脊髓损伤大鼠内源性神经干细胞/前体细胞的增殖与分化

Proliferation and differentiation of endogenous neural stem cells/progenitor cells after spinal cord injury in rats

目的：目前认为大脑和脊髓中有内源性神经干细胞／前体细胞存在，但脑和脊髓损伤后这些内源性神经干细胞／前体细胞的活化、增殖、分化机制仍不清楚。应用5-溴2-脱氧尿嘧啶核苷（5-brom02-deoxyuridine，BrdU）体内标记的方法，观察了大鼠脊髓损伤后内源性神经干细胞／前体细胞的增殖、分化变化过程。方法：实验于2007—04／09在珠江医院中心实验室进行。①实验材料：36只同一窝别雌性SD大鼠由南方医科大学动物实验中心提供，体质量200～220g，按照随机数字表法将大鼠分为对照组、预标记组和损伤后标记组，实验过程中对动物处置符合动物伦理学标准。②实验方法：采用Allen法建立脊髓损伤模型，损伤后连续10d腹腔注射Brdu来标记损伤后活化增殖的细胞：对照组采用Brdu连续10d腹腔注射，以标记脊髓内保持分化活力的细胞；预标记组在Brdu连续10d腹腔注射标记后，于第12天进行脊髓损伤。③实验评估：采用免疫组织化学法检测Brdu标记的内源性神经干细胞／前体细胞增殖情况。结果：①对照组可见整个脊髓切片均有大量的Brdu阳性细胞存在，这些细胞主要分布于脊髓外侧区域。②与对照组比较，预标记组Brdu阳性细胞在损伤后1d明显减少，7d后增多，21d后逐渐恢复并超过对照组水平。③损伤后标记组在损伤后1d即见大量Brdu阳性细胞增殖，阳性细胞数亦较预标后损伤1d时明显增多，损伤后7dBrdu阳性细胞数达到高峰，并超出对照组水平，这些细胞分布于损伤周围的灰质及室管膜区，但在损伤后21d，Brdu阳性细胞数未见继续增加。与对照组相比，损伤后标记组有较多的巢蛋白阳性细胞在室管膜区表达，1d即有增加，在7d达到高峰，21d减少。结论：脊髓损伤后出现明显的细胞增殖、分化反应，主要存在损伤后1周以内，1d即可见明显增生，尤以7d时明显，21d保持平稳，这些细胞主要分布在损伤脊髓中央管周围的室管膜区和损伤区域周围。

AIM： Previous studies have demonstrated that the brain and spinal cord contain endogenous neural stem cells/progenitor cells. However, little is known about their activation, proliferation and differentiation after the injury of brain and spinal cord. Used 5-bromo2-deoxyuridine （BrdU） labeling in vivo, we observed the proliferation and differentiation of endogenous neural stem cells/progenitor cells after spinal cord injury （SCI） in rats. METHODS： Experiments were conducted at the Central Laboratory of Zhujiang Hospital from April to September 2007. ① Thirty-six female SD rats weighing 200 g and 220 g were obtained from the Institute of Experimental Animals of Southern Medical University. They were randomly divided into three groups, control group, Brdu-prelabeled group and Brdu-postlabeled group. The treatment of animals was accordance with the ethical standards. ②Animal SCI models were established by Allen method. To label the activated and proliferating endogenous neural stem cells/progenitor cells, animals received one intraperitoneal injection of BrdU each day for 10 days after SCI. The control group received one intraperitoneal injection of BrdU for 10 days to label the constitutively proliferating endogenous neural stem cells/progenitor cells. The Brdu-prelabeled group received one intraperitoneal injection of BrdU for 10 days. Then the spinal cord injury was made on the 12^th day. ③The tissue was analyzed using immunohistochemical detection to study the response of endogenous neural stem cells/progenitor cells. RESULTS： ①Frequent BrdU-positive cells were detected in the spinal cord section in the control group; They existed in the outer circumference of the spinal cord particularly. ②Compared to the controls, the number of Brdu positive cells in the Brdu-prelabeled group decreased strikingly on the I st day, increased obviously on the 7^th day, and returned to normal levels on the 21^st day. ③In the Brdu-postlabeled group after SCI, the number of Brdu-positive cells increased strikingly on the 1^st day, and increased compared to the Brdu-postlabeled group, reached maximum and exceeded on the 7^th day compared to the control group. These positive cells existed the highest in the gray matter adjacent to the lesion and ependymal layer, but there were no more significantly increase on the 21^st day. Moreover, compared to the control group, more Nestin expression was observed in ependymal cells on the Ist day after SCI in the Brdu-postlabeled group, and the peak was occurred at 7^th day after injury, decreased at 21^st day. CONCLUSION： There are conspicuous proliferation and differentiation after SCI. It occurred in the 1^st week after SCI. There was strikingly cell proliferation on the Ist day, increased obviously on the 7^th day, kept stable on the 21^st day. These cells existed the highest in the ependymal layer of central canal and gray matter adjacent to the lesion.