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Xiaowen Lu, Mitchell A Watsky; Effects of Vitamin D Receptor Knockout on Corneal Epithelial Cell Adherens Junctions. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3877. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Our previous work demonstrated that 1,25-vitamin D3 (Vit D3) influences the function of corneal epithelial cell gap junctions and tight junctions. In addition, we have observed weak epithelial attachment in vitamin D receptor knockout mice (VDR KO) undergoing epithelial debridement for wound healing studies. We hypothesize that VDR KO negatively affects corneal epithelial cell adherens junctions including desmosomes (intracellular junctions) and/or hemidesmosomes (cell to basement membrane junctions).
Corneal epithelial cells from VDR wildtype (WT), heterozygous (HET), and KO mice were collected, and total RNA was isolated. Protein was collected from whole mouse corneas and a human epithelial cell line (HCEC). Transcript levels of desmosome and hemidesmosome proteins were assessed by qPCR. Desmosome transcripts evaluated included desmoglein 1 and desmocollin 2, and hemidesmosome transcripts included Types IV and VII collagen, α6β4 integrin, and bullous pemphigoid antigen 1 (BPAG1). Western blotting was used to detect desmoglein and desmocollin protein levels. Desmoglein 1 protein levels were also assessed in HCEC exposed to 1,25- or 24,25-Vit D3.
Desmoglein 1, desmocollin2, integrin β4, and type IV collagen mRNA were all significantly decreased in VDR KO corneas. Transcript levels of desmocollin2, β4 integrin, and type IV collagen were also significantly decreased in VDR HET mice. BPAG1 mRNA was not affected. Desmosome-associated desmoglein 1 protein expression was reduced in VDR HET and KO mouse corneas as compared to VDR WT. No other desmosome or hemidesmosome protein levels were significantly changed in VDR KO corneas. Treatment of HCEC cells with 1,25- and 24,25-Vit D3 both resulted in increased expression of desmoglein 1 protein.
While both desmosome and hemi-desmosome mRNA levels were affected by VDR KO, the only protein level affected was desmoglein 1. In addition, both 1,25- and 24,25- VitD3 increased desmoglein 1 protein expression levels in HCEC. Thus, Vit D3 appears to be involved in desmosome formation/regulation. The hemidesmosome-associated proteins we examined were not affected by VDR KO or Vit D3 exposure. Poorly formed desmosomes likely contribute to easily removed corneal epithelium in VDR KO mice.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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