Abstract
Purpose: :
Connective tissue growth factor (CTGF) is a key modulator of trabecular meshwork (TM) actin cytoskeleton and of TM extracellular matrix (ECM) synthesis. Both TM actin cytoskeleton and ECM turnover are involved in modulation of aqueous humor outflow resistance. Aqueous humour of patients suffering from primary open-angle glaucoma (POAG) contains higher amounts of CTGF than normal. The molecular mechanisms that lead to a higher expression of CTGF in the eye are unclear. In the present study, we analyzed various substances and stress conditions related to POAG for their capability to stimulate CTGF expression in human TM cells in vitro.
Methods: :
Primary human TM cells were treated under serum free medium conditions with Endothelin 1, Angiotensin II, Insulin-like Growth Factor (IGF), Transforming Growth Factor (TGF)-β1 and 2, or Latrunculin A. Cellular stress was induced by treatment with different concentrations of H2O2 and by heat shock. Changes in the expression of CTGF were examined by quantitative real-time RT-PCR, western blotting and immunohistochemistry.
Results: :
Treatment with TGF-β1 and 2, IGF and Angiotensin II caused a profound increase (p<0.05) of CTGF and its mRNA within 24h. Endothelin-1 did not lead to an alteration of CTGF expression after short-term treatment, but showed a significant (p<0.05) increase of CTGF after 3 days. Following oxidative stress, the expression of CTGF increased within 6h after treatment. Following heat shock at 42°C, the expression of CTGF increased within 30 min after incubation. In contrast, the disruption of the actin cytoskeleton by Latrunculin A led to a substantial decrease of CTGF mRNA expression and CTGF synthesis in TM cells.
Conclusions: :
The expression of CTGF is under positive control of various signaling factors and molecular mechanisms that have been implicated to be causatively involved in the pathogenesis of POAG. CTGF appears to be a central downstream mediator in the pathogenesis of POAG.
Keywords: trabecular meshwork • growth factors/growth factor receptors • stress response