Complex epithelial–mesenchymal interactions modulate transforming growth factor‐β expression in keloid‐derived cells

Abstract

Keloids are proliferative dermal growths representing a pathologic wound healing response. We have previously demonstrated that coculture of fibroblasts derived from either keloid or normal skin have an elevated proliferation rate when cocultured with keloid-derived keratinocytes vs. normal keratinocytes. In these studies, we examined the contribution of transforming growth factor-beta (TGF-beta) to this phenomenon using a two-chamber coculture system. Fibroblast proliferation in coculture was slower with the addition of a pan-TGF-beta neutralizing antibody. Keloid keratinocytes in coculture expressed more TGF-beta1, -beta3, and TGF-beta receptor 1 than normal keratinocytes. Keloid fibroblasts cocultured with keloid keratinocytes expressed more mRNA for TGF-beta1, -beta2, TGF-beta receptor 1, and Smad2. Keloid fibroblasts also produced more type I collagen, connective tissue growth factor, and insulin-like growth factor-II/mannose-6-phosphate receptor when cocultured with keloid keratinocytes vs. normal keratinocytes. Levels of total and activated TGF-beta activity increased when fibroblasts were cocultured with keratinocytes, correlating with the changes in transcriptional activity of TGF-beta. In conclusion, we find a complex paracrine interaction regulates TGF-beta mRNA expression and activation between keratinocytes and fibroblasts. These data suggest that keloid pathogenesis may result from both an increased TGF-beta production and activation by the keloid keratinocyte, and elevated TGF-beta expression, utilization, and signaling in keloid fibroblasts.

Differential Transcriptional Responses of Keloid and Normal Keratinocytes to Serum Stimulation

“…KFs also produced more collagen 1, connective tissue growth factor (CTGF, CCN2), and insulin-like growth factor-II/mannose-6-phosphate receptor when co-cultured with KKs versus NKs. We found a complex paracrine interaction regulated TGF-␤ mRNA expression and activation between keratinocytes and fibroblasts and suggested that keloid pathogenesis results from both an increased TGF-␤ production and activation by the KKs and elevated TGF-␤ expression, utilization, and signaling in KFs [18]. To our knowledge, there is no study to date addressing whether KKs express more TGF-␤ versus NKs in response to in vivo stresses that mimic the wound healing response.…”

“…Fibroblast proliferation in coculture was slower when TGF-␤ activity was inhibited using a pan-TGF-␤ neutralizing antibody [18]. KKs in coculture expressed more TGF-␤1, -␤3, and TGF-␤ receptor (T␤R) 1 than NKs.…”

Hypertrophic Scarring and Keloids: Pathomechanisms and Current and Emerging Treatment Strategies

“…Strong and persistent expression of TGF-β and its receptors has been shown in fibroblasts of post-burn hypertrophic scars (45). Also, overexpression of TGF-β1 and -β2 has been found in keloid and keloid-derived fibroblasts, with significantly lower TGF-β3 mRNA expression (46,47). Comparing the expression profiles of TGF-β1, -β2 and -β3 and their receptors in keloids, hypertrophic scar and normal skin derived fibroblasts, Bock and colleagues found significantly lower TGF-β2 mRNA expression in hypertrophic scar fibroblasts compared with fibroblasts derived from keloids and normal skin, while TGF-β3 mRNA expression was significantly lower in keloid fibroblasts in comparison with fibroblasts derived from hypertrophic scar and normal skin (44).…”

Dynamics of Transforming Growth Factor Beta Signaling in Wound Healing and Scarring

“…115 Studies using cultured keloid fibroblasts have shown that these cells produce higher amounts of ''pro-scarring'' TGF-b1 and TGF-b2 as compared with normal fibroblasts. 130,131 Another study demonstrated that keloid fibroblasts exhibit increased expression of ALK5 and TbRII as well as increased phosphorylation of Smad3 relative to normal fibroblasts. 132 Interestingly, increased TGF-b/Smad3 signaling has been implicated in keloid pathogenesis via epithelialmesenchymal interactions, where keloid keratinocytes act through a paracrine mechanism to increase ALK5 and TbRII expression and Smad3 signaling in keloid fibroblasts.…”