Natural melanin promotes the differentiation of an early epidermal cell fraction and the scavenging of ROS

Abstract

The aim of the study was to determine whether melanin extracted from Sepia officinalis , common cuttlefish ink, affects the phenotype of an interfollicular keratinocyte cell fraction, and therefore propose a strategy to enhance wound re-epithelialization that also provides protection against ROS. To demonstrate the properties of the melanin, rapidly adherent human keratinocytes (KCs, passage<2, n=3) were exposed to different amounts (0.031.5mg) of melanin and cell’s viability, proliferation and phenotype at different culture timepoints were evaluated. The ROS scavenging capacity of melanin-containing keratinocytes was quantified after UVB-induction. Melanin was then incorporated in spongy-like hydrogels dressings that were subcutaneously implanted in mice to evaluate the host reaction. Melanin particles were internalized by the keratinocytes by endocytosis and accumulated in the cytoplasm around the nucleus forming a supranuclear cap. Increasing amounts of melanin, lead to a significant diminishing of KCs proliferation in relation to control cultures (cells without melanin) and enhanced k10 expression. Likewise, the scavenging ability of melanin was dependent on its concentration. The decrease in the amount of ROS for higher amounts of melanin was even more evident after 24 hours of culture. Melanin-containing spongy-like hydrogels did not induce a deleterious host reaction and provide a sustained release of 0.8mg of melanin along 14 days. Overall, these results indicate that at the concentration of melanin that is released from the spongy-like hydrogels, KCs differentiation in vitro is enhanced while significant ROS scavenging occurs. This raises the prospect of using melanin-containing spongy-like hydrogels as wound dressing capable of adding to the healing of skin wounds.