Abstract
Purpose:
Prominin-1 (CD133) is a 5-transmembrane glycoprotein found in both humans and rodents. Prominin-1 was originally identified as a stem cell marker and has recently been identified in neuronal and glial stem cells. It also acts as a key regulator of disk morphogenesis during early retinal development, and mutations in the prominin-1 gene result in retinal degeneration. We recently reported that Prominin-1 interacts with VEGF-A165, enhancing its activity. We have developed a short peptide derived from Prominin-1, PR1P, which also enhances VEGF-A165 activity. We investigated the effects of PR1P on cell death and regeneration of damaged retinal ganglion cells in a rat model of optic nerve injury.
Methods:
Retina and optic nerves obtained from Fischer rats following an optic nerve (ON) crush were utilized in this experiment. 1mm3 Hydron polymer pellets containing either PR1P or vehicle were cast and implanted into the retrobulbar space at the time of crush. Electroretinogram (ERG) assessment of retinal function was performed 6 weeks after surgery. To assess VEGF-A165 signaling, additional rats were treated with either intravitreous anti-VEGF-A165 antibody or recombinant VEGF-A165 protein. Histologic studies of the retina and ON included H&E staining, immunohistochemistry and the TUNEL assay. Total mRNA and proteins were extracted from the retina and ON and analyzed using real-time PCR, western blot and enzyme-linked immunosorbent assay (ELISA) to detect changes in the expression of genes and proteins mediated by PR1P.
Results:
PR1P significantly increased axonal regeneration and prevented retinal ganglion cell (RGC) death. ERG measurements recovered remarkably after PR1P treatment compared to control group. We also observed that PR1P beneficially altered matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of metalloproteinase-1 (TIMP-1) expression, resulting in an increased MMP-9/TIMP-1 ratio in both the retina and ON. Additionally, rats treated with anti-VEGF-A165 antibody had reduced protection of RGC by PR1P, reinforcing the importance of VEGF-A165 signaling in the activity of PR1P.
Conclusions:
PR1P displays neuroprotective effects in the optic nerve crush model through enhanced VEGF-driven neuronal survival. Further development of PR1P as a neuroprotective therapeutic agent is ongoing.
Keywords: 615 neuroprotection •
629 optic nerve •
656 protective mechanisms