雌激素通过抑制破骨细胞促进骨软骨缺损的自发修复

Estrogen promotes spontaneous repair of osteochondral defect via inhibition of osteoclast activity

目的探讨雌激素通过抑制破骨细胞在骨软骨缺损后自发修复中的作用，为雌激素在组织工程技术中的应用提供实验依据。方法健康4个月龄雌性SD大鼠72只，按随机数字表法分为阴性对照组（A组）、去卵巢组（B组）和去卵巢＋雌激素的治疗组（C组），每组24只。C组术后经腹腔注射苯甲酸雌二醇0．1mg／kg，每周1次。术后4周在A、B、C组后腿股骨滑车建立骨软骨缺损模型（直径2mm、深度1．5mm）。于造模后2，10，20周每组分别处死8只大鼠，取后腿股骨髁，对骨软骨缺损区行micro—CT扫描观察骨质修复情况，检测并分析骨体积分数（BVF）、骨小梁数目（Tb．N）、骨小梁厚度（Tb．Th）、骨小梁间隙（Tb．Sp）；HE染色观察形态学变化；番红O-固绿染色观察组织形态学变化并鉴定软骨再生情况；抗酒石酸酸性磷酸酶（TRAP）染色计数破骨细胞数量；免疫组化法检测基质金属蛋白酶-9（MMP-9）的分布情况；实时定量荧光PCR检测代表成骨细胞活性的骨保护素（OPG）和代表破骨细胞活性的核转录因子-κB受体活化因子配体（RANKL）、MMP-9的表达情况。结果（1）各时相点A、C组BVF、Tb．N高于B组，Tb．sp低于B组。2周时，A、C组形成的骨样基质多于B组，骨质修复更快；10，20周时，B组出现再生软骨下骨内囊肿（也称为囊性空洞）及软骨下骨板裂缝，骨质修复比A、C组差，病变部位破骨细胞增生活跃。（2）各时相点A、C组RANKL及MMP-9表达相对值较B组降低（P〈0．05），OPG表达相对值较B组明显增高（P〈0．01）；A、C组破骨细胞计数低于B组（P〈0．05）。（3）各组均未见软骨层再生。结论（1）破骨细胞过度增殖导致囊性空洞及裂缝形成；（2）雌激素通过调控成骨细胞及破骨细胞活性，将提升骨质修复速度与质量，可应用于组织工程技术治疗骨软骨缺损。

Objective To investigate the role of estrogen in spontaneous repair of osteochondral defect, so as to provide guidance for the application of estrogen in tissue engineering. Methods Seventy- two healthy adult female SD rats （4-month-old） were assigned to negative control group （group A, n = 24）, ovariectomized group （ group B, n = 24 ） and ovariectomized ＋ estrogen treatment group （ group C, n = 24） according to the random number table. Rats in group C were intraperitoneally injected 0.1 mg/kg estradiol benzoate once per week after operation. An osteochondral defect model （diameter： 2 mm, height： 1.5 mm） was established in femoral trochlea of rats 4 weeks after operation. At 2, 10 and 20 weeks after the modeling, 8 rats from each group were sacrificed. Femoral condyles were collected to measure bone volume fraction（ BVF）, number of bone trabeculae（ Tb. N）, trabecular thickness（ Tb. Th） and trabecular spacing （ Tb. Sp ） in the osteochondral defect area by micro-CT scanning. Morphological changes were observed by HE staining, histomorphological changes and cartilage regeneration by safranineO- fast green staining, osteoclast count by tartrate-resistant acid phosphatase （TRAP） staining, distribution of matrix metalloproteinase-9 （MMP-9） by immunohistochemistry and expressions of osteoprotegerin （OPG）, receptor activator of nuclear factor-κB ligand （RANKL） and MMP-9 by real-time-PCR. Results Compared to group B, increased BVF and Tb. N and decreased Tb. Sp were observed in groups A and C at each time point. More bone matrix formations were observed in groups A and C than in group B at 2 weeks, cysts （also known as cystic cavities） in regenerated subchondral bone and cracks in subchondral bone plate were observed in group B at 10 and 20 weeks, and proliferation of osteoclasts was active within lesions in group B at 10 and 20 weeks. Compared to group B, lowered levels of RANKL and MMP-9 （P 〈0. 05） and significantly increased level of OPG （P 〈0.01 ） were observed in groups A and C at each time point, and osteoclast count in groups A and C was lowered at 10 and 20 weeks （P 〈0.05）. No regeneration of cartilage layer was observed in all groups. Conclusions Excessive proliferation of osteoclasts results in formation of cystic cavities and cracks. Estrogen improves the speed and quality of bone repair by regulating activities of osteoblasts and osteoclasts, so it can be used to treat osteochondral defect in tissue engineering.