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目的:观察和探讨骨骼肌内源性生肌因子(39kDa)成肌活性随衰老而发生的改变。方法:应用等电聚焦结合聚丙稀酰胺凝胶电泳多步功能测试分筛法对青年和老年大鼠骨骼肌内源性39kDa生肌因子进行分离,利用体外培养和体内模型对青年和老年大鼠骨骼肌生肌因子的成肌活性进行比较,采用增殖细胞抗原(PCNA)免疫组织化学技术观察生肌因子对骨骼肌干细胞—卫星细胞的增殖作用。结果:处理组大鼠骨骼肌内源性39kDa生肌因子C2C12细胞数目显著多于对照组,处理组39kDa生肌因子MTT值显著高于对照组(P <0 . 0 5 )。青年和老年生肌因子处理组都有相当一部分C2C12细胞融合形成肌管,但青年大鼠骨骼肌生肌因子融合形成的肌管数目显著多于老年大鼠。体内研究发现:注射39kDa生肌因子的青年大鼠胫骨前肌中有许多PCNA阳性细胞核,但在对照组中未发现PCNA阳性细胞核。然而,在经注射的老年大鼠胫骨前肌中只发现少量PCNA阳性细胞核。PCNA阳性细胞核半定量计数结果表明:经生肌因子注射的青年大鼠胫骨前肌PCNA阳性细胞核显著多于老年大鼠(P <0 .0 5 )。本研究结果提示:39kDa生肌因子能诱导骨骼肌干细胞—卫星细胞的增殖和分化,青年大鼠骨骼肌中39kDa生肌因子的成肌活性高于老年大鼠,骨骼肌39kDa生肌因子成肌活性随衰老而减弱可能是老年个体
Objective: To observe and discuss the changes of myogenic activity of skeletal muscle with endogenous myogenic factor (39kDa) with aging. Methods: The 39 kDa myogenic factor of skeletal muscle of young and old rats were separated by isoelectric focusing and polyacrylamide gel electrophoresis (MIP). The in vitro and in vivo models were used to detect the expression of 39 kDa myogenic factor in young and old rats The myogenic activity of skeletal muscle myogenic factor was compared. Proliferation cell antigen (PCNA) immunohistochemistry was used to observe the proliferation of skeletal muscle stem cells - satellite cells. Results: The number of endogenous 39kDa myogenic factor C2C12 cells in skeletal muscle of rats in treatment group was significantly higher than that in control group. The MTT value of 39kDa myogenic factor in treatment group was significantly higher than that in control group (P <0.05). A significant proportion of C2C12 cells were fused to form myotubes in young and old muscle factor treatment groups, but the number of myotubes formed by the fusion of skeletal muscle myogenic factor was significantly higher in young rats than in aged rats. In vivo studies showed that there were many PCNA-positive nuclei in the tibialis anterior muscle of young rats injected with 39kDa myogenic factor, but no PCNA positive nuclei were found in the control group. However, only a small number of PCNA positive nuclei were found in the anterior tibialis muscle of the aged rats. Semi-quantitative counting of PCNA-positive nuclei showed that PCNA-positive nuclei in the tibialis anterior muscle of young rats injected with myogenic factor were significantly more than those in the aged rats (P <0.05). The results suggest that: 39kDa myogenic factor can induce skeletal muscle stem cells - satellite cell proliferation and differentiation of young rats skeletal muscle 39kDa myogenic factor myogenic activity than older rats, skeletal muscle 39kDa myogenic factor myogenic Activity diminishes with aging may be elderly individuals