Journal of Dental Research, Vol 75, 912-918, Copyright © 1996 by International & American Associations for Dental Research Online Journals

ARTICLES

Re-epithelialization of human oral keratinocytes in vitro

J. A. Garlick, W. C. Parks, H. G. Welgus and L. B. Taichman
Department of Oral Biology and Pathology, School of Dental Medicine, State University of New York at Stony Brook 11794-8702, USA.

Re-epithelialization involves interactions between keratinocytes and the extracellular matrix upon which these cells move. It is hypothesized that keratinocytes are activated when wounded, and the resultant phenotypic change directs re-epithelialization. We have adapted organotypic cultures, in which oral gingival keratinocytes are fully differentiated, to study re-epithelialization following wounding. To elucidate keratinocyte behavior and phenotype during re-epithelialization, we have investigated this process in the presence and absence of the growth factor TGF-beta 1 and have monitored expression of MMP-1 (Type I collagenase) mRNA by in situ hybridization. In addition, we have followed proliferation and migration of wound keratinocytes by genetically marking these cells with a retroviral vector and by measuring their proliferative index. We found that keratinocytes grown without TGF-beta 1 were hyperproliferative in response to wounding, and re-epithelialization was complete by 24 h. However, 2.5 ng/mL TGF-beta 1 induced a transient delay in re-epithelialization, a reduction in proliferation, and fewer clusters of genetically marked cells. Keratinocytes expressed MMP-1 mRNA only when they covered the wounded surface, suggesting that the cells acquire a collagenolytic phenotype during re-epithelialization and that contact with different ECM components may modulate keratinocyte expression of MMP-1. We conclude that the phenotype of oral keratinocytes is altered during re-epithelialization in vitro and that this process is modulated by TGF-beta 1. Re-epithelialization occurs as keratinocytes are activated to move over the wound bed. Understanding the phenotype of wounded keratinocytes may facilitate treatment of chronic oral wounds and periodontal disease.

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