人胚胎干细胞无血清无饲养层培养体系的建立

背景:研究表明FGF2,TGFβ/activin/nodal和IGF信号通路是人胚胎干细胞保持其多能性所必需的,然而直接添加外源性碱性成纤维细胞生长因子、转化生长因子β和胰岛素是否能够维持人胚胎干细胞的自我更新目前尚无报道.目的:拟建立人胚胎干细胞无饲养层无血清条件下的培养体系.设计,时间及地点:细胞学体外观察,于2007-09/2009-02在中国科学院昆明动物研究所完成.材料:12.5～13.5d龄清洁级ICR孕鼠2只,由昆明医学院动物中心提供.人胚胎干细胞株BG02购自美国Bresagen公司.方法:①消化离心BG02细胞,重悬于无饲养层过渡培养基后接种,常规培养5～7 d,挑去分化的人胚胎干细胞,加入分散酶消化,切割成小团块,离心重悬后按1:3比例重新接种预铺层粘连蛋白的4孔板,此时培养基换成无血清无饲养层培养基,由80%DMEM/F12、20%KSR、2 mmol/L glutamine、1%非必需氨基酸、0.1 mmol/L β-巯基乙醇、ITS(×1)、10~6 U/L青霉素、100 mg/L 链霉素、4 μg/L碱性成纤维细胞生长因子、0.12 μg/L转化生长因子β1组成.②无菌条件下取出ICR胎鼠,组织块胰酶消化法分离培养小鼠胚胎成纤维细胞,接种在0.1%明胶包被的6孔板中即为饲养层.将生长在小鼠胚胎成纤维细胞饲养层上的人胚胎干细胞株BG02预铺至有层粘连蛋白的培养板上,加入含碱性成纤维细胞生长因子、转化生长因子β1及ITS的无血清培养基连续培养.主要观察指标:观察BG02细胞在无血清无饲养层培养体系中的形态,采用细胞免疫组化法检测人胚胎干细胞特异性分子标志的表达,检测BG02细胞体外分化能力及其核型,比较BG02细胞在无血清无饲养层和小鼠胚胎成纤维细胞饲养层培养体系中的生长情况、细胞集落分化率.结果:在无血清无饲养层培养体系中,BG02细胞连续传代20代,细胞呈典型的人胚胎干细胞形态特征;BG02细胞表达SSEA-4,SSEA-3,TRA-1-60,TRA-1-81,Oct-4,但不表达SSEA-1;培养20 d后,BG02细胞进一步分化成3个胚层的细胞,分化细胞能够表达甲胎蛋白、巢蛋白、α-肌动蛋白;培养至20代细胞核型均正常(46XY).与在饲养层培养体系下比较,无血清无饲养层条件下BG02细胞BG02细胞生长速度减慢,细胞倍增时间明显延长(P＜0.05),集落分化率明显升高(P＜0.05).结论:实验初步建立了入胚胎干细胞无血清无饲养层的培养体系,添加碱性成纤维细胞生长因子、转化生长因子β1和ITS可以维持人胚胎干细胞的自我更新.

Establishment of feeder layer-and serum-free culture system of human embryonic stem cells

BACKGROUND:FGF2,TGFβ/activin/nodal and IGF signal pathways are necessary for keeping functions of human embryonic stem calls,but there was no report concerning whether addition of exogenous basic fibroblast growth factor,transforming growth factor β and insulin can maintain self-renewal of human embryonic stern cells.OBJECTIVE:To establish a feeder layer-and serum-free culture system of human embryonic stem cells.DESIGN,TIME AND SETTING:The cytological in vitro study was performed at the Kunming Animal Institute of Chinese Academy of Sciences from September 2007 to February 2009.MATERIALS:Pregnancy 12.5 or 13.5-day ICR strain mica (clean grade) were provided by the Animal Center of Kunming Medical College.Human embryonic stem cell line BG02 was purchased from Bresagen,USA.METHODS:BG02 cells were digested,centrifuged,resuspended in feeder layer-free medium,and then incubated for 5-7 days.Differentiated human embryonic stem cells were removed.Dispase was added for digestion.Samples were cut into blocks,centrifuged,resuspended,and then incubated at 1:3 in a 4-well plate coated with laminin in feeder layer-free and serum-free medium,supplemented with 80% DMEM/F12,20% KSR,2 mmol/L glutamine,1% non-essential amino acid,0.1 mmol/L β-mercaptoethanol,insulin-transferrin-selenium (ITS) (×1),10~6 U/L penicillin,100 mg/L streptomycin,4 μg/L basic fibroblast growth factor (bFGF) and 0.12 μg/L transforming growth factor-β1 (TGF-β1).ICR fetus mica were sterilely obtained to culture mouse embryonic flbroblasts by tissue pancreatin digestion method.These cells were incubated in a 6-well plate coated with 0.1% gelatin.Human embryonic stem cell line BG02 cultured on mouse embryonic fibroblasts feeder layers was transferred to laminin-coated plates in serum-free medium containing bFGF,TGFβ1 and ITS.MAIN OUTCOME MEASURES:The morphology of BG02 cells in feeder layer-and serum-free condition was observed.The specific molecular markers of human embryonic stem cells were determined by immunohistochemical staining.The karyotype and differentiation ability in vitro of BG02 cells were analyzed.The differences in the proliferation and the differentiated rate of BG02 clumps in feeder layer-and serum-free condition or mouse embryonic fibroblast feeder layer condition were compared.RESULTS:BG02 calls had been continuously cultured for at least 20 passages in feeder layer-and serum-free culture condition.BG02 clones in this culture system had typical human embryonic stem cell morphology.BG02 cells all expressed SSEA-4,SSEA-3,TRA-1-60,TRA-1-81,Oct-4,but did not express SSEA-1.After 20 days of culture,BG02 cells had the capacity to differentiate into derivatives of embryonic endoderm,mesoderm,and ectoderm.Differentiated cells could express alpha-fetoprotein,nestin,α-actin.At passage 20,call karyotype was normal (46XY).The growth of BG02 cells cultured in feeder layer-and serum-free condition was more slowly compared with mouse embryonic fibroblast feeder,and doubling time was significantly prolonged (P ＜ 0.05).Differentiation rate of the colonies was significantly increased (P ＜ 0.05).CONCLUSION:A feeder layer-and serum-free condition for culture of BG02 cells has been established.The addition of bFGF,TGFβ1 and ITS can maintain the self-renewal of BG02 cells.