Evidence of inter- and intra-keloid heterogeneity through analysis of dermal fibroblasts: A new insight in deciphering keloid physiopathology.

Keloid scars are hypertrophic and proliferating pathological scars extending beyond the initial lesion and without tendency to regression. Usually, keloids are considered and treated as a single entity but clinical observations suggest heterogeneity in keloid morphologies with distinction of superficial/extensive and nodular entities. Within a keloid, heterogeneity could also be detected between superficial and deep dermis or centre and periphery. Focusing on fibroblasts as main actors of keloid formation, we aimed at evaluating intra- and inter-keloid fibroblast heterogeneity by analysing their gene expression and functional capacities (proliferation, migration, traction forces), in order to improve our understanding of keloid pathogenesis. Fibroblasts were obtained from centre, periphery, papillary and reticular dermis from extensive or nodular keloids and were compared to control fibroblasts from healthy skin. Transcriptional profiling of fibroblasts identified a total of 834 differentially expressed genes between nodular and extensive keloids. Quantification of ECM-associated gene expression by RT-qPCR brought evidence that central reticular fibroblasts of nodular keloids are the population which synthesize higher levels of mature collagens, TGFß, HIF1α and αSMA as compared to control skin, suggesting that this central deep region is the nucleus of ECM production with a centrifuge extension in keloids. Although no significant variations were found for basal proliferation, migration of peripheral fibroblasts from extensive keloids was higher than that of central ones and from nodular cells. Moreover, these peripheral fibroblasts from extensive keloids exhibited higher traction forces than central cells, control fibroblasts and nodular ones. Altogether, studying fibroblast features demonstrate keloid heterogeneity, leading to a better understanding of keloid pathophysiology and treatment adaptation.

MC1R, SLC45A2 and TYR genetic variants involved in melanoma susceptibility in southern European populations: results from a meta-analysis.

BACKGROUND AND METHODS: Seven genetic biomarkers previously associated with melanoma were analysed in a meta-analysis conducted in three South European populations: five red hair colour (RHC) MC1R alleles, one SLC45A2 variant (p.Phe374Leu) and one thermosensitive TYR variant (p.Arg402Gln). The study included 1639 melanoma patients and 1342 control subjects. RESULTS: The estimated odds ratio (OR) associated with carrying at least one MC1R RHC variant was 2.18 (95% confidence interval (CI): 1.86-2.55; p-value=1.02×10(-21)), with an additive effect for carrying two RHC variants (OR: 5.02, 95% CI: 2.88-8.94, p-value=3.91×10(-8)). The SLC45A2 variant, p.Phe374Leu, was significantly and strongly protective for melanoma in the three South European populations studied, with an overall OR value of 0.41 (95% CI: 0.33-0.50; p-value=3.50×10(-17)). The association with melanoma of the TYR variant p.Arg402Gln was also statistically significant (OR: 1.50; 95% CI: 1.11-2.04; p-value=0.0089). Adjustment for all clinical potential confounders showed that melanoma risks attributable to MC1R and SLC45A2 variants strongly persisted (OR: 2.01 95% CI: 1.49-2.72 and OR: 0.50, 95% CI: 0.31-0.80, respectively), while the association of TYR p.Arg402Gln was no longer significant. In addition, stratification of clinical melanoma risk factors showed that the risk of melanoma was strong in those individuals who did not have clinical risk factors. CONCLUSION: In conclusion, our results show without ambiguity that in South European populations, MC1R RHC and SCL45A2 p.Phe374Leu variants are strong melanoma risk predictors, notably in those individuals who would not be identified as high risk based on their phenotypes or exposures alone. The use of these biomarkers in clinical practice could be promising and warrants further discussion.