Co-upregulation of Transforming Growth Factor Beta-1 and Nitric Oxide Synthase in Keloid by comparison to normal human skin-A possible role for TGFβ1 and NOS in pathogenesis of keloid

Abstract

Keloid disease is a benign but progressive form of abnormal wound healing associated with skin fibrosis and can cause a major functional disability and morbidity. TGF beta (TGFβ) and Nitric Oxide (NO) are active biomarkers known to regulate phases of wound healing and have been implicated in pathogenesis of fibrotic disease. There are three isoforms of TGFβ (1, 2 and 3), TGFβ1 and 3 have a crucial role in fibrosis, with TGFβ1 profibrotic and TGFβ3 antifibrotic. NO is produced by Nitric Oxide Synthase (NOS) which exist in three isoforms, inducible NOS (iNOS), endothelial NOS (ecNOS) and neuronal NOS (nNOS). TGFβ isoforms and NO were found to be associated with fibrotic disorders affecting the skin. We hypothesis that the interaction between TGFβ and NO in keloid could promote the excessive collagen deposition associated with this disorder. Using immunohistochemistry, we investigated the profile of TGFβ isoforms (TGFβ1, 3) and NOS isoforms (iNOS and ecNOS) in keloid tissues and normal human skin. The cellular distribution of all the isoforms were studied and the protein levels were assessed by using H-Scoring and Image J Scoring systems. TGFβ1 showed wide cellular distribution in keloid both in the epidermal and dermal cells. There was significant upregulation (P<0.0001) by comparison to normal skin. TGFβ3 showed limited expression in keloid and there was significant downregulation (P<0.03). iNOS and ecNOS showed significant upregulation in keloid by comparison to normal skin (P<0.01 and P<0.02) respectively. Interestingly, iNOS was expressed in the basal epidermal layer and in dermal connective tissue cells while ecNOS was solely expressed in vascular endothelial lining. Although it is documented that TGFβ has a negative feedback effect on iNOS, we have shown co-upregulation of TGFβ1 and iNOS in keloids. Thus, in keloid NO is as important as the profibrotic growth factor TGFβ1 and both could be working in coordination. Moreover, the lack of effective therapy for keloid could be because most of the therapeutic regimen target one factor while the other still in action. In conclusion, understanding the actions of TGFβ and NOS in keloid disease could lead to the development of clinically useful combined anti-fibrotic agents.