Pgc1α Sustains Mitochondrial Health To Attenuate Lens Epithelial Fibrosis In Fibrotic Cataracts

Lens epithelial fibrosis is a predominant pathological process of fibrotic cataracts, including posterior capsular opacification and anterior subcapsular cataract. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α), a member of coactivators that fine-tune vital cellular activities, is the key regulator of mitochondrial biogenesis and function. This study aims to explore the role of PGC1α in lens epithelial fibrosis during the development of fibrotic cataracts.

1. To investigate effects of TGFβ2 on lens epithelial cells (LECs), control and TGFβ2 groups were separated.
2. To explore the role of PGC1α in lens epithelial fibrosis, rat lenses were divided into siNC, siPGC1α, siNC+TGFβ2, siPGC1α+TGFβ2 groups.
3. To examine the impact of PGC1α upregulation on mitochondria, oeNC, oePGC1α, oeNC+TGFβ2, oePGC1α+TGFβ2 groups were separated.
4. To study effects of PGC1α upregulation on lens transparency, rat lenses were divided into DMSO, ZLN005, DMSO+TGFβ2, ZLN005+TGFβ2 groups.

TGFβ2 (10ng/ml) was used to induce epithelial fibrosis in rat lenses for up to 4 days and epithelial-mesenchymal transition (EMT) of rabbit primary LECs (pLECs) for 2 days. PGC1α silencing was conducted in rat lenses to investigate the role of PGC1α in lens epithelial fibrosis. ZLN005 (20uM) was used to activate PGC1α in rat lenses. Immunofluorescent staining showed the expression of PGC1α, mesenchymal markers fibronectin and α-smooth muscle actin. Rat lens transparency was photographed under a stereoscope. H&E staining showed LECs morphology and organization. Transmission electron microscopy showed mitochondrial ultrastructure. ATP content assay was used to assess mitochondrial bioenergetic function.

PGC1α were significantly decreased in fibrotic lens epithelium induced by TGFβ2. In whole rat lenses, anterior subcapsular opacification manifested in lens epithelial fibrosis occurred after 4-day TGFβ2 treatment. Whereas after PGC1α knockdown, TGFβ2-treated lenses turned cloudy early in 2 days. PGC1α deficiency also aggravated EMT of LECs in fibrotic clumps. Notably, TGFβ2 induced dysregulated mitochondria exhibiting distorted cristae and ATP generation in pLECs. However, PGC1α overexpression retained normal cristae structure and mitochondrial ATP generation in pLECs. ZLN005, a small-molecule activator for PGC1α, attenuated the formation of subcapsular fibrotic clumps via increasing PGC1α to restabilizing mitochondria.

PGC1α, a central determinant of mitochondrial function, safeguards lens epithelium against fibrosis and plays an anti-fibrotic role to protect lens epithelial integrity by stabilizing mitochondria under TGFβ2 stress, offering promising strategies targeting PGC1α and mitochondria for preventing and treating fibrotic cataracts.