Enhanced Skin Wound Healing Through Chemically Modified Messenger <scp>RNA</scp> Encoding Epidermal Growth Factor (<scp>EGF</scp>)

Efficient wound healing remains a formidable medical challenge in clinical practice, due to the prevalence of skin defects arising from diverse etiological factors. It is indisputable that epidermal growth factor (EGF) plays a pivotal role in wound repair. However, its clinical application through recombinant proteins encounters challenges, including a short half-life in vivo and high production costs. Addressing these limitations, recent advancements in chemically modified mRNA (cmRNA) technologies offer a promising alternative. This study explores the utilisation of cmRNA in a biocompatible citrate-saline formulation to encode EGF for therapeutic purposes, capitalising on the advantages of cmRNA's inherent stability and the formulation's compatibility with biological systems. CmRNA demonstrated high transfection efficiency in human immortalised keratinocyte (HaCaT) and normal human dermal fibroblasts (NHDF) cells (93.97% ± 1.25% and 90.37% ± 0.97%, respectively), resulting in efficient production of biologically active EGF protein. In vitro, EGF cmRNA significantly promoted HaCaT and NHDF cell cycle, proliferation and migration. In vivo, in vivo imaging system (IVIS) imaging of murine skin confirmed localised and sustained expression of Luciferase cmRNA, with signals detectable up to 11 days post-injection. Immunohistochemistry revealed protein expression in both epidermal and dermal layers as early as 1 h post-injection, peaking at 48 h, further corroborated by enzyme-linked immunosorbent assay (ELISA). In a full-thickness skin defect mouse model, EGF cmRNA significantly accelerated wound healing, with superior re-epithelialisation observed compared to controls by Day 6. Mitogen-activated protein kinase (MEK)/Extracellular signal-regulated kinase (ERK) and Ki67 mRNA expression levels were markedly increased, both in vitro and in vivo. By Day 14, histological and immunohistochemical analyses revealed that EGF cmRNA outperformed recombinant human EGF (rhEGF), as indicated by enhanced formation of hair follicles and cutaneous glands, better-organised collagen fibres, and a reduced collagen Type I/III ratio. No adverse effects were observed in major organs, confirming cmRNA's biosafety. These results highlight the therapeutic potential of EGF-encoding cmRNA as an effective and safe alternative for enhancing wound healing.