Purpose: Matrix metalloproteinases (MMPs) degrade extracellular matrix (ECM) and increase outflow facility in anterior segment perfusion culture. One group is the ADAMTSs (a disintegrin and metalloproteinase with thrombospondin type 1 motifs). In this study, the authors examined the effects of ADAMTS-1, -4, and -5 on outflow facility and investigated their mRNA levels and protein expression in the trabecular meshwork (TM).
Methods: ADAMTS mRNA was quantitated by qRT-PCR in TM cells exposed to TNFalpha, IL-1alpha, TGFbeta2, or mechanical stretch. ADAMTS-4 mRNA was assessed in normal and glaucomatous human anterior segments perfused at physiological or elevated pressure. Immunofluorescence was used to localize ADAMTSs in human TM cells and tissue. Anterior segments in perfusion culture were treated with recombinant ADAMTSs to determine effects on outflow facility.
Results: Cytokine treatment increased mRNA of all three ADAMTSs. Mechanical stretch increased ADAMTS-4 mRNA but conversely decreased ADAMTS-1 and -5 mRNA. ADAMTS-4 mRNA levels increased in response to pressure elevation in normal eyes and to higher levels in glaucomatous eyes. ADAMTS-4 protein was highly increased in the juxtacanalicular region of the TM in anterior segments perfused at increased pressure. In human TM cells, ADAMTS-4 colocalized with cortactin in podosome- or invadopodia-like structures, but ADAMTS-1 and -5 did not. Recombinant ADAMTS-4 increased outflow facility in human and porcine anterior segments, whereas recombinant ADAMTSs-1 and -5 did not.
Conclusions: These results show differential responses and expression of ADAMTS-1, -4, and -5 in human TM cells. Combined, these results suggest that ADAMTS-4 is a potential modifier of outflow facility.