Human bone marrow-derived stem cells acquire epithelial characteristics through fusion with gastrointestinal epithelial cells

Elimination of allogeneic multipotent stromal cells by host macrophages in different models of regeneration

Allogeneic multipotent stromal cells were previously thought to be poorly recognized by host immune system; the prolonged survival in host environments was explained by their immune privileged status. As long as the concept is currently reconsidered, the routes of elimination of allogeneic multipotent stromal cells by host immunity must be taken into account. This is necessary for correct comprehension of their therapeutic action. The study was focused upon survival of umbilical cord-derived allogeneic multipotent stromal cells in different rat models of tissue regeneration induced by partial hepatectomy or by critical limb ischemia. The observations were carried out by means of vital labeling of the cells with PKH26 prior to injection, in combination with differential immunostaining of host macrophages with anti-CD68 antibody. According to the results, allogeneic multipotent stromal cells are specifically eliminated by host immune system; the efficacy can reach 100%. Massive clearance of transplanted cells by host macrophages is accompanied by appropriation of the label by the latter, and this is a pronounced case of misleading presentation of exogenous label by host cells. The study emphasizes the role of macrophages in host response and also the need of additional criteria for correct data interpretation.

Therapeutic potential of amniotic-fluid-derived stem cells on liver fibrosis model in mice

OBJECTIVE

Liver fibrosis results from the wound healing response to chronic liver damage. Advanced liver fibrosis results in cirrhosis and liver failure, and liver transplantation is often the only option for effective therapy; however, the shortage of available donor livers limits this treatment. Thus, new therapies for advanced liver fibrosis are essential.

MATERIALS AND METHODS

Amniotic fluid contains an abundance of stem cells, which are derived from all three germ layers of the developing fetus. These cells do not induce teratomas in vivo and do not pose any ethical concerns. To generate liver fibrosis models, male ICR mice were treated with CCl4 via oral gavage for 4 weeks, and the serum levels of glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, and albumin were higher than in the control group following chemical induction. To assess the potential of amniotic-fluid-derived stem cells (mAFSCs) to ameliorate liver fibrosis in vivo, mAFSCs were isolated from amniotic fluid of 13.5-day-old transgenic mice, which globally express the fluorescent protein, enhanced green fluorescent protein (EGFP), for tracing purposes (EGFP-mAFSCs). Single cells were injected via the mesentery (1 × 10(6) cells/mouse) of transplanted mice with liver fibrosis.

RESULTS

Four weeks after EGFP-mAFSC transplantation, the serum glutamate oxaloacetate transaminase, glutamate pyruvate transaminase, and albumin levels of recipient mice in the EGFP-mAFSC-injected group were significantly decreased when compared with mice in the saline-injected group. Additionally, fibrotic tissues were evaluated using Masson's trichrome staining 4 weeks after cell transplantation. Shrinkage of the fibrotic area was observed in the EGFP-mAFSC-injected group. The tissue-repair effects were also confirmed by hydroxyproline content analysis.

CONCLUSION

The possible repair mechanism from our data revealed that EGFP-mAFSCs may fuse with the recipient liver cells. Overall, EGFP-mAFSCs can ameliorate liver fibrosis in mice, thus providing insight into the future development of regenerative medicine.

Mesenchymal stem cell exosomes

MSCs are an extensively used cell type in clinical trials today. The initial rationale for their clinical testing was based on their differentiation potential. However, the lack of correlation between functional improvement and cell engraftment or differentiation at the site of injury has led to the proposal that MSCs exert their effects not through their differentiation potential but through their secreted product, more specifically, exosomes, a type of extracellular vesicle. We propose here that MSC exosomes function as an extension of MSC's biological role as tissue stromal support cells. Like their cell source, MSC exosomes help maintain tissue homeostasis for optimal tissue function. They target housekeeping biological processes that operate ubiquitously in all tissues and are critical in maintaining tissue homeostasis, enabling cells to recover critical cellular functions and begin repair and regeneration. This hypothesis provides a rationale for the therapeutic efficacy of MSCs and their secreted exosomes in a wide spectrum of diseases. Here, we give a brief introduction of the biogenesis of MSC exosomes, review their physiological functions and highlight some of their biochemical potential to illustrate how MSC exosomes could restore tissue homeostasis leading to tissue recovery and repair.

Hypoxic stress and IL-7 gene overexpression enhance the fusion potential of rat bone marrow mesenchymal stem cells with bovine renal epithelial cells

Transplantation of mesenchymal stem cells (MSCs) has been shown to enhance the improvement in kidney function following injury. However, the poor survival and grafting of the stem cells to the site of injury has restricted their therapeutic efficacy. Accelerated regeneration potential of MSCs has been observed when they were exposed to hypoxic stress or genetic modulation by various cytokines and growth factors. These preconditioning strategies may stimulate endogenous mechanisms resulting in multiple cellular responses. In this study, we used IL-7 gene to transfect MSCs. IL-7 is a hematopoietic growth factor that plays an important role in cell survival, proliferation, and differentiation. MSCs were also subjected to hypoxic stress for 8 and 24 h. These preconditioned MSCs were co-cultured with cisplatin-treated injured Mardin-Darby bovine kidney (MDBK) cells and their fusion potential was analyzed. Flow cytometry of fluorescently labeled preconditioned MSCs and injured MDBK cells revealed evidence of significant (P < 0.001) cell fusion compared to that of the normal MSCs. In addition, we also observed improved migration ability of these preconditioned MSCs in the in vitro wound healing assay, as compared to the normal MSCs. We conclude that hypoxic stress and IL-7 overexpression can enhance the renal regeneration potential of MSCs. This study would help in designing more potent therapeutic strategy in which preconditioned MSCs can be used for renal regeneration.

Evidence of cell fusion in carcinogen-induced mice gastric carcinoma

The role of bone marrow-derived cells in gastric cancer formation was not fully understood. In this study, bone marrow from female green fluorescent protein transgenic mice was transplanted into male wild-type mice to generate sex-mismatched chimeric mice. The chimeric mice were treated with carcinogen to induce gastric cancer. At time of sacrifice, 18.2 % (2/11) of mice showed severe dysplasia and 25 % (3/12) of mice successfully induced with cancer. Fluorescence in situ hybridization results showed that bone marrow-derived cells participated in renewal of gastric mucosa and cell fusion was observed in both precancerous lesions and adenocarcinoma, but no sign of fusion was observed in squamous cell carcinoma. Our findings suggest that bone marrow-derived cells participate in renewal of gastric mucosa during chronic damage and might have acquired the phenotype of gastric epithelial cells through cell fusion. Fusion between gastric epithelial cells and bone marrow-derived cells was involved in increased carcinogenesis.

Effect of human Wharton's jelly mesenchymal stem cell secretome on proliferation, apoptosis and drug resistance of lung cancer cells

Multipotent mesenchymal stem cells (MSCs) are recently found to alter the tumor condition. However their exact role in tumor development is not yet fully unraveled. MSCs were established to perform many of their actions through paracrine effect. Thus investigation of MSC secretome interaction with tumor cells may provide important information for scientists who are attempting to apply stem cells in the treatment of the disease. In this study we investigated the effect of human Wharton's jelly derived MSC (WJ-MSCs) secretome on proliferation, apoptotic potential of A549 lung cancer cells, and their response to the chemotherapeutic agent doxorubicin. WJ-MSCs were isolated from human umbilical cord and then characterized according to the International Society for Cellular Therapy criteria and WJ-MSC secretome was collected. BrdU cell proliferation assay and Annexin V-PI staining were used for the evaluation of cytotoxic and proapoptotic effects of WJ-MSC secretome on A549 cells. WJ-MSC secretome neither induced proliferation of lung cancer cells nor affected the apoptotic potential of the tumor cells. We also studied the combinatorial effect of WJ-MSC secretome and the anticancer drug doxorubicinwhich showed no induction of drug resistance when A549 cells was treated with combination of WJ-MSC secretome and doxorubicin. Although MSCs did not show antitumor properties, our in vitro results showed that MSC secretome was not tumorigenic and also did not make lung cancer cells resistant to doxorubicin. Thus MSC secretome could be considered safe for other medical purposes such as cardiovascular, neurodegenerative, and autoimmune diseases which may exist or occur in cancer patients.

Constitution of fibrin-based niche for in vitro differentiation of adipose-derived mesenchymal stem cells to keratinocytes

Epithelialization of chronic cutaneous wound is troublesome and may require use of skin/cell substitutes. Adipose-derived mesenchymal stem cells (ADMSCs) have immense potential as autologous cell source for treating wounds; they can cross the germ layer boundary of differentiation and regenerate skin. When multipotent adult stem cells are considered for skin regeneration, lineage committed keratinocytes may be beneficial to prevent undesirable post-transplantation outcome. This study hypothesized that ADMSCs may be directed to epidermal lineage in vitro on a specifically designed biomimetic and biodegradable niche. Cells were seeded on the test niche constituted with fibrin, fibronectin, gelatin, hyaluronic acid, laminin V, platelet growth factor, and epidermal growth factor in the presence of cell-specific differentiation medium (DM). The ADMSCs grown on bare tissue culture polystyrene surface in DM is designated DM-control and those grown in basal medium (BM) is the BM-control. Lineage commitment was monitored with keratinocyte-specific markers such as cytokeratin 14, cytokeratin 5, cytokeratin 19, and integrin α6 at the transcriptional/translational level. The in vitro designed biomimetic fibrin composite matrix may have potential application as cell transplantation vehicle.

Exosomes/miRNAs as mediating cell-based therapy of stroke

Cell-based therapy, e.g., multipotent mesenchymal stromal cell (MSC) treatment, shows promise for the treatment of various diseases. The strong paracrine capacity of these cells and not their differentiation capacity, is the principal mechanism of therapeutic action. MSCs robustly release exosomes, membrane vesicles (~30–100 nm) originally derived in endosomes as intraluminal vesicles, which contain various molecular constituents including proteins and RNAs from maternal cells. Contained among these constituents, are small non-coding RNA molecules, microRNAs (miRNAs), which play a key role in mediating biological function due to their prominent role in gene regulation. The release as well as the content of the MSC generated exosomes are modified by environmental conditions. Via exosomes, MSCs transfer their therapeutic factors, especially miRNAs, to recipient cells, and therein alter gene expression and thereby promote therapeutic response. The present review focuses on the paracrine mechanism of MSC exosomes, and the regulation and transfer of exosome content, especially the packaging and transfer of miRNAs which enhance tissue repair and functional recovery. Perspectives on the developing role of MSC mediated transfer of exosomes as a therapeutic approach will also be discussed.

Immunogenicity of allogeneic mesenchymal stem cells transplanted via different routes in diabetic rats

Due to their hypoimmunogenicity and unique immunosuppressive properties, mesenchymal stem cells (MSCs) are considered one of the most promising adult stem cell types for cell therapy. Although many studies have shown that MSCs exert therapeutic effects on several acute and subacute conditions, their long-term effects are not confirmed in chronic diseases. Immunogenicity is a major limitation for cell replacement therapy, and it is not well understood in vivo. We evaluated the immunogenicity of allogeneic MSCs in vivo by transplanting MSCs into normal and diabetic rats via the tail vein or pancreas and found that MSCs exhibited low immunogenicity in normal recipients and even exerted some immunosuppressive effects in diabetic rats during the initial phase. However, during the later stage in the pancreas group, MSCs expressed insulin and MHC II, eliciting a strong immune response in the pancreas. Simultaneously, the peripheral blood mononuclear cells in the recipients in the pancreas group were activated, and alloantibodies developed in vivo. Conversely, in the tail vein group, MSCs remained immunoprivileged and displayed immunosuppressive effects in vivo. These data indicate that different transplanting routes and microenvironments can lead to divergent immunogenicity of MSCs.

Engraftment of mouse amniotic fluid-derived progenitor cells after in utero transplantation in mice

BACKGROUND/PURPOSE

Amniotic fluid-derived progenitor cells (AFPCs) are oligopotent and shed from the fetus into the amniotic fluid. It was reported that AFPCs express stem cell-like markers and are capable of differentiating into specific cell type in in vitro experiments. However, no study has fully investigated the potentiality and destiny of these cells in in vivo experiments.

METHODS

Ds-red transgenic mice (on Day 13.5 of pregnancy) were transplanted in utero with enhanced green fluorescent protein-labeled mouse AFPC (EGFP-mAFPCs). After birth, baby mice were euthanized at 3-week intervals beginning 3 weeks postnatally, and the specimens were examined by polymerase chain reaction, histology, and flow cytometry.

RESULTS

Our results demonstrate the transplantability of mAFPCs into all three germ layers and the potential of mAFPCs in the study of progenitor cell homing, differentiation, and function. Engraftment of EGFP-mAFPCs was detected in the intestine, kidney, muscle, skin, bladder, heart, stomach, etc., at 3 weeks after delivery.

CONCLUSION

This model using EGFP-mAFPCs injected in utero may provide an ideal method for determining the fate of transplanted cells in recipients and these findings may justify a clinical trial of in utero transplantation during gestation for patients who have inherited genetic disorders.

Umbilical cord mesenchymal stem cells: the new gold standard for mesenchymal stem cell-based therapies?

Due to their self-renewal capacity, multilineage differentiation potential, paracrine effects, and immunosuppressive properties, mesenchymal stromal cells (MSCs) are an attractive and promising tool for regenerative medicine. MSCs can be isolated from various tissues but despite their common immunophenotypic characteristics and functional properties, source-dependent differences in MSCs properties have recently emerged and lead to different clinical applications. Considered for a long time as a medical waste, umbilical cord appears these days as a promising source of MSCs. Several reports have shown that umbilical cord-derived MSCs are more primitive, proliferative, and immunosuppressive than their adult counterparts. In this review, we aim at synthesizing the differences between umbilical cord MSCs and MSCs from other sources (bone marrow, adipose tissue, periodontal ligament, dental pulp,…) with regard to their proliferation capacity, proteic and transcriptomic profiles, and their secretome involved in their regenerative, homing, and immunomodulatory capacities. Although umbilical cord MSCs are until now not particularly used as an MSC source in clinical practice, accumulating evidence shows that they may have a therapeutic advantage to treat several diseases, especially autoimmune and neurodegenerative diseases.

Gene expression profiles of various cytokines in mesenchymal stem cells derived from umbilical cord tissue and bone marrow following infection with human cytomegalovirus

Mesenchymal stem cells (MSCs) have both multi-lineage differentiation potential and immunosuppressive properties, making them ideal candidates for regenerative medicine. However, their immunosuppressive properties potentially increase the risk of cancer progression and opportunistic infections. In this study, MSCs isolated from human umbilical cord blood (UCMSCs) and adult bone marrow (BMMSCs) were infected with human cytomegalovirus (HCMV). Cytopathic changes were observed 10 days post infection. PCR products amplified from genomic DNA and cDNA were used to confirm the HCMV infection of the UCMSCs and BMMSCs. Real-time PCR was conducted to quantify the expression of immunomodulatory molecules, including cytokines, chemokines, growth factors, adhesion molecules and cancer-related genes. Our results indicate high upregulation of the majority of these molecules, including many growth factors, tumor necrosis factor alpha, interleukin-8, interleukin-6 and interferon gamma. Adhesion molecules (VCAM-1, TCAM-1 and selectin-E) were downregulated in the infected UCMSCs and BMMSCs. Antibody chip array evaluation of cell culture media indicated that the growth factor secretion by UCMSCs and BMMSCs was greatly influenced (p < 0.001) by HCMV. The stimulation of MSCs with HCMV led to the activation of downstream signaling pathways, including pSTAT3 and Wnt2. Our results show that HCMV can significantly alter the functions of both UCMSCs and BMMSCs, although not in the same way or to the same extent. In both cases, there was an increase in the expression of proangiogenic factors in the microenvironment following HMCV infection. The discrepancy between the two cell types may be explained by their different developmental origin, although further analysis is necessary. Future studies should decipher the underlying mechanism by which HCMV controls MSCs, which may lead to the development of new therapeutic treatments.

Cell fusion phenomena detected after in utero transplantation of Ds-red-harboring porcine amniotic fluid stem cells into EGFP transgenic mice

OBJECTIVES

Amniotic fluid stem cells (AFSCs) are derived from the amniotic fluid of the developing fetus and can give rise to diverse differentiated cells of ectoderm, mesoderm, and endoderm lineages. Intrauterine transplantation is an approach used to cure inherited genetic fetal defects during the gestation period of pregnant dams. Certain disease such as osteogenesis imperfecta was successfully treated in affected fetal mice using this method. However, the donor cell destiny remains uncertain.

METHODS

The purpose of this study was to investigate the biodistribution and cell fate of Ds-red-harboring porcine AFSCs (Ds-red pAFSCs) after intrauterine transplantation into enhanced green fluorescent protein-harboring fetuses of pregnant mice. Pregnant mice (12.5 days) underwent open laparotomy with intrauterine pAFSC transplantation (5 × 10(4) cells per pup) into fetal peritoneal cavity.

RESULTS

Three weeks after birth, the mice were sacrificed. Several samples from different organs were obtained for histological examination and flow cytometric analysis. Ds-red pAFSCs migrated most frequently into the intestines. Furthermore, enhanced green fluorescent protein and red fluorescent protein signals were co-expressed in the intestine and liver cells via immunohistochemistry studies.

CONCLUSION

In utero xenotransplantation of pAFSCs fused with recipient intestinal cells instead of differentiating or maintaining the undifferentiated status in the tissue.

MicroRNA 135a suppresses lymph node metastasis through down-regulation of ROCK1 in early gastric cancer

MicroRNAs (miRNAs) play a critical role in gastric cancer progression and metastasis. This study investigated the role of miRNA-135a in early gastric cancer (EGC) including lymph node (LN) metastasis. We examined the correlation between miRNA-135a expression and clinical outcomes in 59 patients who underwent surgery for EGC. Using gastric cancer cell lines, we performed functional and target gene analyses. miRNA-135a expression was down-regulated in 33.9% of patients. These patients showed a significantly more advanced stage (TNM stage≥IB, 35.0% vs. 12.8%, p = 0.045) and higher rate of LN metastasis (30.0% vs. 5.1%, p = 0.014) than those with up-regulation of miRNA-135a expression. In a multivariate analysis, down-regulation of miRNA-135a was an independent risk factor for LN metastasis (adjusted odds ratio, 8.04; 95% confidence interval, 1.08–59.81; p = 0.042). Functional analyses using gastric cancer cell lines showed that miRNA-135a suppressed cell viability, epithelial-mesenchymal transition, cell invasion, and migration. ROCK1 was a target of miRNA-135a and its expression was inversely correlated to that of miRNA-135a. ROCK1 expression was significantly increased in EGC patients with LN metastasis than in those without LN metastasis. Our results confirm the tumor-suppressive role of miRNA-135a, and demonstrate its role in LN metastasis in EGC. miRNA-135a and its target gene ROCK1 may be novel therapeutic and prognostic targets for EGC.

Effects of salinomycin on human bone marrow-derived mesenchymal stem cells in vitro

Various hypotheses on the origin of cancer stem cells (CSCs) exist, including that CSCs develop from transformed human bone marrow mesenchymal stem cells (hBMSC). Since the polyether antibiotic salinomycin selectively kills CSCs, the present study aims to elucidate the effects of salinomycin on normal hBMSC. The immunophenotype of hBMSC after salinomycin exposure was observed by flow cytometry. The multi-differentiation capacity of hBMSC was evaluated by Oil Red O and van Kossa staining. Cytotoxic effects of salinomycin were monitored by the [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] (MTT) assay. Furthermore, spheroid formation and migration capacity were assessed. There were no differences in the immunophenotype and multi-differentiation capacity of hBMSC induced by salinomycin treatment. Cytotoxic effects were observed at concentrations of 30 μM and above. Neither the migration capability nor the ability to form spheroids was affected. Essential functional properties of hBMSC were unaffected by salinomycin. However, dose-dependent cytotoxicity effects could be observed. Overall, low dose salinomycin showed no negative effects on hBMSC. Since mesenchymal stem cells from various sources respond differently, further in vitro studies are needed to clarify the effect of salinomycin on tissue-specific stem cells.

Fate of intravenously injected mesenchymal stem cells and significance for clinical application

Mesenchymal stromal cells (MSCs) have initially been characterized as a fibroblastlike cell population that can be expanded readily in vitro, and is able to support hematopoiesis in vitro and in vivo. By serendipity it was discovered that MSCs can also be administered into the bloodstream. This mode of application formed a major breakthrough in the clinical use of MSCs, because MSC transplantation was found to cure severe immune hyperactivation states such as graft-versus-host disease after allogeneic bone marrow transplantation, or bacterial sepsis. However, MSCs were found difficult to trace and consensus to date is lacking in the scientific community as to where transplanted MSCs end up in the body and which major principles are responsible for the therapeutic effects of MSCs. This chapter gives an overview of the current knowledge on interactions of freshly transplanted MSCs with the cells in the blood stream and the vessel wall, with major organs such as lung, liver, gut, and spleen, and discusses the limitations of the methodologies used to trace transplanted MSCs. The findings will be put into perspective on how therapeutically applied, culture-expanded MSCs may exert beneficial effects.

Proteolytic Potential of the MSC Exosome Proteome: Implications for an Exosome-Mediated Delivery of Therapeutic Proteasome

Mesenchymal stem cells (MSCs) are used in many of the current stem cell-based clinical trials and their therapeutic efficacy has increasingly been attributed to secretion of paracrine factors. We have previously demonstrated that a therapeutic constituent of this secretion is exosome, a secreted bilipid membrane vesicle of ~50-100 nm with a complex cargo that is readily internalized by H9C2 cardiomyocytes. It reduces infarct size in a mouse model of myocardial ischemia/reperfusion (MI/R) injury. We postulate that this therapeutic efficacy is derived from the synergy of a select permutation of individual exosome components. To identify protein candidates in this permutation, the proteome was profiled and here we identified 20S proteasome as a protein candidate. Mass spectrometry analysis detected all seven α and seven β chains of the 20S proteasome, and also the three beta subunits of "immunoproteasome" with a very high confidence level. We demonstrated that a functional proteasome copurified with MSC exosomes with a density of 1.10-1.18 g/mL, and its presence correlated with a modest but significant reduction in oligomerized protein in a mouse model of myocardial infarction. Circulating proteasomes in human blood also copurified with exosomes. Therefore, 20S proteasome is a candidate exosome protein that could synergize with other constituents to ameliorate tissue damage.

Mechanisms of action of mesenchymal stem cells in cutaneous wound repair and regeneration

Mesenchymal stem cells (MSCs) are multipotent cells with the capacity for self-renewal and differentiation and have a broad tissue distribution. These characteristics make them candidate cells for wound healing and regeneration in a variety of disorders. Endogenous MSCs or exogenously delivered MSCs can traffic and migrate to injured tissue and participate in the healing of this tissue. The concentrated conditioned medium from MSCs can modulate wound repair without MSCs being present in the wound. The therapeutic effects of MSCs might be attributable to their ability to differentiate and transdifferentiate into tissue-specific cells, to fuse with the resident cells, to secrete a wide array of paracrine factors in order to stimulate the survival and functional recovery of the resident cells, or to regulate the local microenviroment or niche and immune response. These mechanisms are probably independent but not mutually exclusive. In many circumstances, a combination of these protective mechanisms might work together to affect cutaneous wound healing. This review gives a brief overview and discusses the mechanisms by which MSCs promote skin repair and regeneration, although the specific mechanisms in each type of cutaneous wound are still unclear and controversial. A comprehensive understanding of the mechanisms should allow us to find advanced and better treatment strategies for various skin diseases, even those that are currently incurable.

Sarcomas as a mise en abyme of mesenchymal stem cells: exploiting interrelationships for cell mediated anticancer therapy

Mise en abyme meaning "placed into abyss or infinite recurrence" is an apt paradigm for the relentless growth of sarcoma cells. Its alternative meaning, "self-reflexive embedding" fits the central role attributed to cancer stem cells (CSCs). Diversely sourced and defined, mesenchymal stem cells (MSCs) may be the cells of sarcoma origin, evolve a CSC phenotype and/or contribute to tumor growth through inherent qualities for homing, neovascularization, paracrine cross-feeding, microvesicle secretion, cell fusion, entosis and immune modulation. Exploiting these qualities, MSC expressing modified forms of the TNF-related apoptosis-inducing ligand (Apo2L/TRAIL) are being developed to complement more conventional radiation and chemotherapy.

Same or not the same? Comparison of adipose tissue-derived versus bone marrow-derived mesenchymal stem and stromal cells

Mesenchymal stem/stromal cells (MSCs) comprise a heterogeneous population of cells with multilineage differentiation potential, the ability to modulate oxidative stress, and secrete various cytokines and growth factors that can have immunomodulatory, angiogenic, anti-inflammatory and anti-apoptotic effects. Recent data indicate that these paracrine factors may play a key role in MSC-mediated effects in modulating various acute and chronic pathological conditions. MSCs are found in virtually all organs of the body. Bone marrow-derived MSCs (BM-MSCs) were discovered first, and the bone marrow was considered the main source of MSCs for clinical application. Subsequently, MSCs have been isolated from various other sources with the adipose tissue, serving as one of the alternatives to bone marrow. Adipose tissue-derived MSCs (ASCs) can be more easily isolated; this approach is safer, and also, considerably larger amounts of ASCs can be obtained compared with the bone marrow. ASCs and BM-MSCs share many biological characteristics; however, there are some differences in their immunophenotype, differentiation potential, transcriptome, proteome, and immunomodulatory activity. Some of these differences may represent specific features of BM-MSCs and ASCs, while others are suggestive of the inherent heterogeneity of both BM-MSC and ASC populations. Still other differences may simply be related to different isolation and culture protocols. Most importantly, despite the minor differences between these MSC populations, ASCs seem to be as effective as BM-MSCs in clinical application, and, in some cases, may be better suited than BM-MSCs. In this review, we will examine in detail the ontology, biology, preclinical, and clinical application of BM-MSCs versus ASCs.

The ailing gut: a therapeutic role for bone marrow cells?

It is obvious that the BM does more than simply supply the GIT with cells of the innate and adaptive immune system. A growing number of studies suggest that BMCs can differentiate into ISEMFs (Lee et al., PLOS ONE 2011;6:e26082) and in the setting of inflammation can be contributors to all lineages of the neovasculature. The role of BMCs in epithelial turnover is more problematic; their contribution after transient mucosal injury seems negligible, but a number of studies in both rodents and man suggest that small numbers of BMCs can be incorporated into the epithelial compartment with more chronic injury (e.g., GvHD in man and chemically induced colitis in rodents); commonly cell fusion seems to be responsible for this. Significantly, this engraftment does not seem to occur in the stem-cell compartment, with the notable single report of the chronically infected murine gastric mucosa, where the BM origin of the stem cells can be the only rational explanation for the complete colonization of the mucosa by BMDCs. In the clinical setting, a role for MSCs in ameliorating colitis seems promising, though the mechanisms by which this is achieved remain somewhat unclear, though both immunomodulatory and regenerative effects of BMCs are likely to be important.

Multipotent mesenchymal stromal cells and the innate immune system

Multipotent mesenchymal stromal cells (MSCs) have unique immunoregulatory and regenerative properties that make them an attractive tool for the cellular treatment of autoimmunity and inflammation. Their underlying molecular mechanisms of action together with their clinical benefit - for example, in autoimmunity - are being revealed by an increasing number of clinical trials and preclinical studies of MSCs. However, autoimmunity and therapy-related alloimmunity are not only triggered and sustained by responses of the adaptive immune system; there is growing evidence that components of the innate immune system also have a key role. It is therefore important to study the crosstalk between MSCs and innate immunity, which ranges from the bone marrow niche to injured tissue.

Mesenchymal stem cell signaling in cancer progression

Mesenchymal (multipotent) stem/stromal cells (MSCs) may affect cancer progression through a number of secreted factors triggering activation of various cell signaling pathways. Depending on receptor status, phosphatase and tensin homolog (PTEN) status, or Wnt activation in the cancer cells, the signals may either result in increased growth and metastasis or lead to inhibition of growth with increased cell death. Thus, MSCs can play a dual role in cancer progression depending on the cellular context wherein they reside. The phosphatidylinositol-3-kinase (PI3K)/Akt signaling pathway has a central role in regulating tumor growth, and several MSC secreted factors stimulate activation of this pathway. A comprehensive understanding of the signals regulating MSC-tumor cross-talk is highly important for the development of MSCs as potential therapeutic vehicles. Thus, the presented review focuses on factors released by MSCs and on the dual role they may have on various stages of tumorigenesis.

Helicobacter pylori infection of gastrointestinal epithelial cells in vitro induces mesenchymal stem cell migration through an NF-κB-dependent pathway

The role of bone marrow-derived mesenchymal stem cells (MSC) in the physiology of the gastrointestinal tract epithelium is currently not well established. These cells can be recruited in response to inflammation due to epithelial damage, home, and participate in tissue repair. In addition, in the case of tissue repair failure, these cells could transform and be at the origin of carcinomas. However, the chemoattractant molecules responsible for MSC recruitment and migration in response to epithelial damage, and particularly to Helicobacter pylori infection, remain unknown although the role of some chemokines has been suggested. This work aimed to get insight into the mechanisms of mouse MSC migration during in vitro infection of mouse gastrointestinal epithelial cells by H. pylori. Using a cell culture insert system, we showed that infection of gastrointestinal epithelial cells by different H. pylori strains is able to stimulate the migration of MSC. This mechanism involves the secretion by infected epithelial cells of multiple cytokines, with a major role of TNFα, mainly via a Nuclear Factor-kappa B-dependent pathway. This study provides the first evidence of the role of H. pylori infection in MSC migration and paves the way to a better understanding of the role of bone marrow-derived stem cells in gastric pathophysiology and carcinogenesis.

Bone marrow cells in murine colitis: multi-signal analysis confirms pericryptal myofibroblast engraftment without epithelial involvement

Background

The contribution of bone marrow-derived cells to epithelial tissues in the inflamed gut remains controversial. Recent reports have suggested that cell fusion between bone marrow-derived cells and the intestinal epithelium takes place in inflammatory conditions.

Methods

In attempts to confirm this, we have undertaken gender mis-matched bone marrow (BM) transplants from male Swiss Webster (SWR) mice to B and T cell-deficient female Rag2 KO mice which, 4 weeks later, were given 5% dextran sodium sulphate in drinking water to induce acute colitis. A further BM-treated group of animals with a graft versus host-like condition was also studied. We developed a new method to combine up to three brightfield or fluorescent lectin- or immuno-histochemical signals with fluorescent in situ hybridisation for the Y and X chromosomes to enable us unequivocally to identify BM-derived male cells which presented as different cell types in the gastrointestinal tract.

Principal Findings

In rolled preparations of whole intestines we scanned around 1.5 million crypts at many tissue levels. In no instance did we see a Y chromosome-positive cell in the epithelial compartment, which was not also CD45-positive. We saw no evidence of cell fusion, based on combined X and Y chromosome analysis. Levels of CD45-positive stromal and lymphoid cells and pericryptal myfibroblasts (positive for α-smooth muscle actin) increased with time up to a plateau, which resembled the level seen in untreated control grafted animals. We saw very few Y chromosome-positive endothelial cells in intestinal stromal vessels.

Conclusions

We conclude that whole BM transplantation does not result in intestinal epithelial engraftment in this model. Our new methods can usefully assist in multi-signal analyses of cell phenotypes following BM transplant and in models of chimaerism and regenerative medicine.