TGF-β2-induced invadosomes in human trabecular meshwork cells.

Area of Science:

• Ophthalmology
• Cell Biology
• Biochemistry

Background:

• Primary open-angle glaucoma (POAG) is a leading cause of blindness linked to retinal ganglion cell degeneration and intraocular pressure dysregulation.
• Elevated intraocular TGF-β2, aberrant ECM deposition, and increased outflow resistance in the trabecular meshwork (TM) are implicated in POAG.
• The precise mechanisms driving TM changes in POAG, particularly TGF-β2's role in ECM regulation, remain unclear.

Purpose of the Study:

• To investigate the effects of TGF-β2 on invadosomes, critical sites of cell-matrix interaction and matrix metalloproteinase (MMP) activity, in human TM (HTM) cells.
• To determine if TGF-β2 promotes ECM degradation or deposition in HTM cells.
• To explore the potential role of invadosomal signaling in POAG pathophysiology.

Main Methods:

• Human TM cells were treated with TGF-β2 and analyzed for invadosome formation, ECM degradation, MMP activity, and gene expression.
• Invadosomes were identified by colocalization of specific proteins to sites of gelatinolysis.
• MMP-2 activity was assessed using zymography, protein levels by western blot, and ECM gene transcription by RT-qPCR.

Main Results:

• TGF-β2 significantly enhanced invadosomal proteolysis and MMP-2 activity in HTM cells.
• Levels of MMP-2, TIMP-2, and PAI-1 were increased by TGF-β2, and these effects were blocked by Rho-kinase inhibition.
• TGF-β2 upregulated the transcription of fibronectin and collagens, with increased fibrillar fibronectin deposits observed around invadosomes.

Conclusions:

• Contrary to prevailing hypotheses, TGF-β2 induces active ECM remodeling in TM cells, characterized by simultaneous increases in ECM digestion and expression.
• Invadosomes are key players in this TGF-β2-mediated ECM remodeling process.
• Invadosomal cell adhesion and signaling pathways may contribute to the pathophysiology of POAG.