Epithelial mesenchymal transition-like phenomenon in trabecular meshwork cells

Area of Science:

• Ocular Biology
• Cellular Biology
• Extracellular Matrix Research

Background:

• The trabecular meshwork (TM) is crucial for aqueous humor outflow; fibrosis and excess extracellular matrix (ECM) in the TM elevate outflow resistance.
• Understanding TM cell behavior in response to ECM is vital for addressing conditions like glaucoma.

Purpose of the Study:

• To investigate how ECM components induce an epithelial mesenchymal transition (EMT)-like phenomenon in TM cells.
• To elucidate the molecular pathways, including c-Jun N-terminal kinase (JNK) and paxillin, involved in ECM-mediated TM cell changes.

Main Methods:

• Isolation and culture of cynomolgus monkey TM cells.
• Stimulation with ECM components (type I collagen, fibronectin, laminin) and assessment of EMT markers via western blot and immunocytochemistry.
• Evaluation of cell motility using wound healing and chemotaxis assays.
• Inhibition studies using a JNK inhibitor (SP600125) and siRNA-mediated knockdown of paxillin.

Main Results:

• ECM components induced cell-cell dissociation, actin stress fiber elongation, and increased expression of mesenchymal markers (fibronectin, α-smooth muscle actin) in TM cells.
• TM cell motility was significantly accelerated by ECM stimulation, an effect inhibited by SP600125.
• Paxillin knockdown blocked EMT-like alterations and chemotaxis toward TGF-β2.

Conclusions:

• The ECM-JNK-paxillin pathway drives an EMT-like phenomenon in TM cells, promoting fibronectin expression and enhanced motility.
• This ECM-induced EMT-like process in TM cells may contribute to abnormal aqueous outflow pathway conditions observed in glaucoma.