Preliminary Study on Biological Properties of Adult Human Bone Marrow-derived Mesenchymal Stem Cells

Objective： To establish a method of culture and expansion of adult human bone marrow-derived MSCs in vitro and to explore their biological properties. Methods： Mononuclear cells were obtained from 5 mL adult human bone marrow by density gradient centrifugation with Percoll solution. Adult human MSCs were cultured in Dulbecco＇s Modified Eagle＇s Medium with low glucose （LG-DMEM） containing 10% fetal calf serum at a density of 2×10^5 cell/cm^2. The morphocytology was observed under phase-contrast microscope. The cell growth was measured by MTT method. The flow cytometer was performed to examine the expression of cell surface molecules and cell cycle. The ultrastructure of MSCs was observed under transmission electron microscope. The immunomodulatory functions of MSCs were measured by MTT method. The effects of MSCs on the growth of K562 cells and the dynamic change of HA, IV-C, LN concentration in the culture supernatant of MSCs was also observed. Results： The MSCs harvested in this study were homogenous population and exhibited a spindle-shaped fibroblastic morphology. The cell growth curve showed that MSCs had a strong ability of proliferation. The cells were positive for CD44, while negative for hematopoietic cell surface marker such as CD3, CD4, CD7, CD13, CD14, CD15, CD19, CD22, CD33, CD34, CD45 and HLA-DR, which was closely related to graft versus host disease. Above 90% cells of MSCs were found at G0/G1 phase. The ultrastructure of MSCs indicated that there were plenty of cytoplasmic organelles. Allogeneic peripheral blood lymphocytes proliferation was suppressed by MSCs and the inhibition ratio was 60.68% （P〈0.01）. The suppressive effect was also existed in the culture supernatant of MSCs and the inhibition ratio was 9.00% （P〈0.05）. When lymphocytes were stimulated by PHA, the suppression effects of the culture supernatant were even stronger and the inhibition ratio was 20.91% （P〈0.01）. Compared with the cell growth curve of the K562 ceils alone, the K562 ceils cocultured with MSCs grew slowly and the exponential phase of growth wasn＇t significant. Seeing from the concentration curve, as time passed, the concentration of HA increased quickly, while those of IV-C and LN didn＇t change much. Conclusion： The method for culture and expansion of adult human bone marrow-derived MSCs in vitro has been successfully established in this study. MSCs were a homogenous population that had unique growth phenotype and multilineage potential. Preliminary study proved that it had the abilities of immunomodulatory function, antitumor, hematopoietic supporting and could act as seed cell of tissue engineering.

Suppression of tumorigenesis by human mesenchymal stem cells in a hepatoma model

Human mesenchymal stem cells （hMSCs） can home to tumor sites and inhibit the growth of tumor cells. Little is known about the underlying molecular mechanisms that link hMSCs to the targeted inhibition of tumor cells. In this study, we investigated the effects of hMSCs on two human hepatoma cell lines （H7402 and HepG2） using an animal transplantation model, a co-culture system and conditioned media from hMSCs. Animal transplantation studies showed that the latent time for tumor formation was prolonged and that the tumor size was smaller when SCID mice were injected with H7402 cells and an equal number of Z3 hMSCs. When co-cultured with Z3 cells, H7402 cell proliferation decreased, apoptosis increased, and the expression of Bcl-2, c-Myc, proliferating cell nuclear antigen （PCNA） and survivin was downregulated. After treatment with conditioned media derived from Z3 hMSC cultures, H4702 cells showed decreased colony-forming ability and decreased proliferation. Immunoblot analysis showed that β-catenin, Bcl-2, c-Myc, PCNA and survivin expression was downregulated in H7402 and HepG2 cells. Taken together, our findings demonstrate that hMSCs inhibit the malignant phenotypes of the H7402 and HepG2 human liver cancer cell lines, which include proliferation, colony-forming ability and oncogene expression both in vitro and in vivo. Furthermore, our studies provide evidence that the Wnt signaling pathway may have a role in hMSC-mediated targeting and tumor cell inhibition.

5-Azacytidine induces changes in electrophysiological properties of human mesenchymal stem cells

Previously, mouse bone marrow-derived stem cells （MSC） treated with the unspecific DNA methyltransferase inhibitor 5-azacytidine were reported to differentiate into cardiomyocytes. The aim of the present study was to investigate the efficiency of a similar differentiation strategy in human mononuclear cells obtained from healthy bone marrow donors. After 1-3 passages, cultures were exposed for 24 h to 5-azacytidine （3 μM） followed by 6 weeks of further culture. Drug treatment did not induce expression of myogenic marker MyoD or cardiac markers Nkx2.5 and GATA-4 and did not yield beating cells during follow-up. In patch clamp experiments, approximately 10-15% of treated and untreated cells exhibited L-type Ca^2＋ currents. Almost all cells showed outwardly rectifying K^＋ currents of rapid or slow activation kinetics. Mean current amplitude at ＋60 mV doubled after 6 weeks of treatment compared with time-matched controls. Membrane capacitance of treated cells was significantly larger than in controls 2 weeks after treatment and remained high after 6 weeks, Expression levels of mRNAs for the K^＋ channels Kv 1,1, Kv 1,5, Kv2,1, Kv4,3 and KCNMA 1 and for the Ca^2＋ channel Cav 1.2 were not affected by 5-azacytidine. Treatment with potassium channel blockers tetraethylammonium and clofilium at concentrations shown previously to inhibit rapid or slowly activating K^＋ currents of hMSC inhibited proliferation of these cells. Our results suggest that despite the absence of differentiation ofhMSC into cardiomyocytes, treatme.nt with 5-azacytidine caused profound changes in current density.

Hepatocytic differentiation of mesenchymal stem cells in cocultures with fetal liver cells

AIM： To investigate the hepatocytic differentiation of mesenchymal stem cells （MSCs） in co-cultures with fetal liver cells （FLC） and the possibility to expand differentiated hepatocytic cells. METHODS： MSCs were marked with green fluorescent protein （GFP） by retroviral gene transduction. Clonal marked MSCs were either cultured under liver stimulating conditions using fibronectin-coated culture dishes and medium supplemented with stem cell factor （SCF）, hepatocyte growth factor （HGF）, epidermal growth factor （EGF）, and fibroblast growth factor 4 （FGF-4） alone, or in presence of freshly isolated FLC. Cells in co-cultures were harvested, and GFP＋ or GFP- cells were separated using fluorescence activated cell sorting. Reverse transcription-polymerase chain reaction （RT-PCR） for the liver specific markers cytokeratin-18 （CK-18）, albumin, and alpha-fetoprotein （AFP） was performed in different cell populations. RESULTS- Under the specified culture conditions, rat MSCs co-cultured with FLC expressed albumin, CK-18, and AFP-RNA over two weeks. At wk 3, MSCs lost hepatocytic gene expression, probably due to overgrowth of the cocultured FLC. FLC also showed a stable liver specific gene expression in the co-cultures and a very high growth potential. CONCLUSION： The rat MSCs from bone marrow can differentiate hepatocytic cells in the presence of FLC in vitro and the presence of MSCs in co-cultures also prorides a beneficial environment for expansion and differentiation of FLC.

Autologous transplantation of bone marrow mesenchymal stem cells on diabetic patients with lower limb ischemia

Objective： To study the efficacy and safety of autologous transplantation of bone marrow mesenchymal stem cells on diabetic patients with lower limb ischemia. Methods： Fifty Type 2 diabetic patients with lower limb ischemia were enrolled and randomized to either transplanted group or control group. Patients in both group received the same conventional treatment. Meanwhile, 20 ml bone marrow from each transplanted patient were collected, and the mesenchymal stem cells were separated by density gradient centrifugation and cultured in the medium with autologous serum. After three-weeks adherent culture in vitro, 7.32×10^8-5.61×10^9 mesenchymal stem cells were harvested and transplanted by multiple intramuscular and hypodermic injections into the impaired lower limbs. Results： At the end of 12-week follow-up, 5 patients were excluded from this study because of clinical worsening or failure of cell culture. Main ischemic symptoms, including rest pain and intermittent claudication, were improved significantly in transplanted patients. The ulcer healing rate of the transplanted group （1 5 of 18, 83.33%） was significantly higher than that of the control group （9 of 20, 45.00%, P=0.012）.The mean of resting ankle-brachial index （ABI） in transplanted group significantly was increased from 0.61±0.09 to 0.74±0.11 （P〈0.001）. Magnetic resonance angiography （MRA） demonstrated that there were more patients whose score of new vessels exceeded or equaled to 2 in the transplant patients （11 of 15） than in control patients （2 of 14, P=0.001）. Lower limb amputation rate was significantly lower in transplanted group than in the control group （P=0.040）. No adverse effects was observed in transplanted group. Conclusion： These results indicate that the autologous transplantation of bone marrow mesenchymal stem cells relieves critical lower limb ischemia and promotes ulcers healing in Type 2 diabetic patients.

Inflammatory bowel disease: Moving toward a stem cell-based therapy

The incidence and prevalence of Crohn's disease (CD) and ulcerative colitis (UC), the two major forms of inflammatory bowel diseases (IBD), are rising in western countries. The modern hygienic lifestyle is probably at the root of a disease where, in genetically susceptible hosts, the intestinal commensal flora triggers dysregulated immune and inflammatory responses. Current therapies ranging from anti-inflammatory drugs to immunosuppressive regimens, remain inadequate. Advances in our understanding of the cell populations involved in the pathogenetic processes and recent findings on the regenerative, trophic and immunoregulatory potential of stem cells open new paths in IBD therapy. Hematopoietic and mesenchymal stem cells are catalyzing the attention of IBD investigators. This review highlights the pivotal fi ndings for stem cell-based approaches to IBD therapy and collects the encouraging results coming in from clinical trials.

Differentiation of hepatocytoid cell induced from whole-bone-marrow method isolated rat myeloid mesenchymal stem cells

AIM： To explore the expansion and differentiation of hepatocytoid cell induced from myeloid mesenchymal stem cell （MSC） in vib＇o, in order to find suitable resource of hepatocytes for bioartiflcial liver or liver transplantation. METHODS： The rat myeloid MSC was isolated and divided into three groups which were cultured by Friedensteion method, and then were induced by culture fluid, culture fluid plus cholestatic serum and culture fluid plus hepatocyte growth factor （HGF）, respectively. Hepatocytoid cell as well as expression of CK18 and AFP was observed by immunohistochemistry. RESULTS： After the induction for 21 d, hepatocytoid cell was observed, and its expression of CK18 and AFP was detected by immunohistochemistry in MSC cultured with cholestatic serum. Furthermore, on the 35^th d, albumin mRNA was expressed in the cell, suggesting the inducing effect was similar to that by HGF.CONCLUSION： Rat myeloid MSC can differentiate into hepatocyte lineage under appropriate condition. This method is easy to operate.

A critical role of IFNγ in priming MSC-mediated suppression of T cell proliferation through up-regulation of BT-H1

Bone-marrow-derived mesenchymal stem cells （MSCs） have been shown to possess immunosuppressive properties, e.g., by inhibiting T cell proliferation. Activated T cells can also enhance the immunosuppression ability of MSCs. The precise mechanisms underlying MSC-mediated immunosuppression remain largely undefined, although both cell-cell contact and soluble factors have been implicated; nor is it clear how the immunosuppressive property of MSCs is modulated by T cells. Using MSCs isolated from mouse bone marrow, we show here that interferon gamma （IFNγ）, a well-known proinflammatory cytokine produced by activated T cells, plays an important role in priming the immunosuppressive property of MSCs. Mechanistically, IFNγ acts directly on MSCs and leads to up-regulation of B7-H1, an inhibitory surface molecule in these stem cells. MSCs primed by activated T cells derived from IFNγ-/- mouse exhibited dramatically reduced ability to suppress T cell proliferation, a defect that can be rescued by supplying exogenous IFNγ. Moreover, siRNA-mediated knockdown of B7-H1 in MSCs abolished immunosuppression by these cells. Taken together, our results suggest that IFNγ plays a critical role in triggering the immunosuppresion by MSCs through upregulating B7-H1 in these cells, and provide evidence supporting the cell-cell contact mechanism in MSC-mediated immunosuppression.

Hepatogenic differentiation of human mesenchymal stem cells from adipose tissue in comparison with bone marrow mesenchymal stem cells

AIM： To investigate and compare the hepatogenic transdifferentiation of adipose tissue-derived stem cells （ADSC） and bone marrow-derived mesenchymal stem cells （BMSC） in vitro. Transdifferentiation of BMSC into hepatic cells in vivo has been described. Adipose tissue represents an accessible source of ADSC, with similar characteristics to BMSC. METHODS： BMSCs were obtained from patients undergoing total hip arthroplasty and ADSC from human adipose tissue obtained from lipectomy. Cells were grown in medium containing 15% human serum. Cultures were serum deprived for 2 d before cultivating under similar pro-hepatogenic conditions to those of liver development using a 2-step protocol with sequential addition of growth factors, cytokines and hormones. Hepatic differentiation was RT-PCR-assessed and liver-marker genes were immunohistochemically analysed.RESULTS： BMSC and ADSC exhibited a fibroblastic morphology that changed to a polygonal shape when cells differentiated. Expression of stem cell marker Thyl decreased in differentiated ADSC and BMSC. However, the expression of the hepatic markers, albumin and CYPs increased to a similar extent in differentiated BMSC and ADSC. Hepatic gene activation could be attributed to increased liver-enriched transcription factors （C/EBPβ and HNF4α）, as demonstrated by adenoviral expression vectors.CONCLUSION： Mesenchymal stem cells can be induced to hepatogenic transdifferentiation in vitro. ADSCs have a similar hepatogenic differentiation potential to BMSC, but a longer culture period and higher proliferation capacity. Therefore, adipose tissue may be an ideal source of large amounts of autologous stem cells, and may become an alternative for hepatocyte regeneration, liver cell transplantation or preclinical drug testing.

Autologous serum can induce mesenchymal stem cells into hepatocyte-like cells

Objective： To investigate whether the rabbit serum after radiofrequency ablation to liver tumor can induce mesenchymal stem cells （MSCs） differentiating into hepatocyte-like cells in order to find a new source and culture process for repairing liver injury. Methods： A tumor piece of 1 mm× 1mm×1 mm was transplanted into a tunnel at right liver of rabbits. The model of liver tumor was established after 2-3 weeks. The serum was collected from rabbits 72 h after being subjected to radiofrequency ablation of the liver tumor. Mesenchymal stem cells were isolated from rabbit bone marrow and cultured in DMEM containing autologous rabbit serum. Three kinds of media （L-DMEM） were tested respectively： ① containing 10% fetal calf serum （FCS）; ② containing 30% rabbit autologous serum after radiofrequency ablation of the liver tumor （ASRF）; ③ containing 30% rabbit autologous serum （AS）. MSCs were cultured on 12-well plates until passage 2 and examined under the light and electron microscopy at indicted intervals. The expression of albumin and CKl8 was detected using immunofluorescence to identify the characteristics of differentiated cells. Results： MSCs performed differently in the presence of fetal calf serum, rabbit autologous serum and rabbit autologous serum after radiofrequency ablation of the liver tumor. Induced by the serum after radiofrequency ablation to liver tumor for 7 d, the spindle-shaped MSCs turned into round shaped and resembled hepatocyte-like cells. The reactions were not found in MSCs cultured in FCS and AS groups. After induction for 14 d, slender microvilli, cell-cell junction structure and cholangiole emerged, and the differentiated cells expressed albumin and CKl 8. All those could not been observed in 10% FCS and 30% autologous serum groups. Conclusion： Mesenchymal stem cells differentiate into hepatocyte-like cells in the serum after radiofrequency ablation of liver tumor, providing us a potential cell source and culture process for clinical application in liver injury repairing.

Human bone morphogenetic protein-2 gene transfer induces human mesenchymal stem cell proliferation and differentiation in vitro

Objective: To identify eukaryotic expression vector of human bone morphogenetic protein 2 pcDNA3/BMP2, verify its expression in transfected human mesenchymal stem cells (hMSCs) and the effect on hMSCs differentiation. Methods: The BMP2 gene was cloned into a eukaryotic expression vector pcDNA3. Transfected the recombinant into hMSCs by liposome. Immunnohistochemistry and in situ hybridization methods were used to identify the expression of BMP2 mRNA and protein; ALP and Von Kossa stains were performed to identify the BMP2 gene differentiated effect on the hMSCs. Results: The pcDNA3/BMP2 fragments were as large as theory. BMP2 mRNA and protein were expressed and synthesized both in 48 h and 4 weeks after transfection, the ALP and Ca deposit exhibition, which marked the osteogenic lineage of hMSCs, were enhanced and sped. Conclusion: Transfection of pcDNA3/BMP2 is able to provide transient and persistent expression in hMSCs, and promote the MSCs differentiation to osteogenic lineage.

The mobilization of rat’s mesenchymal stem cells into peripheral blood by LiCL and its potency differentiation

Mesenchymal stem cells (MSCs) are multipotent cells, which can differentiate into different tissues. It is still controversial whether MSCs can be isolated from adult peripheral blood (PB) under normal conditions and whether they can be mobilized in a way similar to that of hematopoietic stem cells (HSCs). In this study, rat MSCs circulating in the PB under normal conditions can be isolated and cultured, and MSCs from PB and BM can be mobilized by LiCL. The mobilized MSCs can be induced to differentiate into neuron by such factors as β-mercaptoethanol and supernatants of nerve cell cultures. The present study provides a broader perspective on the repair of neural trauma.

MicroRNA encoded by the HSV-1 latency-associated transcript anti-apoptotic function in human mesenchymal stem cells

Human mesenchymal stem cells (HMSCs) have emerged as a promising cell type for tissue repopulat-ing and for use as ex vivo gene delivery vehicles. Herpes simplex virus-1 (HSV-1) possesses many vector features, which make it especially suitable for HMSC applications. Here we performed real-time RT-PCR to detect the level of mature microRNA encoded by the HSV-1 latency-associated transcript (microRNA-LAT) in HMSCs cytoplasm with a specific stem loop reverse primer. Three small interfering RNAs (siRNAs) were chemically synthesized towards microRNA-LAT, TGF-β1 and SMAD3. The results demonstrate that HSV-1 and microRNA-LAT prevented HMSCs from undergoing cisplatin-induced apoptosis. In comparison with cells only treated with cisplatin, the apoptosis phenomenon with HSV-1 and microRNA-LAT were markedly reduced. The apoptosis rates of these two groups were both lower (P<0.05) as determined by flow cytometry analysis. The results of RT-PCR and western blotting analysis confirmed that the mRNA and protein levels of TGF-β1 and SMAD3 were significantly decreased with treatment of HSV-1 and microRNA-LAT. Integral TGF-β signalling pathway components were by these means knocked down. Moreover, the levels of the mature microRNA-LAT were decreased in cis-platin-treated HMSCs. In conclusion, HSV-1 and microRNA-LAT exert their anti-apoptotic effect on HMSCs by down-regulation of the TGF-β signalling pathway. Thus HSV-1, having anti-apoptotic effect naturally encoded in its microRNA-LAT, is a good candidate to be developed for HMSC vector.

Effect of type I collagen on the adhesion, proliferation, and osteoblastic gene expression of bone marrow-derived mesenchymal stem cells

Objective: To investigate the effects of porous poly lactide-co-glycolide (PLGA) modified by type I collagen on the adhesion, proliferation, and differentiation of rabbit marrow-derived mesenchymal stem cells (MSCs). Methods: The third generation MSCs isolated from mature rabbits by density gradient centrifugation were cultured at different initial concentrations on 0.3 cm×1.2 cm×2.0 cm 3-D porous PLGA coated by type I collagen in RPMI 1640 containing 10% fetal calf serum, while cultured on PLGA without type I collagen as control. The cells adhesive and proliferative behavior at 7, 14, and 21 days after inoculation was assessed by determining the incorporation rate of [3H]-TdR. In order to examine MSCs differentiation, the expression of osteoblasts marker genes, osteocalcin (OCN), alkaline phosphatase (ALP), osteopontin (OPN) mRNA, were evaluated by reverse transcription-polymerase chain reaction (RT-PCR), and further more, the cell morphology at 21 days was also observed by scanning electron microscope (SEM). Results: Type I collagen promoted cell adhesion on PLGA. The valve was significantly higher than controls (6 h, 2144 cpm±141cpm vs. 1797 cpm±118 cpm, P=0.017; 8 h, 2311 cpm±113 cpm vs. 1891 cpm±103 cpm, P=0.01). The cells which cultured on PLGA coated with type I collagen showed significantly higher cell proliferation than controls on the 7th day (1021 cpm±159 cpm vs. 451 cpm±67 cpm, P=0.002), the 14th day (1472 cpm±82 cpm vs. 583 cpm±67 cpm, P<0.001) and 21th day (1728 cpm±78 cpm vs. 632 cpm±55 cpm, P<0.001). Osteoblasts markers, OCN, ALP, OPN mRNA, were all detected on PLGA coated by type I collagen on the 21th day, but OCN, OPN mRNA could not be found in controls. Spindle and polygonal cells well distributed on the polymer coated by type I collagen while cylindric or round cells in controls. Conclusions: Type I collagen is effective in promoting the adhesion, proliferation and differentiation of MSCs on PLGA.