Distribution of MMP-26 in Human Anterior Segment Tissues

Abstract

Abstract: : Purpose: Matrix metalloproteinase-26 (MMP-26) is a newly-described zinc endopeptidase with a unique PHCGXXD cysteine-switch motif and unconventional autocatalytic activation mechanisms. MMP-26 is relatively similar to MMP-7 but exhibits distinct tissue expression pattern and gene regulation. This study was undertaken to determine the distribution of MMP-26 in normal human eyes. Methods: Postmortem human eyes from four donors were fixed in methacarn (containing methanol, chloroform, and acetic acid) and anterior segment tissues were embedded in paraffin. Tissue sections were immunostained with an affinity-purified polyclonal rabbit antibody generated against the recombinant catalytic domain of MMP-26 followed by fluorescent goat-anti-rabbit IgG antibodies. Parallel immunostaining was performed with the same primary antibody, followed by a biotinylated secondary antibody, avidin-linked horseradish peroxidase, and diaminobenzidine development. Sclera and adjacent tissues near the angle from an additional eye were homogenized and MMP-26 gene expression was analyzed by RT-PCR and gene arrays. Results: Strong MMP-26 immunoreactivity was observed in the corneal and conjunctival epithelium while moderate immunoreactivity was found in the ciliary epithelium and corneal fibroblasts. Other anterior segment tissues contained minimal MMP-26 immunoreactivity. RT-PCR and gene arrays confirmed the presence of MMP-26 mRNA. Conclusions: MMP-26 is expressed in epithelia adjacent to the cornea, conjunctiva, and ciliary body. Small amounts of MMP-26 also may be expressed in corneal fibroblasts. The role of MMP-26 in these tissues is unknown.

Keywords: anterior segment • ciliary body • anatomy