Role of semaphorin7A in epithelial-mesenchymal transition and proliferative vitreoretinopathy

Proliferative vitreoretinopathy (PVR) is a multifactorial ocular condition characterized by the development of fibrotic membranes inside the vitreous cavity and on the detached retina, which can result in severe blindness. Semaphorin7A (Sema7a) is involved in axon growth, inflammatory responses, and immune regulation; however, its role in PVR and regulatory mechanisms in retinal pigment epithelium (RPE) cells remains unclear. This study aimed to examine Sema7a in PVR and the underlying mechanisms. Transcriptome sequencing was used to investigate the changes in mRNA expression profiles. Western blotting, immunofluorescence, and real-time polymerase chain reaction (RT-PCR) were utilized to investigate the potential mechanism of Sema7a on epithelial-mesenchymal transition (EMT) in RPE cells. Stimulating RPE cells with transforming growth factor beta-1 (TGF-β1) decreased the levels of epithelial markers but increased those of mesenchymal markers. Based on transcriptome sequencing, many molecules associated with PVR progression were regulated. PVR vitreous fluid proteomics data analysis showed that Sema7a significantly changed at different levels. Silencing Sema7a in RPE cells attenuated TGF-β1-induced EMT and their ability to induce experimental PVR; in contrast, recombinant Sema7a (rSema7a) directly triggered EMT in RPE cells. TGF-β1 induction mechanically activated the PI3k-AKT and MAPK pathways, while Sema7a knockdown by short interfering RNA lowered the phosphorylation of the PI3k-AKT/MAPK signaling pathway. Therefore, Sema7a may be a viable therapeutic target for PVR due to its crucial role in the TGF-β1-induced EMT of RPE cells.