A Pedf Peptide Encapsulated in Controlled Release Poly (Lactic–Co–Glycolic Acid) Microspheres Protects Retinal Ganglion Cells From Transient Ischemic Injury

Abstract

Abstract: : Purpose: To determine the neuroprotective function of an N–terminal peptide fragment of PEDF and to test the actions of the PEDF peptide encapsulated in biodegradable PLGA (poly lactic–co–glycolic acid) microspheres. Methods: All experiments followed ARVO guidelines and were approved by the IACUC. Transient retinal ischemia was induced in C57/B6 mice by elevation of IOP to 120 mmHg for 60 min in one eye. The contralateral eye served as control. One group of animals remained uninjected to monitor ischemic damage. Other groups received intravitreous injections of PBS, full length native PEDF protein, PEDF82–121 peptide, blank PLGA microspheres with mean size 200um, and microspheres encapsulating PEDF82–121. The thickness of inner nuclear layer (INL) and inner plexform layer (IPL) were analyzed after ischemic insult in controls and injected eyes. TUNEL staining and cell counts were used to analyze changes in the retinal ganglion cell (RGC) layer. Results: Experimentally induced ischemia caused a decrease in INL and IPL thickness and in RGC number that peaked at 48hr. Intravitreal injection of the PEDF protein or PEDF82–121 at the time of ischemia led to significant preservation of the thickness of all retinal layers at both 48 hr and 7 d post injury compared with PBS injected controls. PEDF protein injection resulted in a 95.87% and 209.5% increase in the number of RGCs at 48 hr and 7d respectively (p<0.001). PEDF82–121 injections led to a 161.42% (p<0.001) and 101.2% increase in RGC number at 48hr and 7d respectively. Compared with the blank microsphere injected eyes, the INL, and IPL thicknesses and RGC number increased by 43.19%, 156.9% and 208.6% (p<0.001) respectively in the PEDF peptide encapsulated microsphere injected eyes after 7d. Conclusions: The PEDF82–121 peptide is effective as a neuroprotective factor. Encapsulating PEDF82–121 in PLGA microspheres is an effective way of achieving controlled release of therapeutically active levels of this peptide and of optimizing retinal protection in ischemic conditions.

Keywords: neuroprotection • oxidation/oxidative or free radical damage • retinal pigment epithelium