Upregulation of Arginase Expression in Wound-Derived Fibroblasts

Background. Wound-derived fibroblasts (WFBs) are phenotypically different from normal dermal fibroblasts (NFBs). We have previously shown that the wound phenotype correlates with expression of the inducible isoform of nitric oxide synthase (iNOS) in fibroblasts. l-Arginine is the sole substrate for iNOS. Arginase is an alternative pathway of l-arginine metabolism in wounds. To clarify the role of l-arginine in wound healing, we investigated arginase expression and activity in WFB. Methods. Male Lewis rats underwent dorsal skin incisions and subcutaneous PVA sponge implantation. WFBs were harvested from sponges retrieved at different days postimplantation. Normal fibroblasts were obtained from uninjured skin by an explant technique. Arginase activity was measured by newly formed urea (nmol/min/mg protein) and protein expression was detected by Western blotting using specific antibodies for type I (AI) and type II (AII). The effect of transforming growth factor β1 (TGF-β1), interleukin-4 (IL-4), lipopolysaccharide, and wound fluid on arginase activity was also investigated. Results. WFB arginase activity was significantly elevated compared with NFB activity at all times postwounding. This was paralleled by increased AI protein expression by Western blotting. AII was not detectable. TGF-β and IL-4 significantly increased arginase activity and protein expression whereas lipopolysaccharide and wound fluid did not affect it. Conclusions. The upregulation of the arginase expression in WFB underlines the distinct regulation of l-arginine metabolism in WFBs. Further work is needed to elucidate the functional implications.