supplementary material, which is available to authorized users.

Mesenchymal stromal cells in clinical kidney transplantation: how tolerant can it be?

PURPOSE OF REVIEW

Progress in the improvement of short-term and long-term outcomes of kidney transplantation seems to have reached a plateau, partially due to consequences of very efficient, but nonspecific immunosuppressive drugs. In recent years, various forms of cell therapy, including the use of mesenchymal stromal cells, have been put forward as an alternative strategy for more defined therapy. It is thought that these therapies will not only allow controlled tapering of immunosuppressive medication, but might bring us also closer to the ambition of generating donor-specific immune regulation and tolerance.

RECENT FINDINGS

Different forms of alloimmunity, including direct, indirect and semi-direct alloantigen presentation have to be controlled before donor-specific immune regulation can be reached. Several mechanisms have been described how mesenchymal stromal cells can affect alloimmunity. Especially, the interaction with professional antigen presenting cells, like dendritic cells, is of critical importance.

SUMMARY

This review will discuss the current status of ongoing clinical trials with mesenchymal stromal cells in kidney transplantation and specifically concentrate on the possibilities and impossibilities of how these therapeutic strategies can contribute to control of the different forms of alloreactivity operation in organ transplantation.

Diagnostic Lessons from a Complex Case of Postintestinal Transplantation Enteropathy

Recent advances in the field of intestinal transplantation have been mitigated by the incidence of allograft rejection. In such events, early identification and appropriate timing of antirejection therapy are crucial in retaining graft function. We present the case of a patient who suffered severe postintestinal transplantation allograft enteropathy, primarily characterized by extensive mucosal ulcerations, and was refractory to all conventional therapy. This progressed as chronic rejection; however crucially this was not definitively diagnosed until allograft function had irreversibly diminished. We argue that the difficulties encountered in this case can be attributed to the inability of our current array of investigative studies and diagnostic guidelines to provide adequate clinical guidance. This case illustrates the importance of developing reliable and specific markers for guiding the diagnosis of rejection and the use of antirejection therapeutics in this rapidly evolving field of transplant surgery.

Administration of mesenchymal stromal cells before renal ischemia/reperfusion attenuates kidney injury and may modulate renal lipid metabolism in rats

Mesenchymal stromal cells (MSC) have been demonstrated to attenuate renal ischemia/reperfusion (I/R) damage in rodent models. The mechanisms of such nephro-protection remain largely unknown. Furthermore, the optimal timing of MSC administration has been poorly investigated. Here, we compare the impact of MSC injection 7 days before (MSCD - 7) versus 1 day after (MSCD + 1) renal I/R in rats. Control groups received equivalent volumes of saline at similar time-points (SD - 7 and SD + 1). Right nephrectomy was performed, and left renal ischemia lasted 45 min. After 48-hour reperfusion, we observed significantly improved renal function parameters, reduced apoptotic index and neutrophil/macrophage infiltration in kidney parenchyma, and lower expression of tubular damage markers and pro-inflammatory cytokines in MSCD - 7 in comparison to MSCD + 1 and saline control groups. Next, comparative high-throughput RNA sequencing of MSCD - 7 vs. SD - 7 non-ischemic right kidneys highlighted significant down-regulation of fatty acid biosynthesis and up-regulation of PPAR-α pathway. Such a preferential regulation towards lipid catabolism was associated with decreased levels of lipid peroxidation products, i.e. malondialdehyde and 4-hydroxy-2-nonenal, in MSCD - 7 versus SD - 7 ischemic kidneys. Our findings suggest that MSC pretreatment may exert protective effects against renal I/R by modulating lipid metabolism in rats.

Mesenchymal stem cells and their immunosuppressive role in transplantation tolerance

Since they were first described, mesenchymal stem cells (MSCs) have been shown to have important effector mechanisms and the potential for use in cell therapy. A great deal of research has been focused on unveiling how MSCs contribute to anti-inflammatory responses, including describing several cell populations involved and identifying soluble and other effector molecules. In this review, we discuss some of the contemporary evidence for use of MSCs in the field of immune tolerance, with a special emphasis on transplantation. Although considerable effort has been devoted to understanding the biological function of MSCs, additional resources are required to clarify the mechanisms of their induction of immune tolerance, which will undoubtedly lead to improved clinical outcomes for MSC-based therapies.

Immunodepletion and Hypoxia Preconditioning of Mouse Compact Bone Cells as a Novel Protocol to Isolate Highly Immunosuppressive Mesenchymal Stem Cells

Compact bones (CB) are major reservoirs of mouse mesenchymal stem cells (mMSC). Here, we established a protocol to isolate MSC from CB and tested their immunosuppressive potential. Collagenase type II digestion of BM-flushed CB from C57B/6 mice was performed to liberate mMSC precursors from bone surfaces to establish nondepleted mMSC. CB cells were also immunodepleted based on the expression of CD45 (leukocytes) and TER119 (erythroid cells) to eliminate hematopoietic cells. CD45^-TER119^- CB cells were subsequently used to generate depleted mMSC. CB nondepleted and depleted mMSC progenitors were cultured under hypoxic conditions to establish primary mMSC cultures. CB depleted mMSC compared to nondepleted mMSC showed greater cell numbers at subculturing and had increased functional ability to differentiate into adipocytes and osteoblasts. CB depleted mMSC had high purity and expressed key mMSC markers (>85% Sca-1, CD29, CD90) with no mature hematopoietic contaminating cells (<5% CD45, CD11b) when subcultured to passage 5 (P5). Nondepleted mMSC cultures, however, were less pure and heterogenous with <72% Sca-1⁺, CD29⁺, and CD90⁺ cells at early passages (P1 or P2), along with high percentages of contaminating CD11b⁺ (35.6%) and CD45⁺ (39.2%) cells that persisted in culture long term. Depleted and nondepleted mMSC nevertheless exhibited similar potency to suppress total (CD3⁺), CD4⁺ and CD8⁺ T cell proliferation, in a dendritic cell allostimulatory one-way mixed lymphocyte reaction. CB depleted mMSC, pretreated with proinflammatory cytokines IFN-γ, TNF-α, and IL-17A, showed superior suppression of CD8⁺ T cell, but not CD4⁺ T cell proliferation, relative to untreated-mMSC. In conclusion, CB depleted mMSC established under hypoxic conditions and treated with selective cytokines represent a novel source of potent immunosuppressive MSC. As these cells have enhanced immune modulatory function, they may represent a superior product for use in clinical allotransplantation.

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.

The Timing of Immunomodulation Induced by Mesenchymal Stromal Cells Determines the Outcome of the Graft in Experimental Renal Allotransplantation

The immunomodulatory characteristics of mesenchymal stromal cells (MSCs) may lead to multifaceted strategies in rejection of organ transplantation. This study was designed to investigate, first, the effect of the donor-type MSCs from Wistar rats on the immune system of immunocompetent Lewis rats and, second, the rejection responses in a renal transplantation model of Wistar to Lewis. In the first experimental model, MSCs from the bone marrow induced a systemic immune response in the immunocompetent Lewis rats, characterized by two different phases. In the initial phase (days 1-3 after MSCs infusion), the main findings were a decrease in the percentage of the main peripheral blood (PB) lymphocyte subpopulations [T cells, B cells, and natural killer (NK) cells], an increase in the FOXP3 MFI in Tregs, and an elevated concentration of circulating proinflammatory cytokines (IL-1β and TNF-α). In the late phase (days 4-6), the percentage of T cells, B cells, and NK cells returned to baseline levels; the concentration of circulating IL-1β and TNF-α decreased; and the level of anti-inflammatory cytokines (IL-10 and IL-4) increased with respect to the initial phase. In the allogeneic kidney transplantation model, rats were randomized into four groups: nontreated, cyclosporine oral administration, and two groups of rats treated with two different schedules of MSC infusion: 4 days (MSCs-4) and 7 days (MSCs-7) before kidney transplantation and in both a further infusion at the day of transplantation. Both MSC treatments decreased the percentage of T, B, and NK cells in PB. Creatinine levels, survival, and histological parameters were better in MSCs-7 than in MSCs-4. We can conclude that MSCs, by themselves, produce changes in the immune system; they do not need a pathological condition to produce immunomodulatory responses. In the renal allograft model, the optimal time schedule for MSC infusion before grafting was 7 days to prevent acute rejection.

Biodistribution and Immunogenicity of Allogeneic Mesenchymal Stem Cells in a Rat Model of Intraarticular Chondrocyte Xenotransplantation

Xenogeneic chondrocytes and allogeneic mesenchymal stem cells (MSC) are considered a potential source of cells for articular cartilage repair. We here assessed the immune response triggered by xenogeneic chondrocytes when injected intraarticularly, as well as the immunoregulatory effect of allogeneic bone marrow-derived MSC after systemic administration. To this end, a discordant xenotransplantation model was established by injecting three million porcine articular chondrocytes (PAC) into the femorotibial joint of Lewis rats and monitoring the immune response. First, the fate of MSC injected using various routes was monitored in an in vivo imaging system. The biodistribution revealed a dependency on the injection route with MSC injected intravenously (i.v.) succumbing early after 24 h and MSC injected intraperitoneally (i.p.) lasting locally for at least 5 days. Importantly, no migration of MSC to the joint was detected in rats previously injected with PAC. MSC were then administered either i.v. 1 week before PAC injection or i.p. 3 weeks after to assess their immunomodulatory function on humoral and adaptive immune parameters. Anti-PAC IgM and IgG responses were detected in all PAC-injected rats with a peak at week 2 postinjection and reactivity remaining above baseline levels by week 18. IgG2a and IgG2b were the predominant and long-lasting IgG subtypes. By contrast, no anti-MSC antibody response was detected in the cohort injected with MSC only, but infusion of MSC before PAC injection temporarily augmented the anti-PAC antibody response. Consistent with a cellular immune response to PAC in PAC-injected rats, cytokine/chemokine profiling in serum by antibody array revealed a distinct pattern relative to controls characterized by elevation of multiple markers at week 2, as well as increases in proliferation in draining lymph nodes. Notably, systemic administration of allogeneic MSC under the described conditions did not diminish the immune response. IL-2 measurements in cocultures of rat peripheral blood lymphocytes with PAC indicated that PAC injection induced some T-cell hyporesponsiveness that was not enhanced in the cohorts additionally receiving MSC. Thus, PAC injected intraarticularly in Lewis rats induced a cellular and humoral immune response that was not counteracted by the systemic administration of allogeneic MSC under the described conditions.

Immunomodulatory effects of OX40Ig gene-modified adipose tissue-derived mesenchymal stem cells on rat kidney transplantation

Recent studies have suggested that adipose tissue-derived mesenchymal stem cell (ADSC) therapy and OX40 costimulation blockade are two immunomodulatory strategies used to suppress the immune response to alloantigens. However, relatively little has been reported regarding the immunomodulatory potential of the abilityof these two strategies to synergize. Thus, in the present study, we aimed to investigate OX40-Ig fusion protein (OX40Ig) expression in ADSCs and to validate their more potent immunosuppressive activity in preventing renal allograft rejection. For this purpose, ADSCs from Lewis rats were transfected with the recombinant plasmid, pcDNA3.1(-)OX40Ig, by nucleofection. The ADSCs transduced with the plasmid (termed ADSCsOX40Ig) or untransduced ADSCs (termed ADSCsnative) were added to allostimulated mixed lymphocyte reaction (MLR) in vitro. In vivo, ADSCsOX40Ig, ADSCsnative, or PBS were administered to an allogeneic renal transplantation model, and the therapeutic effects, as well as the underlying mechanisms were examined. The results revealed that both the ADSCsnative and ADSCsOX40Ig significantly suppressed T cell proliferation and increased the percentage of CD4+CD25+ regulatory T cells in allogeneic MLR assays, with the ADSCsOX40Ig being more effective. Furthermore, the results from our in vivo experiments revealed that compared with the ADSCsnative or PBS group, the administration of autologous ADSCsOX40Ig markedly prolonged the mean survival time of renal grafts, reduced allograft rejection, and significantly downregulated the mRNA expression of intragraft interferon-γ (IFN-γ) , and upregulated the mRNA expression of interleukin (IL)‑10, transforming growth factor-β (TGF-β) and forkhead box protein 3 (Foxp3). The findings of our study indicate that the use of ADSCsOX40Ig is a promising strategy for preventing renal allograft rejection. This strategy provides the synergistic benefits of ADSC immune modulation and OX40-OX40L pathway blockade, and may therefore have therapeutic potential in clinical renal transplantation.

Immunomodulatory Role of Mesenchymal Stem Cell Therapy in Vascularized Composite Allotransplantation

This review aims to summarize contemporary evidence of the in vitro and in vivo immunomodulatory effects of mesenchymal stem cells (MSCs) in promoting vascularized composite allotransplant (VCA) tolerance. An extensive literature review was performed to identify pertinent articles of merit. Prospective preclinical trials in mammal subjects receiving VCA (or skin allograft) with administration of MSCs were reviewed. Prospective clinical trials with intravascular delivery of MSCs in human populations undergoing solid organ transplant were also identified and reviewed. Sixteen preclinical studies are included. Eleven studies compared MSC monotherapy to no therapy; of these, ten reported improved graft survival, which was statistically significantly prolonged in eight. Eight studies analyzed allograft survival with MSC therapy as an adjunct to proven immunosuppressive regimens. In these studies, daily immunosuppression was transiently delivered and then stopped. In all studies, treatment-free graft survival was statistically significantly prolonged in animals that received MSC therapy. MSCs have been safely administered clinically and their use in renal transplant clinical trials provides evidence that they improve allograft transplant tolerance in clinical practice. There is potential for MSC induction therapy to overcome many of the obstacles to widespread VCA in clinical practice. Preclinical studies are needed before MSC-induced VCA tolerance becomes a clinical reality.

Clinical-Grade Isolated Human Kidney Perivascular Stromal Cells as an Organotypic Cell Source for Kidney Regenerative Medicine

Mesenchymal stromal cells (MSCs) are immunomodulatory and tissue homeostatic cells that have shown beneficial effects in kidney diseases and transplantation. Perivascular stromal cells (PSCs) identified within several different organs share characteristics of bone marrow‐derived MSCs (BM‐MSCs). These PSCs may also possess tissue‐specific properties and play a role in local tissue homeostasis. We hypothesized that human kidney‐derived PSCs (hkPSCs) would elicit improved kidney repair in comparison with BM‐MSCs. Here we introduce a novel, clinical‐grade isolation method of hkPSCs from cadaveric kidneys by enriching for the perivascular marker, NG2. hkPSCs show strong transcriptional similarities to BM‐MSCs but also show organotypic expression signatures, including the HoxD10 and HoxD11 nephrogenic transcription factors. Comparable to BM‐MSCs, hkPSCs showed immunosuppressive potential and, when cocultured with endothelial cells, vascular plexus formation was supported, which was specifically in the hkPSCs accompanied by an increased NG2 expression. hkPSCs did not undergo myofibroblast transformation after exposure to transforming growth factor‐β, further corroborating their potential regulatory role in tissue homeostasis. This was further supported by the observation that hkPSCs induced accelerated repair in a tubular epithelial wound scratch assay, which was mediated through hepatocyte growth factor release. In vivo, in a neonatal kidney injection model, hkPSCs reintegrated and survived in the interstitial compartment, whereas BM‐MSCs did not show this potential. Moreover, hkPSCs gave protection against the development of acute kidney injury in vivo in a model of rhabdomyolysis‐mediated nephrotoxicity. Overall, this suggests a superior therapeutic potential for the use of hkPSCs and their secretome in the treatment of kidney diseases. Stem Cells Translational Medicine2017;6:405–418

Tweaking Mesenchymal Stem/Progenitor Cell Immunomodulatory Properties with Viral Vectors Delivering Cytokines

Mesenchymal Stem Cells (MSCs) can be found in various body sites. Their main role is to differentiate into cartilage, bone, muscle, and fat cells to allow tissue maintenance and repair. During inflammation, MSCs exhibit important immunomodulatory properties that are not constitutive, but require activation, upon which they may exert immunosuppressive functions. MSCs are defined as "sensors of inflammation" since they modulate their ability of interfering with the immune system both in vitro and in vivo upon interaction with different factors. MSCs may influence immune responses through different mechanisms, such as direct cell-to-cell contact, release of soluble factors, and through the induction of anergy and apoptosis. Human MSCs are defined as plastic-adherent cells expressing specific surface molecules. Lack of MHC class II antigens makes them appealing as allogeneic tools for the therapy of both autoimmune diseases and cancer. MSC therapeutic potential could be highly enhanced by the expression of exogenous cytokines provided by transduction with viral vectors. In this review, we attempt to summarize the results of a great number of in vitro and in vivo studies aimed at improving the ability of MSCs as immunomodulators in the therapy of autoimmune, degenerative diseases and cancer. We will also compare results obtained with different vectors to deliver heterologous genes to these cells.

Human Mesenchymal Stem Cells Impact Th17 and Th1 Responses Through a Prostaglandin E2 and Myeloid-Dependent Mechanism

: Human mesenchymal stem cells (hMSCs) are being increasingly pursued as potential therapies for immune-mediated conditions, including multiple sclerosis. Although they can suppress human Th1 responses, they reportedly can reciprocally enhance human Th17 responses. Here, we investigated the mechanisms underlying the capacity of hMSCs to modulate human Th1 and Th17 responses. Human adult bone marrow-derived MSCs were isolated, and their purity and differentiation capacity were confirmed. Human venous peripheral blood mononuclear cells (PBMC) were activated, alone, together with hMSC, or in the presence of hMSC-derived supernatants (sups). Cytokine expression by CD4+ T-cell subsets (intracellular staining by fluorescence-activated cell sorting) and secreted cytokines (enzyme-linked immunosorbent assay) were then quantified. The contribution of prostaglandin E2 (PGE2) as well as of myeloid cells to the hMSC-mediated regulation of T-cell responses was investigated by selective depletion of PGE2 from the hMSC sups (anti-PGE2 beads) and by the selective removal of CD14+ cells from the PBMC (magnetic-activated cell sorting separation). Human MSC-secreted products could reciprocally induce interleukin-17 expression while decreasing interferon-γ expression by human CD4+ T cells, both in coculture and through soluble products. Pre-exposure of hMSCs to IL-1β accentuated their capacity to reciprocally regulate Th1 and Th17 responses. Human MSCs secreted high levels of PGE2, which correlated with their capacity to regulate the T-cell responses. Selective removal of PGE2 from the hMSC supernatants abrogated the impact of hMSC on the T cells. Selective removal of CD14+ cells from the PBMCs also limited the capacity of hMSC-secreted PGE2 to affect T-cell responses. Our discovery of a novel PGE2-dependent and myeloid cell-mediated mechanism by which human MSCs can reciprocally induce human Th17 while suppressing Th1 responses has implications for the use of, as well as monitoring of, MSCs as a potential therapeutic for patients with multiple sclerosis and other immune-mediated diseases.

SIGNIFICANCE

Although animal studies have generated a growing interest in the anti-inflammatory potential of mesenchymal stem cells (MSCs) for the treatment of autoimmune diseases, MSCs possess the capacity to both limit and promote immune responses. Yet relatively little is known about human-MSC modulation of human disease-implicated T-cell responses, or the mechanisms underlying such modulation. The current study reveals a novel prostaglandin E2-dependent and myeloid cell-mediated mechanism by which human MSCs can reciprocally regulate human Th17 and Th1 responses, with implications for the use of MSCs as a potential therapeutic for patients with multiple sclerosis and other immune-mediated diseases.

Transplant Tolerance Induction in Newborn Infants: Mechanisms, Advantages, and Potential Strategies

Although several tolerance induction protocols have been successfully implemented in adult renal transplantation, no tolerance induction approach has, as yet, been defined for solid organ transplantations in young infants. Pediatric transplant recipients have a pressing demand for the elaboration of tolerance induction regimens. Indeed, since they display a longer survival time, they are exposed to a higher level of risks linked to long-term immunosuppression (IS) and to chronic rejection. Interestingly, central tolerance induction may be of great interest in newborns, because of their immunological immaturity and the important role of the thymus at this early stage in life. The present review aims to clarify mechanisms and strategies of tolerance induction in these immunologically premature recipients. We first introduce the discovery and mechanisms of neonatal tolerance in murine experimental models and subsequently analyze tolerance induction in human newborn infants. Hematopoietic mixed chimerism in neonates is also discussed based on in utero hematopoietic stem cell (HSC) transplant studies. Then, we review the recent advances in tolerance induction approaches in adults, including the infusion of HSCs associated with less toxic conditioning regimens, regulatory T cells/facilitating cells/mesenchymal stem cells transplantation, costimulatory blockade, and thymus manipulation. Finally, IS withdrawal in pediatric solid organ transplant is discussed. In conclusion, the establishment of transplant tolerance induction in infants is promising and deserves further investigations. Future studies could focus on the selection of patients, on less toxic conditioning regimens, and on biomarkers for IS minimization or withdrawal.

Control of Cross Talk between Angiogenesis and Inflammation by Mesenchymal Stem Cells for the Treatment of Ocular Surface Diseases

Angiogenesis is beneficial in the treatment of ischemic heart disease and peripheral artery disease. However, it facilitates inflammatory cell filtration and inflammation cascade that disrupt the immune and angiogenesis privilege of the avascular cornea, resulting in ocular surface diseases and even vision loss. Although great progress has been achieved, healing of severe ocular surface injury and immunosuppression of corneal transplantation are the most difficult and challenging step in the treatment of ocular surface disorders. Mesenchymal stem cells (MSCs), derived from various adult tissues, are able to differentiate into different cell types such as endothelial cells and fat cells. Although it is still under debate whether MSCs could give rise to functional corneal cells, recent results from different study groups showed that MSCs could improve corneal disease recovery through suppression of inflammation and modulation of immune cells. Thus, MSCs could become a promising tool for ocular surface disorders. In this review, we discussed how angiogenesis and inflammation are orchestrated in the pathogenesis of ocular surface disease. We overviewed and updated the knowledge of MSCs and then summarized the therapeutic potential of MSCs via control of angiogenesis, inflammation, and immune response in the treatment of ocular surface disease.

Mesenchymal stromal cell-dependent reprogramming of Kupffer cells is mediated by TNF-α and PGE2 and is crucial for liver transplant tolerance

The role of mesenchymal stromal cells (MSCs) in the modulation of liver transplant tolerance has attracted significant interest. However, the interaction between MSCs and Kupffer cells (KCs) has received little attention, and the effect of this interaction on liver transplant tolerance remains unclear. KCs were cultured in the presence and absence of MSCs. After 24 h, cells were treated with lipopolysaccharide (LPS), after which the production of cytokines and the expression of surface antigens were measured for cell function identification. Moreover, the effects of the KCs and the prostaglandin E2 (PGE2) levels produced by the MSCs were determined using an experimental rat liver transplantation model. Blood and liver samples were collected at three time points after transplantation for further analysis. After LPS treatment, when compared with the KC single cultures, the expression of pro-inflammatory cytokines (IL-1β, IL-6, MHC-II, CD40, CD80, and CD86) in the coculture system was down-regulated, whereas the expression of anti-inflammatory cytokines (TGF-β, IL-4, PGE2, and IL-10) was markedly increased. These data indicate that MSCs can reprogram the phenotype of KCs. However, KCs treated with miR/TNF-α (tumor necrosis factor) plasmid prior to coculture to inhibit the production of TNF-α resulted in an inhibition of the reprogramming effect of MSCs. Moreover, overexpression of PGE2 in MSCs increased the effect of MSCs on KC reprogramming. After rat liver transplantation, allograft recipients that received MSCs showed better allograft tolerance when compared with rats in which KC function was inhibited. Furthermore, rats treated with MSCs overexpressing PGE2 demonstrated the best liver tolerance of all of the groups tested. MSCs reprogram the phenotype of KCs through TNF-α and PGE2, and this process is crucial for the immunomodulatory function of MSCs in liver transplantation.

Transplantation Tolerance Induction: Cell Therapies and Their Mechanisms

Cell-based therapies have been studied extensively in the context of transplantation tolerance induction. The most successful protocols have relied on transfusion of bone marrow prior to the transplantation of a renal allograft. However, it is not clear that stem cells found in bone marrow are required in order to render a transplant candidate immunologically tolerant. Accordingly, mesenchymal stem cells, regulatory myeloid cells, T regulatory cells, and other cell types are being tested as possible routes to tolerance induction, in the absence of donor-derived stem cells. Early data with each of these cell types have been encouraging. However, the induction regimen capable of achieving consistent tolerance, while avoiding unwanted sided effects, and which is scalable to the human patient, has yet to be identified. Here, we present the status of investigations of various tolerogenic cell types and the mechanistic rationale for their use in tolerance induction protocols.

Mesenchymal stem cell-based therapy in kidney transplantation

Kidney transplantation is the best treatment for end-stage renal disease, but its implementation is limited by organ shortage and immune rejection. Side effects of current immunosuppressive drugs, such as nephrotoxicity, opportunistic infection, and tumorigenic potential, influence long-term graft outcomes. In recent years, continued research and subsequent discoveries concerning the properties and potential utilization of mesenchymal stem cells (MSCs) have aroused considerable interest and expectations. Biological characteristics of MSCs, including multi-lineage differentiation, homing potential, paracrine effect and immunomodulation, have opened new horizons for applications in kidney transplantation. However, many studies have shown that the biological activity of MSCs depends on internal inflammatory conditions, and the safety and efficacy of the clinical application of MSCs remain controversial. This review summarizes the findings of a large number of studies and aims to provide an objective viewpoint based on a comprehensive analysis of the presently established benefits and obstacles of implementing MSC-based therapy in kidney transplantation, and to promote its clinical translation.

Inhibition of B-cell proliferation and antibody production by mesenchymal stromal cells is mediated by T cells

Bone marrow (BM)-derived mesenchymal stromal cells (MSCs), endowed with immunosuppressive and anti-inflammatory properties, represent a promising tool in immunoregulatory and regenerative cell therapy. Clarifying the interactions between MSCs and B-lymphocytes may be crucial for designing innovative MSC-based strategies in conditions in which B cells play a role, including systemic lupus erythematosus (SLE) and rejection of kidney transplantation. In this study, we show that, both in healthy subjects and in patients, in vitro B-cell proliferation, plasma-cell differentiation, and antibody production are inhibited by BM-derived MSCs when peripheral blood lymphocytes are stimulated with CpG, but not when sorted B cells are cultured with MSCs+CpG. Inhibition is restored in CpG+MSC cocultures when sorted T cells are added to sorted B cells, suggesting that this effect is mediated by T cells, with both CD4(+) and CD8(+) cells playing a role. Moreover, cell-cell contact between MSCs and T cells, but not between MSCs and B cells, is necessary to inhibit B-cell proliferation. Thus, the presence of functional T cells, as well as cell-cell contact between MSCs and T cells, are crucial for B-cell inhibition. This information can be relevant for implementing MSC-based therapeutic immune modulation in patients in whom T-cell function is impaired.

Foxp3-modified bone marrow mesenchymal stem cells promotes liver allograft tolerance through the generation of regulatory T cells in rats

Background

The transcription factor forkhead box P3 (Foxp3) is a master regulatory gene necessary for the development and function of CD4⁺CD25⁺ regulatory T cells (Tregs). Mesenchymal stem cells (MSC) have recently emerged as promising candidates for cell-based immunosuppression/tolerance induction protocols. Thus, we hypothesized that MSC-based Foxp3 gene therapy would improve immunosuppressive capacity of MSC and induce donor-specific allograft tolerance in rat’s liver allograft model.

Methods

The present study utilized a lentivirus vector to overexpress the therapeutic gene Foxp3 on MSC. In vivo, Injections of 2 × 10⁶ MSC, FUGW-MSC or Foxp3-MSC into the portal vein were carried out immediately after liver transplantation.

Results

Successful gene transfer of Foxp3 in MSC was achieved by lentivirus carrying Foxp3 and Foxp3-MSC engraftment in liver allograft was confirmed by fluorescence microscopy. Foxp3-MSC treatment significantly inhibited the proliferation of allogeneic ACI CD4⁺ T cells to splenocytes (SC) from the same donor strain or third-party BN rat compared with MSC. Foxp3-MSC suppressive effect on the proliferation of CD4⁺ T cells is contact dependent and associated with Programmed death ligand 1(PD-L1) upregulation in MSC. Co-culture of CD4⁺ T cells with Foxp3-MSC results in a shift towards a Tregs phenotype. More importantly, Foxp3-MSC monotherapy achieved donor-specific liver allograft tolerance and generated a state of CD4⁺CD25⁺Foxp3⁺ Tregs-dependent tolerance.

Conclusion

Foxp3-engineered MSC therapy seems to be a promising and attractive cell therapy approach for inducing immunosuppression or transplant tolerance.

Controlled release strategies for modulating immune responses to promote tissue regeneration

Advances in the field of tissue engineering have enhanced the potential of regenerative medicine, yet the efficacy of these strategies remains incomplete, and is limited by the innate and adaptive immune responses. The immune response associated with injury or disease combined with that mounted to biomaterials, transplanted cells, proteins, and gene therapies vectors can contribute to the inability to fully restore tissue function. Blocking immune responses such as with anti-inflammatory or immunosuppressive agents are either ineffective, as the immune response contributes significantly to regeneration, or have significant side effects. This review describes targeted strategies to modulate the immune response in order to limit tissue damage following injury, promote an anti-inflammatory environment that leads to regeneration, and induce antigen (Ag)-specific tolerance that can target degenerative diseases that destroy tissues and promote engraftment of transplanted cells. Focusing on targeted immuno-modulation, we describe local delivery techniques to sites of inflammation as well as systemic approaches that preferentially target subsets of immune populations.

Safety and efficacy of autologous mesenchymal stromal cells transplantation in patients undergoing living donor kidney transplantation: a pilot study

AIM

This pilot study assesses the safety and feasibility of autologous mesenchymal stromal cell (MSC) transplantation in four patients that underwent living donor renal transplantation, and the effect on the immunophenotype and functionality of peripheral T lymphocytes following transplantation.

METHODS

All patients received low dose ATG induction followed by calcineurin inhibitor-based triple drug maintenance immunosuppression. Autologous MSCs were administered intravenously pre transplant and day 30 post-transplant. Patients were followed up for 6 months. The frequency of regulatory T cells and T cell proliferation was assessed at different time points.

RESULTS

None of the four patients developed any immediate or delayed adverse effects following MSC infusion. All had excellent graft function, and none developed graft dysfunction. Protocol biopsies at 1 and 3 months did not reveal any abnormality. Compared to baseline, there was an increase in the CD4 + CD25+FOXP3+ regulatory T cells and reduction in CD4 T cell proliferation.

CONCLUSION

We conclude that autologous MSCs can be used safely in patients undergoing living donor renal transplantation, lead to expansion of regulatory T cells and decrease in T cell proliferation. Larger randomized trials studies are needed to confirm these findings and evaluate whether this will have any impact on immunosuppressive therapy.

Safety and Efficacy Endpoints for Mesenchymal Stromal Cell Therapy in Renal Transplant Recipients

Despite excellent short-term graft survival after renal transplantation, the long-term graft outcome remains compromised. It has become evident that a combination of sustained alloreactivity and calcineurin-inhibitor- (CNI-) related nephrotoxicity results in fibrosis and consequently dysfunction of the graft. New immunosuppressive regimens that can minimize or eliminate side effects, while maintaining efficacy, are required to improve long-term graft survival. In this perspective mesenchymal stromal cells (MSCs) are an interesting candidate, since MSCs have immunosuppressive and regenerative properties. The first clinical trials with MSCs in renal transplantation showed safety and feasibility and displayed promising results. Recently, the first phase II studies have been started. One of the most difficult and challenging aspects in those early phase trials is to define accurate endpoints that can measure safety and efficacy of MSC treatment. Since both graft losses and acute rejection rates declined, alternative surrogate markers such as renal function, histological findings, and immunological markers are used to measure efficacy and to provide mechanistic insight. In this review, we will discuss the current status of MSCs in renal transplantation with a focus on the endpoints used in the different experimental and clinical studies.

The immunomodulatory function of mesenchymal stem cells: mode of action and pathways

Mesenchymal stem cells (MSCs) are being increasingly investigated as a therapeutic alternative, not only for their possible regenerative potential but also for their immunomodulatory action, which is being exploited for controlling diseases associated with inflammation. Understanding their direct and indirect target cells, as well as their mode of action and relevant pathways, is a prerequisite for the appropriate and optimal use of MSCs in therapy. Here, we review recent findings on the effects of MSCs on adaptive and innate immune cells. We also consider the impact of the environment on MSC profile, both anti- and proinflammatory, and the mechanisms and molecular pathways through which their effects are mediated, both at the MSC and target cell levels.

Human umbilical cord mesenchymal stem cells: an overview of their potential in cell-based therapy

INTRODUCTION

Human umbilical cord mesenchymal stem cells (HUC-MSCs) are one of the typical adult stem cells; they have superiorities including low immunogenicity, non-invasive harvest procedure, easy expansion in vitro, and ethical access compared with stem cells from other sources. Therefore, HUC-MSCs are a promising candidate for cell-based therapy.

AREAS COVERED

Here we reviewed the development of stem cell-based therapy, the manufacturing and banking process of HUC-MSCs, the emerging clinical studies in the field of cancer, central nervous system diseases, liver diseases and graft-versus-host disease, the potential therapeutic mechanisms, as well as challenges of HUC-MSCs in clinical translation.

EXPERT OPINION

HUC-MSCs seem to be an optimal choice for stem cell-based therapy. However, before the cells translate from basic to clinical research, some problems still remain to be solved: i) building regulatory guidelines as well as an efficient and safe manufacturing procedure; ii) establishing donor's genetic testing and long-term closely monitoring system; iii) conducting further clinical trials to determine the optimum and standard dosage, time, route, frequency and many other technical issues of HUC-MSCs transplantation.

Mesenchymal stromal cells to control donor-specific memory T cells in solid organ transplantation

PURPOSE OF REVIEW

Mesenchymal stromal cells (MSCs) represent a promising cell therapy to promote transplant tolerance, as they influence many cells involved in immune response. Herein, we review recent evidence on the ability of MSCs to inhibit antigen-induced memory T cell response in vitro and in preclinical studies as well as immunological studies in kidney transplant recipients highlighting the effects of MSC therapy on memory CD8 T-cell proliferation and function.

RECENT FINDINGS

MSCs are able to inhibit in-vitro proliferation and effector functions of memory T cells in response to auto-antigen and allo-antigen stimulation. MSC infusion in animal transplant models resulted in a skew of the balance between regulatory T cells and effector/memory T cells towards a pro-tolerogenic profile. MSC in clinical transplantation is in its infancy and limited numbers of clinical studies have performed immunomonitoring of MSC-treated patients. However, available data support the capability of MSCs to control effector/memory CD8 T-cell proliferation and donor-specific CD8 T-cell function long lasting in kidney transplant setting.

SUMMARY

Recent studies of MSCs in kidney transplantation highlight the anticipated add-on value of the immunomodulatory properties of bone marrow derived MSCs in persistently inhibiting donor-specific effector/memory CD8 T cells, an effect not shared by the current immunosuppressive drugs.

Mesenchymal stromal cells for prevention and treatment of graft-versus-host disease: successes and hurdles

PURPOSE OF REVIEW

The aim of the present review was to give a critical opinion on the use of mesenchymal stromal cells (MSCs) to treat or to prevent graft-versus-host disease (GVHD).

RECENT FINDINGS

The first part includes a summary of the many clinical trials published so far either to prevent or to treat GVHD in recipients of haematopoietic stem cell transplantation. We discuss in more detail a comparison in a subgroup of studies, including our own clinical work, which have in common the use of the platelet lysate to expand the MSCs from bone marrow origin.In the second part, we describe a few crucial elements of the biology of the GVHD and the biology of the MSCs themselves, showing their possible role in the immune modulation and in the inflammation in several in-vivo experimental models.

SUMMARY

The complexity of the clinical condition that is the object of the trials and the paucity of information on the mechanisms of action in vivo of MSCs at different anatomical sites and in different times of the development of the disease preclude at the moment the identification of a strong rationale for MSC therapeutic schedule. Moreover, the typical development of GVHD requires different time points of clinical evaluation than those previously generally utilized in studies conducted on MSCs.

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.

The role of stem cell therapies in degenerative lumbar spine disease: a review

Degenerative conditions of the lumbar spine are extremely common. Ninety percent of people over the age of 60 years have degenerative change on imaging; however, only a small minority of people will require spine surgery (Hicks et al. Spine (Phila Pa 1976) 34(12):1301-1306, 2009). This minority, however, constitutes a core element of spinal surgery practice. Whilst the patient outcomes from spinal surgeries have improved in recent years, some patients will remain with pain and disability despite technically successful surgery. Advances in regenerative medicine and stem cell therapies, particularly the use of mesenchymal stem cells and allogeneic mesenchymal precursor cells, have led to numerous clinical trials utilising these cell-based therapies to treat degenerative spinal conditions. Through cartilage formation and disc regeneration, fusion enhancement or via modification of pain pathways, stem cells are well suited to enhance spinal surgery practice. This review will focus on the outcomes of lumbar spinal procedures and the role of stem cells in the treatment of degenerative lumbar conditions to enhance clinical practice. The current status of clinical trials utilising stem cell therapies will be discussed, providing clinicians with an overview of the various cell-based treatments likely to be available to patients in the near future.

Inflammatory Chemokines MIP-1δ and MIP-3α Are Involved in the Migration of Multipotent Mesenchymal Stromal Cells Induced by Hepatoma Cells

In vivo, bone marrow-derived multipotent mesenchymal stromal cells (MSC) have been identified at sites of tumors, suggesting that specific signals mobilize and activate MSC to migrate to areas surrounding tumors. The signals and migratory mechanisms that guide MSC are not well understood. Here, we investigated the migration of human MSC induced by conditioned medium of Huh-7 hepatoma cells (Huh-7 CM). Using a transwell migration system, we showed that human MSC migration was increased in the presence of Huh-7 CM. Using a human cytokine antibody array, we detected increased levels of MIP-1δ and MIP-3α in Huh-7 CM. Recombinant chemokines MIP-1δ and MIP-3α induced MSC migration. Anti-MIP-1δ and anti-MIP-3α antibodies added to Huh-7 CM decreased MSC migration, further suggesting that MIP-1δ and MIP-3α were implicated in the Huh-7 CM-induced MSC migration. By real-time polymerase chain reaction, we observed an absence of chemokine receptors CCR2 and CXCR2 and low expression of CCR1, CCR5, and CCR6 in MSC. Expression of these chemokine receptors was not regulated by Huh-7 CM. Furthermore, matrix metalloproteinase 1 (MMP-1) expression was strongly increased in MSC after incubation with Huh-7 CM, suggesting that MSC migration depends on MMP-1 activity. The signaling pathway MAPK/ERK was activated by Huh-7 CM but its inhibition by PD98059 did not impair Huh-7 CM-induced MSC migration. Further, long-term incubation of MSC with MIP-1δ increased α-smooth muscle actin expression, suggesting its implication in the Huh-7 CM-induced evolvement of MSC into myofibroblasts. In conclusion, we report that two inflammatory cytokines, MIP-1δ and MIP-3α, are able to increase MSC migration in vitro. These cytokines might be responsible for migration and evolvement of MSC into myofibroblasts around tumors.

Transplantation tolerance and its outcome during infections and inflammation

Much progress has been made toward understanding the mechanistic basis of transplantation tolerance in experimental models, which implicates clonal deletion of alloreactive T and B cells, induction of cell-intrinsic hyporesponsiveness, and dominant regulatory cells mediating infectious tolerance and linked suppression. Despite encouraging success in the laboratory, achieving tolerance in the clinic remains challenging, although the basis for these challenges is beginning to be understood. Heterologous memory alloreactive T cells generated by infections prior to transplantation have been shown to be a critical barrier to tolerance induction. Furthermore, infections at the time of transplantation and tolerance induction provide a pro-inflammatory milieu that alters the stability and function of regulatory T cells as well as the activation requirements and differentiation of effector T cells. Thus, infections can result in enhanced alloreactivity, resistance to tolerance induction, and destabilization of the established tolerance state. We speculate that these experimental findings have relevance to the clinic, where infections have been associated with allograft rejection and may be a causal event precipitating the loss of grafts after long periods of stable operational tolerance. Understanding the mechanisms by which infections prevent and destabilize tolerance can lead to therapies that promote stable life-long tolerance in transplant recipients.

Mesenchymal stem cells and transplant tolerance

Different strategies are being tried to induce transplant tolerance in clinical settings; however, none of them are both safe and effective. Mesenchymal stem cells have been found to be potent immunomodulators and immunosuppressants. We discuss in this review different sources of mesenchymal stem cells and the potent role of adipose tissue-derived mesenchymal stem cells in induction of transplant tolerance including when to use them and how to use them for achieving the Utopian dream of transplant tolerance.

Autologous bone marrow derived mesenchymal stromal cell therapy in combination with everolimus to preserve renal structure and function in renal transplant recipients

Background

Kidney transplantation has improved survival and quality of life for patients with end-stage renal disease. Despite excellent short-term results due to better and more potent immunosuppressive drugs, long-term survival of transplanted kidneys has not improved accordingly in the last decades. Consequently there is a strong interest in immunosuppressive regimens that maintain efficacy for the prevention of rejection, whilst preserving renal structure and function. In this respect the infusion of mesenchymal stromal cells (MSCs) may be an interesting immune suppressive strategy. MSCs have immune suppressive properties and actively contribute to tissue repair. In experimental animal studies the combination of mammalian target of rapamycin (mTOR) inhibitor and MSCs was shown to attenuate allo immune responses and to promote allograft tolerance. The current study will test the hypothesis that MSC treatment, in combination with the mTOR inhibitor everolimus, facilitates tacrolimus withdrawal, reduces fibrosis and decreases the incidence of opportunistic infections compared to standard tacrolimus dose.

Methods/design

70 renal allograft recipients, 18–75 years old, will be included in this Phase II, open label, randomized, non-blinded, prospective, single centre clinical study. Patients in the MSC treated group will receive two doses of autologous bone marrow derived MSCs IV (target 1,5x10⁶, Range 1-2x10⁶ million MSCs per/kg body weight), 7 days apart, 6 and 7 weeks transplantation in combination with everolimus and prednisolone. At the time of the second MSC infusion tacrolimus will be reduced to 50% and completely withdrawn 1 week later. Patients in the control group will receive everolimus, prednisolone and standard dose tacrolimus. The primary end point is to compare fibrosis by quantitative Sirius Red scoring of MSC treated and untreated groups at 6 months compared to 4 weeks post-transplant. Secondary end points include: composite end point efficacy failure (Biopsy Proven Acute Rejection, graft loss or death); renal function and proteinuria; opportunistic infections; immune monitoring and “subclinical” cardiovascular disease groups by assessing echocardiography in the different treatment groups.

Discussion

This study will provide information whether MSCs in combination with everolimus can be used for tacrolimus withdrawal, and whether this strategy leads to preservation of renal structure and function in renal recipients.

Trial registration

NCT02057965.

Rationale for the potential use of mesenchymal stromal cells in liver transplantation

Mesenchymal stromal cells (MSCs) are multipotent and self-renewing cells that reside essentially in the bone marrow as a non-hematopoietic cell population, but may also be isolated from the connective tissues of most organs. MSCs represent a heterogeneous population of adult, fibroblast-like cells characterized by their ability to differentiate into tissues of mesodermal lineages including adipocytes, chondrocytes and osteocytes. For several years now, MSCs have been evaluated for their in vivo and in vitro immunomodulatory and ‘tissue reconstruction’ properties, which could make them interesting in various clinical settings, and particularly in organ transplantation. This paper aims to review current knowledge on the properties of MSCs and their use in pre-clinical and clinical studies in solid organ transplantation, and particularly in the field of liver transplantation. The first available clinical data seem to show that MSCs are safe to use, at least in the medium-term, but more time is needed to evaluate the potential adverse effects of long-term use. Many issues must be resolved on the correct use of MSCs. Intensive in vitro and pre-clinical research are the keys to a better understanding of the way that MSCs act, and to eventually lead to clinical success.

Mesenchymal stromal cells reset the scatter factor system and cytokine network in experimental kidney transplantation

BACKGROUND

In former studies we showed in a rat model of renal transplantation that Mesenchymal Stromal Cells (MSC) prevent acute rejection in an independent way of their endowing in the graft. In this study we investigated whether MSC operate by resetting cytokine network and Scatter Factor systems, i.e. Hepatocyte Growth Factor (HGF), Macrophage Stimulating Protein (MSP) and their receptors Met and RON, respectively.

METHODS

MSC were injected into the renal artery soon after reperfusion. Controls were grafted untreated and normal rats. Rats were sacrificed 7 days after grafting. Serum and renal tissue levels of IFN-γ, IL-1, IL-2, IL-4, IL-6, IL-10, MSP/RON, HGF/Met systems, Treg lymphocytes were investigated.

RESULTS

In grafted untreated rats IFN-γ increased in serum and renal tissue and IL-6 rose in serum. MSC prevented both the phenomena, increased IL-10 serum levels and Treg number in the graft. Furthermore MSC increased serum and tissue HGF levels, Met tubular expression and prevented the suppression of tubular MSP/RON expression.

CONCLUSIONS

Our results demonstrate that MSC modify cytokine network to a tolerogenic setting, they suppress Th1 cells, inactivate monocytes/macrophage, recruit Tregs. In addition, MSC sustain the expression of the Scatter Factor systems expression, i.e. systems that are committed to defend survival and stimulate regeneration of tubular cells.

Mesenchymal stem cell therapy promotes corneal allograft survival in rats by local and systemic immunomodulation

Mesenchymal stem cells (MSCs) are being investigated extensively due to their ability to dampen immune responses. Here, we tested the ability of MSCs from three distinct sources to prolong rat corneal allograft survival. A fully allogeneic rat cornea transplant model (DA to LEW) was used. Recipient rats received 1 × 10(6) MSCs (syn [LEW], allo [DA] or third-party [Wistar Furth]) intravenously 7 days before transplantation and again on the day of transplantation (day 0). A high percentage of untreated and syn-MSC treated allografts were rejected (80% and 100%, respectively). Preactivation of syn-MSCs with interferon gamma also failed to prolong allograft survival. Conversely, corneal allograft survival was significantly prolonged in allo-MSC treated (90%) and third-party MSC treated (80%) allograft recipients. Flow cytometric analysis revealed less infiltrating natural killer T cells in corneas of both allo- and third-party MSC treated animals, coupled with a higher proportion of splenic CD4+Foxp3+ regulatory T cells, compared to controls. In the case of allo- and third-party MSCs, results from a delayed-type hypersensitivity assay clearly showed that hypo-responsiveness was specific for corneal donor-associated allo-antigens. Thus, allo- and third-party MSC treatment prolongs corneal allograft survival by suppressing peripheral immune responses and promoting an intragraft immunoregulatory milieu.