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K. E. Keller, J. M. Bradley, T. S. Acott; ADAMTS Expression in Trabecular Meshwork and the Effects on Outflow Facility. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4850.
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Matrix metalloproteinases (MMPs) degrade extracellular matrix and increase outflow facility in anterior segment perfusion culture. One subclass of MMPs is the ADAMTSs (a disintegrin and metalloproteinase with thrombospondin type 1 motifs). This study examines the effects of ADAMTSs in outflow facility and investigates their mRNA and protein expression in trabecular meshwork (TM) cells and tissue.
Human and porcine anterior segments in perfusion culture were treated with recombinant ADAMTSs-1, -4, and -5. Outflow facility was constantly monitored. ADAMTS-1, -4, and -5 mRNA expression was quantitated by qRT-PCR in human TM cells treated for 12, 24, and 48 hrs with TNF, IL-1, their combination, and in response to mechanical stretch. ADAMTS-4 mRNA expression was assessed in normal and glaucomatous human anterior segments that were perfused at physiological or increased pressure (2x) for 24 hrs. Immunofluorescence and confocal microscopy was used to determine the localization of ADAMTS-4 and -5 in human TM cells and tissue.
Porcine eyes perfused with 1 µg or 0.5 µg ADAMTS-4 increased outflow facility approximately 2.6- or 2-fold in 48 hrs, respectively. ADAMTS-1 and -5 increased outflow facility 1.3 and 1.4-fold, respectively. Human eyes perfused with 1 µg ADAMTS-4 increased 2.2-fold in 24 hrs, whereas ADAMTS-1 did not increase outflow facility. Cytokine treatments, which increase outflow facility, increased mRNA expression of ADAMTS-4 and -5, especially at 12 and 24 hrs. Mechanical stretch increased ADAMTS-4 mRNA expression but conversely decreased ADAMTS-5 expression. In normal human eyes, ADAMTS-4 mRNA expression increased 2.3-fold in response to pressure. However, glaucoma eyes did not exhibit a similar response. Immunofluorescence and confocal microscopy showed that ADAMTS-4 was expressed in the juxtacanalicular region of the TM in human anterior segments perfused at increased pressure. In human TM cells, ADAMTS-4 co-localized with cortactin in podosome-like structures (PILS), but ADAMTS-5 did not.
These results show differential responses and expression of ADAMTSs -1, -4 and -5 in human TM cells. Combined, these results suggest that ADAMTS-4 is an important regulator of outflow facility.
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