Periostin, a Potential Marker Associated with Human Corneal Epithelial Stem/Progenitor Cells

Abstract

Purpose: Periostin is a non-structural matricellular protein. Little is known about periostin in human corneal epithelial stem cells (CESCs). This study was to explore the unique expression pattern and functional role of periostin in maintaining the properties of human CESCs.<br />

Methods: Fresh donor corneal tissues were used to make cryosections for evaluation of periostin expression on ex vivo tissues. Primary human corneal epithelial cells (HCECs) were generated from limbal explant culture. In vitro culture models for proliferation and epithelial regeneration were performed to explore functional role of periostin in CESCs. The mRNA expression was determined by reverse transcription and quantitative real-time PCR (RT-qPCR), and the protein production and localization were detected by immunofluorescent staining and Western blot analysis.

Results: Periostin protein was found to be exclusively immunolocalized in the basal layer of human limbal epithelium, where corneal epithelial stem cells reside. Periostin localization was well matched with nuclear factor p63 in limbal basal cells, but not with differentiation marker Keratin 3 expressed by superficial layers of corneal epithelium. Periostin transcripts was also highly expressed in limbal than corneal epithelium. In primary HCECs, periostin expression at mRNA and protein levels was significantly higher in 50% and 70% confluent cultures at exponential growth stage than in 100% confluent cultures at slow growth or quiescent condition. This expression pattern was similar to other stem/progenitor cell markers (p63, integrin β1 and TCF4). Periostin expression at transcripts, protein and immunoreactivity levels increased significantly during epithelial regeneration in wound healing process, especially in 16-24 hours at wound edge, which was accompanied by similar upregulation and activation of p63, integrin β1 and TCF4.

Conclusions: Our findings demonstrated that periostin is exclusively produced by limbal basal epithelium and co-localized with p63. Periostin promotes HCEC proliferation and regeneration with accompanied activation of stem/progenitor cell markers p63, integrin β1 and TCF4, suggesting its novel role in serving as a potential marker for human corneal epithelial stem/progenitor cells.