Epithelial–mesenchymal interactions in keloid pathogenesis modulate vascular endothelial growth factor expression and secretion

Abstract

Vascular endothelial growth factor (VEGF) plays an important role in angiogenesis during the wound healing process. As epithelial-mesenchymal interactions have been shown to regulate a plethora of genes in wound healing, we hypothesized that these interactions might have a role in modulating VEGF expression and angiogenesis. A two chamber co-culture model was used, wherein normal and keloid keratinocytes and fibroblasts were physically separated by membrane inserts while allowing cytokine diffusion. Cell lysates obtained from keratinocytes co-cultured with fibroblasts demonstrated increased expression of VEGF. An enzyme-linked immunosorbent assay (ELISA) showed significant increase in VEGF expression in co-culture conditioned media compared with controls. Additionally, the conditioned medium from keloid keratinocyte and fibroblast co-cultures increased proliferation and formation of complex three-dimensional capillary-like structures in human umbilical vein endothelial cells, emphasising the importance of epithelial-mesenchymal interactions in the angiogenic process. Immunostaining of keloid tissue localized VEGF in the basal layer of the epidermis and also demonstrated higher blood vessel density than normal skin. Keloid tissue extract also demonstrated increased expression of VEGF compared with normal skin. It is likely that epidermal VEGF exerts significant paracrine control over the dynamics and expression profile of underlying dermal fibroblasts. Addition of the inhibitors WP631, mitoxantrone, and Rapamycin to keloid keratinocyte and fibroblast co-cultures, downregulated secreted VEGF expression in a dose-dependent manner, suggesting therapeutic potential for these compounds in the treatment of keloid scars.

Sirolimus (rapamycin): From the soil of Easter Island to a bright future

“…Thus, sirolimus may have therapeutic potential in the treatment of keloids and hypertrophic scars. 24 A renal transplant recipient with Muir-Torre syndrome and a MSH2 mutation on a tacrolimus-based regimen experienced an eruption of multiple sebaceous neoplasms. 25,26 Switching to a sirolimus-based regimen arrested the disease; however, switching back to tacrolimus was associated with the rapid appearance of new facial neoplasms.…”

The Role of R-Spondin2 in Keratinocyte Proliferation and Epidermal Thickening in Keloid Scarring

“…Epithelial-mesenchymal interactions, initially applied to normal skin homeostasis (Fusenig, 1994;Maas-Szabowski et al, 1999), were found to be instrumental in modulating keloid pathogenesis by paracrine influences. Previous findings showed that keloid keratinocytes (KKs) enhanced proliferation (Lim et al, 2001), collagen synthesis (Lim et al, 2002), and secretion of vascular endothelial growth factor (Ong et al, 2007) in fibroblasts cultured in an in vitro co-culture system. Furthermore, the hyperplasic but nontumorigenic nature of Rspo1 and Rspo2 might have a role in keloid scarring, a benign dermal fibroproliferative skin disorder.…”

Adenoviral Overexpression and Small Interfering RNA Suppression Demonstrate That Plasminogen Activator Inhibitor-1 Produces Elevated Collagen Accumulation in Normal and Keloid Fibroblasts

“…[5][6][7][8][9][10][11][12] Modifications in growth factor-regulated cell growth and apoptosis, intracellular signal transduction, and epidermis-dermis interactions have been reported. [13][14][15][16][17][18][19][20][21] Changes in the level of genes involved in the above phenomena were also detected in gene profiling studies. 22,23 Despite these findings, knowledge-based specific approaches for prevention and efficacious treatment of keloids are still absent, and the lack of proper in vitro and animal models that recapitulate the pathophysiology of keloids further hampers progress.…”