FILIP1L-mediated cell apoptosis, epithelial-mesenchymal transition and extracellular matrix synthesis aggravate posterior capsular opacification

Aims: The epithelial-mesenchymal transition (EMT), extracellular matrix (ECM) synthesis and cell migration of residual lens cells constitute the canonical mechanisms of posterior capsular opacification (PCO). Recently, myofibroblast cell apoptosis is also observed in the rabbit PCO model. However, whether cell apoptosis is a key factor affecting PCO and regulates EMT/ECM/cell migration remains obscure.

Main methods: Flow cytometry was utilized to assess cell cycle and apoptosis. EMT marker α-smooth muscle actin (α-SMA), ECM markers fibronectin (Fn) and type 1 collagen (COL-1) and apoptosis-associated proteins in the presence or absence of EMT/ECM inhibitor (LY2109761), apoptosis inhibitor (ZVAD) or apoptosis activator (BTSA1) were detected by Western blotting. Downstream effector genes in apoptosis-induced lens epithelial cell lines (LECs) were analyzed by RNA-seq. Gene silencing and overexpression in LECs were performed to validate the role of effector genes. We measured cell migration capability using Wound healing and Transwell assays.

Key findings: We found that TGF-β2 induced cell apoptosis. ZVAD inhibited α-SMA expression in the ex vivo capsule model and decreased the expression of both EMT and ECM markers in TGF-β2-treated LECs. RNA-seq revealed that FILIP1L was significantly decreased in apoptosis-activated cells. We further validated that the knockdown of FILIP1L could enhance EMT and ECM synthesis and promote cell migration and that FILIP1L overexpression could reverse these effects. Apoptosis might contribute to TGF-β2-induced EMT and ECM synthesis during PCO, and these contributions are mediated by FILIP1L.

Significance: Our findings uncover the role of apoptosis in PCO development and provide new drug targets.

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S8650	BTSA1	BTSA1 is a pharmacologically optimized BAX activator that binds with high affinity and specificity to the N-terminal activation site and induces conformational changes to BAX leading to BAX-mediated apoptosis. It effectively promotes apoptosis in leukemia cell lines and patient samples while sparing healthy cells.

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Bcl-2