Salivary VEGF Plays an Essential Role in Oral Mucosal Wound Healing

Abstract

Introduction: Palatal mucosal wound healing occurs more rapidly than in cutaneous wounds. Vascular endothelial growth factor (VEGF) induced angiogenesis is critical for cutaneous wound healing. We have previously demonstrated 1) salivary glands produce high levels of VEGF and 2) an essential role for salivary VEGF (salVEGF) in the intestinal response to injury. This has led us to hypothesize that salVEGF is critical in oral mucosal wound healing and neovascularization. to test this hypothesis, we performed a loss-of-function experiment by selectively inhibiting salVEGF using a novel adenoviral construct (AdVegfTrap) and a gain-of-function experiment by supplementing oral VEGF following submandibular gland (SMG) resection. Methods: In the loss-of-function experiment, C57/BL6 mice underwent SMG duct cannulation and were treated with 1x108 PFU AdVegfTrap, AdLacZ or PBS (n=5/group). 1.5 mm palatal mucosal wounds were created. in the gain-of-function experiment, C57/BL6 mice underwent SMG sialoadenectomy (n=4) or sham operation (n=5). 1.5 mm palatal wounds were created and oral VEGF protein was supplemented. AdVegfTrap was not used due to anticipated consumption of the orally replaced VEGF. in both experiments, salVEGF protein levels were quantified by ELISA. Wounds were harvested at 3 days and analyzed for epithelial gap and vessel density. Data were expressed as mean+SEM. Results: Retrograde SMG duct injection of AdLacZ results in 100% transduction efficiency confirming effective transgene delivery. SMG duct cannulation, SMG administration of AdLacZ and sham operation controls do not result in significantly decreased of salVEGF (PBS513pg/ml±141 vs AdLacZ353pg/ml±56 vs sham472pg/ml±40 vs control514pg/ml±89;p=NS). Administration of AdVegfTrap results in depletion of salVEGF comparable to SMG sialoadenectomy (AdVegfTrap122pg/ml±42 vs SMG resection136pg/ml±15.9;p=NS). Selective inhibition of salVEGF by AdVegfTrap impairs wound closure (AdVegfTrap947μm±22 vs AdLacZ411μm±21 vs PBS355μm±31;p<0.001) and vessel density (AdVegfTrap15.95caps/hpf±0.83 vs AdLacZ30.87caps/hpf±1.1 vs PBS30.5caps/hpf±0.95;p<0.001). Oral replacement of VEGF in SMG resected mice rescues the impaired reepithelialization and neovascularization phenotype (SMG with oral VEGF194μm±43 vs sham350μm±46,p=NS; SMG with oral VEGF24.0caps/hpf±1.4 vs sham18.6caps/hpf±2.1,p=NS). Conclusions: Selective inhibition of salVEGF significantly impairs palatal reepithelialization and neovascularization. Oral supplementation of VEGF rescues the impaired wound healing phenotype in SMG sialoadenectomized mice. Taken together, these findings suggest that salVEGF is an essential growth factor in oral mucosal wound healing which may be a surrogate for intestinal wound healing. the palatal wound model may be a valuable tool in understanding the critical role of salVEGF in the alimentary tract response to injury.