PEDF deficiency increases the susceptibility of rd10 mice to retinal degeneration

The SERPINF1 gene encodes pigment epithelium-derived factor (PEDF), a member of the serpin superfamily with neurotrophic and antiangiogenic properties in the retina. We hypothesized that absence of PEDF would lead to increased stress-associated retinal degeneration in Serpinf1 null mice. Accordingly, using a Serpinf1 null mouse model, we investigated the impact of PEDF absence on retinal morphology, and susceptibility to induced and inherited retinal degeneration. We studied the pattern of Serpinf1 expression in the mouse retina layers. PEDF protein was detected by western blotting. Transmission electron microscopy was performed on mouse retina. Serpinf1 null mice and wild type littermates were injected with NaIO₃ (30 mg/kg body weight) intraperitonially. At post-injection day 1, 3, 4, 6 and 8 mice were euthanized, and eyes were enucleated. Serpinf1 null and rd10 double mutant mice were generated and their eyes enucleated at different time points from post-natal day 15 to post-natal day 28. Enucleated eyes were processed for hematoxylin and eosin staining and histopathological evaluations. We found that Serpinf1 was expressed in the retinal pigment epithelium, in the inner nuclear layer and in the ganglion cell layer, but undetectable in the outer nuclear layer of wild type mice. Plasma PEDF protein levels were undetectable in Serpinf1 null animals. RPE atrophy and retinal thinning were observed in NaIO₃-treated wild type mice that progressed with time post-injection. NaIO₃-treated Serpinf1 null mice showed comparatively better retinal morphology than wild type mice at day 4 post-injection. However, the absence of PEDF in Serpinf1 null x rd10 mice increased the susceptibility to retinal degeneration relative to that of rd10 mice. We concluded that histopathological evaluation of retinas lacking PEDF showed that removal of the Serpinf1 gene may activate PEDF-independent compensatory mechanisms to protect the retina against oxidative stress, while it increases the susceptibility to degenerate the retina in inherited retinal degeneration models.