Hyperactive PDGFRβ signaling induces cataractogenesis via TGFβ and STAT5-IGF1

Cataracts are the world's leading cause of reversible blindness. Although cataract formation is commonly initiated by lens fiber cell defects, cataractogenesis can be characterized by aberrant proliferation and migration of lens epithelial cells. Subsequent overproduction of extracellular matrix components such as fibronectin and collagen by epithelial cells is associated with fibrosis of the lens. Little is known about the role of platelet-derived growth factor receptor β (PDGFRβ) in lens fibrosis. Here, we investigated mice with a conditional knock-in of PDGFRβ hyperactivation using a Fsp1, also known as S100A4, promoter (Fsp1-cre;Pdgfrb^+/D849V), which consistently develop cataracts at a young age.

Lenses from Fsp1-cre;Pdgfrb^+/D849V mice and age-matched controls were dissected and visualized via microscopy from 9 to 15 weeks. Early transcriptional changes of the lenses were investigated between 10 and 12 day old Fsp1-cre;Pdgfrb^+/D849V and control mice via RNA sequencing followed by gene set enrichment analysis. Confirmation of RNA sequencing results and mechanistic investigation of PDGFRβ-induced cataractogenesis were determined in lenses isolated from 15-week-old Fsp1-cre;Pdgfrb^+/D849V and control mice.

Gross examination of cataractous lenses from Fsp1-cre;Pdgfrb^+/D849V mice revealed complete opacification by 15 weeks of age compared to no opacification in age-matched controls. Structural changes in the anterior, equatorial, and posterior lens were observed in histology. RNA sequencing revealed significant enrichment of gene sets related to extracellular matrix deposition and reorganization. Mechanistic investigation revealed major roles for TGFβ, Wnt/β-catenin, SOCS2, and STAT5-IGF1 signaling axes in PDGFRβ-induced cataract formation.

PDGFRβ promoted cataractogenesis by modulating pro-fibrotic extracellular matrix changes, likely through TGFβ, Wnt/β-catenin, SOCS2, and the STAT5-IGF1 pathways. Future experiments will delineate the precise role of the STAT5-IGF1 signaling pathway in PDGFRβ-mediated fibrosis and the interplay between PDGFRβ and TGFβ in the lens and whether this signaling is targetable to modulate cataractogenesis.