PEDF functions as an endogenous anti-angiogenic during dermal wound repair

Objectives:  Pigment epithelium-derived factor (PEDF), one of the most potent endogenous anti-angiogenic agents, was identified from a comprehensive microarray of the transcriptome of murine dermal and tongue wounds as a potentially important mediator during the post-proliferative phase of wound repair when vascular regression is known to occur. The purpose of the current study was to examine the functional role of PEDF in the process of excisional dermal wound healing.

Methods:  Excisional dermal wounds were prepared on BALB/c mice, and wound samples were harvested at eight time points post-injury for analysis. PEDF levels in wounds were evaluated by ELISA (n=10), and PEDF was localized by immunofluorescent histochemistry. To study the function of PEDF during healing, purified recombinant PEDF (rPEDF) was applied to wounds daily, topically or by intradermal injection after wound closure, with phosphate-buffered saline (PBS) as control (n=6). Healing kinetics were evaluated by daily measurement of wound size. Wound samples were harvested at day 10 post-injury and analyzed for microvessel density using immunofluorescent histochemistry for CD31.

Results:  ELISA showed that PEDF protein levels were significantly higher in uninjured tissue than at all time points post-injury (p<0.01) except day 28. Furthermore, PEDF levels increased significantly between days 3 and 28 (p<0.05). Histological analysis confirmed that PEDF is a matricellular protein present in the dermis of normal and wounded skin, with observed co-localization among endothelial cells and fibroblasts. Treatment of dermal wounds with rPEDF resulted in a significant reduction (25%) of microvessel density in the wound bed compared to wounds treated with PBS (p<0.05). Interestingly, rPEDF and PBS-treated wounds exhibited nearly identical wound closure kinetics (p=NS).

Conclusions:  These results suggest that endogenous PEDF functions to regulate angiogenesis in the healing murine dermal wound. Future work will confirm these findings and explore potential mechanisms by which PEDF participates in the process of vascular regression during wound repair.