652 Topical Delivery of Fidgetin-Like 2 siRNA to Enhance Cell Migration for Burn Wound Healing in a Swine Model

Introduction Donor site skin is a precious commodity for burn wounds and graft-sparing procedures are critical for larger total body surface area burns. Currently, large ratio skin grafts have been found to preserve donor skin but at the expense of delayed reepithelialization and increased scar formation at the recipient site. In this study, we propose to utilize a topical gene therapy treatment as an adjunct to higher meshing ratio (4:1) split thickness skin grafts (mSTSG) to improve re-epithelialization and reduce donor skin requirements. Administration of small interfering RNA (siRNA) to suppress the expression of one microtubule regulatory protein, Fidgetin-Like 2 (FL2), has been shown to increase cell migration rate both in vitro and in vivo. We hypothesize that topical application of nanoparticle (NP) encapsulated FL2 siRNA will increase cell migration resulting in expedited reepithelialization in large mesh ratio mSTSG in a full-thickness porcine burn model. A pilot study was conducted to down-select siRNA dose by measuring the rate of reepithelialization of full-thickness grafted burns. Methods Ten full-thickness (FT) 5x5cm burn wounds were created on the dorsum of anesthetized Yorkshire pigs. Four days later, the wounds were surgically debrided to a bleeding wound bed and grafted using a 4:1 mSTSG. Treatments groups (n= 2 per pig) consisted of vehicle control (PBS), scrambled sequence NP siRNA (non-targeting siRNA; negative control), and either 5, 10, or 20uM concentration of NP FL2 siRNA were applied topically to the mSTSG. Rechecks were performed twice a week for four week during which time digital images, non-invasive measurements, punch biopsies were acquired, and treatment was reapplied. Quantitative measurements include rate of reepithelialization and laser speckle imaging. Histopathology was assessed by a blinded pathologist. Results All wounds reepithelialized within 28 days post-grafting without infection. There was a positive trend with increasing concentration of NP FL2 siRNA on the burn wound healing. LSI data showed no statistical differences to vehicle control. Pathology analysis is ongoing. Conclusions Topical application of NP FL2 siRNA did increase the rate of reepithelialization of large ratio mSTSG treated full-thickness injuries. Additional pilot animals are currently ongoing to down-select siRNA dose for future studies comparing the experimental treatment to the current clinical gold standard 1:1.5 mesh ratio. Applicability of Research to Practice A topical gene therapy treatment combined with a higher meshing ratio to improve current treatment modalities by increasing reepithelialization and decreasing multiple donor site harvesting.