Department of Anesthesiology & Center for Shock, Trauma and Anesthesiology Research (STAR), University of Maryland, School of Medicine, Baltimore, MD 21201, USA.
J Neuroinflammation. 2012 Jul 11;9:169. doi: 10.1186/1742-2094-9-169.
Traumatic spinal cord injury (SCI) induces secondary tissue damage that is associated with astrogliosis and inflammation. We previously reported that acute upregulation of a cluster of cell-cycle-related genes contributes to post-mitotic cell death and secondary damage after SCI. However, it remains unclear whether cell cycle activation continues more chronically and contributes to more delayed glial change. Here we examined expression of cell cycle-related proteins up to 4 months following SCI, as well as the effects of the selective cyclin-dependent kinase (CDKs) inhibitor CR8, on astrogliosis and microglial activation in a rat SCI contusion model.
Adult male rats were subjected to moderate spinal cord contusion injury at T8 using a well-characterized weight-drop model. Tissue from the lesion epicenter was obtained 4 weeks or 4 months post-injury, and processed for protein expression and lesion volume. Functional recovery was assessed over the 4 months after injury.
Immunoblot analysis demonstrated a marked continued upregulation of cell cycle-related proteins - including cyclin D1 and E, CDK4, E2F5 and PCNA - for 4 months post-injury that were highly expressed by GFAP+ astrocytes and microglia, and co-localized with inflammatory-related proteins. CR8 administrated systemically 3 h post-injury and continued for 7 days limited the sustained elevation of cell cycle proteins and immunoreactivity of GFAP, Iba-1 and p22PHOX - a key component of NADPH oxidase - up to 4 months after SCI. CR8 treatment significantly reduced lesion volume, which typically progressed in untreated animals between 1 and 4 months after trauma. Functional recovery was also significantly improved by CR8 treatment after SCI from week 2 through week 16.
These data demonstrate that cell cycle-related proteins are chronically upregulated after SCI and may contribute to astroglial scar formation, chronic inflammation and further tissue loss.
外伤性脊髓损伤 (SCI) 会引发继发性组织损伤，这与星形胶质细胞增生和炎症有关。我们之前报道过，细胞周期相关基因簇的急性上调会导致 SCI 后有丝分裂后细胞死亡和继发性损伤。然而，目前尚不清楚细胞周期激活是否会持续更长时间，并导致更多延迟的神经胶质变化。在这里，我们检查了 SCI 后长达 4 个月的细胞周期相关蛋白的表达情况，以及选择性细胞周期蛋白依赖性激酶 (CDKs) 抑制剂 CR8 对大鼠 SCI 挫伤模型中星形胶质细胞增生和小胶质细胞激活的影响。
成年雄性大鼠在 T8 处使用经过充分验证的重物坠落模型接受中度脊髓挫伤损伤。伤后 4 周或 4 个月，从损伤中心采集组织，并进行蛋白表达和损伤体积分析。损伤后 4 个月内评估功能恢复情况。
免疫印迹分析表明，细胞周期相关蛋白（包括 cyclin D1 和 E、CDK4、E2F5 和 PCNA）在损伤后 4 个月内显著持续上调，这些蛋白在 GFAP+星形胶质细胞和小胶质细胞中高表达，并与炎症相关蛋白共定位。CR8 在损伤后 3 小时内系统给药并持续 7 天，可限制细胞周期蛋白和 GFAP、Iba-1 和 p22PHOX（NADPH 氧化酶的关键组成部分）免疫反应性的持续升高，直至 SCI 后 4 个月。CR8 治疗可显著减少损伤体积，未治疗动物的损伤体积通常在创伤后 1 至 4 个月之间进展。CR8 治疗还可显著改善 SCI 后的功能恢复，从伤后第 2 周到第 16 周。
这些数据表明，细胞周期相关蛋白在 SCI 后会持续上调，并可能导致星形胶质细胞瘢痕形成、慢性炎症和进一步的组织损失。
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