Transcriptomic Differences between Oral and Skin Keratinocytes

Compared to skin wounds, oral mucosal wounds heal more rapidly with less inflammation, faster re-epithelialization, and minimal scarring. One cell type that may be a differentiating factor is keratinocytes. Using immortalized skin and oral keratinocytes, HaCaT and TIGK, respectively, we found that oral keratinocytes have an enhanced migratory and proliferative capacity. To examine the transcriptomic differences that underlie the improved healing abilities of oral keratinocytes, we generated an RNA-sequencing (RNA-seq) gene expression dataset utilizing HaCaT and TIGK. Differentially expressed genes (DEGs) were identified between HaCaT and TIGK at baseline and throughout the injury response. Gene Ontology (GO) or Reactome enrichment analysis was performed to understand the biological significance of DEGs. Processes related to inflammation and migration were uniquely enriched in TIGK. Additionally, TIGK retained its enhanced migratory capacity when grown on various basement membrane (BM) and extracellular matrix (ECM) substrates. This may be due to the differential expression of matrix metalloproteinases (MMPs) and integrins between HaCaT and TIGK. We also identified genes differentially over or under-expressed in HaCaT and TIGK following injury when compared to each respective cell type’s unwounded gene expression levels. Lastly, we showed that the post-injury secretome of TIGK promotes keratinocyte migration. Our comparative analyses suggest specific transcriptomic differences between oral and skin keratinocytes at unwounded baseline and in response to injury may underlie the distinct wound healing phenotypes seen in these two tissues. This work also provides a source of HaCaT and TIGK gene expression data over healing that can be used for future analyses. To examine the transcriptomic differences that underlie the improved healing abilities of oral keratinocytes, we generated an RNA-sequencing (RNA-seq) gene expression dataset utilizing skin and oral keratinocyte cell lines, HaCaT and TIGK, at 3 distinct time points following in vitro wounding. We first performed comparative gene expression analysis between HaCaT and TIGK to determine differentially down- or upregulated genes in HaCaT relative to TIGK at unwounded baseline (0 h) and throughout healing (6 h and 24 h). Downregulated genes in HaCaT relative to TIGK were considered upregulated in TIGK. Then, to compare the injury responses of HaCaT and TIGK, we studied the differentially expressed genes in HaCaT or TIGK at 6 h or 24 h relative to their 0 h.