ID1 and ID3 are Negative Regulators of TGFbeta2-Induced Ocular Hypertension and Compromised Aqueous Humor Outflow Facility in Mice

Purpose: In POAG, elevated IOP remains the major risk factor in irreversible vision loss. Increased TGFbeta2 expression in POAG aqueous humor and in the trabecular meshwork (TM) amplifies extracellular matrix (ECM) deposition and reduces ECM turnover in the TM, leading to a decreased aqueous humor (AH) outflow facility and increased IOP. Inhibitor of DNA binding proteins (ID1 and ID3) inhibit TGFbeta2-induced fibronectin and PAI-1 production in TM cells. We examined the effects of ID1 and ID3 gene expression on TGFbeta2-induced ocular hypertension and decreased AH outflow facility in living mouse eyes. Methods: IOP and AH outflow facility changes were determined using a mouse model of Ad5-hTGFbeta2C226S/C288S-induced ocular hypertension. The physiological function of ID1 and ID3 genes were evaluated using Ad5 viral vectors to enhance or knockdown ID1/ID3 gene expression in the TM of BALB/cJ mice. IOP was measured in conscious mice using a Tonolab impact tonometer. AH outflow facilities were determined by constant flow infusion in live mice. Results: Over-expressing ID1 and ID3 significantly blocked TGFbeta2-induced ocular hypertension (P < 0.0001). Although AH outflow facility was significantly decreased in TGFbeta2-transduced eyes (P < 0.04), normal outflow facility was preserved in eyes injected concurrently with ID1 or ID3 along with TGFbeta2. Knockdown of ID1 or ID3 expression exacerbated TGFbeta2-induced ocular hypertension. Conclusions: Increased expression of ID1 and ID3 suppressed both TGFbeta2-elevated IOP and decreased AH outflow facility. ID1 and/or ID3 proteins thus may show promise as future candidates as IOP-lowering targets in POAG.