Unique Expression Pattern and Functional Role of Periostin in Human Limbal Stem Cells

Abstract

Periostin is a non-structural matricellular protein. Little is known about periostin in human limbal stem cells (LSCs). This study was to explore the unique expression pattern and functional role of periostin in maintaining the properties of human LSCs. Fresh donor corneal tissues were used to make cryosections for evaluation of periostin expression on ex vivo tissues. Primary human limbal epithelial cells (HLECs) were generated from limbal explant culture. In vitro culture models for proliferation and epithelial regeneration were performed to explore functional role of periostin in LSCs. 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. Periostin protein was found to be exclusively immunolocalized in the basal layer of human limbal epithelium. Periostin localization was well matched with nuclear factor p63, but not with corneal epithelial differentiation marker Keratin 3. Periostin transcripts was also highly expressed in limbal than corneal epithelium. In primary HLECs, 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. Our findings demonstrated that periostin is exclusively produced by limbal basal epithelium and co-localized with p63, where limbal stem cells reside. Periostin promotes HLEC proliferation and regeneration with accompanied activation of stem/progenitor cell markers p63, integrin β1 and TCF4, suggesting its novel role in maintaining the phenotype and functional properties of LSC.

Proteomic profiling of TGFBI‐null mouse corneas reveals only minor changes in matrix composition supportive of TGFBI knockdown as therapy against TGFBI‐linked corneal dystrophies

“…The apparent discrepancy between site of POSTN mRNA expression and protein deposition indicates that corneal surrounding tissues are responsible for active POSTN expression, which then translocates to the corneal periphery. This is supported by a previous study showing that human POSTN is expressed by limbal stem cells which differentiate into the corneal epithelium .…”

Immunohistochemical localization of periostin in human gingiva

“…This is in good agreement with the expected molecular mass of this protein (93.3 kDa), 3 and was similar to that found in other human epithelial tissues like the cornea. 20 The small differences between our results and others could be related to occurrence of tissue specific periostin isoforms, or post-translational processes of the protein. Based on image densitometry the relative level of periostin varies among different segments of the gingiva.…”

“…Nevertheless, other studies on epithelial tissues reported the presence of periostin immunoreactivity in the basal keratinocytes, basal lamina, and dermal fibroblasts in healthy human skin, 21 , 22 or in the basal layer cells of the human corneal epithelium. 20 According to those authors periostin only becomes extracellular during tissue remodeling of wound repair. 21 , 22 Since in normal gingiva periostin is exclusively extracellular, its function may be distinct from that of skin, 17 and the presence of intracellular periostin probably reflects non-secreted protein.…”

Activated hepatic stellate cells secrete periostin to induce stem cell-like phenotype of residual hepatocellular carcinoma cells after heat treatment

“…POSTN also induces proliferation and regeneration of human limbal stem cells with accompanied activation of integrin β1 and TCF4 19 . AKT/GSK-3β/β-catenin pathway has been well studied in cancer stem cell and β-catenin/TCF4/Nanog also has been reported to drive a progenitor-like cell phenotype of tumor cells 20, 21 .…”

“…It has been reported that stromal derived POSTN promotes cancer progression including maintaining the phenotype of cancer stem cell via Akt, Wnt/β-catenin signaling pathway through binding to integrin receptors 18 . POSTN also induces proliferation and regeneration of human limbal stem cells with accompanied activation of integrin β1 and TCF4 19 . AKT/GSK-3β/β-catenin pathway has been well studied in cancer stem cell and β-catenin/TCF4/Nanog also has been reported to drive a progenitor-like cell phenotype of tumor cells 20 , 21 .…”