The synergistic immunoregulatory effects of culture-expanded mesenchymal stromal cells and CD4(+)25(+)Foxp3+ regulatory T cells on skin allograft rejection

Cancer Cell De-Differentiation: Plasticity-Driven Stratagem For Tumor Metastasis and Recurrence

Tumor recurrence is a colossal challenge in clinical oncology. This multifactorial problem is attributed to the emergence of additional genetic mutations and the presence of dormant cancer cells. However, the plasticity of non-stem cancer cells and the acquisition of cancer stem cell (CSC) functionality is another contributing factor to tumor recurrence. Herein, I focus attention on the mechanisms that fuel cancer cell de-differentiation and the interplay between intra-cellular regulators and tumor microenvironment (TME) landscape that promotes cancer cell stemness. Our understanding of the mechanisms underlying tumor cell de-differentiation is crucial for developing innovative therapeutic strategies that prevent cancer from ever recurring.

Myeloid-derived suppressor cells therapy enhance immunoregulatory properties in acute graft versus host disease with combination of regulatory T cells

Background

Myeloid-derived suppressor cells (MDSCs) play a critical role in modulating the immune response and promoting immune tolerance in models of autoimmunity and transplantation. Regulatory T cells (Tregs) exert therapeutic potential due to their immunomodulatory properties, which have been demonstrated both in vitro and in clinical trials. Cell-based therapy for acute graft-versus-host disease (aGVHD) may enable induction of donor-specific tolerance in the preclinical setting.

Methods

We investigated whether the immunoregulatory activity of the combination of MDSCs and Tregs on T cell and B cell subset and alloreactive T cell response. We evaluated the therapeutic effects of combined cell therapy for a murine aGVHD model following MHC-mismatched bone marrow transplantation. We compared histologic analysis from the target tissues of each groups were and immune cell population by flow cytometric analysis.

Results

We report a novel approach to inducing immune tolerance using a combination of donor-derived MDSCs and Tregs. The combined cell-therapy modulated in vitro the proliferation of alloreactive T cells and the Treg/Th17 balance in mice and human system. Systemic infusion of MDSCs and Tregs ameliorated serverity and inflammation of aGVHD mouse model by reducing the populations of proinflammatory Th1/Th17 cells and the expression of proinflammatory cytokines in target tissue. The combined therapy promoted the differentiation of allogeneic T cells toward Foxp3 + Tregs and IL-10-producing regulatory B cells. The combination treatment control also activated human T and B cell subset.

Conclusions

Therefore, the combination of MDSCs and Tregs has immunomodulatory activity and induces immune tolerance to prevent of aGVHD severity. This could lead to the development of new clinical approaches to the prevent aGVHD.

Immunological challenges associated with artificial skin grafts: available solutions and stem cells in future design of synthetic skin

The repair or replacement of damaged skins is still an important, challenging public health problem. Immune acceptance and long-term survival of skin grafts represent the major problem to overcome in grafting given that in most situations autografts cannot be used. The emergence of artificial skin substitutes provides alternative treatment with the capacity to reduce the dependency on the increasing demand of cadaver skin grafts. Over the years, considerable research efforts have focused on strategies for skin repair or permanent skin graft transplantations. Available skin substitutes include pre- or post-transplantation treatments of donor cells, stem cell-based therapies, and skin equivalents composed of bio-engineered acellular or cellular skin substitutes. However, skin substitutes are still prone to immunological rejection, and as such, there is currently no skin substitute available to overcome this phenomenon. This review focuses on the mechanisms of skin rejection and tolerance induction and outlines in detail current available strategies and alternatives that may allow achieving full-thickness skin replacement and repair.

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.

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.

Enhanced immunoregulation of mesenchymal stem cells by IL-10-producing type 1 regulatory T cells in collagen-induced arthritis

Mesenchymal stem cells (MSCs) possess immunomodulatory properties and have potential, however, there have been conflicting reports regarding their effects in rheumatoid arthritis (RA), which causes inflammation and destruction of the joints. Through a comparative analysis of regulatory T (Treg) and IL-10-producing type 1 regulatory T (Tr1) cells, we hypothesized that Tr1 cells enhance the immunoregulatory functions of MSCs, and that a combinatorial approach to cell therapy may exert synergistic immunomodulatory effects in an experimental animal model of rheumatoid arthritis (RA). A combination of MSCs and Tr1 cells prevented the development of destructive arthritis compared to single cell therapy. These therapeutic effects were associated with an increase in type II collagen (CII)-specific CD4+CD25+Foxp3+ Treg cells and inhibition of CII-specific CD4+IL-17+ T cells. We observed that Tr1 cells produce high levels of IL-10-dependent interferon (IFN)-β, which induces toll-like receptor (TLR) 3 expression in MSCs. Moreover, induction of indoleamine 2,3-dioxygenase (IDO) by TLR3 involved an autocrine IFN-β that was dependent on STAT1 signaling. Furthermore, we observed that production of IFN-β and IL-10 in Tr1 cells synergistically induces IDO in MSCs through the STAT1 pathway. These findings suggest co-administration of MSCs and Tr1 cells to be a novel therapeutic modality for clinical autoimmune diseases.

Overcoming immunoregulatory plasticity of mesenchymal stem cells for accelerated clinical applications

Mesenchymal stem cells (MSCs) are multipotent stromal cells with the potential to differentiate into different tissue lineages. In addition to their differentiation potential, MSCs possess immunomodulatory properties that have created growing interest in both pre-clinical and clinical research. Over the years, MSCs have been applied rapidly in the clinic in a wide variety of immune-mediated disorders; however, MSC therapy has shown contradictory results, often with poor clinical outcomes. Recently, studies on MSC-based immune modulation have provided possible explanations for the conflicting clinical reports. It is now generally recognized that the immunomodulatory properties of MSCs are not constitutive but are induced by various mediators present in the inflammatory microenvironment. Different inflammatory stimuli are able to polarize MSCs to elicit distinct immunomodulatory phenotypes. Thus, the concepts of plasticity and polarization of MSC-based immune modulation may have important therapeutic implications in the clinic. In this review, we focus on the underlying mechanisms of MSC-mediated immune regulation that contribute to their therapeutic potential. Importantly, we discuss novel strategic approaches that enhance the therapeutic potential of MSCs through a consideration of MSC plasticity in immune modulation.

IL-21-Expressing Mesenchymal Stem Cells Prevent Lethal B-Cell Lymphoma Through Efficient Delivery of IL-21, Which Redirects the Immune System to Target the Tumor

Interleukin (IL)-21, a proinflammatory cytokine, has been developed as an immunotherapeutic approach due to its effects on various lymphocytes, including natural killer (NK) cells and T cells; however, the clinical success in cancer patients has been limited. Recently, mesenchymal stem cells (MSCs) have emerged as vehicles for cancer gene therapy due to their inherent migratory abilities toward tumors. In the present study, we hypothesized that MSCs, genetically modified to express high levels of IL-21 (IL-21/MSCs), can enhance antitumor responses through localized delivery of IL-21. For tumor induction, BALB/c mice were injected intravenously with syngeneic A20 B-cell lymphoma cells to develop a disseminated B-cell lymphoma model. Then, 6 days following tumor induction, the tumor-bearing mice were treated with IL-21/MSCs weekly, four times. Systemic infusion of A20 cells led to hind-leg paralysis as well as severe liver metastasis in the control group. The IL-21/MSC-treated group showed delayed tumor incidence as well as improved survival, whereas the MSC- and recombinant adenovirus-expressing IL-21 (rAD/IL-21)-treated groups did not show significant differences from the untreated mice. These therapeutic effects were associated with high levels of IL-21 delivered to the liver, which prevented the formation of tumor nodules. Furthermore, the infusion of IL-21/MSCs led to induction of effector T and NK cells, while potently inhibiting immune suppressor cells. Our findings demonstrate that IL-21-expressing MSCs have the therapeutic potential to induce potent antitumor effects against disseminated B-cell lymphoma through localized IL-21 delivery and induction of systemic antitumor immunity.

Adoptive Transfer of Treg Cells Combined with Mesenchymal Stem Cells Facilitates Repopulation of Endogenous Treg Cells in a Murine Acute GVHD Model

Therapeutic effects of combined cell therapy with mesenchymal stem cells (MSCs) and regulatory T cells (Treg cells) have recently been studied in acute graft-versus-host-disease (aGVHD) models. However, the underlying, seemingly synergistic mechanism behind combined cell therapy has not been determined. We investigated the origin of Foxp3+ Treg cells and interleukin 17 (IL-17+) cells in recipients following allogeneic bone marrow transplantation (allo-BMT) to identify the immunological effects of combined cell therapy. Treg cells were generated from eGFP-expressing C57BL/6 mice (Tregegfp cells) to distinguish the transferred Treg cells; recipients were then examined at different time points after BMT. Systemic infusion of MSCs and Treg cells improved survival and GVHD scores, effectively downregulating pro-inflammatory Th×and Th17 cells. These therapeutic effects of combined cell therapy resulted in an increased Foxp3+ Treg cell population. Compared to single cell therapy, adoptively transferred Tregegfp cells only showed prolonged survival in the combined cell therapy group on day 21 after allogeneic BMT. In addition, Foxp3+ Treg cells, generated endogenously from recipients, significantly increased. Significantly higher levels of Tregegfp cells were also detected in aGVHD target organs in the combined cell therapy group compared to the Treg cells group. Thus, our data indicate that MSCs may induce the long-term survival of transferred Treg cells, particularly in aGVHD target organs, and may increase the repopulation of endogenous Treg cells in recipients after BMT. Together, these results support the potential of combined cell therapy using MSCs and Treg cells for preventing aGVHD.

New strategies for overcoming limitations of mesenchymal stem cell-based immune modulation

Mesenchymal stem cells (MSCs) have rapidly been applied in a broad field of immune-mediated disorders since the first successful clinical use of MSCs for treatment of graft-versus-host disease. Despite the lack of supporting data, expectations that MSCs could potentially treat most inflammatory conditions led to rushed application and development of commercialized products. Today, both pre-clinical and clinical studies present mixed results for MSC therapy and the discrepancy between expected and actual efficacy of MSCs in various diseases has evoked a sense of discouragement. Therefore, we believe that MSC therapy may now be at a critical milestone for re-evaluation and re-consideration. In this review, we summarize the current status of MSC-based clinical trials and focus on the discrepancy between expected and actual outcome of MSC therapy from bench to bedside. Importantly, we discuss the underlying limitations of MSCs and suggest a new guideline for MSC therapy in hopes of improving their therapeutic efficacy.

Aqueous extract of Caesalpinia sappan decelerates allograft rejection by inducing imbalance between CD4(+) CD25(+) T cells and Th17 cells

OBJECTIVE

Aqueous extract of Caesalpinia sappan (CSE) has immunosuppressive activities, but the mechanism remains unknown. This study was to investigate the effect of CSE on the balance between CD4(+) CD25(+) T cells and Th17 cells.

METHODS

Allografted Balb/c recipients were intraperitoneally treated with CSE for 14 continuous days, and the graft survival was observed. The spleen cells and peripheral blood of the recipient mice were harvested for phenotyping by flow cytometry, detection of gene expression by real-time PCR and cytokine detection by ELISA.

RESULTS

CSE prolonged skin allograft survival, increased the percentage and number of CD4(+) CD25(+) T cells, the expression of Foxp3 and STAT5 in spleen cells, the serum levels of IL-10 and TGF-β1, whereas reduced the percentage and number of Th17 cells and serum IL-17 level in Balb/c recipients.

CONCLUSION

CSE expanded CD4(+) CD25(+) T cells and decreased Th17 cells in vivo thereby improving skin allograft survival in mice, indicating that CSE affects the balance between CD4(+) CD25(+) T cells and Th17 cells in the graft to induce rejection.

Granulomatous dysimmune reactions (sarcoidosis, granuloma annulare, and others) on differently injured skin areas

Granulomatous disorders are chronic cell-mediated immune responses histologically characterized by collections of macrophages, epithelioid cells, and multinucleated giant cells. This disease spectrum often has an infectious origin, but sometimes neither an infective agent nor an inciting antigenic stimulus can be identified. The skin may be a preferential target for these disorders, especially in the areas that have been damaged by various forms of skin injury (eg, herpetic infections, trauma, thermal or solar burns, vaccinations, tattoos). These damaged skin sites frame the new concept of an immunocompromised cutaneous district (ICD), which defines a skin area with acquired immune dysregulation that can pave the way for the local onset of opportunistic disorders, such as infections, tumors, and granulomatous disorders. Sarcoidosis, granuloma annulare (GA), and forms of granulomatous vasculitis, such as Churg-Strauss syndrome (CSS) and Wegener's granulomatosis (WG), are the most common granulomatous disorders that occur in an ICD and may share common pathogenic mechanisms. Recent studies have found clinical and pathologic overlapping features across noninfectious granulomas. Although no unifying etiology exists, the development of granulomatous processes in the ICD has often been reported and the literature contains various hypotheses to explain it: (1) overactive immune response in a previously injured region with or without loss of immune tolerance; (2) overall reduced immune response; (3) retention of an exogeneous antigen or foreign body; (4) altered neural signaling; and (5) a combination of all the aforementioned processes. T helper cells, T regulatory cells, and macrophages, as well as a number of antigenic proteins, have been identified as potential contributing factors. In addition, a genetic predisposition and an intact systemic immune system are both instrumental for the persistence of local granuloma formation in the ICD.

Engineering β-cell islets or islet-like structures for type 1 diabetes treatment

Type 1 diabetes mellitus is a disease characterized by the destruction of the β-cells in the pancreatic islets of Langerhans. The current primary treatment for type 1 diabetes is insulin injections administered multiple times throughout the day. However, this treatment cannot provide sustained physiological release of insulin and the insulin amount is not finely tuned to the glycemia condition. Pancreatic transplantation or islet transplantation would be the preferred treatment strategy but the lack of donor tissue and immunoincompatibility has been shown to be a roadblock to their widespread use. Bioengineering strategies are poised to combat these challenges. Islet encapsulation is expected to offer both immunoisolation and immunomodulation effects by: (1) physically protecting islets from the attacks of immunoglobulins, complements, and host immune cells, and (2) delivering immune regulatory and immunomodulatory factors locally to the islets to protect those islets from immune rejection. Semi-permeable coatings using biocompatible biomaterials can be used for immunoisolating islets away from the host immune systems. Immunoisolation technology also provides an opportunity to use other cell sources for cell therapy to treat type 1 diabetes. Recently, some studies reported that co-transplantation of islets with mesenchymal stem cells (MSCs) can control graft inflammation. MSCs have immunomodulatory property. They are able to secrete anti-inflammatory factors and repress the activity of various immune cells. Growth factors like interleukin 10 (IL-10) and leukemia inhibitory factor (LIF) also have immune regulatory properties. Therefore immunoisolation and immunomodulation technologies can be integrated and applied to β-cell encapsulation for the treatment of type 1 diabetes. Through engineering β-cell islets or islet-like microtissues, the viability and function of transplanted β-cells may be improved. In the meantime, the survival of transplanted β-cells can be further improved by promoting vascular network formation surrounding the transplanted islets or microtissues.

Negative impact of bone-marrow-derived mesenchymal stem cells on dextran sulfate sodium-induced colitis

AIM: To investigate the effects of mesenchymal stem cells (MSCs) on dextran sulfate sodium-induced inflammatory bowel disease (IBD).

METHODS: C57BL/6 mice were fed 3.5% (g/L) dextran sulfate sodium. On day seven, the mice received intraperitoneal injections of 1 × 10⁶ MSCs. The survival rate, disease activity index values, and body weight, were monitored daily. On day ten, colon lengths and histopathologic changes were assessed. In addition, immunoregulatory changes following MSC administration were evaluated by determining the levels of effector T cell responses in the spleen and mesenteric lymph nodes, and the expression levels of inflammatory cytokines in homogenized colons.

RESULTS: Intraperitoneal administration of MSCs did not prevent development of colitis and did not reduce the clinicopathologic severity of IBD. No significant difference was evident in either survival rate or disease activity index score between the control and MSC-treated group. Day ten-sacrificed mice exhibited no significant difference in either colon length or histopathologic findings. Indeed, the MSC-treated group exhibited elevated levels of interleukin (IL)-6 and transforming growth factor-β, and a reduced level of IL-10, in spleens, mesenteric lymph nodes, and homogenized colons. The IL-17 level was lower in the mesenteric lymph nodes of the MSC-treated group (P = 0.0126). In homogenized colons, the IL-17 and tumor necrosis factor-α (P = 0.0092) expression levels were also lower in the treated group.

CONCLUSION: MSC infusion provided no significant histopathologic or clinical improvement, thus representing a limited therapeutic approach for IBD. Functional enhancement of MSCs is needed in further study.