Molecular analysis of different phases in human wound healing

Cultured granulation fibroblasts grown from punch biopsies of the same lower arm area, obtained 3, 6, 9 and 14 days after wounding, were used as a human wound healing model in comparison to quiescent fibroblasts. We investigated the expression of key extracellular matrix components at the protein level by flow cytometry and mRNA steady state levels by Northern blotting of the different fibroblasts and compared these data to the ability to migrate towards a chemotactic signal. Procollagen alpha 1 (I), fibronectin and matrix metalloprotease-1 synthesis was strongly up-regulated at the mRNA steady state level on days 3 and 14. Tissue inhibitor of metalloprotease-1 mRNA is only 20% down-regulated between day 3 and 14. Chemotaxis towards conditioned medium reflects a net effect of several factors and is distinctly different from chemotaxis towards platelet-derived growth factor, which peaks at day 3. Compared to the protein level, the enhanced expression of the corresponding PDGF receptor beta chain mRNA is delayed by 3 to 6 days. PDGF receptor alpha shows no regulatory changes during the observation period. This data further supports the idea that functionally divergent subpopulations of fibroblasts exist during wound healing.