Silk sericin enhances in vitro wound healing, modulates cytokeratin 16 and 17 expression, and exhibits immunomodulatory effects: an in vitro study for potential biomedical applications.

Silk sericin, a hydrophilic protein extracted from Bombyx mori cocoons, has emerged as a promising biomaterial for wound healing applications due to its bioactivity and cost-effective production. In this study, isolated sericin was characterized by Fourier transform infrared (FTIR) spectroscopy and mass spectrometry, confirming high purity with minimal fibroin contamination. Endotoxin contamination was excluded by LAL gel clot assay (<0.03 EU/ml). In vitro studies using human keratinocytes (HaCaT) and rat fibroblasts demonstrated that sericin at 600 μg/ml significantly enhanced cell viability (30% increase, p < 0.01) and accelerated in vitro wound healing (p < 0.001). Real-time PCR and Western blot analyses revealed modulation of cytokeratins 16 and 17 (KRT16/17) and up-regulation of junctional adhesion molecule A (JAM-A), suggesting enhanced epithelial activation and cell-cell adhesion. This response coincided with increased NF-κB and IL-17 expression. In fibroblasts, sericin significantly increased the expression of matrix metalloproteinase-9 (MMP9) and vascular endothelial growth factor (VEGF) (p < 0.01), suggesting pro-remodeling and pro-angiogenic potential. In HaCaT cells, sericin induced a transient increase in IL-1β (p < 0.01) followed by a reduction in tumor necrosis factor α (TNF-α) (p < 0.05) and an increase in IL-10 at 48 h. In THP-1-derived macrophages, sericin reduced IL-1β and TNF-α (p < 0.001), increased IL-10 (p < 0.05), and shifted polarization toward the M2 phenotype, as indicated by upregulation of CD163 and downregulation of CD86 (p < 0.001). Sericin showed no antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Its accessibility, cytocompatibility, and ability to modulate epithelial activation, matrix-remodeling responses, and inflammation position sericin as a promising candidate for advanced wound care strategies.