The effect of collagenase on ischemic wound healing: Results of an in vivo study

Many chronic wounds have a limited blood supply and contain necrotic tissue that must be debrided. The effect of col- lagenase, an enzymatic debriding agent, has been studied in acute but not in chronic wounds. The purpose of this in vivo study is to evaluate the effect of collagenase on wound healing in ischemic wounds. The ears of eight young New Zealand White rabbits were rendered ischemic by ligation of caudal and central arteries and dermal circulation circum- ferentially so both ears were perfused only by the rostral artery, preserving the caudal, central, and rostra veins. Three 6-mm, full-thickness dermal punches were made on the inner surface of both ears down to perichondrium. One ear on each rabbit was treated with either collagenase or petrolatum ointment covered with a semi-occlusive dressing; wounds on the other ear of the same rabbit were covered with a semi-occlusive dressing only (control). On post-wounding day 8, wound samples were collected and processed for histological analysis of reepithelialization (epithelial gap, percentage healed, epithelial height, and epidermal area) and granulation tissue formation (peak height, granulation tissue distance, and area). Within-animal comparison showed no significant differences between the petrolatum and control wounds but epithelial height, epidermal area, wound peak height, and granulation tissue distance and area were significantly different between the collagenase and control-treated wounds. Between-animal comparison of petrolatum- and collagenase- covered wounds showed statistically significant (P <0.05) differences for the following outcomes: epithelial gap, per- cenatge healed, epithelial height, epidermal area, wound peak height, and granulation tissue distance and area. In this ischemic wound model, outcomes for most of the variables associated with healing were significantly better in wounds covered with collagenase and a semi-occlusive dressing than in the control or petrolatum group. Additional in vivo stud- ies are warranted to confirm these results.