Cellular fibronectin expression in human trabecular meshwork and induction by transforming growth factor-β2

Area of Science:

• Ophthalmology
• Cell Biology
• Biochemistry

Background:

• Elevated transforming growth factor-beta 2 (TGF-β2) in primary open-angle glaucoma (POAG) aqueous humor correlates with extracellular matrix (ECM) deposition in the human trabecular meshwork (HTM).
• This ECM deposition, including fibronectin (FN), may contribute to increased intraocular pressure (IOP) in glaucoma.

Purpose of the Study:

• To investigate the expression of cellular fibronectin (cFN) isoforms, specifically EDA and EDB, in HTM cells and tissues.
• To determine if TGF-β2 can stimulate cFN expression and fibril formation in cultured HTM cells.

Main Methods:

• Quantitative RT-PCR was used to assess cFN mRNA isoform expression and TGF-β2 induction.
• Western immunoblots and immunocytochemistry analyzed TGF-β2's effect on EDA isoform protein and FN fibril formation.
• Immunohistochemistry examined total FN and EDA isoform levels in normal (NTM) and glaucomatous (GTM) trabecular meshwork tissues.

Main Results:

• Both cFN mRNA isoforms were expressed in HTM cells and significantly upregulated by TGF-β2 over 7 days.
• TGF-β2 treatment increased EDA isoform protein expression and FN fibril formation in cultured HTM cells.
• GTM tissues exhibited significantly higher EDA isoform protein levels (1.7-fold) compared to NTM tissues.

Conclusions:

• Cellular fibronectin (cFN) isoforms are expressed and induced by TGF-β2 in human trabecular meshwork (HTM) cells.
• Elevated EDA isoform protein levels in glaucomatous human trabecular meshwork (GTM) tissues were observed.
• Induction of cFN isoform expression in the trabecular meshwork ECM represents a potential novel mechanism in glaucoma pathogenesis.