Characterization of OP9 as authentic mesenchymal stem cell line

Mesenchymal stem cells (MSCs) are multipotent stem cells capable of differentiating into various cell types,including osteocytes,chondrocytes,adipocytes,myocytes,and tenocytes.However,the difficulty or failure in expanding the mouse MSCs in vitro greatly hampered important research in animal models.The OP9,a stromal cell line from mouse bone marrow,has hematopoietic supportive capacity.Here,we report that the OP9 has the immunophenotype (CD45-,CD11b-,FLK-1-,CD31-,CD34-,CD44+,CD29+,Sca-1+,CD86-,and MHCII-) identical to canonical mouse MSCs.The expression of CD140a+,CD140b+,α-SMA+ and Calponin+ suggested the perivascular origin of OP9.Functionally,the OP9 had strong clonogenic ability and could be induced into osteocytes,chondrocytes and adipocytes.The lymphocyte transformation test (LTT) and mixed leukocyte reaction (MLR) showed that the OP9 could suppress T lymphocyte proliferation stimulated by nonspecific mitogens (PHA) or allogeneic lymphocytes (BALB/c T cells).Finally,the migration of OP9 could be efficiently induced by bFGF,IGF-1,IL-3,PDGF-BB,TGF-β1 and TGF-β3.In conclusion,the OP9 were bona fide MSCs,and such homogenous cell line will be helpful to delineate biological features of MSCs at the stem cell level.     

Fates and osteogenic differentiation potential of human mesenchymal stem cells in immunocompromised mice

Human mesenchymal stem cells (hMSCs) from bone marrow were genetically marked by using a murine leukaemia virus construct encoding enhanced green fluorescent protein (eGFP). The marked cells were either directly implanted into the tibialis anterior muscle or introduced into a variety of other tissue sites in immunocompromised mice (NOD/SCID and C.B-17 SCID/beige) to investigate their fates and differentiation potentials. It was observed that the hMSCs survived for up to 12 weeks and showed site-specific morphological phenotypes. hMSCs delivered by intravenous injection were found mainly in the lungs and were detected rarely in other organs. Histomorphometry showed that, after implantation of hMSCs into the tibialis anterior muscle juxtaskeletally, the areas of reactive host callus formation at 1 and 2 weeks and of ectopic human bone formation at 1 week were significantly increased compared with the control group. Expression of eGFP and human RUNX2, alkaline phosphatase, osteocalcin, osteopontin, and collagen type I mRNAs were detected in mice implanted with the labelled hMSCs but not in sham-treated samples. Active clearance of the reactive callus and ectopic calcified tissue by osteoclast-like tartrate-resistant acid phosphatase-positive cells was observed. We conclude that the eGFP-labelled hMSCs can survive and retain the potential to differentiate morphologically into a variety of apparent mesenchymal phenotypes in vivo. Absolute confirmation of differentiation capacity requires further study and is complicated by known possibilities of fusion of donor and host cells or limited transfer of genetic material. Nevertheless, the genetically marked hMSCs are shown to participate extensively in bone formation and turnover. Control of the host osteoclast/macrophage responses resulting in clearance of formed osteogenic tissue warrants further investigation to promote prolonged human osteogenesis in immunocompromised mice. Furthermore, any proposed general cytotherapeutic strategy for enhanced osteogenesis is likely to require supplementation of local bone-forming biological signals.     

Trafficking and differentiation of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are a heterogeneous population of stem/progenitor cells with pluripotent capacity to differentiate into mesodermal and non‐mesodermal cell lineages, including osteocytes, adipocytes, chondrocytes, myocytes, cardiomyocytes, fibroblasts, myofibroblasts, epithelial cells, and neurons. MSCs reside primarily in the bone marrow, but also exist in other sites such as adipose tissue, peripheral blood, cord blood, liver, and fetal tissues. When stimulated by specific signals, these cells can be released from their niche in the bone marrow into circulation and recruited to the target tissues where they undergo in situ differentiation and contribute to tissue regeneration and homeostasis. Several characteristics of MSCs, such as the potential to differentiate into multiple lineages and the ability to be expanded ex vivo while retaining their original lineage differentiation commitment, make these cells very interesting targets for potential therapeutic use in regenerative medicine and tissue engineering. The feasibility for transplantation of primary or engineered MSCs as cell‐based therapy has been demonstrated. In this review, we summarize the current knowledge on the signals that control trafficking and differentiation of MSCs. J. Cell. Biochem. 106: 984–991, 2009. © 2009 Wiley‐Liss, Inc.     

Neural differentiation of adipose-derived stem cells isolated from GFP transgenic mice

Taking advantage of homogeneously marked cells from green fluorescent protein (GFP) transgenic mice, we have recently reported that adipose-derived stromal cells (ASCs) could differentiate into mesenchymal lineages in vitro. In this study, we performed neural induction using ASCs from GFP transgenic mice and were able to induce these ASCs into neuronal and glial cell lineages. Most of the neurally induced cells showed bipolar or multipolar appearance morphologically and expressed neuronal markers. Electron microscopy revealed their neuronal morphology. Some cells also showed glial phenotypes, as shown immunocytochemically. The present study clearly shows that ASCs derived from GFP transgenic mice differentiate into neural lineages in vitro, suggesting that these cells might provide an ideal source for further neural stem cell research with possible therapeutic application for neurological disorders.     

Comparative osteogenic transcription profiling of various fetal and adult mesenchymal stem cell sources

Human mesenchymal stem cells (MSC) from adult and fetal tissues are promising candidates for cell therapy but there is a need to identify the optimal source for bone regeneration. We have previously characterized MSC populations in first trimester fetal blood, liver, and bone marrow and we now evaluate their osteogenic differentiation potential in comparison to adult bone marrow MSC. Using quantitative real-time RT-PCR, we demonstrated that 16 osteogenic-specific genes (OC, ON, BSP, OP, Col1, PCE, Met2A, OPG, PHOS1, SORT, ALP, BMP2, CBFA1, OSX, NOG, IGFII) were expressed in both fetal and adult MSC under basal conditions and were up-regulated under osteogenic conditions both in vivo and during an in vitro 21-day time-course. However, under basal conditions, fetal MSC had higher levels of osteogenic gene expression than adult MSC. Upon osteogenic differentiation, fetal MSC produced more calcium in vitro and reached higher levels of osteogenic gene up-regulation in vivo and in vitro. Second, we observed a hierarchy within fetal samples, with fetal bone marrow MSC having greater osteogenic potential than fetal blood MSC, which in turn had greater osteogenic potential than fetal liver MSC. Finally, we found that the level of gene expression under basal conditions was positively correlated with both calcium secretion and gene expression after 21 days in osteogenic conditions. Our findings suggest that stem cell therapy for bone dysplasias such as osteogenesis imperfecta may benefit from preferentially using first trimester fetal blood or bone marrow MSC over fetal liver or adult bone marrow MSC.     

重组杆状病毒转导恒河猴骨髓间充质干细胞

[目的]研究重组杆状病毒(Bac-CMV-EGFP)能否能有效转导恒河猴骨髓间充质干细胞(rhesus Bone marrow-derived Mesenchymal Stem Cells,rBMSCs),及杆状病毒转导后对细胞活力,增殖及分化能力的影响.[方法]体外原代培养rBMSCs,不同剂量的杆状病毒转导3代以后的细胞,并用流式细胞仪分别检测其转导效率.在较高的杆状病毒转导效率下,检测rBMSCs细胞活力,增殖及分化能力,并与正常对照组细胞进行比较.[结果]杆状病毒在感染指数(Multiplicity Of Infection,MOI)为300v.g/cell,孵育温度为25度,孵育时间为4h的转导条件下,对rBMSCs转导效率可达80%左右.进一步检测后发现,高效转导杆状病毒后的rBMSCs的细胞活力,增殖及分化能力与未转导病毒细胞组无明显变化.[结论]重组杆状病毒可安全有效地基因修饰rBMSCs,且不影响其生物特性,为今后的体内基因治疗灵长类动物模型试验奠定了基础.     

Characterization of cell signaling,morphology, and differentiation potential of human mesenchymal stem cells based on cell adhesion mechanism

It is essential to characterize the cellular properties of mesenchymal stem cell populations to maintain quality specifications and control in regenerative medicine. Biofunctional materials have been designed as artificial matrices for the stimulation of cell adhesion and specific cellular functions. We have developed recombinant maltose-binding protein (MBP)-fused proteins as artificial adhesion matrices to control human mesenchymal stem cell (hMSC) fate by using an integrin-independent heparin sulfate proteoglycans-mediated cell adhesion. In this study, we characterize cell adhesion-dependent cellular behaviors of human adipose-derived stem cells (hASCs) and human bone marrow stem cells (hBMSCs). We used an MBP-fused basic fibroblast growth factor (MF)-coated surface and fibronectin (FN)-coated surface to restrict and support, respectively, integrin-mediated adhesion. The cells adhered to MF exhibited restricted actin cytoskeleton organization and focal adhesion kinase phosphorylation. The hASCs and hBMSCs exhibited different cytoplasmic projection morphologies on MF. Both hASCs and hBMSCs differentiated more dominantly into osteogenic cells on FN than on MF. In contrast, hASCs differentiated more dominantly into adipogenic cells on MF than on FN, whereas hBMSCs differentiated predominantly into adipogenic cells on FN. The results indicate that hASCs exhibit a competitive differentiation potential (osteogenesis vs. adipogenesis) that depends on the cell adhesion matrix, whereas hBMSCs exhibit both adipogenesis and osteogenesis in integrin-mediated adhesion and thus hBMSCs have noncompetitive differentiation potential. We suggest that comparing differentiation behaviors of hMSCs with the diversity of cell adhesion is an important way to characterize hMSCs for regenerative medicine.     

间充质干细胞特性与应用前景

间充质干细胞是中胚层发育的早期细胞,具备干细胞的基本特性。在发育的不同阶段和特定环境条件下,间充质干细胞可向骨、软骨、肌肉、神经、血管及血液细胞等多种方向分化。在成体的很多器官和组织中也存在着间充质干细胞,以备修复和再生所用。间充质干细胞易于体外培养,扩增迅速,可以分化为多种细胞,为干细胞生物工程提供了一个很好的种子细胞。在明确间充质干细胞生物学特性和分化的机制后,可在体外和体内将其定向诱导分化为多种细胞。间充质干细胞具有巨大的临床应用价值和科学研究价值。     

Adult mesenchymal stem cells: characterization, differentiation, and application in cell and gene therapy

A considerable amount of retrospective data is available that describes putative mesenchymal stem cells (MSCs). However, there is still very little knowledge available that documents the properties of a MSC in its native environment. Although the precise identity of MSCs remains a challenge, further understanding of their biological properties will be greatly advanced by analyzing the mechanisms that govern their self-renewal and differentiation potential. This review begins with the current state of knowledge on the biology of MSCs, specifically with respect to their existence in the adult organism and postulation of their biological niche. While MSCs are considered suitable candidates for cell-based strategies owing to their intrinsic capacity to self-renew and differentiate, there is currently little information available regarding the molecular mechanisms that govern their stem cell potential. We propose here a model for the regulation of MSC differentiation, and recent findings regarding the regulation of MSC differentiation are discussed. Current research efforts focused on elucidating the mechanisms regulating MSC differentiation should facilitate the design of optimal in vitro culture conditions to enhance their clinical utility cell and gene therapy.     

Differentiation of embryonic stem cell to astrocytes visualized by green fluorescent protein

Green fluorescent protein (GFP) gene was transfected and expressed in murine embryonic stem (ES) cells under the control of the astrocyte-specific glial fibrillary acidic protein (GFAP) promoter. Stably transfected cells were characterized by immunohistochemistry and by fluorescence microscopy. Cells containing GFP were differentiated to Type I and Type II astrocytes after induction by all-trans retinoic acid. Differentiated cells were expressed GFP and visualized by fluorescence microscopy. Differentiated cells expressed GFP were correlated with the expression of GFAP and morphological change. It demonstrates that the cell line expressed GFP can be used to trace the morphological changes of astrocytes during differentiation, and further for the isolation of astrocytes from the mixed cells differentiated from ES cell.     

Expression of Thy 1.2 surface antigen increases significantly during the murine mesenchymal stem cells cultivation period

This study sought to investigate the absence or expression of some surface antigens on murine mesenchymal stem cells (mMSCs) during the cultivation period of primary culture to passage 3 (equivalent to about 15 or 16 population doubling number). For this purpose, bone marrow cells from 6-8-week-old mice (either NMRI or Balb/c) were cultivated in 75-cm(2) culture flask for three successive passages, in each of which the culture was examined for the expression of CD135, CD44, CD31, Thy1.2, CD11b, CD45, CD34, Vcam1, Sca-1, and c-Kit antigens, using flow cytometry. Passage-3 cells from each strain can easily be differentiated into bone and fat, which was indicative of their mesenchymal nature. Our results demonstrated that for each given antigen, the percentages of the cells expressing that antigen had been changed by subcultures. The statistical analysis showed that nearly all differences between the passages were statistically significant. In this term, the expressional changes of Thy 1.2 seemed to be very significant in such a way that the expression increased to about half of the whole population in passage 3. In conclusion, it seems that this antigen could be considered as an enriching antigen for mMSCs population from bone marrow adherent cell culture.     

慢病毒载体感染成年食蟹猴骨髓间充质干细胞

骨髓间充质干细胞(Mesenchymal stem cells,MSCs)具有增殖和多向分化潜能,临床应用广泛,近年来备受关注。另一方面,MSCs易于转导和表达外源基因,是理想的基因工程细胞。非人灵长类(NHPs)和人类具有非常相近的遗传背景,NHPs模型在评价药物疗效和移植治疗等方面具有不可替代的价值。本研究采用密度梯度离心法分离成年食蟹猴骨髓单核细胞(Marrow mononuclear cells,MNCs),贴壁培养MSCs。同时构建表达绿色荧光蛋白(Green fluorescent protein,GFP)的慢病毒载体,感染成年食蟹猴MSCs。结果显示,体外培养的成年食蟹猴MSCs均感染猴泡沫病毒(Simian foamy virus,SFV),体外培养成年食蟹猴MSCs必须添加抗病毒药物Tenofovir。但由于食蟹猴MSCs感染SFV,以及培养中添加了抗病毒药物Tenofovir,慢病毒载体的感染效率明显降低(10%)。本研究通过停用抗病毒药,在细胞复苏后6d转染慢病毒,可大幅提高慢病毒的感染效率(50%)。为成年食蟹猴MSCs作为基因工程细胞应用于实验和临床研究提供了技术保证。     

Cell adhesion and mechanical stimulation in the regulation of mesenchymal stem cell differentiation

Stem cells have been shown to have the potential to provide a source of cells for applications to tissue engineering and organ repair. The mechanisms that regulate stem cell fate, however, mostly remain unclear. Mesenchymal stem cells (MSCs) are multipotent progenitor cells that are isolated from bone marrow and other adult tissues, and can be differentiated into multiple cell lineages, such as bone, cartilage, fat, muscles and neurons. Although previous studies have focused intensively on the effects of chemical signals that regulate MSC commitment, the effects of physical/mechanical cues of the microenvironment on MSC fate determination have long been neglected. However, several studies provided evidence that mechanical signals, both direct and indirect, played important roles in regulating a stem cell fate. In this review, we summarize a number of recent studies on how cell adhesion and mechanical cues influence the differentiation of MSCs into specific lineages. Understanding how chemical and mechanical cues in the microenvironment orchestrate stem cell differentiation may provide new insights into ways to improve our techniques in cell therapy and organ repair.     

Perfusion bioreactor system for human mesenchymal stem cell tissue engineering: dynamic cell seeding and construct development

Human mesenchymal stem cells (hMSCs) have great potential for therapeutic applications. A bioreactor system that supports long-term hMSCs growth and three-dimensional (3-D) tissue formation is an important technology for hMSC tissue engineering. A 3-D perfusion bioreactor system was designed using non-woven poly (ethylene terepthalate) (PET) fibrous matrices as scaffolds. The main features of the perfusion bioreactor system are its modular design and integrated seeding operation. Modular design of the bioreactor system allows the growth of multiple engineered tissue constructs and provides flexibility in harvesting the constructs at different time points. In this study, four chambers with three matrices in each were utilized for hMSC construct development. The dynamic depth filtration seeding operation is incorporated in the system by perfusing cell suspensions perpendicularly through the PET matrices, achieving a maximum seeding efficiency of 68%, and the operation effectively reduced the complexity of operation and the risk of contamination. Statistical analyses suggest that the cells are uniformly distributed in the matrices. After seeding, long-term construct cultivation was conducted by perfusing the media around the constructs from both sides of the matrices. Compared to the static cultures, a significantly higher cell density of 4.22 x 10(7) cell/mL was reached over a 40-day culture period. Cellular constructs at different positions in the flow chamber have statistically identical cell densities over the culture period. After expansion, the cells in the construct maintained the potential to differentiate into osteoblastic and adipogenic lineages at high cell density. The perfusion bioreactor system is amenable to multiple tissue engineered construct production, uniform tissue development, and yet is simple to operate and can be scaled up for potential clinical use. The results also demonstrate that the multi-lineage differentiation potential of hMSCs are preserved even after extensive expansion, thus indicating the potential of hMSCs for functional tissue construct development. The system has important applications in stem cell tissue engineering.     

骨髓间质干细胞向心肌细胞分化的可塑性及应用研究进展

减少心肌缺血后损伤,促进心肌细胞和血管再生是治疗心肌缺血损伤、心力衰竭的重要思路,而干细胞移植为该思路带来了新的曙光。骨髓间质干细胞（-mesenchymal stem cells,MSCs）,也称为骨髓基质细胞,能分化为骨、软骨和脂肪细胞表型。研究表明,MSCs还能分化为内皮细胞、神经细胞、平滑肌细胞、骨骼肌细胞和心肌细胞表型。MSCs具有多向分化的潜能,且自体移植可以避免免疫排斥反应,同时也易于在体外大量扩增。研究显示,MSCs移植能抑制损伤心肌的重塑和改善心肌功能。因此,骨髓间质干细胞移植给人们展示了一个诱入的前景。本文综述了近年来有关MSCs特性的新认识,尤其是MSCs向心肌细胞方向分化的可塑性、影响因素和信号转导机制,以及MSCs治疗心肌梗死的动物实验和临床研究进展。