Are excessive granulation tissue formation and retarded wound contraction due to decreased collagenase activity in wounds in tight-skin mice?

Wound contraction is delayed in tight-skin mice but the mechanism(s) are unknown. The purpose of this study was to investigate collagenase levels and the formation of granulation tissue in experimental wounds in tight-skin mice. One full-thickness skin excision (20 x 20 mm) was made on the back of nine tight-skin and eight normal mice. Granulation tissue analyses were performed 7 days post-operatively. The collagenase activity was determined by the use of a radiolabelled telopeptide-free collagen substrate, and the amount of granulation tissue was determined gravimetrically. Wound contraction was delayed (P < 0.001) in tight-skin mice (mean 22%) compared with normal mice (mean 46%). The collagenase activity was decreased (P < 0.05) by 40%, whereas the quantity of granulation tissue was increased (P < 0.001) by 60% in the wounds of tight-skin mice. Decreased collagenase content may provide one explanation for the delayed contraction of full-thickness wounds in tight-skin mice. Furthermore, this animal would model may prove useful in the understanding of the pathogenesis, and in exploration of treatment, of excessive granulation tissue formation during wound healing.