Immunohistochemical study during healing of free palatal mucosa grafts on plastic-embedded samples

This immunohistochemical study describes changes in the histology and in the distribution of the basement membrane components laminin and collagen IV as well as of the cytokeratins (CK)1/2/10/11, CK5/6, CK13, CK14, CK17, CK19 during the take of free split mucosa (epithelial and connective tissue) transplants in humans up to 36 months post-operative. Histology showed a flattening of the epithelial layer within the first 2 weeks after grafting, followed initially by an increase (25-30 layers, week 6) and later on by a decrease of cell layers in the epithelium (15-20 layers, week 20). From that time onwards, clear stratification and reteridges as signs of differentiation were present. Up to day 14 of graft take, the linear staining patterns for laminin and collagen IV were interrupted, which was not observed at any later stage. During this early interval CK5/6, CK1/2/10/11, CK14 and CK17 were expressed in all epithelial layers. The reactions for CK5/6 and CK1/2/10/11 were less intensive. At 6 weeks, CK1/2/10/11 stained the intermediate and superficial layers, being consistent with findings after longer graft take. CK5/6 reacted in the basal and intermediate cell layers, and CK13, CK14 and CK17 reacted in all layers. In the following period up to week 20, CK5/6 were found in the parabasal cells of the intermediate cell layers and the basal cells. CK14 staining was confined to these cell layers too, but also showed some reaction in the superficial layers. CK13 and CK17 were still bound to all layers. At 7 months post-operative, CK5/6 and CK14 were seen in their typical localisation in the basal cell layer and the parabasal cells of the intermediate layers, CK17 was seen mainly in the intermediate layer and CK13 was seen in focal areas of all layers. Anti-CK19 reacted only with single basal and parabasal cells up to week 20. These results suggest that during healing of mucosal autografts there is a sequence of changes in the expression of cell biological differentiation markers that may involve an epithelio-connective tissue interaction before the typical patterns for the donor side were observed again on the gingiva or mucosa of the hard palate.