Abstract
Purpose:
Periostin functions as a ligand for integrins to support adhesion and migration of epithelial cells. Periostin has been recently known as a component of the extracellular matrix expressed by fibroblasts in normal tissues and stroma of primary tumors. Periostin over-expression was reported in several types of cancers. However, little is known about periostin in human corneal epithelium. This study was to explore the expression pattern and potential role of periostin in maintaining the properties of human corneal epithelial progenitor cells.
Methods:
Fresh donor corneal limbal tissues were used to make cryosections and isolate corneal and limbal epithelia. The primary human corneal epithelial cells (HCECs) were generated from limbal tissue explants. The mRNA expression was evaluated by reverse transcription and quantitative real-time PCR, and the protein production and localization were detected by immunofluorescent staining and Western blot analysis. The expression and functional role of periostin were further evaluated in primary HCECs at different growth stages and in an in vitro wound healing model at different time points
Results:
Periostin protein was highly immunolocalized in the basal cells of human limbal epithelium where corneal epithelial stem cells locate. Periostin immunoreactivity was co-localized with epithelial stem cell associated marker nuclear p63, but not co-localized with the corneal epithelial differentiated marker Keratin 3. Periostin mRNA was expressed higher in limbal epithelium than that in central corneal epithelium. In primary HCECs, the mRNA expression and protein production of periostin were much higher in the 50% confluent cultures containing higher proliferative cells, than that in the 70% and 100% confluent cultures containing more differentiated cells. In an in vitro wound healing model, periostin mRNA levels were significantly and gradually up-regulated in 4-16 hours, and this up-regulation was further confirmed at protein levels in 16-48 hours by Western blot analysis
Conclusions:
These findings demonstrated that periostin is a novel protein that is mainly expressed by basal layer of human limbal epithelial cells and co-localized with p63. Periostin expression is associated with higher proliferative capacity and less differentiation conditions in HCECs. Periostin may have a potential role in maintaining the properties of human corneal epithelial progenitor cells
Keywords: 482 cornea: epithelium •
721 stem cells •
654 proliferation