Apoptosis in proliferative vitreoretinopathy

Purpose. To study the involvement of apoptosis using different apoptosis markers in PVR pathogenesis. Methods. The presence of mRNA coding for Fas, Fas ligand (FasL), and TNF-related apoptosis inducing ligand (TRAIL) was investigated in vitreous samples from 46 consecutive patients-25 with PVR, 11 with retinal detachment (RD) not complicated by PVR, and 10 with macular hole (MH)-using RT-PCR. From previously examined vitreous samples, 21 PVR, 9 RD, and 10 MH were examined for their levels of TGF-beta2 protein with sandwich ELISA kits. Five epiretinal membranes excised from five patients with PVR were also examined for apoptotic cell death using the terminal deoxytransferase (TdT) mediated dUTP-biotin nick end labeling (TUNEL) technique. Results. FAS mRNA was detected in 72% of patients with PVR, 55% of patients with RD and 20% of patients with MH. TRAIL mRNA was detected in 67% of patients with PVR, 89% of patients with RD, and 20% of patients with MH FasL mRNA was detected in 20% of patients with PVR, 9% of patients with RD, and 10% of patients with MH. The median levels of Fas and TRAIL mRNA were significantly higher (P<0.05) in patients with PVR than in those with MH hole but between patients with PVR and those with RD the difference was not significant (P>0.05). A significant difference was detected between RD and MH for TRAIL mRNA levels (P=0.008). For FasL, no significant difference between groups was found. TGF-beta2 was detected in all investigated vitreous samples. A significant difference was found between the PVR and MH groups (P=0.001) and between the RD and MH groups (P=0.004), but not between the PVR and RD groups (P<0.05). The level of TGF-beta 2 was significantly correlated to the level of TRAIL mRNA (r=0.86), but no correlation was found between TGF-beta 2 and Fas mRNA levels (r=0.21). Four of five examined PVR epiretinal membranes showed positive staining for apoptotic cells using the TUNEL technique. Conclusions. Apoptosis is one of the mechanisms that is involved in PVR pathogenesis. Different apoptosis markers suggest different pathways occur in PVR, including Fas/FasL, TRAIL, and TGF-beta 2 mediated processes.