活化素是转化生长因子一B超家族成员之一。近年研究发现，活化素及活化素A在各种脑损伤模型中呈异常表达，补充外源性活化素或活化素A对神经元有明显的保护作用。活化素及活化素A可作为一种新的指标预测脑损伤，并为脑损伤的治疗提供新思路。

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The increasing prevalence of diabetes mellitus has been become one of the diseases which threaten the heath of human being in the 21st century. Islet transplantation is considered to be the most effective approach to cure type Ⅰ diabetes mellitus. However, lack of donor tissue limits the application of this therapy. However, recent progress of stem cell research shows that stem cell therapy may be a potential means to solve this problem.OBJECTIVE: To take activin A and all-trans retinoic acid (AR) in inducing the differentiation of bone marrow mesenchymal stem cells (MSCs) and explore its possibility DESIGN: A randomized controlled experiment.SETTING: Institute of Biotechnology, Academy of Military Medical SciencesMATERIALS: This experiment was conducted at the Institute of Biotechnology, Academy of Military Medical Sciences from November 2004to June 2005. Six male Sprague-Dawley rats, with body mass of 150-160g, were provided by the Experimental Animal Center of Academy of Military Medical Sciences.METHODS: Femoral bone marrow of the rats was extracted under aseptic condition. Bone marrow mesenchymal stem cells (MSCs) were isolated with density gradient centrifugation. Passaged MSCs were randomly divided into 4 groups: high concentration of glucose (HG), AR, beta-mercaptoethanol (ME) and negative control groups. MSCs were induced to differentiate into IPCs with conditional medium containing high concentration glucose, activin A, RA and ME etc. After induction, phenotypes of differentiated cells were examined by immunocytochemistry and reverse transcription-polymerase chain reaction (RT-PCR).MAIN OUTCOME MEASURES: Expression of insulin and glucagon of differentiated cells were examined by immunocytochemistry. Insulin-1 mR-NA expression of differentiated cells was detected by RT-PCR.RESULTS: After bone marrow mesenchymal stem cells were induced,there were scattered insulin-and glucagon-positive cells in the HG group,many insulin-and glucagon-positive cells in the AR and ME groups, and these cells formed insulin-like structure. The expression of insulin-1mRNA could be observed in the HG, AR and ME groups. Insulin-and glucagonpositive cells and the expression of insulin-1mRNA were not observed in the negative control group.CONCLUSION: We adopt an induction scheme based on AR and other matured factors, and successfully make bone marrow mesench.ymal stem cells induce and differentiate into insulin positive reaction cells and form insulin-like structure, but its induction efficiency needs further improvement.