甲状旁腺激素对大鼠脊髓损伤后骨质疏松的作用和机制

Effect of parathyroid hormone on osteoporosis after spinal cord injury in rats and its mechanism

目的探究甲状旁腺激素(parathyroid hormone, PTH)对脊髓损伤(spinal cord injury, SCI)后大鼠骨质疏松的影响及其作用机制。方法 SD大鼠随机性分为假手术组(Sham)、SCI模型组(SCI)、SCI+甲状旁腺激素组(SCI+PTH)、SCI+PTH+转染miR-146a无关片段组(SCI+PTH+NC)以及SCI+PTH+转染miR-146抑制剂组(SCI+PTH+miR-146a inhibitor组)。分别每3 d一次尾静脉注射给予大鼠60μg·kg^(-1)PTH(SCI+PTH组)、60μg·kg^(-1)PTH和20 pm miR-146a NC(SCI+PTH+NC组)或60μg·kg^(-1)PTH和20 pm miR-146a inhibitor(SCI+PTH+miR-146a inhibitor组),连续8周。Sham组和SCI组大鼠同法给予等量的生理盐水。BBB评分法记录术后大鼠行为运动评分;试剂盒检测大鼠血清血钙(Ca)和碱性磷酸酶(ALP)含量;骨密度扫描仪测定股骨和胫骨的骨密度;HE染色观察大鼠脊髓形态变化;qRT-PCR检测miR-146a表达;Western blot检测p-PI3K、p-Akt蛋白表达。结果与Sham组相比,SCI组大鼠BBB评分降低(P<0.05或P<0.01)、血清Ca、股骨和胫骨骨密度含量以及miR-146a、p-PI3K、p-Akt表达均降低,ALP升高(P<0.01)。与SCI组相比,SCI+PTH组大鼠BBB评分升高(P<0.05或P<0.01)、血清Ca、股骨和胫骨骨密度含量以及miR-146 a、p-PI3K、p-Akt蛋白表达均增加,ALP降低(P<0.01)。与SCI+PTH组相比,SCI+PTH+miR-146a inhibitor组大鼠上述指标均显著被抑制。结论 PTH对SCI骨质疏松症具有一定的治疗作用,其机制可能通过调控miR-146a/PI3K/Akt信号实现。

Aim To explore the effect of parathyroid hormone on osteoporosis in rats after spinal cord injury(SCI) and its mechanism. Methods SD rats were divided into sham operation group(Sham), SCI model group(SCI), SCI+parathyroid hormone group(SCI+PTH) and SCI+PTH+transfected miR-146 a irrelevant fragment group(SCI+PTH+NC) and SCI+PTH+transfection miR-146 a inhibitor group(SCI+PTH+miR-146 a inhibtor), and then given 60 μg·kg^(-1)PTH(SCI+PTH group), 60 μg·kg^(-1)PTH and 20 pm miR-146 a NC(SCI+PTH+NC group) or 60 μg·kg^(-1)PTH and 20 pm miR-146 a inhibitor(SCI+PTH+miR-146 a inhibitor group) by tail vein injection every 3 d for 8 weeks. Rats in Sham group and SCI group were given equal amount of saline in the same way. The behavioral movement scores of rats were recorded by the BBB scoring method 1 d, 7 d, 14 d, 21 d, 28 d, and 56 d after operation;serum calcium(Ca) and alkaline phosphatase(ALP) were measured using the kits;bone mineral density of femur and tibia was measured by a bone mineral density scanner;the morphological changes of rat spinal cord were observed by HE staining;expression of miR-146 a was detected by qRT-PCR and protein expression of p-PI3 K and p-Akt was detected by Western blot. Results Compared with Sham group, SCI group had decreased BBB score(P<0.05 or P<0.01), serum Ca, femoral and tibial bone mineral density content and expression of miR-146 a, p-PI3 K and p-Akt, but increased serum ALP(P<0.01). Compared with SCI group, BBB score(P<0.05 or P<0.01), serum Ca, femoral and tibia bone mineral density content, and the expression of miR-146 a, p-PI3 K and p-Akt( P<0.01) increased, together with decreased serum ALP in SCI+PTH group(P<0.01). Compared with SCI+ PTH group, the above indicators of rats were significantly inhibited in SCI+PTH+miR-146 a inhibitor group. Conclusions PTH has certain therapeutic effect on SCI osteoporosis, achieved possibly by regulating miR-146 a/PI3 K/Akt signaling.