PPARγ抑制脊髓损伤大鼠胶质瘢痕形成的研究

Research on PPARγ-mediated inhibitcon of the formation of glial scar after spinal cord injury in the rats

目的:研究大鼠脊髓损伤后过氧化物酶体增殖物激活受体γ(PPARγ)抑制胶质瘢痕形成作用及机制。方法:健康成年雌性SD大鼠52只随机取4只作为假手术组;余48只行脊髓半横断(右侧)损伤,并随机分为两大组:罗格列酮组和溶媒对照组。罗格列酮组在术后5 min、6 h、24 h均以2.5 mg/kg剂量腹腔注射PPARγ激动剂罗格列酮,溶媒对照组注射等量的溶剂。分别在术后1、3、7、14、21和28 d行BBB评分,各时间点取材后采用免疫组织化学方法检测PPARγ、基质金属蛋白酶-9(MMP-9)、磷酸化表皮生长因子受体(p-EGFR)及胶质纤维酸性蛋白(GFAP)的表达,并经Image-Pro Plus 6.0系统进行半定量分析后行方差分析。结果:罗格列酮组在7、14、21、28 d BBB评分均显著高于溶媒对照组。脊髓损伤后PPARγ、MMP-9、p-EGFR及GFAP表达均增高,罗格列酮组PPARγ在3、7和14 d较溶媒对照组水平较高,其峰值出现在第3 d;MMP-9和p-EGFR较溶媒对照组在3、7和14 d明显减少,其峰值出现在第7 d;GFAP随时间增加而增长,14 d基本达高峰,从第3 d开始两组具有显著差异(P<0.05)。结论:PPARγ可能通过抑制MMP-9,下调p-EGFR及GFAP表达水平,减少胶质瘢痕形成,促进脊髓损伤后大鼠运动功能恢复。

Objective： To investigate whether peroxisome proliferator activated receptor ~/ （PPARγ） attenuates formation of glial scar and to clarify its mechanism. Methods ： Four rats were randomly selected as the sham group from 52 healthy adult female SD rats, and the rest 48 rats were randomly divided into 2 groups after spinal cord hemiseetion （ right side） ： rosiglitazone group and vehicle group. Rosiglitazone group was injected with PPARγ/agonist rosiglitazone introperitoneally in dose of 2.5 mg/kg at the time of 5 rain, 6 h and 24 h after operation. The vehicle group was injected with equivalent solvent. BBB score was assessed at 1, 3, 7, 14, 21, 28 d after operation. The spinal cord tissues were processed by immunohistochemistry to detect the expression of PPARγ, MMP-9, p-EGFR and GFAP. Analysis of variance was used after processing a semi-quantitative analysis via Image-Pro Plus 6.0. Results ： BBB score of rosiglitazone group was significantly higher than vehicle group at 7, 14, 21,28 d, which showed improved motor function. The expression of PPARγ, MMP-9, p-EGFR and GFAP all increased after spinal cord injury. The level of PPARγ of rosiglitazone group was significantly higher than that of vehicle group at 3,7 d and 14 d and, the peak level was at 3 d. Compared to vehicle group, the expression of MMP-9 and p-EGFR decreased significantly at 3, 7 d and 14 d, and the peak level was at 7 d. The expression level of GFAP increased over time, and nearly came to the peak level at 14 d, it was significantly different between groups since the time point of 3 d. Conclusion： PPARγ suppresses the expression of MMP-9, and downregulates p-EGFR and GFAP, thus inhibits the activation of astrocytes, attenuates formation of glial scar and, finally improves motor function after spinal cord injury.