p21 is a cyclin-dependent kinase inhibitor, and it can prevent cells from going through the G₁/S phase checkpoint and inhibit cell proliferation.Stuies determined that the expression level of p21^WAF1/CIP1is associated with proliferative diseases.Traumatic proliferative vitreoretinopathy (PVR) is a proliferative response of eye.Understaining the relationship of dynamic expression levels of p21^WAF1/CIP1in PVR is of significance for the prevention and management of PVR.

This study was to investigate the expression of p21^WAF1/CIP1during the course of experimental traumatic PVR in rabbits.

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 p21^WAF1/CIP1protein 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.

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 p21^WAF1/CIP1was 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 p21^WAF1/CIP1protein 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 p21^WAF1/CIP1protein 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 p21^WAF1/CIP1mRNA 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).

The dynamic expression of p21^WAF1/CIP1in the retinas is consistant with the prograssion of traumatic PVR, and the reduce tendency of p21^WAF1/CIP1expression is similar to cell prolieration change, indicating that reduce of p21^WAF1/CIP1expression in the retinas may promote the development of traumatic PVR.

Cyclin-dependent kinase inhibitor p21/analysis; Vitreoretinopathy, proliferative/etiology; Retinal detachment/complications; Ocular trauma; Disease model, animal; Rabbits