Aloe vera: an in vitro study of effects on corneal wound closure and collagenase activity

Purpose To evaluate the in vitro effects of an aloe vera solution on (i) the viability and wound healing response of corneal cells and (ii) the ability to alter collagenase and gelatinase activities. Methods Primary cultures of corneal epithelial cells and fibroblasts were prepared from grossly normal enucleated canine globes and treated with an aloe solution (doses ranging from 0.0-2 mg/mL). Cellular viability was evaluated using a colorimetric assay. A corneal wound healing model was used to quantify cellular ingrowth across a defect made on the confluent surface. Anticollagenase and antigelatinase activities were evaluated by incubating a bacterial collagenase/gelatinase with aloe solution (doses ranging from 0.0-500 mu g/mL) and comparing outcome measures to a general metalloproteinase inhibitor, 1, 10-phenanthroline, and canine serum (doses ranging from 0.0-100%). Results None of the concentrations of aloe solution tested significantly affected the viability of corneal epithelial cells or fibroblasts. Concentrations <= 175 mu g/mL slightly accelerated corneal epithelial cell wound closure; this change was not significant. Concentrations >= 175 mu g/mL significantly (P <= 0.001) slowed the rate of corneal fibroblast wound closure, while aloe concentrations < 175 mu g/mL did not significantly alter fibroblast wound closure. Aloe solution did not alter the ability for collagenase to degrade gelatin or collagen Type I but increased the ability for collagenase to degrade Type IV collagen. Conclusions Although additional experiments are required, lower concentrations of aloe solution may be beneficial in healing of superficial corneal wounds to help decrease fibrosis and speed epithelialization. An increase in collagenase activity with aloe vera warrants further testing before considering in vivo studies.