In vivo contribution of murine mesenchymal stem cells into multiple cell-types under minimal damage conditions

Tissues from equine cadaver ligaments up to 72 hours of post-mortem: a promising reservoir of stem cells

Background

Mesenchymal stem cells (MSCs) harvested from cadaveric tissues represent a promising approach for regenerative medicine. To date, no study has investigated whether viable MSCs could survive in cadaveric tissues from tendon or ligament up to 72 hours of post-mortem. The purpose of the present work was to find out if viable MSCs could survive in cadaveric tissues from adult equine ligaments up to 72 hours of post-mortem, and to assess their ability (i) to remain in an undifferentiated state and (ii) to divide and proliferate in the absence of any specific stimulus.

Methods

MSCs were isolated from equine cadaver (EC) suspensory ligaments within 48–72 hours of post-mortem. They were evaluated for viability, proliferation, capacity for tri-lineage differentiation, expression of cell surface markers (CD90, CD105, CD73, CD45), pluripotent transcription factor (OCT-4), stage-specific embryonic antigen-1 (SSEA-1), neuron-specific class III beta-tubulin (TUJ-1), and glial fibrillary acidic protein (GFAP). As well, they were characterized by transmission electron microscope (TEM).

Results

EC-MSCs were successfully isolated and maintained for 20 passages with high cell viability and proliferation. Phase contrast microscopy revealed that cells with fibroblast-like appearance were predominant in the culture. Differentiation assays proved that EC-MSCs are able to differentiate towards mesodermal lineages (osteogenic, adipogenic, chondrogenic). Flow cytometry analysis demonstrated that EC-MSCs expressed CD90, CD105, and CD73, while being negative for the leukocyte common antigen CD45. Immunofluorescence analysis showed a high percentage of positive cells for OCT-4 and SSEA-1. Surprisingly, in absence of any stimuli, some adherent cells closely resembling neuronal and glial morphology were also observed. Interestingly, our results revealed that approximately 15 % of the cell populations were TUJ-1 positive, whereas GFAP expression was detected in only a few cells. Furthermore, TEM analysis confirmed the stemness of EC-MSCs and identified some cells with a typical neuronal morphology.

Conclusions

Our findings raise the prospect that the tissues harvested from equine ligaments up to 72 hours of post-mortem represent an available reservoir of specific stem cells. EC-MSCs could be a promising alternative source for tissue engineering and stem cell therapy in equine medicine.

Mesenchymal stem cells inhibit Th17 cells differentiation via IFN-γ-mediated SOCS3 activation

Mesenchymal stem cells (MSCs) are immunoregulatory, and the administration of them has been shown to ameliorate inflammation caused by Th17 cells. However, the mechanisms that contribute to MSC regulation on Th17 cell development are unclear. Here, we found that MSCs could inhibit Th17 cell differentiation through the activation of suppressors of cytokine signaling 3 (SOCS3) when coculture of MSCs and CD4(+)CD25(low)CD44(low)CD62L(high) T cells. Further analysis demonstrated that the inhibitory action was mediated via interferon gamma (IFN-γ), which activated signal transducer and activator of transcription-1 (STAT1) to enhance the expression of SOCS3, leading to STAT3 inhibition. Moreover, stable and reciprocal changes in H3K4me3 and H3K27me3 at the promoters of STAT1, STAT3 and RORγt determined the fate of Th17 cells. These results demonstrate that MSCs may inhibit Th17 differentiation via IFN-γ that activates SOCS3 leading to immunomodulatory effects, suggesting a possible mechanism by which MSCs could act as a cellular approach to attenuate the clinical and pathological manifestations of some autoimmune diseases.

Epigenetic Mechanisms Regulating Mesenchymal Stem Cell Differentiation

Human Mesenchymal Stem Cells (hMSCs) have emerged in the last few years as one of the most promising therapeutic cell sources and, in particular, as an important tool for regenerative medicine of skeletal tissues. Although they present a more restricted potency than Embryonic Stem (ES) cells, the use of hMCS in regenerative medicine avoids many of the drawbacks characteristic of ES cells or induced pluripotent stem cells. The challenge in using these cells lies into developing precise protocols for directing cellular differentiation to generate a specific cell lineage. In order to achieve this goal, it is of the upmost importance to be able to control de process of fate decision and lineage commitment. This process requires the coordinate regulation of different molecular layers at transcriptional, posttranscriptional and translational levels. At the transcriptional level, switching on and off different sets of genes is achieved not only through transcriptional regulators, but also through their interplay with epigenetic modifiers. It is now well known that epigenetic changes take place in an orderly way through development and are critical in the determination of lineage-specific differentiation. More importantly, alteration of these epigenetic changes would, in many cases, lead to disease generation and even tumour formation. Therefore, it is crucial to elucidate how epigenetic factors, through their interplay with transcriptional regulators, control lineage commitment in hMSCs.

Engraftability of Murine Bone Marrow-Derived Multipotent Mesenchymal Stem Cell Subpopulations in the Tissues of Developing Mice following Systemic Transplantation

INTRODUCTION

Cell therapies for generalized musculoskeletal diseases would require distribution of cells to all the skeletal tissues; however, there are controversies regarding the transplantability of multipotent mesenchymal stems cells (MSCs). We generated single-cell subpopulations of MSCs from murine bone marrow and assessed them for differences in trafficking through the circulatory system and engraftment in bone and other tissues.

MATERIALS AND METHODS

Seven single-cell clonal subpopulations were generated by serial dilution of GFP-marked MSCs isolated from bone marrow. The subpopulations were examined for putative MSC surface marker expression, in vitro differentiation toward osteogenic and adipogenic lineages, migration and engraftment in different tissues following intravenous delivery in normal, sublethally irradiated neonatal mice.

RESULTS

The surface marker expression profile revealed notable differences among clonal cells, specifically CD44 and CD105. All the cell subpopulations differentiated toward osteogenic and adipogenic lineages, with some committed to only one or the other. Two clones enriched in CXCR4 expression were highly efficient in migrating and engrafting in skeletal tissue including bone; this confirmed the role of this chemokine in cell migration. Donor cells retrieved from various tissues displayed different morphologies and potential differentiation into tissue cell type of engraftment, suggesting modification by the tissues in which the donor cells engrafted.

CONCLUSION

We have reported that, within bone marrow, there are heterogeneous subpopulations of MSCs that may differ in their ability to migrate in the circulatory system and engraft in different tissues.

Isolation, selection and culture methods to enhance clonogenicity of mouse bone marrow derived mesenchymal stromal cell precursors

Introduction

Conventionally cultured mouse bone marrow mesenchymal stromal cells (mBM-MSC) are a heterogeneous population that often initially contain contaminating haematopoietic cells. Variability in isolation methods, culture protocols and the lack of specific mBM MSC markers might explain this heterogeneity. The aim of this study is to optimise the isolation, culture conditions and selection of mBM-MSC.

Methods

Mouse BM-MSCs were isolated from crushed long bones (cBM) or flushed bone marrow (fBM) from 6–8 week old C57Bl/6 mice. These subpopulations were analysed by flow cytometry using commonly used mBM-MSC cell surface marker, e.g. Sca-1, CD29 and CD44. Cells were cultured and expanded in vitro in hypoxic conditions of either 2 % or 5 % oxygen. Cell sorting and qRT-PCR was used to determine transcript levels of stem cell and lineage related genes in individual subpopulations.

Results

During early passaging not only do contaminating haematopoietic cells disappear, but there is a change in the phenotype of mBM-MSC affecting particularly CD44 and Sca-1 expression. By fluorescence activated cell sorting of CD45⁻/Ter119⁻ mBM stroma based on Sca-1 expression and expansion in hypoxic conditions, we show that Sca-1⁺ cells had higher CFU-F frequencies and showed enhanced proliferation compared with Sca-1⁻ cells. As evaluated by in vitro assays and qRT-PCR, these cells presented in vitro tri-lineage differentiation along osteocyte, chondrocyte, and adipocyte lineages. Finally, by prospective isolation of Sca-1⁺PDGFRα⁺CD90⁺ cells we have isolated mBM-MSC on a single cell level, achieving a CFU-F frequency of 1/4. Functional investigations demonstrated that these MSC clones inhibited T-lymphocyte proliferation.

Conclusion

By positive selection using a combination of antibodies to Sca-1, CD90 and PDGFRα and culturing in hypoxia, we have found a subpopulation of BM cells from C57Bl/6 mice with a CFU-F cloning efficiency of 1/4. To our knowledge these results represent the highest frequencies of mouse MSC cloning from C57Bl/6 mice yet reported.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-015-0139-5) contains supplementary material, which is available to authorized users.

The Effect of Bone Marrow-Derived Mesenchymal Stem Cell Transplantation on Allodynia and Hyperalgesia in Neuropathic Animals: A Systematic Review with Meta-Analysis

Stem cell transplantation has been considered a possible therapeutic method for neuropathic pain. However, no quantitative data synthesis of stem cell therapy for neuropathic pain exists. Therefore, the present systematic review and meta-analysis assessed the efficacy of bone marrow mesenchymal stem cell (BMMSC) transplantation on alleviating pain symptoms in animal models of neuropathic pain. In the present meta-analysis, controlled animal studies assessing the effect of administrating BMMSC on neuropathic pain were included through an extensive literature search of online databases. After collecting data, effect sizes were computed and the standardized mean difference (SMD) with 95% confidence interval (CI) was entered in all analyses. Random-effects models were used for data analysis. Sensitivity and subgroup analyses were performed to investigate expected or measured heterogeneity. Finally, 14 study were included. The analyses showed that BMMSC transplantation lead to significant improvement on allodynia (SMD = 2.06; 95% CI, 1.09 to 3.03; I(2) = 99.7%; P < .001). The type of neuropathy (P = .036), time between injury and intervention (P = .02), and the number of transplanted cells (P = .023) influence the improvement of allodynia after BMMSC transplantation. BMMSC transplantation has no effect on hyperalgesia (SMD = .3; 95% CI, -1.09 to 1.68; I(2) = 100%; P < .001) unless it occurs during the first 4 days after injury (P = .02). The present systematic review with meta-analysis suggests that BMMSC transplantation improves allodynia but does not have any significant effect on hyperalgesia unless it is given during the first 4 days after injury.

Mucopolysaccharidosis enzyme production by bone marrow and dental pulp derived human mesenchymal stem cells

Mucopolysaccharidoses (MPS) are inherited metabolic disorders that arise from a complete loss or a reduction in one of eleven specific lysosomal enzymes. MPS children display pathology in multiple cell types leading to tissue and organ failure and early death. Mesenchymal stem cells (MSCs) give rise to many of the cell types affected in MPS, including those that are refractory to current treatment protocols such as hematopoietic stem cell (HSC) based therapy. In this study we compared multiple MPS enzyme production by bone marrow derived (hBM) and dental pulp derived (hDP) MSCs to enzyme production by HSCs. hBM MSCs produce significantly higher levels of MPS I, II, IIIA, IVA, VI and VII enzyme than HSCs, while hDP MSCs produce significantly higher levels of MPS I, IIIA, IVA, VI and VII enzymes. Higher transfection efficiency was observed in MSCs (89%) compared to HSCs (23%) using a lentiviral vector. Over-expression of four different lysosomal enzymes resulted in up to 9303-fold and up to 5559-fold greater levels in MSC cell layer and media respectively. Stable, persistent transduction of MSCs and sustained over-expression of MPS VII enzyme was observed in vitro. Transduction of MSCs did not affect the ability of the cells to differentiate down osteogenic, adipogenic or chondrogenic lineages, but did partially delay differentiation down the non-mesodermal neurogenic lineage.

Delayed post-treatment with bone marrow-derived mesenchymal stem cells is neurorestorative of striatal medium-spiny projection neurons and improves motor function after neonatal rat hypoxia-ischemia

Perinatal hypoxia-ischemia is a major cause of striatal injury and may lead to cerebral palsy. This study investigated whether delayed administration of bone marrow-derived mesenchymal stem cells (MSCs), at one week after neonatal rat hypoxia-ischemia, was neurorestorative of striatal medium-spiny projection neurons and improved motor function. The effect of a subcutaneous injection of a high-dose, or a low-dose, of MSCs was investigated in stereological studies. Postnatal day (PN) 7 pups were subjected to hypoxia-ischemia. At PN14, pups received treatment with either MSCs or diluent. A subset of high-dose pups, and their diluent control pups, were also injected intraperitoneally with bromodeoxyuridine (BrdU), every 24h, on PN15, PN16 and PN17. This permitted tracking of the migration and survival of neuroblasts originating from the subventricular zone into the adjacent injured striatum. Pups were euthanized on PN21 and the absolute number of striatal medium-spiny projection neurons was measured after immunostaining for DARPP-32 (dopamine- and cAMP-regulated phosphoprotein-32), double immunostaining for BrdU and DARPP-32, and after cresyl violet staining alone. The absolute number of striatal immunostained calretinin interneurons was also measured. There was a statistically significant increase in the absolute number of DARPP-32-positive, BrdU/DARPP-32-positive, and cresyl violet-stained striatal medium-spiny projection neurons, and fewer striatal calretinin interneurons, in the high-dose mesenchymal stem cell (MSC) group compared to their diluent counterparts. A high-dose of MSCs restored the absolute number of these neurons to normal uninjured levels, when compared with previous stereological data on the absolute number of cresyl violet-stained striatal medium-spiny projection neurons in the normal uninjured brain. For the low-dose experiment, in which cresyl violet-stained striatal medium-spiny neurons alone were measured, there was a lower statistically significant increase in their absolute number in the MSC group compared to their diluent controls. Investigation of behavior in another cohort of animals showed that delayed administration of a high-dose of bone marrow-derived MSCs, at one week after neonatal rat hypoxia-ischemia, improved motor function on the cylinder test. Thus, delayed therapy with a high- or low-dose of adult MSCs, at one week after injury, is effective in restoring the loss of striatal medium-spiny projection neurons after neonatal rat hypoxia-ischemia and a high-dose of MSCs improved motor function.

Concise Review: Differentiation of Human Adult Stem Cells Into Hepatocyte-like Cells In vitro

Adult stem cells (ASCs) are undifferentiated cells found throughout the body that divide to replenish dying cells and regenerate damaged tissues, which are the powerful sources for cell therapy and tissue engineering. Bone marrow-derived mesenchymal stem cells (BMSCs), adipose tissue-derived mesenchymal stem cells (ADSCs), and peripheral blood monocytes (PBMCs) are the common ASCs, and many studies indicated that ASCs isolated from various adult tissues could be induced to hepatocyte-like cells in vitro. However, the isolation, culture protocols, characterization of ASCs and hepatocyte-like cells are different. This review aims to describe the isolation and culture procedures for ASCs, to summarize the molecular characterization of ASCs, to characterize function of hepatocyte-like cells, and to discuss the future role of ASCs in cell therapy and tissue engineering.

Bone marrow mesenchymal stem cells altered the immunoregulatory activities of hepatic natural killer cells

We explored the biological characteristics of bone marrow-derived mesenchymal stem cells (BMSCs) and their immunological effects in vivo. To establish the characteristics of BMSCs, we first examined their morphology, differentiation ability, phenotype, and growth patterns. We further explored the effects of intravenous infusion of BMSCs on the immunological activities in vivo and the possible mechanism involved in it. The results showed that BMSCs displayed a fibroblast-like morphology and could differentiate into bone, fat and cartilage cells. Phenotypic analysis indicated the cells were negative for CD34 and CD31 but positive for Flk1, CD29, CD44 and CD105. In addition, BMSC culture supernatants could not improve the resistance against H2O2-induced apoptosis in L02 cells. We also found that infusion of BMSCs suppressed the activity of intrahepatic natural killer T cells. In summary, BMSCs are an ideal candidate for therapeutic application because they are relatively easy to harvest, easily expandable in vitro, and can be isolated from adult bone marrow while retaining their differentiation potential. BMSCs have stem cell properties, and BMSC therapy is an alternative treatment for acute liver disease.

New insights in hepatocellular carcinoma: from bench to bedside

Hepatocarcinogenesis is a multistep process involving different genetic alterations that ultimately lead to malignant transformation of the hepatocyte. The liver is one of the main targets for different metastatic foci, but it represents an important and frequent locus of degeneration in the course of chronic disease. In fact, Hepatocellular carcinoma (HCC) represents the outcome of the natural history of chronic liver diseases, from the condition of fibrosis, to cirrhosis and finally to cancer. HCC is the sixth most common cancer in the world, some 630,000 new cases being diagnosed each year. Furthermore, about the 80% of people with HCC, have seen their clinical history developing from fibrosis, to cirrhosis and finally to cancer. The three main causes of HCC development are represented by HBV, HCV infection and alcoholism. Moreover, metabolic disease [starting from Non Alcoholic Fatty Liver Disease (NAFLD), Non Alcoholic Steatohepatitis (NASH)] and, with reduced frequency, some autoimmune disease may lead to HCC development. An additional rare cause of carcinogenetic degeneration of the liver, especially developed in African and Asian Countries, is represented by aflatoxin B1. The mechanisms by which these etiologic factors may induce HCC development involve a wide range of pathway and molecules, currently under investigation. In summary, the hepatocarcionogenesis results from a multifactorial process leading to the common condition of genetic changes in mature hepatocytes mainly characterized by uncontrolled proliferation and cell death. Advances in understanding the mechanism of action are fundamental for the development of new potential therapies and results primarily from the association of the research activities coming from basic and clinical science. This review article analyzes the current models used in basic research to investigate HCC activity, and the advances obtained from a basic and clinical point of view.

Mesenchymal Stem Cells Overexpressing Angiotensin-Converting Enzyme 2 Rescue Lipopolysaccharide-Induced Lung Injury

Bone marrow-derived mesenchymal stem cells (MSCs), which have beneficial effects in acute lung injury (ALI), can serve as a vehicle for gene therapy. Angiotensin-converting enzyme 2 (ACE2), a counterregulatory enzyme of ACE that degrades angiotensin (Ang) II into Ang 1-7, has a protective role against ALI. Because ACE2 expression is severely reduced in the injured lung, a therapy targeted to improve ACE2 expression in lung might attenuate ALI. We hypothesized that MSCs overexpressing ACE2 would have further benefits in lipopolysaccharide (LPS)-induced ALI mice, when compared with MSCs alone. MSCs were transduced with ACE2 gene (MSC-ACE2) by a lentiviral vector and then infused into wild-type (WT) and ACE2 knockout (ACE2(-/y)) mice following an LPS-induced intratracheal lung injury. The results demonstrated that the lung injury of ALI mice was alleviated at 24 and 72 h after MSC-ACE2 transplantation. MSC-ACE2 improved the lung histopathology and had additional anti-inflammatory effects when compared with MSCs alone in both WT and ACE2(-/y) ALI mice. MSC-ACE2 administration also reduced pulmonary vascular permeability, improved endothelial barrier integrity, and normalized lung eNOS expression relative to the MSC group. The beneficial effects of MSC-ACE2 could be attributed to its recruitment into the injured lung and enhanced local expression of ACE2 protein without changing the serum ACE2 levels after MSC-ACE2 transplantation. The biological activity of the increased ACE2 protein decreased the Ang II amount and increased the Ang 1-7 level in the lung when compared with the ALI and MSC-only groups, thereby inhibiting the detrimental effects of accumulating Ang II. Therefore, compared to MSCs alone, the administration of MSCs overexpressing ACE2 resulted in a further improvement in the inflammatory response and pulmonary endothelial function of LPS-induced ALI mice. These additional benefits could be due to the degradation of Ang II that accompanies the targeted overexpression of ACE2 in the lung.

Caveats of mesenchymal stem cell therapy in solid organ transplantation

In the past decade, therapeutic use of mesenchymal stem cells (MSCs) has increased dramatically. The weight of existing evidence supports that the short-term application of MSCs is safe and feasible; however, concerns remain over the possibility of unwanted long-term effects. One fundamental difference between MSCs and pharmacotherapy is that, once applied, the effects of cell products cannot be easily reversed. Therefore, a carefully considered decision process is indispensable before cell infusion. In addition to unwanted interactions of MSCs with the host immune system, there are concerns that MSCs may promote tumor progression or even give rise to cancer themselves. As animal models and first-in-man clinical studies have provided conflicting results, it is challenging to estimate the long-term risk of individual patients. In addition, most animal models, especially rodents, are ill-suited to adequately address questions over long-term side effects. Based on the available evidence, we address the potential pitfalls for the use of MSCs as a therapeutic agent to control alloimmune effects. The aim of this review was not to discourage investigators from clinical studies, but to raise awareness of the intrinsic risks of MSC therapy.

Treating patients with "thin" endometrium - an ongoing challenge

OBJECTIVE

To review the literature regarding inadequate growth ("thin") of the endometrium and to present the hitherto published methods aimed to improve endometrial thickness and the consequent endometrial receptivity.

MATERIALS AND METHODS

A literature review was conducted for all relevant articles assessing the effect of various treatment modalities on "thin" endometrium and the consequent reproductive outcome.

RESULTS

Several treatment modalities have been offered to patients with "thin" endometrium, including hysteroscopic adhesiolysis, hormonal manipulation by estrogen and GnRH-agonist, vasoactive measures such as aspirin, vitamin E, pentoxifylline, l-arginine or sildenafil, intra-uterine infusion of growth factor such as G-CSF and the recent application of regenerative medicine. In spite of the vast diversity of treatment, most of the options accomplish only minor change in the endometrium thickness and subsequent pregnancy rate, and when they fail, patients are usually referred to surrogacy.

CONCLUSIONS

"Thin" endometrium is known to adversely affect reproductive performance. Treatment of "thin endometrium" remains a challenge and future large researches are required to further elucidate and optimal management of patients with "thin" endometrium.

Mesenchymal stem cells regulate airway contractile tissue remodeling in murine experimental asthma

Background

Mesenchymal stem cells may offer therapeutic potential for asthma due to their immunomodulatory properties and host tolerability, yet prior evidence suggests that bloodborne progenitor cells may participate in airway remodeling. Here, we tested whether mesenchymal stem cells administered as anti‐inflammatory therapy may favor airway remodeling and therefore be detrimental.

Methods

Adipose tissue‐derived mesenchymal stem cells were retrovirally transduced to express green fluorescent protein and intravenously injected into mice with established experimental asthma induced by repeat intranasal house dust mite extract. Controls were house dust mite‐instilled animals receiving intravenous vehicle or phosphate‐buffered saline‐instilled animals receiving mesenchymal stem cells. Data on lung function, airway inflammation, and remodeling were collected at 72 h after injection or after 2 weeks of additional intranasal challenge.

Results

The mesenchymal stem cells homed to the lungs and rapidly downregulated airway inflammation in association with raised T‐helper‐1 lung cytokines, but such effect declined under sustained allergen challenge despite a persistent presence of mesenchymal stem cells. Conversely, airway hyperresponsiveness and contractile tissue underwent a late reduction regardless of continuous pathogenic stimuli and inflammatory rebound. Tracking of green fluorescent protein did not show mesenchymal stem cell integration or differentiation in airway wall tissues.

Conclusions

Therapeutic mesenchymal stem cell infusion in murine experimental asthma is free of unwanted pro‐remodeling effects and ameliorates airway hyper‐responsiveness and contractile tissue remodeling. These outcomes support furthering the development of mesenchymal stem cell‐based asthma therapies, although caution and solid preclinical data building are warranted.

Engineered hair follicle mesenchymal stem cells overexpressing controlled-release insulin reverse hyperglycemia in mice with type L diabetes

Genetically engineered stem cells that overexpress genes encoding therapeutic products can be exploited to correct metabolic disorders by repairing and regenerating diseased organs or restoring their function. Hair follicles are readily accessible and serve as a rich source of autologous stem cells for cell-based gene therapy. Here we isolated mesenchymal stem cells from human hair follicles (HF-MSCs) and engineered them to overexpress the human insulin gene and release human insulin in a time- and dose-dependent manner in response to rapamycin. The engineered HF-MSCs retained their characteristic cell surface markers and retained their potential to differentiate into adipocytes and osteoblasts. When mice with streptozotocin-induced type 1 diabetes were engrafted with these engineered HF-MSCs, these cells expressed and released a dose of human insulin, dramatically reversed hyperglycemia, and significantly reduced death rate. Moreover, the engineered HF-MSCs did not form detectable tumors throughout the 120-day animal tests in our experiment. Our results show that HF-MSCs can be used to safely and efficiently express therapeutic transgenes and therefore show promise for cell-based gene therapy of human disease.

Contribution of murine bone marrow mesenchymal stem cells to pancreas regeneration after partial pancreatectomy in mice

The implantation of BMSCs (bone marrow mesenchymal stem cells) has emerged as a potential method of treating tissue damage, but the in vivo differentiation of BMSCs in an injured pancreas and its therapeutic effects have not been determined. Our aim has been to investigate the potential of BMSCs to contribute to the parenchyma and mesenchymal components of the pancreas during rapid regeneration, with preliminary exploration of the molecular mechanisms of this process. GFP(+) (green fluorescent protein(+) ) BMSCs were intravenously infused into the tail veins of mice that had received a 65-70% partial pancreatectomy, while mice that had only received a partial pancreatectomy and mice that had only been injected with BMSCs served as controls. Four weeks later, the injected GFP(+) BMSCs were diffusely engrafted in the pancreatic parenchyma and mesenchyma of the recipient mice with pancreatic injuries and had differentiated into pancreatic ductal epithelial cells (accounting for 1.7±0.3%), vascular endothelial cells (3.2±0.6%) and PSCs (pancreatic stellate cells) (5.2±1.6%), but no β or neural cells. Significantly, more engrafted and differentiated GFP(+) BMSCs were observed in the regenerating pancreas than in the normal pancreas. For the mice that received a partial pancreatectomy, the pancreatic weight/body weight of the mice with BMSC treatment was greater than mice without BMSC treatment (P<0.05). In addition, real-time RT-PCR (reverse transcription-PCR) showed that the expression levels of miR-9 (microRNA 9) and miR-204 in the engrafted BMSCs (5.2- and 2.6-fold, P<0.05, respectively) were increased compared with wild-type BMSCs. We also observed a significant reduction in the expression of miR-375 (0.71-fold, P<0.05) in engrafted GFP(+) BMSCs compared with wild-type BMSCs. BMSCs can therefore be a potential cell bank for treating pancreatic injuries by contributing to a variety of cell types. This process might be related to the expression of miR-9, miR-204 and miR-375.

The challenge of pancreatic cancer therapy and novel treatment strategy using engineered mesenchymal stem cells

Mesenchymal stem cells (MSCs) have attracted significant attention in cancer research as a result of their accessibility, tumor-oriented homing capacity, and the feasibility of auto-transplantation. This review provides a comprehensive overview of current challenges in pancreatic cancer therapy, and we propose a novel strategy for using MSCs as means of delivering anticancer genes to the site of pancreas. We aim to provide a practical platform for the development of MSC-based therapy for pancreatic cancer.

Rat bone marrow mesenchymal stem cells improve regeneration of thin endometrium in rat

OBJECTIVE

To investigate whether bone marrow mesenchymal stem cell (BMSC) treatment could improve the regeneration of endometrium and improve the endometrial receptivity in an experimental model of thin endometrium.

DESIGN

Randomized, control trial, animal research.

SETTING

National key laboratory.

ANIMAL(S)

Sprague-Dawley rats.

INTERVENTION(S)

Bone marrow mesenchymal stem cell transplantation by tail vein IV injection.

MAIN OUTCOME MEASURE(S)

Endometrial thickness, the expression of mark proteins for endometrial cell, and endometrial receptivity.

RESULT(S)

The endometrium was significantly thicker and the expression of cytokeratin, vimentin, integrin αγβ3, and leukemia inhibitor factor were significantly stronger compared with the control group. Some proinflammatory cytokines, such as tumor necrosis factor-α (TNF-α) messenger RNA (mRNA) and interleukin-1β mRNA, were significantly down-regulated, and anti-inflammatory cytokines, such as fibroblast growth factor-β (bFGF) mRNA and interleukin-6 mRNA, were significantly up-regulated in the experimental group compared with the control group.

CONCLUSION(S)

The BMSCs have beneficial effect on thin endometrium, and may play a role through migration and immunomodulatory of BMSCs.

Kidney regeneration and stem cells

The kidney has the capacity to recover from ischemic and toxic insults. Although there has been debate about the origin of cells that replace injured epithelial cells, it is now widely recognized that intrinsic surviving tubular cells are responsible for the repair. On the other hand, the cells, which have stem cell-like characteristics, have been isolated in the kidney using various methods, but it remains unknown if these stem cells actually exist in the adult kidney and if they are involved in kidney regeneration. This review will focus on the pathophysiology of kidney regeneration and the contribution of renal stem cells. We also discuss possible therapeutic applications to kidney disease.

Bone marrow-derived mesenchymal stem cells favor the immunosuppressive T cells skewing in a Helicobacter pylori model of gastric cancer

Bone marrow-derived mesenchymal stem cells (BM-MSCs) play an important role in Helicobacter pylori-induced gastric carcinogenesis. While the mechanism is not well understood, BM-MSCs have been shown to contribute to the immunosuppressive response found in a number of diseases. Here, BM-MSCs were transplanted into the stomach of mice with a 44-week mouse-adapted H. pylori infection. At day 28 post-transplantation, BM-MSCs migrated from the subserosal to the mucosal layer of the stomach. The grafted BM-MSCs significantly stimulated systemic and local interleukin-10 (IL-10)-secreting T cell and regulatory T cell (Treg) functions. This observation was correlated with an increased percentage of CD4⁺IL-10⁺ cells and CD4⁺CD25⁺FoxP3⁺ cells in splenic mononuclear cells compared with H. pylori-infected mice not receiving BM-MSCs. Moreover, inhibitory cytokines IL-10 and transforming growth factor-β1 increased in the gastric tissue, while there was a decrease in inflammatory interferon-γ (IFN-γ). BM-MSC-transplanted mice also developed elevated IL-10/IFN-γ secreting and Treg/Th17 ratios. A coculture system in the presence or absence of BM-MSCs was also established to evaluate the immune responses in vitro. An increase in IL-10-secreting T cells and Tregs, associated with increased expression of Gata-3 and FoxP3, generation of IL-10 in the supernatant, and proliferation of gastric epithelial cells (GECs) was observed. These findings demonstrate that transplantation of BM-MSCs into a chronic H. pylori-infected mouse model results in the generation of an immunosuppressive environment. The local and systemic immunosuppression mediated by BM-MSCs likely contributed to an environment that is compatible with the development of H. pylori-induced gastric cancer.

Pericytes, stem-cell-like cells, but not mesenchymal stem cells are recruited to support microvascular tube stabilization

An experimental model is introduced for the induction of endothelial cell (EC) tubulogenesis after 24 h of incubation on micropatterned polymer surfaces. Pericytes or mesenchymal stem cells are added separately to this system to evaluate their effect on tubular stabilization. In the absence of additional cells, the tubular structures are lost after 36 h. Addition of only pericytes, however, stabilizes the EC vasculogenic tubes.

Genetically modified adipose tissue-derived stem/stromal cells, using simian immunodeficiency virus-based lentiviral vectors, in the treatment of hemophilia B

Hemophilia is an X-linked bleeding disorder, and patients with hemophilia are deficient in a biologically active coagulation factor. This study was designed to combine the efficiency of lentiviral vector transduction techniques with murine adipose tissue-derived stem/stromal cells (mADSCs) as a new method to produce secreted human coagulation factor IX (hFIX) and to treat hemophilia B. mADSCs were transduced with simian immunodeficiency virus (SIV)-hFIX lentiviral vector at multiplicities of infection (MOIs) from 1 to 60, and the most effective dose was at an MOI of 10, as determined by hFIX production. hFIX protein secretion persisted over the 28-day experimental period. Cell sheets composed of lentiviral vector-transduced mADSCs were engineered to further enhance the usefulness of these cells for future therapeutic applications in transplantation modalities. These experiments demonstrated that genetically transduced ADSCs may become a valuable cell source for establishing cell-based gene therapies for plasma protein deficiencies, such as hemophilia.

Cell surface structures influence lung clearance rate of systemically infused mesenchymal stromal cells

The promising clinical effects of mesenchymal stromal/stem cells (MSCs) rely especially on paracrine and nonimmunogenic mechanisms. Delivery routes are essential for the efficacy of cell therapy and systemic delivery by infusion is the obvious goal for many forms of MSC therapy. Lung adhesion of MSCs might, however, be a major obstacle yet to overcome. Current knowledge does not allow us to make sound conclusions whether MSC lung entrapment is harmful or beneficial, and thus we wanted to explore MSC lung adhesion in greater detail. We found a striking difference in the lung clearance rate of systemically infused MSCs derived from two different clinical sources, namely bone marrow (BM-MSCs) and umbilical cord blood (UCB-MSCs). The BM-MSCs and UCB-MSCs used in this study differed in cell size, but our results also indicated other mechanisms behind the lung adherence. A detailed analysis of the cell surface profiles revealed differences in the expression of relevant adhesion molecules. The UCB-MSCs had higher expression levels of α4 integrin (CD49d, VLA-4), α6 integrin (CD49f, VLA-6), and the hepatocyte growth factor receptor (c-Met) and a higher general fucosylation level. Strikingly, the level of CD49d and CD49f expression could be functionally linked with the lung clearance rate. Additionally, we saw a possible link between MSC lung adherence and higher fibronectin expression and we show that the expression of fibronectin increases with MSC culture confluence. Future studies should aim at developing methods of transiently modifying the cell surface structures in order to improve the delivery of therapeutic cells.

Clinical applications of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are self-renewing, multipotent progenitor cells with multilineage potential to differentiate into cell types of mesodermal origin, such as adipocytes, osteocytes, and chondrocytes. In addition, MSCs can migrate to sites of inflammation and exert potent immunosuppressive and anti-inflammatory effects through interactions between lymphocytes associated with both the innate and adaptive immune system. Along with these unique therapeutic properties, their ease of accessibility and expansion suggest that use of MSCs may be a useful therapeutic approach for various disorders. In the clinical setting, MSCs are being explored in trials of various conditions, including orthopedic injuries, graft versus host disease following bone marrow transplantation, cardiovascular diseases, autoimmune diseases, and liver diseases. Furthermore, genetic modification of MSCs to overexpress antitumor genes has provided prospects for clinical use as anticancer therapy. Here, we highlight the currently reported uses of MSCs in clinical trials and discuss their efficacy as well as their limitations.

Transient proteolytic modification of mesenchymal stromal cells increases lung clearance rate and targeting to injured tissue

Systemic infusion of therapeutic cells would be the most practical and least invasive method of administration in many cellular therapies. One of the main obstacles especially in intravenous delivery of cells is a massive cell retention in the lungs, which impairs homing to the target tissue and may decrease the therapeutic outcome. In this study we showed that an alternative cell detachment of mesenchymal stromal/stem cells (MSCs) with pronase instead of trypsin significantly accelerated the lung clearance of the cells and, importantly, increased their targeting to an area of injury. Cell detachment with pronase transiently altered the MSC surface protein profile without compromising cell viability, multipotent cell characteristics, or immunomodulative and angiogenic potential. The transient modification of the cell surface protein profile was sufficient to produce effective changes in cell rolling behavior in vitro and, importantly, in the in vivo biodistribution of the cells in mouse, rat, and porcine models. In conclusion, pronase detachment could be used as a method to improve the MSC lung clearance and targeting in vivo. This may have a major impact on the bioavailability of MSCs in future therapeutic regimes.

Effect of neuroglobin genetically modified bone marrow mesenchymal stem cells transplantation on spinal cord injury in rabbits

Objective

This study aims to investigate the potentially protective effect of neuroglobin (Ngb) gene-modified bone marrow mesenchymal stem cells (BMSCs) on traumatic spinal cord injury (SCI) in rabbits.

Methods

A lentiviral vector containing an Ngb gene was constructed and used to deliver Ngb to BMSCs. Ngb gene-modified BMSCs were then injected at the SCI sites 24 hours after SCI. The motor functions of the rabbits were evaluated by the Basso–Beattie–Bresnahan rating scale. Fluorescence microscopy, quantitative real-time PCRs, Western blots, malondialdehyde (MDA) tests, and terminal deoxynucleotidyltransferase-mediated UTP end labeling assays were also performed.

Results

Ngb expression in the Ngb-BMSC group increased significantly. A more significant functional improvement was observed in the Ngb-BMSC group compared with those in the other groups. Traumatic SCI seemingly led to an increase in MDA level and number of apoptotic cells, which can be prevented by Ngb-BMSC treatment.

Conclusion

This study demonstrates that Ngb gene-modified BMSCs can strengthen the therapeutic benefits of BMSCs in reducing secondary damage and improving the neurological outcome after traumatic SCI. Therefore, the combined strategy of BMSC transplantation and Ngb gene therapy can be used to treat traumatic SCI.

Intratracheal transplantation of bone marrow-derived mesenchymal stem cells reduced airway inflammation and up-regulated CD4⁺CD25⁺ regulatory T cells in asthmatic mouse

Mesenchymal stem cells attenuate the severity of lung injury due to their immunomodulatory properties. The effect of bone marrow-derived mesenchymal stem cells on asthma is seldom reported. We have examined the effect of BMSCs on airway inflammation in asthma. Forty female BALB/c mice were equally randomised into PBS group, BMSCs treatment group, BMSCs control group and asthmatic group. Reactivity of the airway to acetylcholine was measured by barometric plethysmography. Cytokine profiles of bronchoalveolar lavage fluid and serum were determined by enzyme-linked immunosorbent assay. Morphometric analysis was done with haematoxylin and periodic-acid Schiff staining. Engraftment of BMSCs in asthmatic mice significantly decreased the number of eosinophils and mononuclear cells in bronchoalveolar lavage fluid and the airway (P < 0.05). Both goblet cell hyperplasia and responsiveness to acetylcholine were significantly reduced in BMSCs treatment groups. Moreover, BMSCs engraftment caused significant increases the ratio of Treg in pulmonary lymph node and interleukin-10 (IL-10) and interleukin-12 levels in BALF and serum. We conclude that BMSCs engraftment ameliorated airway inflammation and improved lung function in asthmatic mouse and the protective effect might be mediated by upregulating Treg and partly involved with increasing IL-10.

Anti-inflammatory role and immunomodulation of mesenchymal stem cells in systemic joint diseases: potential for treatment

INTRODUCTION

Mesenchymal stem cells (MSCs) are multipotent stromal cells characterized by their ability to differentiate into adipocytes, chondrocytes, osteocytes and a number of other lineages. Investigation into their use has increased in recent years as characterization of their immunomodulatory properties has developed, and their role in the pathophysiology of joint disease has been suggested.

AREAS COVERED

MSCs demonstrate immunosuppressive functionality by suppressing T- and B-cell responses following activation by cytokines such as IL-6 and IL-1α. They also can be induced to exert pro-inflammatory effects in the presence of acute inflammatory environment due to the actions of TNF-α and IFN-γ. In inflammatory joint diseases such as rheumatoid arthritis, MSCs in bone marrow migrate to joints by a TNF-α-dependent mechanism and may be in part responsible for the disease process. MSCs have also been demonstrated in increased numbers in periarticular tissues in osteoarthritis, which may reflect an attempt at joint regeneration.

EXPERT OPINION

Clinical applications for MSCs have shown promise in a number of inflammatory and autoimmune disorders. Future work is likely to further reveal the immunosuppressive characteristics of MSCs, their role in the pathophysiology of joint diseases and provide the basis for new avenues for treatment.

Mesenchymal stem cells facilitate fracture repair in an alcohol-induced impaired healing model

OBJECTIVES

Clinical studies have shown alcohol to be a risk factor for traumatic orthopaedic injuries and for nonunion. Data from animal studies suggest that alcohol exposure inhibits fracture healing. This report presents a novel rodent model of impaired fracture healing caused by repeated alcohol exposure. Using this model, we examined the regenerative effects of an intravenously administered population of isolated and expanded mesenchymal stem cells (MSCs) on fracture healing.

METHODS

Bone marrow-derived MSC were isolated from transgenic green fluorescent protein C57BL/6 mice, and culture expanded using a lineage depletion protocol. Adult wild-type C57BL/6 mice were subjected to a 2-week binge alcohol exposure paradigm (3 days during which they received daily intraperitoneal injections of a 20% alcohol/saline solution followed by a 4-day rest period and another binge cycle for 3 consecutive days). At completion of the second binge cycle, mice were subjected to a mid-shaft tibia fracture while intoxicated. Twenty-four hours after the fracture, animals were administered an intravenous transplant of green fluorescent protein-labeled MSC. Two weeks after the fracture, animals were euthanized and injured tibiae were collected and subjected to biomechanical, histologic, and microcomputed tomography analysis.

RESULTS

Pre-injury binge alcohol exposure resulted in a significant impairment in biomechanical strength and decrease in callus volume. MSC transplants restored both fracture callus volume (P < 0.05) and biomechanical strength (P < 0.05) in animals with alcohol-impaired healing. In vivo imaging demonstrated a time-dependent MSC migration to the fracture site.

CONCLUSIONS

These data suggest that a 2-week binge alcohol exposure significantly impairs fracture healing in a murine tibia fracture model. Intravenously administered MSC were capable of specifically homing to the fracture site and of normalizing biomechanical, histologic, and microcomputed tomography parameters of healing in animals exposed to alcohol. Understanding MSC recruitment patterns and functional contributions to fracture repair may lead to their use in patients with impaired fracture healing and nonunion.

Impact of passing mesenchymal stem cells through smaller bore size needles for subsequent use in patients for clinical or cosmetic indications

Background

Numerous preclinical and clinical studies have investigated the regenerative potential and the trophic support of mesenchymal stem cells (MSCs) following their injection into a target organ. Clinicians favor the use of smallest bore needles possible for delivering MSCs into vascular organs like heart, liver and spleen. There has been a concern that small needle bore sizes may be detrimental to the health of these cells and reduce the survival and plasticity of MSCs.

Methods

In this report, we aimed to investigate the smallest possible bore size needle which would support the safe delivery of MSCs into various tissues for different clinical or cosmetic applications. To accomplish this we injected cells via needle sizes 24, 25 and 26 G attached to 1 ml syringe in the laboratory and collected the cells aseptically. Control cells were ejected via 1 ml syringe without any needle. Thereafter, the needle ejected cells were cultured and characterized for their morphology, attachment, viability, phenotypic expression, differentiation potential, cryopreservation and in vivo migration abilities. In the second phase of the study, cells were injected via 26 G needle attached to 1 ml syringe for 10 times.

Results

Similar phenotypic and functional characteristics were observed between ejected and control group of cells. MSCs maintained their cellular and functional properties after single and multiple injections.

Conclusions

This study proves that 26 G bore size needles can be safely used to inject MSCs for clinical/therapeutics purposes.

Effects of transplanted bone-marrow-derived mesenchymal stem cells in animal models of acute hepatitis

Our aim was to evaluate the therapeutic effects of bone-marrow-derived mesenchymal stem cells (BMMSCs) on ConA-induced hepatitis and to elucidate the possible mechanism involved. MSCs were isolated from bone marrow and their characteristics and anti-apoptotic effects on the L02 cell line were analyzed. The effect of intravenous infusion of BMMSCs on liver damage was also tested. Furthermore, the recruitment of donor BMMSCs to the liver of recipient animals and their effects on the activity of intrahepatic natural killer T (NKT) cells were investigated. BMMSCs ameliorated liver damage in a time- and dose-dependent manner. Donor BMMSCs were detected in the livers of recipient animals, suggesting that tissue damage stimulated the migration of BMMSCs. Transplanted BMMSCs also suppressed the activity of intrahepatic NKT cells, not only in the liver but throughout the body. The general infusion of BMMSCS ameliorated immunoregulatory activities by the suppression of intrahepatic NKT cells.

Equal modulation of endothelial cell function by four distinct tissue-specific mesenchymal stem cells

Mesenchymal stem cells (MSCs) can generate multiple end-stage mesenchymal cell types and constitute a promising population of cells for regenerative therapies. Additionally, there is increasing evidence supporting other trophic activities of MSCs, including the ability to enable formation of vasculature in vivo. Although MSCs were originally isolated from the bone marrow, the presence of these cells in the stromal vascular fraction of multiple adult tissues has been recently recognized. However, it is unknown whether the capacity to modulate vasculogenesis is ubiquitous to all MSCs regardless of their tissue of origin. Here, we demonstrated that tissue-resident MSCs isolated from four distinct tissues have equal capacity to modulate endothelial cell function, including formation of vascular networks in vivo. MSCs were isolated from four murine tissues, including bone marrow, white adipose tissue, skeletal muscle, and myocardium. In culture, all four MSC populations secreted a plethora of pro-angiogenic factors that unequivocally induced proliferation, migration, and tube formation of endothelial colony-forming cells (ECFCs). In vivo, co-implantation of MSCs with ECFCs into mice generated an extensive network of blood vessels with ECFCs specifically lining the lumens and MSCs occupying perivascular positions. Importantly, there were no differences among all four MSCs evaluated. Our studies suggest that the capacity to modulate the formation of vasculature is a ubiquitous property of all MSCs, irrespective of their original anatomical location. These results validate multiple tissues as potential sources of MSCs for future cell-based vascular therapies.

Hepatocyte differentiation of mesenchymal stem cells

BACKGROUND

Liver cell transplantation and bioartificial liver may provide metabolic support of liver function temporary and are prospective treatments for patients with liver failure. Mesenchymal stem cells (MSCs) are expected to be an ideal cell source for transplantation or liver tissue engineering, however the hepatic differentiation of MSCs is still insufficient for clinical application.

DATA SOURCES

A PubMed search on "mesenchymal stem cells", "liver cell" and "hepatocyte differentiation" was performed on the topic, and the relevant articles published in the past ten years were reviewed.

RESULTS

Hepatocyte-like cells differentiated from MSCs are a promising cell source for liver regeneration or tissue engineering. Although it is still a matter of debate as to whether MSC-derived hepatocytes may efficiently repopulate a host liver to provide adequate functional substitution, the majority of animal studies support that MSCs can become key players in liver-directed regenerative medicine. However the clinical application of human stem cells in the treatment of liver diseases is still in its infancy.

CONCLUSIONS

Future studies are required to improve the efficacy and consistency of hepatic differentiation from MSCs. It is necessary to better understand the mechanism to achieve transdifferentiation with high efficiency. More clinical trials are warranted to prove their efficacy in the management of patients with liver failure.

A novel strategy to enhance mesenchymal stem cell migration capacity and promote tissue repair in an injury specific fashion

Mesenchymal stem cells (MSCs) of bone marrow origin appear to be an attractive candidate for cell-based therapies. However, the major barrier to the effective implementation of MSC-based therapies is the lack of specific homing of exogenously infused cells and overall the inability to drive them to the diseased or damaged tissue. In order to circumvent these limitations, we developed a preconditioning strategy to optimize MSC migration efficiency and potentiate their beneficial effect at the site of injury. Initially, we screened different molecules by using an in vitro injury-migration setting, and subsequently, we evaluated the effectiveness of the different strategies in mice with acute kidney injury (AKI). Our results showed that preconditioning of MSCs with IGF-1 before infusion improved cell migration capacity and restored normal renal function after AKI. The present study demonstrates that promoting migration of MSCs could increase their therapeutic potential and indicates a new therapeutic paradigm for organ repair.

Impaired osteoblastogenesis in a murine model of dominant osteogenesis imperfecta: a new target for osteogenesis imperfecta pharmacological therapy

The molecular basis underlying the clinical phenotype in bone diseases is customarily associated with abnormal extracellular matrix structure and/or properties. More recently, cellular malfunction has been identified as a concomitant causative factor and increased attention has focused on stem cells differentiation. Classic osteogenesis imperfecta (OI) is a prototype for heritable bone dysplasias: it has dominant genetic transmission and is caused by mutations in the genes coding for collagen I, the most abundant protein in bone. Using the Brtl mouse, a well-characterized knockin model for moderately severe dominant OI, we demonstrated an impairment in the differentiation of bone marrow progenitor cells toward osteoblasts. In mutant mesenchymal stem cells (MSCs), the expression of early (Runx2 and Sp7) and late (Col1a1 and Ibsp) osteoblastic markers was significantly reduced with respect to wild type (WT). Conversely, mutant MSCs generated more colony-forming unit-adipocytes compared to WT, with more adipocytes per colony, and increased number and size of triglyceride drops per cell. Autophagy upregulation was also demonstrated in mutant adult MSCs differentiating toward osteogenic lineage as consequence of endoplasmic reticulum stress due to mutant collagen retention. Treatment of the Brtl mice with the proteasome inhibitor Bortezomib ameliorated both osteoblast differentiation in vitro and bone properties in vivo as demonstrated by colony-forming unit-osteoblasts assay and peripheral quantitative computed tomography analysis on long bones, respectively. This is the first report of impaired MSC differentiation to osteoblasts in OI, and it identifies a new potential target for the pharmacological treatment of the disorder.

Microvascular remodeling and wound healing: a role for pericytes

Physiologic wound healing is highly dependent on the coordinated functions of vascular and non-vascular cells. Resolution of tissue injury involves coagulation, inflammation, formation of granulation tissue, remodeling and scarring. Angiogenesis, the growth of microvessels the size of capillaries, is crucial for these processes, delivering blood-borne cells, nutrients and oxygen to actively remodeling areas. Central to angiogenic induction and regulation is microvascular remodeling, which is dependent upon capillary endothelial cell and pericyte interactions. Despite our growing knowledge of pericyte-endothelial cell crosstalk, it is unclear how the interplay among pericytes, inflammatory cells, glia and connective tissue elements shape microvascular injury response. Here, we consider the relationships that pericytes form with the cellular effectors of healing in normal and diabetic environments, including repair following injury and vascular complications of diabetes, such as diabetic macular edema and proliferative diabetic retinopathy. In addition, pericytes and stem cells possessing "pericyte-like" characteristics are gaining considerable attention in experimental and clinical efforts aimed at promoting healing or eradicating ocular vascular proliferative disorders. As the origin, identification and characterization of microvascular pericyte progenitor populations remains somewhat ambiguous, the molecular markers, structural and functional characteristics of pericytes will be briefly reviewed.

Mesenchymal stem cell-derived hepatocytes for functional liver replacement

Mesenchymal stem cells represent an alternate cell source to substitute for primary hepatocytes in hepatocyte transplantation because of their multiple differentiation potential and nearly unlimited availability. They may differentiate into hepatocyte-like cells in vitro and maintain specific hepatocyte functions also after transplantation into the regenerating livers of mice or rats both under injury and non-injury conditions. Depending on the underlying liver disease their mode of action is either to replace the diseased liver tissue or to support liver regeneration through their anti-inflammatory and anti-apoptotic as well as their pro-proliferative action.

Mesenchymal stem cells inhibit Th17 cell differentiation by IL-10 secretion

Recent findings indicate that mesenchymal stem cells (MSCs) may act as a regulator of Th17 cell differentiation, however, the underlying mechanism is still under debate. To investigate the underlying mechanisms of MSCs' regulatory effect, mouse bone marrow-derived MSCs were cocultured with mouse CD4(+)CD25(low)CD44(low)CD62L(high) T cells in vitro, and the proportion of induced Th17 cells, cytokines secretion, and transcription factors expression were examined by flow cytometry, enzyme-linked immunosorbent assay, quantitative reverse transcription polymerase chain reaction, and Western blotting. For the first time, our results showed that bone marrow-derived MSCs were able to inhibit Th17 cell differentiation via interleukin (IL)-10 secretion as the Th17 cell proportion was significantly regained when IL-10 was neutralized, or expression of IL-10 by bone marrow-derived MSCs was downregulated by RNA interference technique. Furthermore, IL-10 may suppress expression of Rorγt, the key transcription factor for Th17 cells, both by activating suppressor of cytokine signaling 3 through signal transducers and activators of transcription 5 phosphorylation, and decreasing signal transducers and activators of transcription 3 binding, which is at the promoter of Rorγt. Thus, our results demonstrate the inhibitory effect of MSCs on Th17 cells differentiation, and suggest increased IL-10 secretion might be the key factor.

Isolation of the stromal-vascular fraction of mouse bone marrow markedly enhances the yield of clonogenic stromal progenitors

The low incidence of CFU-F significantly complicates the isolation of homogeneous populations of mouse bone marrow stromal cells (BMSCs), a common problem being contamination with hematopoietic cells. Taking advantage of burgeoning evidence demonstrating the perivascular location of stromal cell stem/progenitors, we hypothesized that a potential reason for the low yield of mouse BMSCs is the flushing of the marrow used to remove single-cell suspensions and the consequent destruction of the marrow vasculature, which may adversely affect recovery of BMSCs physically associated with the abluminal surface of blood vessels. Herein, we describe a simple methodology based on preparation and enzymatic disaggregation of intact marrow plugs, which yields distinct populations of both stromal and endothelial cells. The recovery of CFU-F obtained by pooling the product of each digestion (1631.8 + 199) reproducibly exceeds that obtained using the standard BM flushing technique (14.32 + 1.9) by at least 2 orders of magnitude (P < .001; N = 8) with an accompanying 113.95-fold enrichment of CFU-F frequency when plated at low oxygen (5%). Purified BMSC populations devoid of hematopoietic contamination are readily obtained by FACS at P0 and from freshly prepared single-cell suspensions. Furthermore, this population demonstrates robust multilineage differentiation using standard in vivo and in vitro bioassays.

In vitro and in vivo properties of distinct populations of amniotic fluid mesenchymal progenitor cells

Human mesenchymal progenitor cells (MPCs) are considered to be of great promise for use in tissue repair and regenerative medicine. MPCs represent multipotent adherent cells, able to give rise to multiple mesenchymal lineages such as osteoblasts, adipocytes or chondrocytes. Recently, we identified and characterized human second trimester amniotic fluid (AF) as a novel source of MPCs. Herein, we found that early colonies of AF-MPCs consisted of two morphologically distinct adherent cell types, termed as spindle-shaped (SS) and round-shaped (RS). A detailed analysis of these two populations showed that SS-AF-MPCs expressed CD90 antigen in a higher level and exhibited a greater proliferation and differentiation potential. To characterize better the molecular identity of these two populations, we have generated a comparative proteomic map of SS-AF-MPCs and RS-AF-MPCs, identifying 25 differentially expressed proteins and 10 proteins uniquely expressed in RS-AF-MPCs. Furthermore, SS-AF-MPCs exhibited significantly higher migration ability on extracellular matrices, such as fibronectin and laminin in vitro, compared to RS-AF-MPCs and thus we further evaluated SS-AF-MPCs for potential use as therapeutic tools in vivo. Therefore, we tested whether GFP-lentiviral transduced SS-AF-MPCs retained their stem cell identity, proliferation and differentiation potential. GFP-SS-AF-MPCs were then successfully delivered into immunosuppressed mice, distributed in different tissues and survived longterm in vivo. In summary, these results demonstrated that AF-MPCs consisted of at least two different MPC populations. In addition, SS-AF-MPCs, isolated based on their colony morphology and CD90 expression, represented the only MPC population that can be expanded easily in culture and used as an efficient tool for future in vivo therapeutic applications.

Kidney repair and stem cells: a complex and controversial process

Over the last decade, stem cells have been the topic of much debate and investigation for their regenerative potential in the case of renal injury. This review focuses on bone marrow stem cells (BMSC) for renal repair and the potential origins of the controversial results between studies. Some authors have shown that BMSC can differentiate into renal cells and reverse renal dysfunction while others obtained contradictory results. One significant variation between these studies is the choice of BMSC used. According to the literature and our own experience, unfractionated bone marrow cells and hematopoietic stem cells are able to lead to long-term cell tissue engraftment and repair, whereas mesenchymal stem cells have a short-term paracrine effect. Detection of the bone-marrow-derived cells is also an important source of error. However, the major difference between studies is the model of kidney injury used. Two categories of models have to be distinguished: acute and chronic kidney disease. However, variation within these categories also exists. The outcomes of various strategies for BMSC transplantation after injury to the kidney must be compared within a single model and cannot be transposed from one model to another.

Bone marrow cells repair cigarette smoke-induced emphysema in rats

The therapeutic potential of stem cells in chronic obstructive pulmonary disease is not well known although stem cell therapy is effective in models of other pulmonary diseases. We tested the capacities of bone marrow cells (BMCs), mesenchymal stem cells (MSCs), and conditioned media of MSCs (MSC-CM) to repair cigarette smoke-induced emphysema. Inbred female Lewis rats were exposed to cigarette smoke for 6 mo and then received BMCs, MSCs, or MSC-CM from male Lewis rats. For 2 mo after injection, the BMC treatment gradually alleviated the cigarette smoke-induced emphysema and restored the increased mean linear intercept. The BMC treatment significantly increased cell proliferation and the number of small pulmonary vessels, reduced apoptotic cell death, attenuated the mean pulmonary arterial pressure, and inhibited muscularization in small pulmonary vessels. However, only a few male donor cells were detected from 1 day to 1 mo after BMC administration. The MSCs and cell-free MSC-CM also induced the repair of emphysema and increased the number of small pulmonary vessels. Our data show that BMC, MSCs, and MSC-CM treatment repaired cigarette smoke-induced emphysema. The repair activity of these treatments is consistent with a paracrine effect rather than stem cell engraftment because most of the donor cells disappeared and because cell-free MSC-CM also induced the repair.

Mesenchymal stem cells as a therapeutic approach to glomerular diseases: benefits and risks

Most studies using adult stem cells (ASCs) and progenitor cells as potential therapeutics for kidney disorders have been conducted in models of acute kidney injury, where the damage mainly affects the tubulointerstitium. The results are promising, whereas the underlying mechanisms are still being discussed controversially. Glomerular diseases have not received as much attention. Likely reasons include the often insidious onset, rendering the choice of optimal treatment timing difficult, and the fact that chronic diseases may require long-term therapy. In this mini review, we summarize current strategies in adult stem cell-based therapies for glomerular diseases. In addition, we focus on possible side effects of stem cell administration that have been reported recently, that is, profibrotic actions and maldifferentiation of mesenchymal stem cells.