间充质干细胞的生物学特性及多向分化潜能

Bio-characteristics and multi-differentiation potency of mesenchymal stem cells

学术背景:间充质干细胞是造血微环境中的一种重要细胞成分,可以向多种组织增殖分化,且免疫原性低,临床实验证实间充质干细胞移植可用于组织修复及治疗间充质组织遗传缺陷性疾病。目的:深入认识间充质干细胞的生物学特性及其多向分化潜能。检索策略:由该论文的研究人员应用计算机检索Pubmed数据库1995-01/2005-12的相关文献,检索词"mesenchymal stem cells,differentiation,biological character",并限定文章语言种类为English。同时计算机检索中国期刊全文数据库1995-01/2005-12的相关文献,检索词"间充质干细胞,多向分化,生物学性质",并限定文章语言种类为中文。共检索到78篇文献,对资料进行初审,纳入标准:①文章所述内容应与间充质干细胞的生物学特性或多向分化潜能密切相关。②同一领域选择近期发表或在权威杂志上发表的文章。排除标准:①重复性研究。②Meta分析。文献评价:文献的来源主要是通过对间充质干细胞的生物学特性及其多向分化潜能方面内容进行汇总分析。所选用的30篇文献中,4篇为综述,其余均为临床或基础实验研究。资料综合:①间充质干细胞在骨髓组织中的含量最为丰富,此外还存在于胎盘、羊水、脐静脉内皮下层、外周血及肝脏、脂肪、肌肉、皮肤等多种组织中。间充质干细胞具有高度增殖、自我更新和多向分化潜能,在不同诱导条件下可分化为软骨、骨、骨骼肌、肌腱、脂肪、神经及肾脏实质的细胞等。②间充质干细胞体外培养的方法目前主要有3种:密度梯度离心与贴壁筛选法:鉴于间充质干细胞与其他细胞密度的差异,采用Percoll或者Ficoll分离液来实现细胞间的分离,同时依据间充质干细胞贴壁生长的特性,将其与非贴壁细胞分离。流式细胞仪分选法:根据间充质干细胞体积小、相对缺少颗粒这一特性采用流式细胞仪对其进行分选。磁珠分选法:根据间充质干细胞表面带有或缺失的抗原成分进行正选或负选,用抗体包被磁珠,获得相对纯化的间充质干细胞。现今常用含5%～20%胎牛血清的DMEM培养基培养间充质干细胞。目前对于间充质干细胞的鉴定也主要是根据形态、功能等,而且不同来源的间充质干细胞表面标志物也不尽相同。③间充质干细胞在特定的理化环境和细胞因子诱导下,能够分化为成骨细胞、脂肪细胞、神经细胞、心肌细胞、内皮等多种细胞类型,受到很多因素的影响,而且免疫原性弱,是组织工程理想的种子细胞来源。此外,间充质干细胞易于外源基因的转染和表达,在细胞治疗和基因治疗中也有着广泛的应用。结论:间充质干细胞的多向分化特性使其在组织工程创伤修复、细胞替代治疗、支持造血、基因治疗等方面的应用前景相当广阔。但目前采用的体外分离培养无法得到单克隆的细胞成分,也缺乏可靠的鉴定标准,不同来源的间充质干细胞有何差异等问题亟待解决。

BACKGROUND： Mesenchymal stem cells （MSCs） are an important cell type in hematopoietic microenvironment. They can differentiate to lots of tissues and have low immunogenicities. It has been verified by clinical tests that MSCs transplanting can be used for tissue repair and disease treatment of mesenchymal tissue genetic defects. OBJECTIVE： To understand bio-characteristics and multi-differentiations potency of MSCs. RETRIEVAL STRATEGY： A computerized search through the PubMed database was undertaken during January 1995 to December 2005. The key words were ＂mesenchymal stem cells, differentiation, biological character＂, and searching language was restricted in English. Meanwhile, a resemble search was conducted to the correlated articles basing on Chinese Journal Full-Text Database from January 1995 to December 2005, with the key words of ＂mesenchymal stem cells, differentiation, biological character＂, and the language was restricted in Chinese. Totally 78 related papers were searched out. Data were checked in the first trial. Inclusion criteria：OThe literatures should be closely related with biological character and differentiation of MSCs.（1）The recent articles of the same field and that published in authority journals were preferred. Exclusion criteria： （2）Repetitive study. （3）Meta analysis. LITERATURE EVALUATION： The literature was compiled and analyzed about the biological character and multiple differentiation of MSCs. Thirty papers were selected, in which 4 were reviews and the others were clinical or fundamental researches. DATA SYNTHESIS： （1）MSCs are especially rich in myeloid tissue and also present in placent, amniotic fluid, umbilical vein subendothelial layer, peripheral blood, liver, fat, muscles and skin. MSCs have potentials of fast proliferation, self renewing and multi-differentiation. Based on different inducing conditions, they can be differentiated into cartilage, bone, skeletal muscles, muscle tendon, fat, nerve and kidney parenchymal cell, etc.（2）Three isolation and culture methods are mainly used in vitro： Density gradient centrifugation and adherent culture methods： Basing on the density difference between MSCs and other cells, Percoll or Ficoll separation liquid can be used to separate cells and meanwhile separate the MSCs from the non-adherent cells depending on the adherent growing character of MSCs; Flow cytometer： It can be used for MSCs separation on the basis of its small volume and particle deficiency; Magnetic activated cell sorting： Positive or negative selection is carried out according to MSCs surface antigenic component is presented or deleted, and the relatively pure MSCs can be obtained by immobilizing with antibody. DMEM medium containing 5%--20% fetal bovine serum is commonly used for culturing MSCs. The identification of MSCs is mainly according to its morphous and functions. Furthermore, the surface marker is different from different sources.（3）Under specific physical and chemical environment or induced by cytokine, MSCs can differentiate into multiple types of cells, such as osteoblast, fat cell, nerve cell, cardiac myocyte, endothelium cell and so on. It can be affected by lots of factors and has low immunogenicity. So it is an ideal source of tissue engineering seed cells. Moreover, MSCs are easy to transfect and express the exogenous gene, so they will be widely used in cell therapy and genetic therapy. CONCLUSION： Because of the multi-differentiation properties, MSCs will be widely used in tissue engineering damage repair, cell replacement therapy, supporting effect of hemopoiesis and genetic therapy. But the monoclonal cell can not be obtained by separation and culture approaches currently used in vitro, and now the reliable identification standard also lacks. The problems, such as what are the differences between MSCs of different sources, should be solved.