Earlier protocol for cultivated oral mucosal epithelial transplantation (COMET) requires trypsin/EDTA to isolate epithelial cells from tissue, and uses murine 3T3 cells as feeder cells, which results in biosafety concern. This study uses collagenase instead of trypsin/EDTA to isolate epithelial cells, and does not use 3T3 cells co-culture, so as to make an animal ingredient-free cell culture product. The purpose of the study is to evaluate the feasibility of the new protocol of COMET in clinical use.