Transcription and Expression of Transforming Growth Factor Type Beta in the Skin of Progressive Systemic Sclerosis: A Mediator of Fibrosis?

Progressive systemic sclerosis is characterized by extensive generalized fibrotic destruction associated with increased accumulation of collagen and other extracellular macromolecules in the skin and other involved organs. It has been suggested that mediators released from mononuclear or endothelial cells play a critical role in the initial activation of connective tissue metabolism. Transforming growth factors β(TGF-β1, TGF-β2) mediate the inhibition of epithelial cell proliferation and the induction of fibronectin and collagen gene expression. Therefore, we investigated the distribution of both TGF-β1 and TGF-β2 mRNA and the final proteins in PSS skin in comparison with other inflammatory dermatoses and healthy controls by means of in situ hybridization and immunohistochemistry. Our studies revealed TGF-β1 and -β2 mRNA in dermal and subcutaneous infiltrating cells in both acute and chronic PSS, but also in the other inflammatory skin disorders. In the vicinity of this infiltrate single TGF-β positive fibroblasts could be found in acute PSS. The cytoplasm of epithelial cells of all skin adnexa showed TGF-β transcripts and no apparent differences were seen in the distribution and number of auto-radiographic grains between diseased and healthy skin samples. Especially, we could demonstrate abundant expression of TGF-β1/2 in epithelial hair follicle cells of the outer root sheath. Generally, the expression of TGF-β2 was less abundant than TGF-β1. Immunohistochemical studies revealed the same distribution pattern of the final proteins. Our data indicate that TGF-β expression in infiltrating cells is not a specific feature of fibrotic disease, but seems to be associated with highly proliferating cells in general, perhaps functioning as common mediator in regulation of cellular physiology with special importance for negative control of cell growth.