Mesenchymal stromal cells: facilitators of successful transplantation? Cell Stem Cell. 2010;7:431-442. [PMID: 20887949 DOI: 10.1016/j.stem.2010.09.009]

Mesenchymal stem cells differentially mediate regulatory T cells and conventional effector T cells to protect fully allogeneic islet grafts in mice

AIMS/HYPOTHESIS

Limited information is available on the cellular interactions between regulatory T (T(reg)) cells and mesenchymal stem cells (MSCs). In particular, a direct effect of MSCs on the survival and proliferation of T(reg) cells has not been demonstrated.

METHODS

We investigated the effects of MSCs on effector T (T(eff)) cells and T(reg) cells, and the molecular mechanisms involved in the distinct regulation of these two cell populations by MSCs in vivo and in vitro.

RESULTS

We show that MSCs are capable of selectively suppressing T(eff) cells and fostering the generation of T(reg) cells. T(eff) cells, but not T(reg) cells, fail to respond to IL-2 and undergo profound apoptosis in the presence of MSCs. The differential regulations of these two T cell subsets by MSCs are associated with their distinct expressions of CD25, with MSCs specifically reducing the expression of CD25 on T(eff) and sparing T(reg) cells intact. In vivo, the administration of MSCs significantly delays the rejection of allogeneic islet grafts in adaptive transferred recipients by favouring the induction of T(reg) cells. In this model, MSCs inhibit the proliferation and development of alloreactive T(eff) but potently enhance the induction of T(reg) cells.

CONCLUSIONS/INTERPRETATION

We demonstrate that MSCs are capable of regulating T(eff) and T(reg) cells differentially in vitro. MSCs inhibit T(eff) cells by inducing apoptosis and impairing the proliferative response to IL-2 in T(eff) cells, but favour the survival and expansion of T(reg) cells. This result is further demonstrated in mice that have undergone allogeneic islet transplantation, in which MSCs suppress alloreactive T(eff) cells while favouring the induction of T(reg) cells, thus protecting the islet allografts from rejection.

In vitro reprogramming of rat bone marrow-derived mesenchymal stem cells into insulin-producing cells by genetically manipulating negative and positive regulators

Islet cell replacement therapy represents the most promising approach for the cure of type 1 diabetes if autoimmunity to β cells is under control. However, this potential is limited by a shortage of pancreas donors. To address the donor shortage problem, we determined whether bone marrow-derived mesenchymal stem cells (bmMSCs) can be directly reprogrammed to islet lineages by simultaneously forced suppression and over-expression of key regulator genes that play critical roles during pancreas development. Here, we report that rat bmMSCs were converted in vitro into insulin-producing cells by suppressing two-repressor genes repressor element-1 silencing transcription factor/neuronal restrictive silencing factor (Rest/Nrsf) and sonic hedgehog (Shh) and by over-expressing pancreas and duodenal transcription factor 1 (Pdx1). The reprogrammed bmMSCs expressed both genes and proteins specific for islet cells. These converted cells were capable of releasing insulin in a glucose-responsive manner. Our study suggests that bmMSCs may ultimately be reprogrammed to functional insulin-secreting cells.

Proliferative potential of multipotent mesenchymal stromal cells from human bone marrow

We studied the capacity of multipotent mesenchymal stromal cells isolated from human bone marrow (BM) to long-term passaging, cloning, and re-cloning. Initial multipotent mesenchymal stromal cells and cells after gene labeling were studied. Multipotent mesenchymal stromal cells were obtained from donors (13-59 years) and cultured for 7 passages. Third generation lentivector was used for delivery of green fluorescent protein marker gene. The procedure of infection revealed reduced proliferative potential of multipotent mesenchymal stromal cells from elder donors. Hierarchy of precursor cells differing by their proliferative potential was demonstrated in the culture of multipotent mesenchymal stromal cells. Three categories of multipotent mesenchymal stromal cells were identified: mature cells incapable of proliferation (75.7±2.4% population) and cells with low and high proliferative potential (17.6±2.1 and 6.7±0.3%, respectively). The relative content of these cells insignificantly differed from passage to passage. The efficiency of cloning also remains stable, but re-cloning capacity sharply decreased after passage 3 and completely disappeared in multipotent mesenchymal stromal cells after cryopreservation. Thus, cultured multipotent mesenchymal stromal cells represent a heterogeneous and hierarchically organized population and the characteristics of this population depend of the duration of culturing and age of BM donor. This should be taken into account when using multipotent mesenchymal stromal cells in clinical practice.

Immunomodulatory properties of mesenchymal stem cells and their therapeutic applications

Mesenchymal stem cells (MSCs) are adult stem cells that can be isolated from most adult tissues, including bone marrow, adipose, liver, amniotic fluid, lung, skeletal muscle and kidney. The term MSC is currently being used to represent both mesenchymal stem cells and multipotent mesenchymal stromal cells. Numerous reports on systemic administration of MSCs leading to functional improvements based on the paradigm of engraftment and differentiation have been published. However, it is not only difficult to demonstrate extensive engraftment of cells, but also no convincing clinical results have been generated from phase 3 trials as of yet and prolonged responses to therapy have been noted after identification of MSCs had discontinued. It is now clear that there is another mechanism by which MSCs exert their reparative benefits. Recently, MSCs have been shown to possess immunomodulatory properties. These include suppression of T cell proliferation, influencing dendritic cell maturation and function, suppression of B cell proliferation and terminal differentiation, and immune modulation of other immune cells such as NK cells and macrophages. In terms of the clinical applications of MSCs, they are being tested in four main areas: tissue regeneration for cartilage, bone, muscle, tendon and neuronal cells; as cell vehicles for gene therapy; enhancement of hematopoietic stem cell engraftment; and treatment of immune diseases such as graft-versus-host disease, rheumatoid arthritis, experimental autoimmune encephalomyelitis, sepsis, acute pancreatitis and multiple sclerosis. In this review, the mechanisms of immunomodulatory effects of MSCs and examples of animal and clinical uses of their immunomodulatory effects are described.

PDGFRβ expression and function in fibroblasts derived from pluripotent cells is linked to DNA demethylation

Platelet-derived growth factor receptor-beta (PDGFRβ) is required for the development of mesenchymal cell types, and plays a diverse role in the function of fibroblasts in tissue homeostasis and regeneration. In this study, we characterized the expression of PDGFRβ in fibroblasts derived from human embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs), and showed that this expression is important for cellular functions such as migration, extracellular matrix production and assembly in 3D self-assembled tissues. To determine potential regulatory regions predictive of expression of PDGFRβ following differentiation from ESCs and iPSCs, we analyzed the DNA methylation status of a region of the PDGFRB promoter that contains multiple CpG sites, before and after differentiation. We demonstrated that this promoter region is extensively demethylated following differentiation, and represents a developmentally regulated, differentially methylated region linked to PDGFRβ expression. Understanding the epigenetic regulation of genes such as PDGFRB, and identifying sites of active DNA demethylation, is essential for future applications of iPSC-derived fibroblasts for regenerative medicine.

Targeting lysophosphatidic acid signaling retards culture-associated senescence of human marrow stromal cells

Marrow stromal cells (MSCs) isolated from mesenchymal tissues can propagate in vitro to some extent and differentiate into various tissue lineages to be used for cell-based therapies. Cellular senescence, which occurs readily in continual MSC culture, leads to loss of these characteristic properties, representing one of the major limitations to achieving the potential of MSCs. In this study, we investigated the effect of lysophosphatidic acid (LPA), a ubiquitous metabolite in membrane phospholipid synthesis, on the senescence program of human MSCs. We show that MSCs preferentially express the LPA receptor subtype 1, and an abrogation of the receptor engagement with the antagonistic compound Ki16425 attenuates senescence induction in continually propagated human MSCs. This anti-aging effect of Ki16425 results in extended rounds of cellular proliferation, increased clonogenic potential, and retained plasticity for osteogenic and adipogenic differentiation. Expressions of p16(Ink4a), Rb, p53, and p21(Cip1), which have been associated with cellular senescence, were all reduced in human MSCs by the pharmacological inhibition of LPA signaling. Disruption of this signaling pathway was accompanied by morphological changes such as cell thinning and elongation as well as actin filament deformation through decreased phosphorylation of focal adhesion kinase. Prevention of LPA receptor engagement also promoted ubiquitination-mediated c-Myc elimination in MSCs, and consequently the entry into a quiescent state, G(0) phase, of the cell cycle. Collectively, these results highlight the potential of pharmacological intervention against LPA signaling for blunting senescence-associated loss of function characteristic of human MSCs.

Emerging roles for multipotent, bone marrow-derived stromal cells in host defense

Multipotent, bone marrow-derived stromal cells (BMSCs, also known as mesenchymal stem cells [MSCs]), are culture-expanded, nonhematopoietic cells with immunomodulatory effects currently being investigated as novel cellular therapy to prevent and to treat clinical disease associated with aberrant immune response. Emerging preclinical studies suggest that BMSCs may protect against infectious challenge either by direct effects on the pathogen or through indirect effects on the host. BMSCs may reduce pathogen burden by inhibiting growth through soluble factors or by enhancing immune cell antimicrobial function. In the host, BMSCs may attenuate pro-inflammatory cytokine and chemokine induction, reduce pro-inflammatory cell migration into sites of injury and infection, and induce immunoregulatory soluble and cellular factors to preserve organ function. These preclinical studies provide provocative hints into the direction MSC therapeutics may take in the future. Notably, BMSCs appear to function as a critical fulcrum, providing balance by promoting pathogen clearance during the initial inflammatory response while suppressing inflammation to preserve host integrity and facilitate tissue repair. Such exquisite balance in BMSC function appears intrinsically linked to Toll-like receptor signaling and immune crosstalk.

Human embryonic stem cell-derived mesenchymal stromal cells

Mesenchymal stromal cells (MSCs) originally isolated from marrow have multipotent differentiation potential and favorable immunomodulatory and anti-inflammatory properties that make them very attractive for regenerative cellular therapy. Cells with similar phenotypic characteristics have now been derived from almost all fetal, neonatal, and adult tissues; furthermore, more recently similar cells have also been generated from human embryonic stem cells (ESCs). Generation of MSCs from human ESCs provides an opportunity to study the developmental biology of human mesenchymal lineage generation in vitro. Generation of bone and cartilage from human ESC-derived MSCs and their functional characterization, both in vitro and in vivo, is also an active area of investigation as ESCs could provide an unlimited source of MSCs for potential repair of bone and cartilage defects. MSCs from adult sources are being investigated in numerous Phase I-III clinical trials for a wide variety of indications, mainly based on their immunomodulatory properties. Our group and others have shown MSCs derived from human ESCs possess immunomodulatory properties similar to marrow-derived MSCs. Immunomodulatory properties of ESC-derived MSCs could prove to be highly valuable for their potential clinical applications in the future as derivatives of human ESCs have already entered clinical arena in the context of Phase I clinical trials.

Human mesenchymal stem cells protect human islets from pro-inflammatory cytokines

Transplantation of human islets is an attractive alternative to daily insulin injections for patients with type 1 diabetes. However, the majority of islet recipients lose graft function within five years. Inflammation is a primary contributor to graft loss, and inhibiting pro-inflammatory cytokine activity can reverse inflammation mediated dysfunction of islet grafts. As mesenchymal stem cells (MSCs) possess numerous immunoregulatory properties, we hypothesized that MSCs could protect human islets from pro-inflammatory cytokines. Five hundred human islets were co-cultured with 0.5 or 1.0 × 10(6) human MSCs derived from bone marrow or pancreas for 24 hours followed by 48 hour exposure to interferon-γ, tumor necrosis factor-α and interleukin 1β. Controls include islets cultured alone (± cytokines) and with human dermal fibroblasts (± cytokines). For all conditions, glucose stimulated insulin secretion (GSIS), total islet cellular insulin content, islet β cell apoptosis, and potential cytoprotective factors secreted in the culture media were determined. Cytokine exposure disrupted human islet GSIS based on stimulation index and percentage insulin secretion. Conversely, culture with 1.0 × 10(6) bMSCs preserved GSIS from cytokine treated islets. Protective effects were not observed with fibroblasts, indicating that preservation of human islet GSIS after exposure to pro-inflammatory cytokines is MSC dependent. Islet β cell apoptosis was observed in the presence of cytokines; however, culture of bMSCs with islets prevented β cell apoptosis after cytokine treatment. Hepatocyte growth factor (HGF) as well as matrix metalloproteinases 2 and 9 were also identified as putative secreted cytoprotective factors; however, other secreted factors likely play a role in protection. This study, therefore, demonstrates that MSCs may be beneficial for islet engraftment by promoting cell survival and reduced inflammation.

Mesenchymal stem cell-based tissue regeneration is governed by recipient T lymphocytes via IFN-γ and TNF-α

Stem cell-based regenerative medicine is a promising approach in tissue reconstruction. Here we show that proinflammatory T cells inhibit the ability of exogenously added bone marrow mesenchymal stem cells (BMMSCs) to mediate bone repair. This inhibition is due to interferon γ (IFN-γ)-induced downregulation of the runt-related transcription factor 2 (Runx-2) pathway and enhancement of tumor necrosis factor α (TNF-α) signaling in the stem cells. We also found that, through inhibition of nuclear factor κB (NF-κB), TNF-α converts the signaling of the IFN-γ-activated, nonapoptotic form of TNF receptor superfamily member 6 (Fas) in BMMSCs to a caspase 3- and caspase 8-associated proapoptotic cascade, resulting in the apoptosis of these cells. Conversely, reduction of IFN-γ and TNF-α concentrations by systemic infusion of Foxp3(+) regulatory T cells, or by local administration of aspirin, markedly improved BMMSC-based bone regeneration and calvarial defect repair in C57BL/6 mice. These data collectively show a previously unrecognized role of recipient T cells in BMMSC-based tissue engineering.

A chemically defined carrier for the delivery of human mesenchymal stem/stromal cells to skin wounds

Skin has a remarkable capacity for regeneration, but age- and diabetes-related vascular problems lead to chronic non-healing wounds for many thousands of U.K. patients. There is a need for new therapeutic approaches to treat these resistant wounds. Donor mesenchymal stem/stromal cells (MSCs) have been shown to assist cutaneous wound healing by accelerating re-epithelialization. The aim of this work was to devise a low risk and convenient delivery method for transferring these cells to wound beds. Plasma polymerization was used to functionalize the surface of medical-grade silicone with acrylic acid. Cells attached well to these carriers, and culture for up to 3 days on the carriers did not significantly affect their phenotype or ability to support vascular tubule formation. These carriers were then used to transfer MSCs onto human dermis. Cell transfer was confirmed using an MTT assay to assess viable cell numbers and enhanced green fluorescent protein-labeled MSCs to demonstrate that the cells post-transfer attached to the dermis. We conclude that this synthetic carrier membrane is a promising approach for delivery of therapeutic MSCs and opens the way for future studies to evaluate its impact on repairing difficult skin wounds.

Mesenchymal Stromal Cells as a Therapeutic Strategy to Support Islet Transplantation in Type 1 Diabetes Mellitus

Type 1 diabetes is an autoimmune disorder that leads to destruction of pancreatic β islet cells and is a growing global health issue. While insulin replacement remains the standard therapy for type 1 diabetes, exogenous insulin does not mimic the physiology of insulin secretion. Transplantation of pancreatic islets has the potential to cure this disease; however, there are several major limitations to widespread implementation of islet transplants. The use of mesenchymal stromal cells (MSCs) in the treatment of type 1 diabetes has been investigated as an adjunct therapy during islet graft administration to prevent initial islet loss and promote engraftment and revascularization of islets. In this review we will discuss the results of recent MSC studies in animal models of diabetes with a focus on islet transplantation and explore the potential for these findings to be extended to clinical use for the treatment of type 1 diabetes.

Controlling the growth and differentiation of human mesenchymal stem cells by the arrangement of individual carbon nanotubes

Carbon nanotube (CNT) networks on solid substrates have recently drawn attention as a means to direct the growth and differentiation of stem cells. However, it is still not clear whether cells can recognize individual CNTs with a sub-2 nm diameter, and directional nanostructured substrates such as aligned CNT networks have not been utilized to control cell behaviors. Herein, we report that human mesenchymal stem cells (hMSCs) grown on CNT networks could recognize the arrangement of individual CNTs in the CNT networks, which allowed us to control the growth direction and differentiation of the hMSCs. We achieved the directional growth of hMSCs following the alignment direction of the individual CNTs. Furthermore, hMSCs on aligned CNT networks exhibited enhanced proliferation and osteogenic differentiation compared to those on randomly oriented CNT networks. As a plausible explanation for the enhanced proliferation and osteogenic differentiation, we proposed mechanotransduction pathways triggered by high cytoskeletal tension in the aligned hMSCs. Our findings provide new insights regarding the capability of cells to recognize nanostructures smaller than proteins and indicate their potential applications for regenerative tissue engineering.

[Preclinical experience in stem cell therapy for digestive tract diseases]

Adult stem cells are multipotent and self-renewing cells that contain several functions; i) migration and homing potential: stem cells can migrate to injured and inflamed tissues. ii) differentiation potential: stem cells which migrated to injured tissues can be differentiated into multiple cell types for repairing and regenerating the tissues. iii) immunomodulatory properties: stem cells, especially mesenchymal stem cells can suppress immune system such as inflammation. All those characteristics might be useful for the treatment of the digestive tract diseases which are complex and encompass a broad spectrum of different pathogenesis. Preclinical stem cell therapy showed some promising results, especially in liver failure, pancreatitis, sepsis, and inflammatory bowel disease. If we can understand more about the mechanism of stem cell action, stem cell therapy can become a promising alternative treatment for refractory digestive disease in the near future. In this review, we summarized current preclinical experiences in diseases of the digestive tract using stem cells. (Korean J Gastroenterol 2011;58:133-138).

New hope for type 2 diabetics: targeting insulin resistance through the immune modulation of stem cells

The prevalence of type 2 diabetes (T2D) is increasing worldwide, highlighting the need for a better understanding of the pathogenesis of the disease and the development of innovative therapeutic approaches for the prevention and cure of the condition. Mounting evidence points to the involvement of immune dysfunction in insulin resistance in T2D, suggesting that immune modulation may be a useful tool in treating the disease. Recent advances in the use of adult stem cells from human umbilical cord blood and bone marrow for immune modulation hold promise for overcoming immune dysfunction in T2D without many of the complications associated with traditional immunosuppressive therapies. This review focuses on recent progress in the use of immune modulation in T2D and discusses the potential for future therapies. New insights are provided on the use of cord blood-derived multipotent stem cells (CB-SC) in T2D.

Mesenchymal stem cell inhibition of T-helper 17 cell- differentiation is triggered by cell-cell contact and mediated by prostaglandin E2 via the EP4 receptor

Mesenchymal stem cells (MSCs) inhibit T-cell activation and proliferation but their effects on individual T-cell-effector pathways and on memory versus naïve T cells remain unclear. MSC influence on the differentiation of naïve and memory CD4(+) T cells toward the Th17 phenotype was examined. CD4(+) T cells exposed to Th17-skewing conditions exhibited reduced CD25 and IL-17A expression following MSC co-culture. Inhibition of IL-17A production persisted upon re-stimulation in the absence of MSCs. These effects were attenuated when cell-cell contact was prevented. Th17 cultures from highly purified naïve- and memory-phenotype responders were similarly inhibited. Th17 inhibition by MSCs was reversed by indomethacin and a selective COX-2 inhibitor. Media from MSC/Th17 co-cultures contained increased prostaglandin E2 (PGE2) levels and potently suppressed Th17 differentiation in fresh cultures. MSC-mediated Th17 inhibition was reversed by a selective EP4 antagonist and was mimicked by synthetic PGE2 and a selective EP4 agonist. Activation-induced IL-17A secretion by naturally occurring, effector-memory Th17 cells from a urinary obstruction model was also inhibited by MSC co-culture in a COX-dependent manner. Overall, MSCs potently inhibit Th17 differentiation from naïve and memory T-cell precursors and inhibit naturally-occurring Th17 cells derived from a site of inflammation. Suppression entails cell-contact-dependent COX-2 induction resulting in direct Th17 inhibition by PGE2 via EP4.

Hepatocellular carcinoma cells and their fibrotic microenvironment modulate bone marrow-derived mesenchymal stromal cell migration in vitro and in vivo

Hepatocellular carcinoma (HCC) is the fifth most common cancer and the third cause of cancer-related death. Fibrogenesis is an active process characterized by the production of several proinflammatory cytokines, chemokines and growth factors. It involves the activation of hepatic stellate cells (HSCs) which accumulate at the site of injury and are the main source of the extracellular matrix deposits. There are no curative treatments for advanced HCC, thus, new therapies are urgently needed. Mesenchymal stromal cells (MSCs) have the ability to migrate to sites of injury or to remodeling tissues after in vivo administration; however, in several cancer models they demonstrated limited efficacy to eradicate experimental tumors partially due to poor engraftment. Thus, the aim of this work was to analyze the capacity of human MSCs (hMSCs) to migrate and anchor to HCC tumors. We observed that HCC and HSCs, but not nontumoral stroma, produce factors that induce hMSC migration in vitro. Conditioned media (CM) generated from established HCC cell lines were found to induce higher levels of hMSC migration than CM derived from fresh patient tumor samples. In addition, after exposure to CM from HCC cells or HSCs, hMSCs demonstrated adhesion and invasion capability to endothelial cells, type IV collagen and fibrinogen. Consistently, these cells were found to increase metalloproteinase-2 activity. In vivo studies with subcutaneous and orthotopic HCC models indicated that intravenously infused hMSCs migrated to lungs, spleen and liver. Seven days post-hMSC infusion cells were located also in the tumor in both models, but the signal intensity was significantly higher in orthotopic than in subcutaneous model. Interestingly, when orthotopic HCC tumors where established in noncirrhotic or cirrhotic livers, the amount of hMSCs localized in the liver was higher in comparison with healthy animals. A very low signal was found in lungs and spleens, indicating that liver tumors are able to recruit them at high efficiency. Taken together our results indicate that HCC and HSC cells produce factors that efficiently induce hMSC migration toward tumor microenvironment in vitro and in vivo and make MSCs candidates for cell-based therapeutic strategies to hepatocellular carcinoma associated with fibrosis.

Mesenchymal stem cell effects on T-cell effector pathways

Mesenchymal stem (stromal) cells (MSCs) are rare, multipotent progenitor cells that can be isolated and expanded from bone marrow and other tissues. Strikingly, MSCs modulate the functions of immune cells, including T cells, B cells, natural killer cells, monocyte/macrophages, dendritic cells, and neutrophils. T cells, activated to perform a range of different effector functions, are the primary mediators of many autoimmune and inflammatory diseases as well as of transplant rejection and graft-versus-host disease. Well-defined T-cell effector phenotypes include the CD4⁺ (T helper cell) subsets Th1, Th2, and Th17 cells and cytotoxic T lymphocytes derived from antigen-specific activation of naïve CD8⁺ precursors. In addition, naturally occurring and induced regulatory T cells (T_reg) represent CD4⁺ and CD8⁺ T-cell phenotypes that potently suppress effector T cells to prevent autoimmunity, maintain self-tolerance, and limit inflammatory tissue injury. Many immune-mediated diseases entail an imbalance between T_reg and effector T cells of one or more phenotypes. MSCs broadly suppress T-cell activation and proliferation in vitro via a plethora of soluble and cell contact-dependent mediators. These mediators may act directly upon T cells or indirectly via modulation of antigen-presenting cells and other accessory cells. MSC administration has also been shown to be variably associated with beneficial effects in autoimmune and transplant models as well as in several human clinical trials. In a small number of studies, however, MSC administration has been found to aggravate T cell-mediated tissue injury. The multiple effects of MSCs on cellular immunity may reflect their diverse influences on the different T-cell effector subpopulations and their capacity to specifically protect or induce T_reg populations. In this review, we focus on findings from the recent literature in which specific modulatory effects of MSCs on one or more individual effector T-cell subsets and T_reg phenotypes have been examined in vitro, in relevant animal models of in vivo immunological disease, and in human subjects. We conclude that MSCs have the potential to directly or indirectly inhibit disease-associated Th1, Th2, and Th17 cells as well as cytotoxic T lymphocytes but that many key questions regarding the potency, specificity, mechanistic basis, and predictable therapeutic value of these modulatory effects remain unanswered.

Three-dimensional spheroid culture of human gingiva-derived mesenchymal stem cells enhances mitigation of chemotherapy-induced oral mucositis

Mesenchymal stem cells (MSCs) are capable of regenerative and immunomodulatory functions in cell-based therapies in a variety of human diseases and injuries; however, their therapeutic efficacy and potential side effects remain major obstacles in clinical applications. We report here a 3D spheroid culture approach to optimize stem cell properties and therapeutic effects of human gingiva-derived mesenchymal stem cells (GMSCs) in mitigation of experimental oral mucositis. Under growth condition of ultra-low attachment, GMSCs spontaneously aggregated into 3D spheroids and exhibited distinct early stem cell phenotype characterized by elevated expression Stro-1 and CXC chemokine receptor 4 (CXCR-4) as well as OCT-4 and Nanog, 2 important transcriptional factors relevant to stem cell properties, and decreased expression of MSC-associated markers, including CD29, CD90, and CD105. Functionally, spheroid GMSCs are capable of enhanced multipotency and augmented secretion of several chemokines and cytokines relevant to cell migration, survival, and angiogenesis. More importantly, spheroid GMSCs expressed increased levels of reactive oxygen species, hypoxia-inducible factor (HIF)-1 and -2α, and manganese superoxide dismutase, which correlated with improved resistance to oxidative stress-induced apoptosis. Using an in vivo murine model of chemotherapy-induced oral mucositis, we demonstrated that spheroid-derived GMSCs possessed better therapeutic efficacy than their adherent cells in reversing body weight loss and promoting the regeneration of disrupted epithelial lining of the mucositic tongues. These findings suggest that 3D spheroid culture allows early stemness preservation and potentially precondition GMSCs for enhanced mitigation of oral mucositis.

Preclinical studies with umbilical cord mesenchymal stromal cells in different animal models for muscular dystrophy

Umbilical cord mesenchymal stromal cells (MSC) have been widely investigated for cell-based therapy studies as an alternative source to bone marrow transplantation. Umbilical cord tissue is a rich source of MSCs with potential to derivate at least muscle, cartilage, fat, and bone cells in vitro. The possibility to replace the defective muscle cells using cell therapy is a promising approach for the treatment of progressive muscular dystrophies (PMDs), independently of the specific gene mutation. Therefore, preclinical studies in different models of muscular dystrophies are of utmost importance. The main objective of the present study is to evaluate if umbilical cord MSCs have the potential to reach and differentiate into muscle cells in vivo in two animal models of PMDs. In order to address this question we injected (1) human umbilical cord tissue (hUCT) MSCs into the caudal vein of SJL mice; (2) hUCT and canine umbilical cord vein (cUCV) MSCs intra-arterially in GRMD dogs. Our results here reported support the safety of the procedure and indicate that the injected cells could engraft in the host muscle in both animal models but could not differentiate into muscle cells. These observations may provide important information aiming future therapy for muscular dystrophies.

Effects of obstetric factors and storage temperatures on the yield of endothelial colony forming cells from umbilical cord blood

As umbilical cord blood (UCB) is a rich source of endothelial colony-forming cells (ECFC), our aim was twofold: (1) to examine potential obstetric selection criteria for achieving the highest ECFC yields from UCB units, and (2) to determine whether transient storage temperatures of fresh UCB and cryopreservation of UCB units affected ECFC yield and function. ECFC quality was assessed before and after cryopreservation by their clonogenic proliferative potential. Of the 20 factors examined, placental weight was the only statistically significant obstetric factor that predicted ECFC frequency in UCB. Studies on the effects of storage revealed that transient storage of fresh UCB at 4°C reduced ECFC yield compared with storage at 22°C, while cryopreservation of UCB MNCs significantly reduced ECFC recoveries. To our knowledge, this is the first demonstration that placental weight and temperature of storage prior to processing or culture have significant effects on ECFC frequency in UCB. Our studies further support the evidence that cryopreservation of UCB MNCs compromises ECFC recovery.

Mesenchymal stem cells for the treatment of systemic lupus erythematosus: is the cure for connective tissue diseases within connective tissue?

Mesenchymal stem cells (MSCs) are now known to display not only adult stem cell multipotency but also robust anti-inflammatory and regenerative properties. After widespread in vitro and in vivo preclinical testing in several autoimmune disease models, allogenic MSCs have been successfully applied in patients with severe treatment-refractory systemic lupus erythematosus. The impressive results of these uncontrolled phase I and II trials - mostly in patients with non-responding renal disease - point to the need to perform controlled multicentric trials. In addition, they suggest that there is much to be learned from the basic and clinical science of MSCs in order to reap the full potential of these multifaceted progenitor cells in the treatment of autoimmune diseases.

Intestinal myofibroblasts: targets for stem cell therapy

The subepithelial intestinal myofibroblast is an important cell orchestrating many diverse functions in the intestine and is involved in growth and repair, tumorigenesis, inflammation, and fibrosis. The myofibroblast is but one of several α-smooth muscle actin-positive (α-SMA(+)) mesenchymal cells present within the intestinal lamina propria, including vascular pericytes, bone marrow-derived stem cells (mesenchymal stem cells or hematopoietic stem cells), muscularis mucosae, and the lymphatic pericytes (colon) and organized smooth muscle (small intestine) associated with the lymphatic lacteals. These other mesenchymal cells perform many of the functions previously attributed to subepithelial myofibroblasts. This review discusses the definition of a myofibroblast and reconsiders whether the α-SMA(+) subepithelial cells in the intestine are myofibroblasts or other types of mesenchymal cells, i.e., pericytes. Current information about specific, or not so specific, molecular markers of lamina propria mesenchymal cells is reviewed, as well as the origins of intestinal myofibroblasts and pericytes in the intestinal lamina propria and their replenishment after injury. Current concepts and research on stem cell therapy for intestinal inflammation are summarized. Information about the stem cell origin of intestinal stromal cells may inform future stem cell therapies to treat human inflammatory bowel disease (IBD).

Mesenchymal stem cells enhance the engraftment and myelinating ability of allogeneic oligodendrocyte progenitors in dysmyelinated mice

Multiple sclerosis is an autoimmune disease characterized by demyelination and axonal loss throughout the central nervous system. No regenerative treatment exists for patients who fail to respond to conventional immunosuppressive and immunomodulating drugs. In this scenario, stem cell therapy poses as a rational approach for neurological regeneration. Transplantation of embryonic-derived oligodendrocyte progenitor cells (OPCs) has been shown to promote remyelination and ameliorate animal models of neurodegenerative diseases. However, its therapeutic application is limited due to potential transplant rejection. In multiple sclerosis, an added concern is that transplant rejection would be most pronounced at sites of previous lesions, exacerbating a hyperactive immune response which could prevent remyelination and precipitate additional demyelination. Routine systemic immunosuppression may not be sufficient to prevent transplant rejection-associated immune reactions in the cerebral microenvironment. Mesenchymal stem cells (MSCs), due to their homing properties and inherent immunosuppressive nature, are a promising tool for clinical application targeted toward immunosuppression at sites of injury. In this study, we used a co-transplantation strategy to investigate the effect of syngeneic MSCs on the survival and remyelination abilities of allogeneic OPCs in adult nonimmunosuppressed shiverer mice. At all time points examined, cotransplantation with MSCs increased OPC engraftment, migration, and maturation in myelinating oligodendrocytes, which produced widespread myelination in the host corpus callosum. In addition, MSCs reduced microglia activation and astrocytosis in the brain of transplanted animals as well as T-cell proliferation in vitro. These data suggest that combining the immunomodulatory and trophic properties of MSCs with the myelinating ability of OPCs might be a suitable strategy for promoting neurological regeneration in demyelinating diseases.