Investigating wound healing characteristics of gingival and skin keratinocytes

Oral tissue, including gingiva, is recognised for its ability to heal both at an accelerated rate and with reduced scarring. The aim of this project was to explore the contrasting healing efficiencies of gingival versus skin keratinocytes, alongside investigating their differential gene expression patterns. To achieve these aims, three‐dimensional (3D) organotypic culture models of human gingiva and skin were developed using temporarily immortalised primary keratinocytes. Wounding these models enabled the visualisation of re‐epithelialisation and analysis of keratinocyte migration and proliferation to close the wound gap. Concurrently, differentially expressed genes between primary gingival and skin keratinocytes were identified and validated. Immunofluorescence characterisation of the 3D cultures of gingiva and skin showed differentiation and junctional marker localisation that recapitulated organisation of the corresponding in vivo tissue. Upon wounding, gingival models displayed a significantly higher efficiency in re‐epithelialisation and stratification versus skin, repopulating the wound gap within 24 hours. This difference was likely due to distinct patterns of migration, with gingival cells demonstrating a form of sheet migration, in contrast to skin, where the leading edge was typically 1‐2 cells thick. A candidate approach was used to identify a number of genes, including PITX1, PITX2, PAX9, NOS1, HAS3 and SIM2 that were differentially expressed between human gingival and skin keratinocytes, both prior to and during wounding. Transient knockdown of the transcription factor PITX1 in gingival keratinocytes resulted in a significant reduction in wound closure in monolayer culture. The differences in cell migration, alongside the contrasting gene expression patterns, suggest that there are intrinsic differences between keratinocytes of the gingiva and skin that impact wound healing. Finally, the successful development of organotypic models that recapitulate re‐epithelialisation, will underpin further comparison of epithelial tissues in their response to wound stimuli, and potential therapeutic interventions, in an in vitro environment.