Mesenchymal stem cells can affect solid organ allograft survival

Mesenchymal stem cell tailored bioengineered scaffolds derived from bubaline diaphragm and aortic matrices for reconstruction of abdominal wall defects

Bioengineered scaffolds derived from the decellularized extracellular matrix (ECM) obtained from discarded animal organs and tissues are attractive candidates for regenerative medicine applications. Tailoring these scaffolds with stem cells enhances their regeneration potential making them a suitable platform for regenerating damaged tissues. Thus, the study was designed to investigate the potential of mesenchymal stem cells tailored acellular bubaline diaphragm and aortic ECM for the repair of full-thickness abdominal wall defects in a rabbit model. Tissues obtained from bubaline diaphragm and aorta were decellularized and bioengineered by seeding with rabbit bone marrow derived mesenchymal stem cells (r-BMSC). Full-thickness abdominal wall defects of 3 cm × 4 cm size were created in a rabbit model and repaired using five different prostheses, namely, polypropylene sheet, nonseeded diaphragm ECM, nonseeded aorta ECM, r-BMSC bioengineered diaphragm ECM, and r-BMSC bioengineered aorta ECM. Results from the study revealed that biological scaffolds are superior in comparison to synthetic polymer mesh for regeneration in terms of collagen deposition, maturation, neovascularization, and lack of any significant (P > 0.05) adhesions with the abdominal viscera. Seeding with r-BMSC significantly increased (P < 0.05) the collagen deposition and biomechanical strength of the scaffolds. The bioengineered r-BMSC seeded acellular bubaline diaphragm showed even superior biomechanical strength as compared to synthetic polymer mesh. Tailoring of the scaffolds with the r-BMSC also resulted in significant reduction (P < 0.01) in antibody and cell mediated immune reactions to the xenogeneic scaffolds in rabbit model.

Protective action of bone marrow mesenchymal stem cells in immune tolerance of allogeneic heart transplantation by regulating CD45RB+ dendritic cells

BACKGROUND

Bone marrow-derived mesenchymal stem cells (BMSCs) could exert a potent immunosuppressive effect and therefore may have a therapeutic potential in T-cell-dependent pathologies. We aimed to examine the effects of BMSCs on immune tolerance of allogeneic heart transplantation and the involvement of CD45RB⁺ dendritic cells (DCs).

METHODS

Bone marrow-derived DCs and BMSCs were co-cultured, with CD45RB expression on the surface of DCs measured by flow cytometry. qRT-PCR and Western blotting were used to detect mRNA and protein levels. Cytometric bead array was performed to determine the serum level of IL-10. Survival time of transplanted heart and expression of CD4⁺ , CD8⁺ , IL-2, IL-4, IL-10, IFN-γ were determined. Immunofluorescence assay was employed to determine intensity of C3d and C4d.

RESULTS

DCs co-cultured with BMSCs showed increased CD45RB and Foxp3 levels. CD45RB⁺ DCs co-cultured with T-cells CD4⁺ displayed increased T-cell CD4⁺ Foxp3 ratio and IL-10 than DCs. Both of them extended survival time of transplanted heart, decreased histopathological classification and score, intensity of C3d, C4d, proportion of CD4⁺ , expression levels of IL-2 and IFN-γ, and increased the CD4⁺ Foxp3 ratio and levels of IL-4 and IL-10. CD45RB⁺ DCs achieved better protective effects than DCs.

CONCLUSION

BMSCs increased the expression of CD45RB in the bone marrow-derived DCs, thereby strengthening immunosuppression capacity of T cells and immune tolerance of allogeneic heart transplantation.

Systematic implantation of dedifferentiated fat cells ameliorated monoclonal antibody 1-22-3-induced glomerulonephritis by immunosuppression with increases in TNF-stimulated gene 6

INTRODUCTION

Implantation of mesenchymal stem cells (MSCs) has recently been reported to repair tissue injuries through anti-inflammatory and immunosuppressive effects. We established dedifferentiated fat (DFAT) cells that show identical characteristics to MSCs.

METHODS

We examined the effects of 10(6) of DFAT cells infused through renal artery or tail vein on monoclonal antibody (mAb) 1-22-3-induced glomerulonephritis (as an immunological type of renal injury) and adriamycin-induced nephropathy (as a non-immunological type of renal injury) in rats. The mAb 1-22-3-injected rats were also implanted with 10(6) of DFAT cells transfected with TSG-6 siRNA through tail vein.

RESULTS

Although DFAT cells transfused into blood circulation through the tail vein were trapped mainly in lungs without reaching the kidneys, implantation of DFAT cells reduced proteinuria and improved glomerulosclerosis and interstitial fibrosis. Implantation of DFAT cells through the tail vein significantly decreased expression of kidney injury molecule-1, collagen IV and fibronectin mRNAs, whereas nephrin mRNA expression was increased. Implantation of DFAT cells did not improve adriamycin-induced nephropathy, but significantly decreased the glomerular influx of macrophages, common leukocytes and pan T cells. However, the glomerular influx of helper T cells, was increased. Implantation of DFAT cells decreased expression of interleukin (IL)-6 and IL-12β mRNAs and increased expression of TNF-stimulated gene (TSG)-6 mRNA in renal cortex from mAb 1-22-3-injected rats. The basal level of TSG-6 protein was significantly higher in DFAT cells than in fibroblasts. Expression of TSG-6 mRNA in MCs cocultured with DFAT cells was significantly higher than in mesangial cells or DFAT cells alone. Systematic implantation of DFAT cells with TSG-6 siRNA through tail vein did not improve proteinuria, renal dysfunction and renal degeneration in the mAb 1-22-3-injected rats.

CONCLUSION

Systematic implantation of DFAT cells effectively ameliorated mAb 1-22-3-induced glomerulonephritis through immunosuppressive effects accompanied by the suppression of macrophage infiltration and expression of IL-6, IL-10 and IL-12β, and increased production of serum and renal TSG-6 that improved the mAb 1-22-3-induced renal degeneration by the immunosuppressive effects of TSG-6. Thus DFAT cells will be suitable cell source for the treatment of immunological progressive renal diseases.

Mesenchymal stem cell pretreatment of non-heart-beating-donors in experimental lung transplantation

Background

Lung transplantation (LTx) is still limited by organ shortage. To expand the donor pool, lung retrieval from non-heart-beating donors (NHBD) was introduced into clinical practice recently. However, primary graft dysfunction with inactivation of endogenous surfactant due to ischemia/reperfusion-injury is a major cause of early mortality. Furthermore, donor-derived human mesenchymal stem cell (hMSC) expansion and fibrotic differentiation in the allograft results in bronchiolitis obliterans syndrome (BOS), a leading cause of post-LTx long-term mortality. Therefore, pretreatment of NHBD with recipient-specific bone-marrow-(BM)-derived hMSC might have the potential to both improve the postischemic allograft function and influence the long-term development of BOS by the numerous paracrine, immunomodulating and tissue-remodeling properties especially on type-II-pneumocytes of hMSC.

Methods

Asystolic pigs (n = 5/group) were ventilated for 3 h of warm ischemia (groups 2–4). 50x106 mesenchymal-stem-cells (MSC) were administered in the pulmonary artery (group 3) or nebulized endobronchially (group 4) before lung preservation. Following left-lung-transplantation, grafts were reperfused, pulmonary-vascular-resistance (PVR), oxygenation and dynamic-lung-compliance (DLC) were monitored and compared to control-lungs (group 2) and sham-controls (group 1). To prove and localize hMSC in the lung, cryosections were counter-stained. Intra-alveolar edema was determined stereologically. Statistics comprised ANOVA with repeated measurements.

Results

Oxygenation (p = 0.001) and PVR (p = 0.009) following endovascular application of hMSC were significantly inferior compared to Sham controls, whereas DLC was significantly higher in endobronchially pretreated lungs (p = 0.045) with overall sham-comparable outcome regarding oxygenation and PVR. Stereology revealed low intrapulmonary edema in all groups (p > 0.05). In cryosections of both unreperfused and reperfused grafts, hMSC were localized in vessels of alveolar septa (endovascular application) and alveolar lumen (endobronchial application), respectively.

Conclusions

Preischemic deposition of hMSC in donor lungs is feasible and effective, and endobronchial application is associated with significantly better DLC as compared to sham controls. In contrast, transvascular hMSC delivery results in inferior oxygenation and PVR. In the long term perspective, due to immunomodulatory, paracrine and tissue-remodeling effects on epithelial and endothelial restitution, an endobronchial NHBD allograft-pretreatment with autologous mesenchymal-stem-cells to attenuate limiting bronchiolitis-obliterans-syndrome in the long-term perspective might be promising in clinical lung transplantation. Subsequent work with chronic experiments is initiated to further elucidate this important field.

Electronic supplementary material

The online version of this article (doi:10.1186/s13019-014-0151-3) contains supplementary material, which is available to authorized users.

Rapid tolerance induction by hematopoietic progenitor cells in the absence of donor-matched lymphoid cells

BACKGROUND

Donor specific hematopoietic cell transplantation has long been recognized for its potential in tolerance induction for subsequently transplanted organs. We have recently published that co-administration of Myeloid Progenitor (MP) and third party Hematopoietic Stem Cells (HSC) can induce MP-specific tolerance for subsequently transplanted organs [1].

METHODS

Mice received an allogeneic HSC and third party MP transplantation simultaneous with placement of a MP-matched skin graft. Variants tested include time of graft placement, MP genotype and source of cells.

RESULTS

Using B10;B6-Rag2(-/-)Il2rg(-/-) mice, we demonstrate that specific tolerance can be induced by MP given simultaneous with the skin graft in the complete absence of MP-donor-matched lymphoid cells. Ex vivo expanded MP function as well as sorted cells in inducing tolerance. In addition we demonstrate that tolerance can be induced by MP in the context of autologous HSC transplantation.

CONCLUSIONS

Our results demonstrate that the previously observed expansion of organ donor matched Treg is not essential for tolerance, and that MP tolerance protocols can be envisioned in most clinical settings, including those involving deceased donor organs.

Mesenchymal stem cells attenuate rat graft-versus-host disease

Mesenchymal stem cells (MSCs) derived from bone marrow are feasible for the exertion of a powerful immunoregulatory effect and thus shall hold a curative potency in T lymphocyte-dependent pathologies. This current article is intended to describe the method to investigate that MSCs might take advantage of regulation in graft-versus-host disease (GvHD), a major etiology of attack rate and lethality post allogeneic hematopoietic stem cell transplantation (HSCT). MSCs were isolated from Lewis rat bone morrow and cultured for 4 weeks. The purification of enriched conventional MSCs and macrophages was achieved by autoMACS. Using the limiting dilution method, MSCs were cloned and then expanded until more than 6 months. The cultured MSCs showed a typical spindle-shaped morphology and immunophenotypes, lack of CD45 and CD11b/c expression. MSCs are also known for their ability to differentiate into adipocytes. MSCs, like macrophages, exhibit the immunomodulatory propensity to inhibit T lymphocyte proliferation. Following the adoptive transfer, MSCs regulate systemic Lewis to (Lewis × DA) F1 rat GvHD. Meanwhile, the cloned MSCs surprisingly enhanced T cell proliferation in vitro and yielded no clinical benefit in regard to the incidence or severity of GvHD. This is in contradistinction to the immunosuppressive activities of MSCs as conventionally described. Hence, this rat GvHD model treated with MSCs has shown intriguing differences in the regulatory effects of lymphocyte proliferation and GvHD repression between short-term cultured conventional MSCs and cloned MSCs.

Xenotransplantation of human cultured parathyroid progenitor cells into mouse peritoneum does not induce rejection reaction

INTRODUCTION

Parathyroid progenitor cells devoid of immunogenic antigens were used for human allotransplantation. Although there were many potential reasons for the expiry of transplant activity in humans, we decided to exclude a subclinical form of rejection reaction, and test the rejection reaction in an animal model.

MATERIAL AND METHODS

Experiments were carried out on 40 conventional male mice in their third month of life. The animals were housed in groups of 10 per cage in 4 cages with fitted water dispensers and fed a conventional diet based on standard pellet food. They were divided into four groups of 10 animals each, three experimental groups and one control group. Identified progenitor cells were stored in a cell bank. After testing the phenotype, viability, and absence of immunogenic properties, the cells were transplanted into mouse peritoneum cavity.

RESULTS

Animals were observed for 9 weeks. At 9 weeks of observation, the mean serum PTH concentration in the experimental groups was 2.0-2.5 pg/ml, while in the control group it did not exceed 1.5 pg/ml. The immunohistochemical assays demonstrated that millions of viable cells with a phenotype identical to the endocrine cells had survived in the peritoneum. Histologic specimens from different internal organs stained for PTH revealed positive cells labelled with anti-PTH Ab in the intestinal lamina, brain, liver, and spleen.

CONCLUSIONS

In the present paper we have demonstrated that xenotransplantation may be used as a model for an explanation of the immunogenic properties of cells generated from postnatal organs for regenerative therapy.

Stem cells from trabecular meshwork home to TM tissue in vivo

PURPOSE

To investigate the potential of human trabecular meshwork stem cells (TMSCs) for homing to mouse TM tissue and survival in vivo.

METHODS

Human TMSCs and fibroblasts were labeled with fluorescent membrane dye DiO and injected into normal mouse anterior chamber. Stem cell and TM cell markers were identified by immunofluorescent staining of cryosections or tissue whole mounts. Apoptosis was determined by TUNEL assay. Replicating and inflammatory cells were detected by bromodeoxyuridine (BrdU) incorporation and anti-CD45 staining, respectively. Quantitative RT-PCR detected gene expression of injected cells after isolation by fluorescence activated cell sorting. Intraocular pressure was measured using a TonoLab rebound tonometer.

RESULTS

Expanded cultures of DiO-labeled TMSCs expressed stem cell markers preferentially in DiO positive cells, demonstrating a slow-cycling, label-retaining stem cell phenotype. DiO-labeled TMSCs injected into the anterior chamber of normal mice localized primarily in TM, remaining in the tissue at least 4 months. Within 1 week, TM-associated TMSCs began expressing TM marker protein CHI3L1. Fibroblasts injected in mouse anterior chamber showed distributed localization in corneal endothelium, lens epithelium, and TM and did not express CHI3L1. Little apoptosis was detected in injected TM tissue and intraocular pressure was not elevated during the experiment. Dividing cells or CD45-staining cells were not detected after TMSC-injection.

CONCLUSIONS

Stem cells isolated from human TM and expanded in vitro exhibit the ability to home to the TM and differentiate into TM cells in vivo. Such cells present a potential for development of a novel cell-based therapy for glaucoma.

Host stem cells repopulate liver allografts: reverse chimerism

Liver transplant has become life-saving therapy for thousands of patients with end stage liver disease in the United States, but chronic rejection and the toxicities of immunosuppression remain significant obstacles to the further expansion of this modality and "transplant tolerance" remains a central goal in the field. So we and others are looking for alternative post-transplant strategies. We set out to 'engineer' repopulation after transplantation in a strain combination [dark agouti (DA) to Lewis green fluorescent protein+ (LEW GFP+)] which rejects liver grafts strongly, a model that more closely resembles the situation in humans. Our central finding is purposeful manipulation of the immune response with low dose immunosuppression and liberation of stem cells for a very short period after transplantation results in long-term transplant acceptance by two mechanisms: transforming the liver (donor) to self (host) phenotype, and auto-suppression of the specific allograft response.

Bone marrow-derived conventional, but not cloned, mesenchymal stem cells suppress lymphocyte proliferation and prevent graft-versus-host disease in rats

Bone marrow-derived mesenchymal stem cells (MSCs) could exert a potent immunosuppressive effect, and therefore may have a therapeutic potential in T-cell-dependent pathologies. In the present study, we aimed to determine whether MSCs could be used to control graft-versus-host disease (GvHD), a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). MSCs were isolated from Lewis rat bone morrow and then cultured in 10% FBS DMEM at 37°C for 4 weeks. The enriched conventional MSCs and macrophages were purified by auto-MACS. Cloned MSCs were obtained by cloning using the limiting dilution method and expanded up to more than 6 months. The identity of MSCs was confirmed by their typical spindle-shaped morphology and immunophenotypic criteria, based on the absence of expression of CD45 and CD11b/c molecules. Both types of MSCs were also tested for their ability to differentiate into adipocytes. We showed that MSCs, like macrophages, exhibit immunomodulatory properties capable of inhibiting T-cell proliferation stimulated by alloantigens, anti-CD3e/CD28 mAbs, and ConA in a dose-dependent manner in vitro. After performing adoptive transfer, MSCs suppressed systemic Lewis to (Lewis × DA)F1 rat GvHD. In contrast to the immunosuppressive activities of conventional MSCs, the cloned MSCs enhanced T-cell proliferation in vitro and yielded no clinical benefit in regard to the incidence or severity of GvHD. Therefore, these rat models have shown intriguing differences in the suppression effects of lymphocyte proliferation and GvHD prevention between short-term cultured conventional MSCs and cloned MSCs.

Bone marrow mesenchymal stem cells can differentiate and assume corneal keratocyte phenotype

It remains elusive as to what bone marrow (BM) cell types infiltrate into injured and/or diseased tissues and subsequently differentiate to assume the phenotype of residential cells, for example, neurons, cardiac myocytes, keratocytes, etc., to repair damaged tissue. Here, we examined the possibility of whether BM cell invasion via circulation into uninjured and injured corneas could assume a keratocyte phenotype, using chimeric mice generated by transplantation of enhanced green fluorescent protein (EGFP)⁺ BM cells into keratocan null (Kera^−/−) and lumican null (Lum^−/−) mice. EGFP⁺ BM cells assumed dendritic cell morphology, but failed to synthesize corneal-specific keratan sulfate proteoglycans, that is KS-lumican and KS-keratocan. In contrast, some EGFP⁺ BM cells introduced by intrastromal transplantation assumed keratocyte phenotypes. Furthermore, BM cells were isolated from Kera-Cre/ZEG mice, a double transgenic mouse line in which cells expressing keratocan become EGFP⁺ due to the synthesis of Cre driven by keratocan promoter. Three days after corneal and conjunctival transplantations of such BM cells into Kera^−/− mice, green keratocan positive cells were found in the cornea, but not in conjunctiva. It is worthy to note that transplanted BM cells were rejected in 4 weeks. MSC isolated from BM were used to examine if BM mesenchymal stem cells (BM-MSC) could assume keratocyte phenotype. When BM-MSC were intrastromal-transplanted into Kera^−/− mice, they survived in the cornea without any immune and inflammatory responses and expressed keratocan in Kera^−/− mice. These observations suggest that corneal intrastromal transplantation of BM-MSC may be an effective treatment regimen for corneal diseases involving dysfunction of keratocytes.

Intravenous mesenchymal stem cells prevented rejection of allogeneic corneal transplants by aborting the early inflammatory response

Mesenchymal stem/progenitor cells (MSCs) were reported to enhance the survival of cellular and organ transplants. However, their mode of action was not established. We here used a mouse model of corneal allotransplantation and demonstrated that peri-transplant intravenous (i.v.) infusion of human MSCs (hMSCs) decreased the early surgically induced inflammation and reduced the activation of antigen-presenting cells (APCs) in the cornea and draining lymph nodes (DLNs). Subsequently, immune rejection was decreased, and allograft survival was prolonged. Quantitative assays for human GAPDH revealed that <10 hMSCs out of 1 × 10(6) injected cells were recovered in the cornea 10 hours to 28 days after i.v. infusion. Most of hMSCs were trapped in lungs where they were activated to increase expression of the gene for a multifunctional anti-inflammatory protein tumor necrosis factor-α stimulated gene/protein 6 (TSG-6). i.v. hMSCs with a knockdown of TSG-6 did not suppress the early inflammation and failed to prolong the allograft survival. Also, i.v. infusion of recombinant TSG-6 reproduced the effects of hMSCs. Results suggest that hMSCs improve the survival of corneal allografts without engraftment and primarily by secreting TSG-6 that acts by aborting early inflammatory responses. The same mechanism may explain previous reports that MSCs decrease rejection of other organ transplants.

Detrimental effects of rat mesenchymal stromal cell pre-treatment in a model of acute kidney rejection

Mesenchymal stromal cells (MSC) have shown immunomodulatory and tissue repair potential including partial tolerance induction by pre-treatment of donor-specific cells in a rat heart transplantation model. Very recently, we could show that autologous MSC attenuated ischemia reperfusion injury in a highly mismatched donor–recipient rat kidney transplant model. Therefore, we investigated donor-specific MSC pre-treatment in this rat kidney transplantation model to study whether graft function could be improved, or if tolerance could be induced. Donor- and recipient-type MSC or phosphate buffered saline (PBS) as a control was injected i.v. 4 days before kidney transplantation. Mycophenolate mofetil immunosuppression (20mg/kg body weight) was applied for 7 days. Kidney grafts and spleens were harvested between days 8 and 10 and analyzed by quantitative RT-PCR and immunohistology. In addition, creatinine levels in the blood were measured and serum was screened for the presence of donor-specific antibodies. Surprisingly, application of both donor- and recipient-specific MSC resulted in enhanced humoral immune responses verified by intragraft B cell infiltration and complement factor C4d deposits. Moreover, signs of inflammation and rejection were generally enhanced in both MSC-treated groups relative to PBS control group. Additionally, pre-treatment with donor-specific MSC significantly enhanced the level of donor-specific antibody formation when compared with PBS- or recipient MSC-treated groups. Pre-treatment with both MSC types resulted in a higher degree of kidney cortex tissue damage and elevated creatinine levels at the time point of rejection. Thus, MSC pre-sensitization in this model impairs the allograft outcome. Our data from this pre-clinical kidney transplantation model indicate that pre-operative MSC administration may not be optimal in kidney transplantation and caution must be exerted before moving forward with clinical studies in order to avoid adverse effects.

Bone marrow-derived mesenchymal stem cells as immunosuppressants in liver transplantation: a review of current data

This article provides an overview of the current knowledge relating to the potential use of bone marrow-derived mesenchymal stem cells (BM-MSCs) acting as immunosuppressants after liver transplantation. Clinical use of BM-MSCs in liver transplantation remains experimental, as there is uncertainty as to their mechanism of action, conflicting studies in animal models, and the possibility of their cellular fusion with hepatocytes leading to potentially genetically unstable hepatocytes. These obstacles, to their underuse, have been decreasing, and BM-MSCs have elicited great interest for possible use in solid organ transplantation. Bone marrow-derived-MSCs, when transplanted systemically, might positively influence grafted organ outcome through cell-cell contact or the secretion of soluble factors that are immunomodulatory. Thus, the use of BM-MSCs to modulate organ rejection may directly or indirectly influence the survival properties of transplanted livers.

Bone marrow transplantation combined with mesenchymal stem cells induces immune tolerance without cytotoxic conditioning

BACKGROUND

Transplantation of allogeneic donor bone marrow (BM) into sufficiently conditioned recipients is an effective approach to induce immune tolerance as assessed by mixed chimerism. However, this approach is hampered by the lack of feasible protocols devoid of cytoreductive conditioning. We investigated whether mixed chimerism could be established by intra-bone marrow-bone marrow transplantation (IBM-BMT) combined with bone marrow-derived mesenchymal stem cells (BMSCs) treatment without additional cytoreductive conditioning.

MATERIALS AND METHODS

The recipient mice (C57BL/6) accepted BMSCs from donor mice (Balb/c) through daily tail vein injection for 4 d followed by IBM-BMT immediately. Full-thickness skin grafts from donor mice as well as from the third party mice (ICR) were transplanted to the dorsum of the recipient mice after the combined IBM-BMT with BMSCs treatment. The immune tolerance was assessed by the survival time of skin allografts. The establishment of mixed chimerism and cytokine expression profile in recipient peripheral blood were determined by flow cytometry and enzyme-linked immunosorbent assay, respectively.

RESULTS

IBM-BMT combined with BMSCs treatment led to stable mixed chimerism and donor-specific skin graft tolerance. The flow cytometry analysis revealed that recipient mice developed 20%-25% chimerism levels among the myeloid lineage. The skin allografts survived more than 1 y and the hair re-grew normally on the grafts. Cytokine profile showed that IBM-BMT combined with BMSCs treatment prolonged humoral tolerance in recipient chimeras.

CONCLUSIONS

Our results demonstrate that donor specific immune tolerance can be effectively induced by IBM-BMT combined with BMSCs treatment without any additional cytoreductive recipient treatment. This approach provides a promising allograft transplantation strategy when the donor bone marrow is available.

Immunosuppressive mechanisms of embryonic stem cells and mesenchymal stem cells in alloimmune response

Although both embryonic stem cells (ESCs) and mesenchymal stem cells (MSCs) are known to have immunosuppressive effects, the mechanisms of immunosuppression are still controversial. Both types of stem cells suppressed not only the proliferation but also survival of CD4(+) T cells in vitro. They suppressed secretion of various cytokines (IL-2, IL-12, IFN-γ, TNF-α, IL-4, IL-5, IL-1β, and IL-10), whereas there was no change in the levels of TGF-β or IDO. Classic and modified transwell experiments demonstrated that immunosuppressive activities were mainly mediated by cell-to-cell contact. Granzyme B in the ESCs played a significant role in their immunosuppression, whereas PDL-1, Fas ligand, CD30 or perforin was not involved in the contact-dependent immunosuppression. However, none of the above molecules played a significant role in the immunosuppression by the MSCs. Interestingly, both stem cells increased the proportion of Foxp3(+) regulatory T cells. Our results showed that both ESCs and MSCs suppressed the survival as well as the proliferation of T cells by mainly contact-dependent mechanisms and increased the proportion of regulatory T cells. Granzyme B was involved in immunosuppression by the ESCs in a perforin-independent manner.

Immunogenicity and immunomodulatory properties of umbilical cord lining mesenchymal stem cells

We here present an immunologic head-to-head comparison between human umbilical cord lining mesenchymal stem cells (clMSCs) and adult bone marrow MSCs (bmMSCs) from patients >65 years of age. clMSCs had significantly lower HLA class I expression, higher production of tolerogenic TGF-β and IL-10, and showed significantly faster proliferation. In vitro activation of allogeneic lymphocytes and xenogeneic in vivo immune activation was significantly stronger with bmMSCs, whereas immune recognition of clMSCs was significantly weaker. Thus, bmMSCs were more quickly rejected in immunocompetent mice. IFN-γ at 25 ng/ml increased both immunogenicity by upregulation of HLA class I/ HLA-DR expression and tolerogenicity by increasing intracellular HLA-G and surface HLA-E expression, augmenting TGF-β and IL-10 release, and inducing indoleamine 2,3-dioxygenase (IDO) expression. Higher concentrations of IFN-γ (>50 ng/ml) further enhanced the immunosuppressive phenotype of clMSCs, more strongly downregulating HLA-DR expression and further increasing IDO production (at 500 ng/ml). The net functional immunosuppressive efficacy of MSCs was tested in mixed lymphocyte cultures. Although both clMSCs and bmMSCs significantly reduced in vitro immune activation, clMSCs were significantly more effective than bmMSCs. The veto function of both MSC lines was enhanced in escalating IFN-γ environments. In conclusion, clMSCs show a more beneficial immunogeneic profile and stronger overall immunosuppressive potential than aged bmMSCs.

Cell therapy of congenital corneal diseases with umbilical mesenchymal stem cells: lumican null mice

BACKGROUND

Keratoplasty is the most effective treatment for corneal blindness, but suboptimal medical conditions and lack of qualified medical personnel and donated cornea often prevent the performance of corneal transplantation in developing countries. Our study aims to develop alternative treatment regimens for congenital corneal diseases of genetic mutation.

METHODOLOGY/PRINCIPAL FINDINGS

Human mesenchymal stem cells isolated from neonatal umbilical cords were transplanted to treat thin and cloudy corneas of lumican null mice. Transplantation of umbilical mesenchymal stem cells significantly improved corneal transparency and increased stromal thickness of lumican null mice, but human umbilical hematopoietic stem cells failed to do the same. Further studies revealed that collagen lamellae were re-organized in corneal stroma of lumican null mice after mesenchymal stem cell transplantation. Transplanted umbilical mesenchymal stem cells survived in the mouse corneal stroma for more than 3 months with little or no graft rejection. In addition, these cells assumed a keratocyte phenotype, e.g., dendritic morphology, quiescence, expression of keratocyte unique keratan sulfated keratocan and lumican, and CD34. Moreover, umbilical mesenchymal stem cell transplantation improved host keratocyte functions, which was verified by enhanced expression of keratocan and aldehyde dehydrogenase class 3A1 in lumican null mice.

CONCLUSIONS/SIGNIFICANCE

Umbilical mesenchymal stem cell transplantation is a promising treatment for congenital corneal diseases involving keratocyte dysfunction. Unlike donated corneas, umbilical mesenchymal stem cells are easily isolated, expanded, stored, and can be quickly recovered from liquid nitrogen when a patient is in urgent need.

The immunosuppressive effect of embryonic stem cells and mesenchymal stem cells on both primary and secondary alloimmune responses

Recently, both embryonic stem cells and mesenchymal stem cells have been demonstrated to have immunosuppressive effects. The purpose of this study was to elucidate whether the embryonic stem cells and/or mesenchymal stem cells modulate both primary and secondary alloimmune responses. Both stem cells suppressed in vitro proliferation and cytokine production in primary alloimmune responses. They also suppressed in vitro proliferation and cytokine production of the allosensitized CD44+ memory T cells. However, they failed to prolong skin graft survival across both a major mismatch barrier (BALB/C, C57BL6/J) and a minor mismatch barrier (male to female). In conclusion, both embryonic stem cells and mesenchymal stem cells can suppress secondary alloimmune response in vitro as well as primary alloimmune responses; however, neither embryonic stem cells nor mesenchymal stem cells suppressed allograft rejection in stringent murine skin transplantation models.

Toward MSC in solid organ transplantation: 2008 position paper of the MISOT study group

The following position paper summarizes the recommendations for early clinical trials and ongoing basic research in the field of mesenchymal stem cell-induced solid organ graft acceptance--agreed upon on the first meeting of the Mesenchymal Stem Cells In Solid Organ Transplantation (MISOT) study group in late 2008.