Objective: To explore the therapeutic effect of basic fibroblast growth factor (bFGF) on spinal cord injury (SCI) in rats and the influence of Notch/signal transducer and activator of transcription 3 (STAT3) signaling pathway.
Methods: A total of 40 10-week-old male Sprague Dawley (SD) rats were selected to establish T 10-segment SCI model by a free falling object. Among them, 32 successful models were randomly divided into model group and bFGF group, with 16 in each group. Another 16 SD rats were selected as sham-operation group, with only T 10 processes, dura mater, and spinal cord exposed. After modeling, the rats in bFGF group were intraperitoneally injected with 100 μg/kg bFGF (once a day for 28 days), and the rats in model group and sham-operation group were injected with normal saline in the same way. The survival of rats in each group were observed after modeling. Basso-Beattie-Bresnahan (BBB) scores were performed before modeling and at immediate, 14 days, and 28 days after modeling to evaluate the functional recovery of hind limbs. Then, the spinal cord tissue at the site of injury was taken at 28 days and stained with HE, Nissl, and propidium iodide (PI) to observe the pathological changes, neuronal survival (number of Nissl bodies) and apoptosis (number of PI red stained cells) of the spinal cord tissue; immunohistochemical staining and ELISA were used to detect the levels of astrocyte activation markers [glial fibrillary acidic protein (GFAP)] and inflammatory factors [interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), interferon γ (IFN-γ)] in tissues, respectively. Western blot was used to detect the expressions of Notch/STAT3 signaling pathway related proteins [Notch, STAT3, phosphoryl-STAT3 (p-STAT3), bone morphogenetic protein 2 (BMP-2)] in tissues.
Results: All rats survived until the experiment was completed. At immediate after modeling, the BBB scores in model group and bFGF group significantly decreased when compared to sham-operation group ( P<0.05). At 14 and 28 days after modeling, the BBB scores in model group significantly decreased when compared to sham-operation group ( P<0.05); the bFGF group showed an increase compared to model group ( P<0.05). Compared with before modeling, the BBB scores of model group and bFGF group decreased at immediate after modeling, and gradually increased at 14 and 28 days, the differences between different time points were significant ( P<0.05). The structure of spinal cord tissue in sham-operation group was normal; in model group, there were more necrotic lesions in the spinal cord tissue and fewer Nissl bodies with normal structures; the number of necrotic lesions in the spinal cord tissue of the bFGF group significantly reduced compared to the model group, and some normally structured Nissl bodies were visible. Compared with sham-operation group, the number of Nissl bodies in spinal cord tissue significantly decreased, the number of PI red stained cells, GFAP, IL-1β, TNF-α, IFN-γ, Notch, p-STAT3 /STAT3, BMP-2 protein expression levels significantly increased in model group ( P<0.05). The above indexes in bFGF group significantly improved when compared with model group ( P<0.05).
Conclusion: bFGF can improve motor function and pathological injury repair of spinal cord tissue in SCI rats, improve neuronal survival, and inhibit neuronal apoptosis, excessive activation of astrocytes in spinal cord tissue and inflammatory response, the mechanism of which may be related to the decreased activity of Notch/STAT3 signaling pathway.
目的: 探讨bFGF对脊髓损伤（spinal cord injury，SCI）大鼠的治疗作用及Notch/STAT3信号通路的影响。.
方法: 取10周龄雄性SD大鼠40只，采用自由落体打击法建立T 10 节段SCI模型，其中32只造模成功随机分为模型组、bFGF组，每组16只；另取16只SD大鼠仅暴露T 10棘突、硬脊膜和脊髓，作为假手术组。造模后bFGF组腹腔注射100 μg/kg bFGF（1次/d，共28 d），模型组和假手术组大鼠同法注射生理盐水。造模后观察各组大鼠存活情况，于造模前及造模后即刻、14 d、28 d行BBB评分评估后肢功能。造模后28 d取损伤部位脊髓组织，行HE、Nissl和碘化丙啶（propidium iodide，PI）染色，观察脊髓组织病理变化、神经元存活（尼氏体数量）和凋亡（PI红染细胞数量）情况；免疫组织化学染色和ELISA法分别检测组织中星形胶质细胞活化标志物 ［胶质纤维酸性蛋白（glial fibrillary acidic protein，GFAP）］ 及炎症因子 ［IL-1β、TNF-α、干扰素γ（interferon γ，IFN-γ）］水平；Western blot检测组织Notch/STAT3信号通路相关蛋白 ［Notch、STAT3、磷酸化-STAT3（phosphoryl-STAT3，p-STAT3）、BMP-2］ 表达。.
结果: 各组大鼠均存活至实验完成。造模后即刻，模型组及bFGF组BBB评分均较假手术组降低（ P<0.05）；14、28 d时模型组BBB评分较假手术组降低（ P<0.05），bFGF组较模型组升高（ P<0.05）。模型组、bFGF组与造模前比较，造模后即刻BBB评分降低，14 、28 d评分逐渐升高，各时间点间差异均有统计学意义（ P<0.05）。假手术组脊髓组织结构正常；模型组脊髓组织出现较多坏死灶，结构正常尼氏体较少；bFGF组脊髓组织坏死灶较模型组明显减少，可见部分结构正常尼氏体。与假手术组比较，模型组脊髓组织尼氏体数量减少，PI红染细胞数量增多，GFAP、IL-1β、TNF-α、IFN-γ以及Notch、p-STAT3/STAT3、BMP-2蛋白表达水平升高（ P<0.05）；而bFGF组上述指标均较模型组改善（ P<0.05）。.
结论: bFGF能改善SCI大鼠运动功能和脊髓组织病理损伤，有利于神经元存活，抑制神经元凋亡、脊髓组织星形胶质细胞过度活化及炎症反应，其作用机制可能与Notch/STAT3信号通路活性降低有关。.
Keywords: Basic fibroblast growth factor; Notch; rat; signal transducer and activator of transcription 3; spinal cord injury.