Keratinocytes stimulate fibroblast hyaluronan synthesis through the release of stratifin: a possible role in the suppression of scar tissue formation.

Scar tissue formation during healing of extensive skin wounds may be related to delayed reepithelialization, while elevated levels of hyaluronan may suppress scar tissue formation. This study investigates the expression of hyaluronan by human skin fibroblasts in response to keratinocyte-conditioned medium (KCM), and attempts to identify any active factors within the conditioned medium. Serum-free KCM was assessed for its ability to stimulate the incorporation of 3H-glucosamine into fibroblast glycosaminoglycans, and hyaluronan synthesis. Conditioned medium was concentrated with an ultrafiltration membrane with a 30 kDa cutoff. Stratifin was assessed for its ability to stimulate hyaluronan synthesis and its role in KCM. KCM stimulated fibroblast glycosaminoglycan synthesis up to a 3.3-fold increase and a 6.5-fold increase in hyaluronan synthesis compared with serum-free controls. Preliminary characterization of the active factors showed that they are retained by a > 30 kDa ultrafiltration membrane, and are protease sensitive and heat resistant. Emmprin and stratifin were shown to stimulate fibroblast hyaluronan synthesis, and the hyaluronan-stimulating activity of KCM was removed following stratifin depletion and to a lesser extent by emmprin depletion. Keratinocytes release soluble factors, including stratifin, that stimulate fibroblast hyaluronan synthesis, and this stimulation of fibroblast hyaluronan may contribute to the suppression of scar tissue formation.