Coacervates Made of Elastin-Like Polypeptides Fused with Melanocyte-Stimulating Hormone and Monocyte Chemoattractant Protein Enhance Skin Wound Healing in Spinal Cord-Injured Mice.

Abstract

Pressure wounds of the skin are common but challenging complications after spinal cord injury (SCI). Due to altered circulation, reduced macrophage recruitment, and compromised immunity at early time points, skin wound healing is impaired in SCI patients. To promote macrophage recruitment, topical elastin-like polypeptides (ELP) fused with α-melanocyte-stimulating hormone (MSH-ELP) and monocyte chemoattractant protein-1 (MCP-ELP) were developed. Constructs encoding MSH-ELP or MCP-ELP in a pET25b+ vector were transformed into E. coli for expression. Physical and biological in vitro assays were conducted to ensure that the fusion proteins exhibited the expected bioactivity; subsequently, they were tested as topical treatments on experimental skin wounds on SCI mice. SDS-PAGE and western blot analysis confirmed single bands with molecular weights of 26.3 kDa (MSH-ELP) and 33.4 kDa (MCP-ELP), respectively, forming nanoparticles of 100-250 nm in diameter at the tested concentrations, with a lack of toxicity. MSH-ELP reduced lipopolysaccharide-induced inflammation and enhanced the chemotactic response of THP-1 cells. In experimental skin wounds on SCI mice, the nanoparticles enhanced the recruitment of macrophages in a time-dependent manner. We also observed a reduction in scar area and wound width, together with increased macrophage (M2) activity, increased angiogenesis, and extracellular matrix protein deposition in the wound area. In conclusion, we developed a nanoparticle system that demonstrates superior chemotactic response relative to its native form, maintains a safe biocompatibility profile, and significantly improves cutaneous wound healing in an SCI mouse model.