雌激素对生长板软骨细胞增殖的调节

Regulation of estrogen for chondrocyte proliferation in the rib growth plate

背景:雌激素是生长板闭合过程必不可少的因素,但目前尚无实验从不同层次揭示雌激素对生长板软骨细胞增殖率、细胞周期分析、细胞凋亡的超微结构改变的影响。目的:探讨雌激素对生长板软骨细胞增殖能力的调节特点及其在生长板增殖能力老化过程中的作用。方法:选取12周龄新西兰雌兔30只,切除双侧卵巢制备去卵巢模型,4周后雌二醇组每周注射苯甲酸雌二醇,模型组注射灭菌棉籽油。分别于23,26,29周龄时处死白兔,并于处死前7,1h皮下注射BrdU,免疫组织化学染色检测肋骨生长板软骨BrdU阳性细胞;分离单细胞悬液,采用流式细胞仪作细胞周期分析;透射电镜观察软骨细胞超微结构。结果与结论:两组大鼠BrdU阳性细胞染色率均逐渐下降,雌二醇组肋骨生长板软骨细胞BrdU阳性染色率在23,26周龄时高于模型组(P<0.05),29周龄时两组差异无显著性意义(P>0.05)。雌二醇组在23,26周龄时S期软骨细胞增多,至29周龄时明显减少;模型组S期软骨细胞的比例无明显改变,至29周出现G2/M期软骨细胞比例减少,细胞增殖指数降低。电镜观察发现,雌二醇组生长板有更多"暗细胞"形式的凋亡增殖软骨细胞。说明雌激素作用早期可促进软骨细胞增殖,但在作用后期出现细胞周期阻滞,软骨细胞增殖率降低,凋亡增多,从而促进生长板老化过程。

BACKGROUND： Estrogen is an indispensable factor in the closure of growth plate. However, no experiment studies the effect of estrogen on chondrocytes proliferation, cell cycle or ultrastructure alteration during apoptosis. OBJECTIVE： To explore the effects of estrogen on regulating chondrocytes proliferation and senescence of the ribs growth plate. METHODS： Totally 30 New Zealand white rabbits were prepared for ovariectomized models and received either estradiol benzoate （estradiol group） or sterilized cottonseed oil （model group）. All rabbits were sacrificed at 23, 26 and 29 weeks. BrdU was subcutaneous injected at 7 and 1 hours before execution. The BrdU positive rate of growth plates from the ribs was detected by immunohistochemistry. The chondrocytes cell cycle was examined by flow cytometry, and ultrastructure was observed by a transmission electron microscope. RESULTS AND CONCLUSION： BrdU positive-staining rate of both groups were gradually decreased. During early time （23 to 26 weeks of age）, the percentage of BrdU positive-staining chondrocytes in the estradiol group were higher than those of the model group （P 〈 0.05）, but the differences had no significance at 39 weeks of age （P 〉 0.05）. After the injection of estradiol, there were accumulations of chondrocytes in the S phase of the rib growth plate with higher proliferation index. By the end of the experiment the proliferation index was decreased. Our data suggested that chondrocyte proliferation was enhanced by estrogen during the early time with significant replicative senescence induced thereafter and causing the process of growth plate senescence.