HUMAN KERATINOCYTES ARE A MAJOR SOURCE OF CUTANEOUS PLATELET-DERIVED GROWTH-FACTOR

PDGF has been implicated as one of the principal mitogens involved in cutaneous wound healing. While it has been previously reported that bo th platelets and monocytes are a source of PDGF in human dermal wound repair, the production of PDGF by human keratinocytes has not yet been described. In this manuscript, we report the production of PDGF by cu ltured human keratinocytes. Both PDGF A and B chain mRNA can be detect ed in cultured cells. While only PDGF-AA polypeptide is found in signi ficant levels in keratinocyte-conditioned culture media, all three PDG F isoforms (AA, AB, and BB) are present in detergent-solubilized cell extracts. No evidence of PDGF receptor expression was observed in cult ured keratinocytes when analyzed for either mRNA levels or polypeptide expression, suggesting that PDGF does not play an autocrine role in k eratinocyte growth. Analysis of cryosections of human cutaneous wounds by immunostaining for PDGF showed that both PDGF A and B chain is con stitutively expressed in normal epidermis, as well as in newly reconst ituted wound epidermis. No evidence for PDGF receptor polypeptide expr ession in the epidermis was detected by immunostaining of cryosections .