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Joseph Stevenson, Yan Wang, Mahbubul H Shihan, Melinda K Duncan; Cholesterol-25 Hydroxylase Mediates PCO Pathogenesis. Invest. Ophthalmol. Vis. Sci. 2020;61(7):5036.
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© ARVO (1962-2015); The Authors (2016-present)
Cataract surgery is effective but causes acute sterile inflammation within 24 hours after surgery which can take days or weeks to subside. Further, the wound healing activity of lens epithelial cells (LECs) induces posterior capsular opacification (PCO). However, the relationship between inflammation post cataract surgery (PCS) and PCO is not known. RNAseq revealed that cholesterol-25 hydroxylase (CH25H) expression is upregulated 6.5-fold within 24 hours PCS. Its product, 25-hydroxycholesterol, is a major mediator of both inflammatory and fibrotic responses via its interactions with α5β1 integrin, NFκB, and AP-1 transcription factors. However, the functional significance of CH25H upregulation in LECs PCS is unknown.
The time course of CH25H mRNA expression levels PCS was extracted from RNAseq data obtained from mouse LECs isolated at 0, 6, 24, 48, and 120 hours after lens fiber cell removal from wild-type (WT) lenses which models cataract surgery. CH25H-/- mice (B6.129S6-Ch25htm1Rus/J) and WT controls were subjected to surgery, and eyes harvested, at 0, 6, 24, 48, 72, and 120 hours PCS. The extent of inflammatory and fibrotic responses was assessed by immunostaining eye sections with antibodies specific for inflammation, fibrosis, and indicators of pathway activation.
Unoperated adult CH25H-/- lenses are phenotypically identical to WT. However, the expression of some inflammatory markers, including S100a9 and Cox2, are attenuated in CH25H-/- LECs at 24 hours PCS. Some indicators of fibrosis, including Tenascin-C and αSMA expression, and elevated LEC count, are attenuated in CH25H-/- lenses at 3 and 5 days PCS when robust fibrosis is seen in WT. However, the elevated levels of the integrin subunits α5 and β1, and FAK phosphorylation, which typically are associated with LEC fibrosis, are similar in WT and CH25H-/- lenses at 3 and 5 days PCS. Invasion of CD11b positive neutrophils into the capsular bag at 24 hours PCS, and F4/80 positive macrophages at 3 days PCS are also unaltered in CH25H-/- mice.
LECs lacking CH25H mount diminished inflammatory and fibrotic responses to surgery. However, this effect is likely not mediated via its known influence on a5b1 integrin signaling, suggesting that other mechanisms are responsible for the observed effects.
This is a 2020 ARVO Annual Meeting abstract.
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