Equine ANXA2 and MMP1 expression analyses in an experimental model of normal and pathological wound repair

Wounds on horse limbs can develop exuberant granulation tissue which resembles the human keloid. Clues gained from the study of over-scarring in horses might help control fibro-proliferative disorders.

The aim of the present study was to clone full-length equine ANXA2 cDNA then to study spatio-temporal expression of ANXA2 and MMP1 mRNA and protein, potential contributors to remodeling, during repair of body (normal) and limb (fibro-proliferative) wounds in an established horse wound model.

Cloning of ANXA2 was achieved by screening size-selected cDNA libraries. Expression was studied in intact skin and in biopsies of 1, 2, 3, 4 and 6-week-old wounds of the body and limb. Temporal gene expression was determined by semi-quantitative RT-PCR while protein expression was mapped immunohistochemically.

ANXA2 mRNA was up-regulated only in body wounds, corroborating the superior and prompt tissue turnover at this location. Immunohistochemistry partially substantiated the mRNA data in that increased staining for ANXA2 protein was detected in neo-epidermis which formed more rapidly and completely in body wounds. MMP1 mRNA levels in body wounds significantly surpassed those of limb wounds in week one biopsies. The protein was abundant in migrating epithelium of limb wounds at weeks two and four; conversely, body wounds in which epithelialization was near complete showed diminished staining of MMP1.

We conclude that ANXA2 and MMP1 might participate in remodeling during wound healing in the horse, and that differences in expression may contribute to the excessive proliferative response seen in the limb.