p21WAF1/CIP1在兔外伤性增生性玻璃体视网膜病变发生和发展中的抑制作用

Suppressing effect of p21WAF1/CIP1 on traumatic proliferative vitreoretinopathy in rabbits

背景p21是一种细胞周期蛋白依赖性激酶抑制剂，能阻止细胞从G．期进入s期，抑制细胞增生，研究认为内源性p21表达的动态变化可能与细胞增生性病变有关。外伤性增生性玻璃体视网膜病变（PVR）是眼部增生性反应相关性疾病，了解PVR过程中p21表达的动态变化可能为PVR的靶向治疗提供依据。目的检测p21WAF1/CIP1在兔外伤性PVR中的动态变化，探讨其在外伤性PVR发病机制中的作用。方法选取青紫蓝兔54只，采用随机数字表法将实验兔随机分为正常对照组（6只）和造模后7、14、21和28d组（每组12只），每只兔任意选取一眼作为实验眼。各模型组兔眼玻璃体腔注射人富含血小板血浆（PRP）0．4ml，同时于鼻上方角巩膜缘后5mm处行巩膜外冷冻约5s，以建立外伤性PVR模型。各组兔眼行眼部B型超声检查以评估建模情况。分别于造模后7、14、21和28d以过量麻醉法处死实验兔并制备实验眼视网膜组织切片，采用苏木精-伊红染色法检测兔眼视网膜的形态表现，分别采用免疫组织化学染色、Westernbla及逆转录PCR（RT—PCR）法检测兔视网膜中p21WAF1/CIP1蛋白及其mRNA的相对表达。结果正常对照组兔眼眼前后节均正常，模型组兔造模后1～7d兔眼玻璃体中增生条索逐渐变粗，可见视网膜皱褶，造模后14d兔眼出现牵引性视网膜脱离，造模后28d兔眼漏斗状视网膜脱离。视网膜病理组织学检查显示，造模后7d兔眼视网膜表面有增生膜和炎性细胞聚集，造模后28d可见视网膜呈花瓣形固定皱褶，视网膜结构紊乱。免疫组织化学染色显示，p21WAF1/CIP1蛋白在正常对照组兔眼视网膜神经节细胞层及内核层的细胞核内呈强阳性表达，造模后7、14、21和28d表达强度减弱，以造模后14d表达量最低。Westernbla结果显示，正常对照组和造模后7、14、21和28d组兔眼视网膜中p21WAF1/CIP1蛋白相对表达量分别为0．74±0．08、0．60±0．05、0．56±0．03、0．74±0．02和0．65±0．04，组间总体比较差异有统计学意义（F=20．55，P=0．00），造模后7d和14d的表达量均明显低于正常对照组和造模后21d和28d组，差异均有统计学意义（均P〈0．05）。RT—PCR结果显示，正常对照组和造模后7、14、21和28d组兔眼视网膜中p21WAF1/CIP1。mRNA的相对表达量分别为0．65±O．09、0．57±0．05、0．45±0．04、0．46±0．02和0．47±0．04，总体比较差异有统计学意义（F=18．06，P=0．00），造模后14、21和28dp21WAF1/CIP1mRNA的相对表达量均明显低于正常对照组和造模后7d组，差异均有统计学意义（均P〈0．05）。结论p21WAF1/CIP1在外伤性PVR兔眼视网膜中的动态表达变化与PVR的病程发展过程相吻合，p21可能参与外伤性PVR发生和发展的病理过程，p21WAF1/CIP1表达量的下降与细胞增生的动态变化过程一致，可能促进了PVR的进展。

Background p21 is a cyelin-dependent kinase inhibitor, and it can prevent cells from going through the G/S phase checkpoint and inhibit cell proliferation. Stuies determined that the expression level ofp21 WAF1/CIPI is associated with proliferative diseases. Traumatic proliferative vitreoretinopathy （PVR） is a proliferative response of eye. Understaining the relationship of dynamic expression levels of p21WAF1/CIP1in PVR is of significance for the prevention and management of PVR. Objective This study was to investigate the expression of p21WAF1/CIP1 during the course of experimental traumatic PVR in rabbits. Methods Fifty-four pigmented rabbits were randomized into the normal control group and different experimerital groups, and one lateral eye of each rabbit served as experimental eye. PVR models were established by intravitreal injection of human platelet-rich plasma （PRP） （0. 4 ml） combined with cryotherapy for 5 seconds,and vitreous and retinas were examined with B type sonography. The rabbits were sacrificed in 7,14,21 and 28 days after operation, and histopathological examination of the retinas was performed by haematoxylin and eosin stain. The expression levels of p21WAF1/CIP1 protein and gene were detected by immunohistochemistry,Western blot and reverse transcription-PCR （RT-PCR）. The use and care of the rabbits complied with Statement of ARVO. Results B type sonography showed that the retinal morphology was normal in the normal control group. However, the proliferative membrane was gradually thickened 1 to 7 days after operation. Retinal folds of rabbits were seen in 7 days,and tractional retinal detachment was found in 14 days and 28 days after operation. The histopathological examination of the retinas showed epiretinal membrane and infiltration of inflammatory cells 7 days and fixed ruffle 28 days after operation. The p21WAF1/CIP1 was strongly expressed in the cell nucleus of retinal ganglion cell layer （GCL） and inner nuclear layer （INL） in the normal control group,and the expression was gradually weakened after modeling,with the weakest expression in the retinas in 14 days after modeling. The relative expression levels of p21WAF1/CIP1 protein was 0. 74±0. 08 ,0. 60±0. 05,0.56±0.03,0. 74±0. 02 and 0. 65±0.04 in the normal control group, postoperative 7-day group, postoperative 14-day group, postoperative 21-day group and postoperative 28-day group, respectively, showing a significant difference among the groups （ F = 20. 55, P = 0.00 ） , and the expression levels of p21wAn/clvl protein were significantly lower in the postoperative 7-day group and postoperative 14-day group than those of the normal control group,postoperative 21-day group and postoperative 28-day group （ all at P 〈 0. 05 ）. The relative expression levels of p21WAF1/CIP1 mRNA was 0. 65 ± 0.09,0. 57 ± 0. 05,0.45 ± 0.04,0.46 ±0. 02 and 0.47±0.04 in the normal control group, postoperative 7-day group, postoperative 14-day group, postoperative 21-day group and postoperative 28-day group, respectively, with a significant difference among the groups （F= 18.06, P = 0.00）, and the expression levels were significantly lower in the postoperative 14-day group, postoperative 21-day group and postoperative 28-day group than those of the normal control group and postoperative 7-day group （all at P〈0. 05）. Conclusions The dynamic expression of p21WAF1/CIP1 in the retinas is consistant with the prograssion of traumatic PVR, and the reduce tendency of p21WAF1/CIP1 expression is similar to cell prolieration change,indicating that reduce of p21WAF1/CIP1 expression in the retinas may promote the development of traumatic PVR.