Aqueous humor TGF-β2 levels in patients with open-angle glaucoma: A meta-analysis

INTRODUCTION Elevated intraocular pressure (IOP) in glaucomatous eyes is often due to increased resistance to aqueous outflow. Previous studies have shown that increased extracellular material deposition in outflow pathways leads to increased resistance to aqueous outflow, and transforming growth factor (TGF)-β seems to play a role in the deposition of extracellular material. TGF-β2 is the predominant isoform in ocular tissue. Hence, comparison of the aqueous humor TGF-β2 level between patients with open-angle glaucoma (OAG) and controls would provide direct evidence for the role of TGF-β2 in the etiology of OAG. Hence, we performed this meta-analysis to develop an accurate estimate of the changes in aqueous humor TGF-β2 levels among OAG patients. METHODS We undertook the meta-analysis of data from all available studies that had a case-control design and investigated the aqueous humor levels of TGF-β2 (total, active, or both) in OAG patients. OAG included primary OAG (POAG), secondary glaucoma, pseudoexfoliation syndrome, and exfoliation glaucoma (EXG). RESULTS We selected a total of eight studies that measured TGF-β2 levels in the aqueous humor of glaucomatous eyes. The studies included in this meta-analysis clearly demonstrated that in OAG eyes, total TGF-β2 levels are significantly elevated, whereas in POAG eyes, both the total and active TGF-β2 levels are significantly higher than in controls. CONCLUSIONS The analysis of pooled data showed that aqueous humor TGF-β2 levels are elevated in patients with OAG and POAG.