骨髓间充质干细胞诱导分化表达角蛋白的信号机制

目的探讨大鼠骨髓间充质干细胞（mesenchymal stem cells,MSC）分化为表皮样细胞过程中,相关P38、ERK、Rho等信号机制.方法（1）采用Ficoll-Paque淋巴细胞分离液分离扩增大鼠骨髓MSC,免疫细胞化学及流式细胞仪进行表面标志的检测.（2）定向诱导中磷酸化P38和ERK表达：分为正常对照组、单纯诱导组、Rho阻断组;培养1、3、5、7 d后,流式细胞检测磷酸化P38和ERK.（3）SB203580和PD98059对MSC诱导为表皮样细胞的影响：分为对照组、单纯诱导组、p38阻断组（在诱导液基础上加入SB203580）,ERK阻断组（在诱导液基础上加入PD98059）,诱导7 d后分别采用免疫细胞化学和流式细胞仪检测各组细胞细胞角蛋白CK5/8、CK19的阳性表达率.（4）Rho阻断剂HA1077对CK5/8、CK19的影响：设正常对照组、单纯诱导组、RHO阻断组.取培养7 d的细胞,流式细胞检测CK5/8、CK19表达.结果（1）大鼠骨髓MSC在体外扩增后,免疫细胞化学及流式细胞仪检测结果显示CD29、CD44表达阳性,CD34、CD45表达阴性.（2）磷酸化P38正常对照水平为0.02%.在诱导组1d（0.01%）、3 d（0.01%）变化不大,诱导5 d为0.04%,明显升高,7 d时（0.01%）复接近诱导前水平;磷酸化ERK对照水平为4.23%,诱导后3 d（0.39%）、5 d（0.40%）均呈下降趋势,7 d时（5.10%）恢复至诱导前水平.RHO阻断组：磷酸化P38水平在1、3、5和7 d,分别为1.11%、71.19%、0.25%、6.86%,均升高;ERK磷酸化在1、3、5和7 d,分别为6.17%、4.13%、3.97%和0.41%,其中7 d低于对照水平.（3）SB203580和PD98059对MSC诱导为表皮样细胞的影响：流式细胞显示诱导7 d后CK5/8、CK19阳性率分别为3.01%、6.47%;p38阻断组CK5/8、CK19阳性表达率分别为1.43%、5.41%,低于诱导组.ERK阻断组CK5/8、CK19阳性表达率分别为5.54%、7.56%.（4）HA1077对CK5/8、CK19的影响：单纯诱导组CK5/8阳性率为1.81%,CK19为10.19%;加入HA1077后,CK5/8为21.65%,CK19为39.41%,升高显著.结论P38途径在促进MSC分化为表皮样细胞过程中可能起积极作用,上游信号Rho阻断后可能增加P38途径途径激活,一定程度上促进MSC分化为表皮样细胞.

Mechanism of signal transduction of differentiation of mesenchymal stem cells into cytokeratin-expressing epidermoid cells

Objective To investigate the role of the signal routes P38, ERK, and Rho in the differentiation of bone marrow mesenchymal stem cells(MSCs)into epidermoid cells.Methods (1) MSCs were separated from the bone marrow of Wistar rats by Ficoll-Pague lymphocyte separating medium and proliferated in culture medium. Then the MSCs were immunocytochemically stained to detect the expression of surface antigens. (2) The MSCs were randomly divided into 3 groups: control group; pure induction induced group, cultured with epithelial growth factor (EGF) added into the culture fluid, and Rho inhibition group, cultured with EGF and HA1077, a ROK inhibitor, added into the culture fluid. One, 3, 5, and 7 days later FC was used to detect the levels of phosphorylated P38 and ERK. (3) MSCs were randomly divided into 4 groups: control group, cultured with low-sugar DMEM complete culture fluid; pure induction group, cultured with supernatant of rat fibroblasts and EGF added into the culture fluid, p38 blocking group, with SB203580, inhibitor of P38 added into the culture fluid; and ERK blocking group, with PD98059, inhibitor of ERK added into the culture fluid. Seven days later, SP method was used to detect the expression of CK5/8 and CK19 induced by MSCs. (4) MSCs were randomly divided into 4 groups: control group; pure induction group, with supernatant of rat fibroblasts and EGF added into the culture fluid; and RHO blocking group, with HA1007 added into the culture fluid. Seven days later, FC was used to detect the expression of CK5/8 and CK19. Results (1) Both FC and immunocytochemistry showed that the MSCs were uniformly positive in CD29 and CD44, but did not express CD34 and CD45. (2) The phosphorylated P38 rate remained 0.01% in the control group. The phosphorylated P38 rate was 0.04%, significantly higher than that of the control group(0.01%, P<0.05)at day 5, and then lowered to 0.01% at day 5 in the pure induction group; and became 6.17%,4.13%, 3.97%, and 0.41% respectively at day 1, 3, 5, and 7, all significantly higher than those of the control group (all P<0.05), in the Rho inhibition group. The phosphorylated ERK level was 4.23% in the control group; became 0.39% and 0.40% at day 3 and day 5 (both P<0.05), and then returned to 5.10% at day 7 in the pure induction group; and was not significantly changed at days 1, 3, and 5, and then became 0.41%, significantly lower than that of the control group (P<0.05), in the Rho blocking group,(3)The control group was CK5/8 and CK19 negative. The CK5/8 and CK19 rates at day 7 of the pure induction group were 3.01% and 6.47% respectively, both significantly higher than those of the p38 inhibition group (1.43% and 5.41% respectively, both P< 0.05). The CK5/8 and CK19 expression rates of the ERK inhibition group were 5.54% and 7.56% respectively, both significantly higher than those of the pure induction group (both P<0.05), (4) The CK5/8 and CK19 expression rates of the HA1077 group were 21.65% and 39.41%pure, both significantly higher that hose of the pure induction group (1.81% and 10.19% respectively, both P<0.05). Conclusion p38 route may play an active role in the differentiation of MSCs into epidermoid cells.Blocking of the upstream signal Rho may enhance the activation of p38 route and then promote the differentiation of MSCs into epidermoid cells.