The Effect of CTGF on Trabecular Meshwork and the Implications for Pseudoexfoliative Syndrome

Abstract

Purpose: : Connective Tissue Growth Factor (CTGF) is a recognised profibrotic downstream mediator of transformation growth factor–beta (TGF–ß) in many diseases. Pseudoexfoliation syndrome (PXF) is a generalised disorder of the extracellular matrix (ECM) characterized by excessive production and progressive accumulation of fibrillar material in ECM in both ocular and extraocular tissues. The trabecular meshwork (TM) cells are a common source of pseudoexfoliative material (PXM) and the accumulation of the PXM has been shown to be one of the major factors for development of severe glaucoma associated with this disease.

Methods: : Aqueous humour samples were obtained from patients who were undergoing routine cataract surgery or trabeculectomy after informed consent. Patient demographic data, preoperative intraocular pressures and medcations were recorded. CTGF levels were quantified in each sample using enzyme immunoassays. Investigation of the effect of CTGF on the ECM component of the primary human TM cells using both RT–PCR and real–time PCR (Taqman) was carried out. Western blotting was used to study the MAP Kinase signalling pathway and the parallel activity of JNK following stimulation of these cells by CTGF.

Results: : The PXF with glaucoma group had the highest aqueous humour mean CTGF level of 5.15 ± 0.79 (SEM)ng/ml and this is statistically significant (p<0.01) when compared with PXF without glaucoma (2.76 ± 0.64ng/ml), POAG (3.05 ± 0.40ng/ml) and controls (2.60 ± 0.29ng/ml). Moreover in vitro exposure of TM cells to CTGF resulted in a 50% upregulation of extracellular component fibrillin and 30% upregulation of fibronectin. Western blot analysis demonstrates increased phosphorylation of both the ERK1/2 and the JNK pathways in response to CTGF.

Conclusions: : PXF patients with glaucoma have higher aqueoues CTGF than POAG and PXF without glaucoma. CTGF drives the production of fibrillin and fibronectin by TM cells – two important ECM components in PXF. CTGF mediates its effects via the ERK1/2 and JNK signalling pathways.

Keywords: trabecular meshwork • extracellular matrix • growth factors/growth factor receptors