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.     

Differentiation potential of conditionally immortalized mesenchymal progenitor cells from adult marrow of a H-2Kb-tsA58 transgenic mouse

Primary cultures were initiated from marrow, spleen, and bone explants of an adult H-2K^b-tsA58 transgenic mouse (immortomouse). All cultures were initiated in immortalizing conditions, and an additional marrow culture was first incubated for 1 week in standard conditions and then switched to immortalizing conditions. Marrow cells immediately immortalized were designated the marrow immediate population (MIP); those immortalized after 1 week were termed the marrow delayed population (MDP). MIP and MDP cells both contained a mixture of fibroblastic or flattened cells, and the MIP cells contained an additional subpopulation of adipocytic (Oil Red-O positive) cells. Alkaline phosphatase expression was induced by dexamethasone (10⁻⁷ M) in MDP cells while MIP, spleen, and bone explant cells had only a low level of expression. MDP and MIP cells differentiated into bone when combined with porous calcium phosphate ceramics and implanted subcutaneously into nude mice while bone- and spleen-derived cells did not. Clones were isolated from the MDP and MIP cell populations and tested for differentiated phenotypes. Some MIP-derived clones exhibited adipocytic characteristics while MDP-derived subclones were negative. Histologic examination of porous ceramic implanted clones showed that all of the clones had osteogenic potential. Clones exposed to either dexamethasone, human recombinant bone morphogenetic protein-2, or horse serum plus hydrocortisone showed differences in expression of adipocytic or osteogenic markers. These immortalized cultures have retained both adipocytic and osteogenic potential even after 1 year of continuous culture, and provide a model system for clonal analysis of the developmental potential of marrow-derived mesenchymal precursor cells. © 1996 Wiley-Liss, Inc.     

Ex vivo enrichment of mesenchymal cell progenitors by fibroblast growth factor 2

Bone marrow stromal cells, obtained from postnatal bone marrow, contain progenitors able to differentiate into several mesenchymal lineages. Their use in gene and cell therapy requires their in vitro expansion and calls for the investigation of the culture conditions required to preserve these cells as a stem compartment with high differentiative potential during their life span. Here we report that fibroblast growth factor 2 (FGF-2)-supplemented bone marrow stromal cell primary cultures display an early increase in telomere size followed by a gradual decrease, whereas in control cultures telomere length steadily decreases with increasing population doublings. Together with clonogenic culture conditions, FGF-2 supplementation prolongs the life span of bone marrow stromal cells to more than 70 doublings and maintains their differentiation potential until 50 doublings. These results suggest that FGF-2 in vitro selects for the survival of a particular subset of cells enriched in pluripotent mesenchymal precursors and is useful in obtaining a large number of cells with preserved differentiation potential for mesenchymal tissue repair.     

Plastic adherent stromal cells from the bone marrow of commonly used strains of inbred mice: variations in yield, growth, and differentiation

Bone marrow stroma contains a unique cell population, referred to as marrow stromal cells (MSCs), capable of differentiating along multiple mesenchymal cell lineages. A standard liquid culture system has been developed to isolate MSCs from whole marrow by their adherence to plastic wherein the cells grow as clonal populations derived from a single precursor termed the colony-forming-unit fibroblast (CFU-F). Using this liquid culture system, we demonstrate that the relative abundance of MSCs in the bone marrow of five commonly used inbred strains of mice varies as much as 10-fold, and that the cells also exhibit markedly disparate levels of alkaline phosphatase expression, an early marker of osteoblast differentiation. For each strain examined, the method of isolating MSCs by plastic adherence yields a heterogeneous cell population. These plastic adherent cells also exhibit widely varying growth kinetics between the different strains. Importantly, of three inbred strains commonly used to prepare transgenic mice that we examined, only cells derived from FVB/N marrow readily expand in culture. Further analysis of cultures derived from FVB/N marrow showed that most plastic adherent cells express CD11b and CD45, epitopes of lymphohematopoietic cells. The later consists of both pre-B-cell progenitors, granulocytic and monocytic precursors, and macrophages. However, a subpopulation of the MSCs appear to represent bona fide mesenchymal progenitors, as cells can be induced to differentiate into osteoblasts and adipocytes after exposure to dexamethasone and into myoblasts after exposure to amphotericin B. Our results point to significant strain differences in the properties of MSCs and indicate that standard methods cannot be applied to murine bone marrow to isolate relatively pure populations of MSCs.     

Circulating mesenchymal stem cells

Mesenchymal precursor cells (MPCs) are multipotent cells capable of differentiating into various mesenchymal tissues, such as bone, cartilage, fat, tendon and muscle. They are present within both mesenchymal tissues and the bone marrow (BM). If marrow-derived MPCs are to have a role in repair and fibrosis of mesenchymal tissues, transit of these cells through the peripheral blood is to be expected. Although there is evidence for the existence of MPCs within the peripheral blood, results are debated and are not always reproducible. Variations in the methods of cell purification, culture and characterisation may explain the inconsistent results obtained in different studies.     

小鼠骨髓间充质干细胞的分离、培养及鉴定

目的建立一种从小鼠骨髓中分离培养间充质干细胞（MSCs）的高效方法。方法采取贴壁细胞分离法分离和纯化小鼠骨髓间充质干细胞（mMSCs）,检测mMSCs在不同诱导条件下向成骨细胞及脂肪细胞分化能力,用流式细胞术及显微镜分别检测mMSCs纯度和形态特征。结果mMSCs贴壁生长后形态较均一,细胞形态呈成纤维细胞样,流式细胞术检测：CD45、CD11b、CD44及CD29分别为（3.34）%、（2.41）%、（98.46）%及（99.36）%。第4代mMSCs经诱导后可向成骨细胞和脂肪细胞分化。结论通过贴壁培养可以从小鼠骨髓中分离培养出高纯度mMSCs,该方法效率高,稳定性好。     

Histological and cytological technique for the quantitation of cultured human bone-marrow cells:formation of aggregates

A bone-marrow culture system is described that provides a simple, quantitative and rapid assessment of marrow bone cells in vitro. Aggregation of bone-marrow cells, an in vitro phenomenon, occurs within 24 hr of culture and is observed utilizing Millipore filters. Daily quantitation shows both an increase in the number and a change in the morphology of these aggregates. The maximum number of aggregates is achieved on the 2nd or 3rd day of incubation. Histologically, aggregates are composed of myeloid, mononuclear and mesenchymal fibroblastic cells. Mesenchymal cells form a matrix for apposed mononuclear and myeloid cells. Scanning electron micrographs show intimate cell contact and spreading by the marrow cells. Fluctuation of the absolute numbers of various cell types are observed. The system can be utilized for long-term culture of bone marrow.     

猫骨髓间充质干细胞的体外分离培养、纯化、鉴定

目的:分离、培养、纯化家猫的骨髓间充质干细胞,并对获得细胞的表面标志物进行鉴定,为进一步利用骨髓间充质干细胞的细胞移植实验奠定基础。方法:采用全骨髓贴壁法体外分离、培养、纯化家猫骨髓间充质干细胞,通过多次更换培养液获得较纯化的骨髓间充质干细胞,倒置相差显微镜下对细胞形态进行观察;根据第1、3、5、7、9代细胞的镜下增殖情况绘制出生长曲线;通过流式细胞仪检测细胞表面标志抗原CD34、CD44和CD90的表达率。结果:在倒置相差显微镜下观察,分离培养的骨髓间充质干细胞贴壁呈梭形或纺锤形;原代细胞生长丛集成片,5~7 d达到融合,进行传代;培养到第三代以后,细胞出现相对均匀的梭形扁平外观,迅速增殖的细胞呈涡流样排列;第3、5代骨髓间充质干细胞增殖能力强于第7、9代;采用流式细胞仪分析结果显示细胞的CD34、CD44和CD90阳性率分别为17.5%、97.9%和91%,这与骨髓间充质干细胞表面抗原的表达一致。结论:分离培养的细胞具有骨髓间充质干细胞特性,成分相对单一,第3、5代细胞纯度高,增殖能力强,适用于进一步的实验研究。     

Differentiation of mesenchymal stem cells into osteoblasts on honeycomb collagen scaffolds

Tissue engineering using living cells is emerging as an alternative to tissue or organ transplantation. The adult mesenchymal stem cells can be differentiated into multilineage cells, such as adipocytes, chondrocytes, or osteoblasts when cultured with specific growth factors. In the present investigation, we have studied the effect of honeycomb collagen scaffolds for the adhesion, differentiation and proliferation of bone marrow-derived mesenchymal stem cells into osteoblasts. Mesenchymal stem cells were isolated from 6-week old albino rat femur bone marrow, and cultured in alpha-MEM medium without beta-glycerophosphate and dexamethasone. Honeycomb collagen discs were prepared from bovine dermal atelocollagen, cross-linked by UV-irradiation and sterilized by heat. The honeycomb discs were placed on the culture dishes before seeding the stem cells. The cells attached quickly to the honeycomb collagen scaffold, differentiated and proliferated into osteoblasts. The differentiated osteoblasts were characterized by morphological examination and alkaline phosphatase activity. The osteoblasts also synthesized calcium-deficient hydroxyapatite (pseudo-hydroxyapatite) crystals in the culture. The mineralization was confirmed by Von Kossa staining and the crystals were analyzed by X-ray diffraction. Light microscopy and DNA measurements showed that the differentiated osteoblasts multiplied into several layers on the honeycomb collagen scaffold. The results demonstrated that the honeycomb collagen sponge is an excellent scaffold for the differentiation and proliferation of mesenchymal stem cells into osteoblasts. The data further proved that honeycomb collagen is an effective substrate for tissue engineering applications, and is very useful in the advancing field of stem cell technology and cell-based therapy.     

基质衍生因子(SDF-1)对骨髓间充质干细胞定向迁移的影响

目的:研究基质细胞衍生因子-1(SDF-1)/CXCR4轴在骨髓间充质干细胞迁徙到受损胰腺中的作用。方法:密度梯度离心、贴壁培养骨髓间充质干细胞,建立STZ诱导糖尿病模型并制备正常和受损胰腺组织提取液,利用Transwell小室体外迁移体系观察不同浓度SDF-1和不同组织提取液对骨髓间充质干细胞的趋化作用,及SDF-1/CXCR4特异抑制剂AMD3100对骨髓间充质干细胞迁移的影响。结果:成功培养了骨髓间充质干细胞并建立了糖尿病大鼠模型。SDF-l对骨髓间充质干细胞有剂量依赖性的趋化作用,造模1周的胰腺组织提取液对骨髓间充质干细胞有明显的趋化作用,而这种作用可部分被SDF-1受体CXCR4的抑制剂AMD3100抑制。结论:受损胰腺组织提取液对骨髓间充质干细胞有明显的趋化作用,SDF-1/CXCR4轴可能在组织提取液趋化骨髓间充质干细胞迁移中起主要的作用。     

Multi-lineage potential of human mesenchymal stem cells following clonal expansion

Bone marrow contains mesenchymal cells that can be isolated and grown in vitro. Using appropriate treatment protocols such cultures can be induced to differentiate to yield osteoblasts, adipocytes, and chondrocytes. However, previous experiments had not addressed the question whether single pluripotent stem cells exist and can give rise to these different cell lineages or whether bone marrow mesenchymal cell preparations represent a mixture of committed precursors. We have used human adult bone marrow-derived mesenchymal cells obtained from iliac crest biopsies to demonstrate clonal outgrowth after limiting dilution and we show that some clones can be expanded over more than 20 cumulative population doublings and differentiated to osteoblasts, adipocytes, and chondrocytes. Our data provide direct experimental evidence that cultures of bone marrow-derived mesenchymal cells contain individual cells that fulfil two essential stem cell criteria: (i) extensive self-renewal capacity and (ii) multi-lineage potential.     

Proliferative and Differentiation Potential of Individual Clones Derived from Bone Marrow Stromal Precursor Cells

We present the results of a study on the proliferative and differentiation potential of individual clones of stromal fibroblasts growing in monolayer cultures of bone marrow cells. Each precursor cell yielding a large colony in primary culture is capable of up to 34 doublings in vitro. The transplantation of clones or monoclonal strains of stromal fibroblasts into the open system results in the formation of microenvironment consisting of the bone and reticular tissue and is suitable for the differentiation of all three lines of hemopoiesis. Evidence has been obtained that, in a closed system, individual clones are capable of differentiation into the bone, cartilaginous, and reticular tissues. In other words, the adult organism has a common cell precursor for these tissues.     

骨髓间充质干细胞在大鼠实验中的移植途径及比较

骨髓间充质干细胞是具有自我更新能力和分化潜能的一类成体干细胞,经过局部微环境的诱导,可在体内外进行扩展,到晚期可分化成为多种细胞系。当组织受损伤时,可迅速到达损伤部位,分化为特异的组织细胞,参与组织修复。骨髓间充质干细胞这种惊人的分化及组织修复能力,为治疗退行性疾病和器官损伤性疾病提供广阔前景,故成为科研热点。国内外相关实验研究多以大鼠为动物模型,而骨髓间充质干细胞如何进入大鼠体内并定植,是实验成功的重要前提。因此如何找到最合适、最安全的移植途径将骨髓间充质干细胞有效地移植进入大鼠疾病模型体内的受损区域,是研究者关心的重点。本文就目前骨髓间充质干细胞在大鼠实验中不同移植途径进行综述,并比较各种途径的优缺点,希望能对临床科研工作提供参考,并期待能有更成熟的移植手段来推动骨髓间充质干细胞实验研究的进展。     

Switching from bone marrow-derived neurons to epithelial cells through dedifferentiation and translineage redifferentiation

While the ability of stem cells to switch lineages has been suggested, the route(s) through which this may happen is unclear. To date, the best characterized adult stem cell population considered to possess transdifferentiation capacity is BM-MSCs (bone marrow mesenchymal stem cells). We investigated whether BM-MSCs that had terminally differentiated into the neural or epithelial lineage could be induced to transdifferentiate into the other phenotype in vitro. Our results reveal that neuronal phenotypic cells derived from adult rat bone marrow cells can be switched to epithelial phenotypic cells, or vice versa, by culture manipulation allowing the differentiated cells to go through, first, dedifferentiation and then redifferentiation to another phenotype. Direct transdifferentiation from differentiated neuronal or epithelial phenotype to the other differentiated phenotype cannot be observed even when appropriate culture conditions are provided. Thus, dedifferentiation appears to be a prerequisite for changing fate and differentiating into a different lineage from a differentiated cell population.     

脂肪干细胞与间充质干细胞体外诱导分化为心肌细胞的差别

本文旨在探讨脂肪干细胞(adipose-derived stem cells, ASCs)和骨髓间充质干细胞(mesenchymal stem cells, MSCs)在组织含量、体外培养和诱导分化为心肌细胞方面的差别.ASCs从新西兰白兔皮下脂肪组织提取,MSCs从大鼠四肢长骨骨髓提取,体外培养扩增,免疫细胞学方法鉴定.采用细胞集落形成法检测组织中干细胞的含量.将不同代的干细胞用不同浓度的5-氮胞苷诱导,观察其形态变化,免疫细胞化学方法检测诱导后细胞是否转化为心肌细胞.结果显示,体外培养的ASCs呈短梭形,分布均匀,生长迅速,细胞形态单一、稳定.MSCs原代生长非常缓慢,呈簇生长,细胞纯度偏低,容易混杂其它细胞类型,传代细胞容易分化和老化.脂肪组织中ASCs含量显著高于骨髓中MSCs含量,且前者含量受年龄影响小.5-氮胞苷诱导ASCs分化为心肌细胞的有效浓度为6～9μmol/L,而MSCs在3～15μmol/L 5-氮胞苷诱导下可见心肌细胞形成.ASCs诱导分化的心肌细胞呈球形细胞团,MSCs分化的心肌细胞呈条形或棒状,其心肌细胞分化率低于ASCs.幼年动物MSCs的组织含量和心肌细胞分化率均高于老年动物,而ASCs受动物年龄影响较小.结果表明,ASCs在组织含量、细胞纯度、生长速度和心肌细胞分化率等方面均明显优于骨髓MSCs,在心肌细胞再生方面较MSCs具有更大的优势.     

A familiar stranger:CD34 expression and putative functions in SVF cells of adipose tissue

Human adipose tissue obtained by liposuction is easily accessible and an abundant potential source of autologous cells for regenerative medicine applications. After digestion of the tissue and removal of differentiated adipocytes, the so-called stromal vascular fraction (SVF) of adipose, a mix of various cell types, is obtained. SVF contains mesenchymal fibroblastic cells, able to adhere to culture plastic and to generate large colonies in vitro , that closely resemble bone marrow-derived colony forming units-fibroblastic, and whose expanded progeny, adipose mesenchymal stem/stromal cells (ASC), show strong similarities with bone marrow mesenchymal stem cells. The sialomucin CD34, which is well known as a hematopoietic stem cell marker, is also expressed by ASC in native adipose tissue but its expression is gradually lost upon standard ASC expansion in vitro . Surprisingly little is known about the functional role of CD34 in the biology and tissue forming capacity of SVF cells and ASC. The present editorial provides a short introduction to the CD34 family of sialomucins and reviews the data from the literature concerning ex- pression and function of these proteins in SVF cells and their in vitro expanded progeny.     

Characterization of fibroblast-like cells from the rat olfactory bulb

The isolation and characterization of stem cells from an alternative tissue is a subject of intensive investigation. In the present study, we have focused on the characterization of fibroblastic cells in olfactory bulb tissue of the rat. To this end, 4-6 week old rats were killed and their olfactory bulb tissue was dissected out. Olfactory bulb derived fibroblast-like cells were recovered by adhesion to cell culture plastic. The plastic adherent cultivated cells were induced to differentiate along osteoblastic, adipogenic and chondrogenic lineages. Furthermore, the expression of some surface antigens was investigated. We obtained purified cells with spindle shaped morphology in primary culture, which differentiated into mesenchymal lineages. These cells expressed CD29 and CD90 (Thy1.1) surface antigens, but not CD31, CD34 and CD45. Our results indicate that fibroblast-like cells from the olfactory bulb are mesenchymal stem cells in nature. Taken together, our data suggest that olfactory bulb tissue may constitute a new source of mesenchymal stem cells and could be used for the treatment of injury.     

Investigation of the mesenchymal stem cell compartment by means of a lentiviral barcode library

The hematopoietic bone marrow microenvironment is formed by proliferation and differentiation of mesenchymal stem cells (MSCs). The MSC compartment has been less studied than the hematopoietic stem cell compartment. To characterize the structure of the MSC compartment, it is necessary to trace the fate of distinct mesenchymal cells. To do so, mesenchymal progenitors need to be marked at the single-cell level. A method for individual marking of normal and cancer stem cells based on genetic “barcodes” has been developed for the last 10 years. Such approach has not yet been applied to MSCs. The aim of this study was to evaluate the possibility of using such barcoding strategy to mark MSCs and their descendants, colony-forming units of fibroblasts (CFU-Fs). Adherent cell layers (ACLs) of murine long-term bone marrow cultures (LTBMCs) were transduced with a lentiviral library with barcodes consisting of 32 + 3 degenerate nucleotides. Infected ACLs were suspended, and CFU-F-derived clones were obtained. DNA was isolated from each individual colony, and barcodes were analyzed in marked CFU-F-derived colonies by means of conventional polymerase chain reaction and Sanger sequencing. Barcodes were identified in 154 marked colonies. All barcodes appeared to be unique: there were no two distinct colonies bearing the same barcode. It was shown that ACLs included CFU-Fs with different proliferative potential. MSCs are located higher in the hierarchy of mesenchymal progenitors than CFU-Fs, so the presented data indicate that MSCs proliferate rarely in LTBMCs. A method of stable individual marking and comparing the markers in mesenchymal progenitor cells has been developed in this work. We show for the first time that a barcoded library of lentiviruses is an effective tool for studying stromal progenitor cells.