SOX9 modulates Müller cell gliosis in diabetic retinopathy through upregulating TXNIP transcription

Diabetic retinopathy (DR), a common complication of diabetes, involves excessive proliferation and inflammation of Muller cells and ultimately leads to vision loss and blindness. SRY-box transcription factor 9 (SOX9) has been reported to be highly expressed in Müller cells in retinal light-damaged rats, but the functional role of SOX9 in DR remains unclear. To explore this issue, the DR rat model was successfully constructed via injecting with streptozotocin (STZ, 65 mg/kg) and the retinal thicknesses and blood glucose levels were evaluated. Müller cells were treated with 25 mmol/L glucose to create a cell model in vitro. The results indicated that SOX9 expression was significantly increased in DR rat retinas and high glucose (HG)-stimulated Müller cells. HG treatment promoted the proliferation and migration capabilities of Müller cells, whereas SOX9 knockdown reversed those behaviors. Moreover, SOX9 knockdown protected against HG-induced inflammatory response, as evidenced by reduced tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 levels in serum and decreased NLRP3 inflammasome activation. Notably, SOX9, acted as a transcription factor that positively regulated thioredoxin-interacting protein (TXNIP), a positive regulator of Müller cells gliosis under HG conditions. Dual luciferase assay demonstrated that SOX9 could enhance TXNIP expression at the transcriptional level through binding to the promoter of TXNIP. Moreover, TXNIP overexpression restored the effects caused by SOX9 silencing. In conclusion, these findings demonstrate that SOX9 may accelerate the progression of DR by promoting glial cell proliferation, metastasis, and inflammation, which involves the transcriptional regulation of TXNIP, providing new theoretical fundamentals for DR therapy.

Müller cell gliosis; SRY-box transcription factor 9 (SOX9); diabetic retinopathy; inflammation; the TXNIP promoter.