A novel chitosan–collagen bilayer scaffold prevents contraction and accelerates cutaneous repair in a rat splint-skin model

Introduction: The treatment of chronic wound is extremely challenging and is often exacerbated by inflammation, poor angiogenesis and recurrent bacterial infections. To address this, we have developed a novel biomimetic bilayer three-dimensional scaffold with a chitosan-collagen upper epidermal layer, on top of a porous collagen-glycosaminoglycan dermal layer. Methods: In this study we assess this scaffold's efficacy in a preclinical wound model. In addition, we examined the scaffold with the addition of plasmid DNA encoding pro-angiogenic stromal derived factor-1α (SDF-1α) and anti-fibrotic β-klotho in a splinted full-thickness skin wound model on young Sprague Dawley rats for 14 days. Results: All the scaffold groups showed uniform deposition of extracellular matrix and showed no signs of wound contraction unlike our 'empty' defect group. Both the 'bilayer chitosan- collagen' group and 'gene activated group' showed that the upper chitosan layer was filled with exudate, which dried over time and formed a protective scab that delaminated easily at day 14. Our Chitosan- collagen scaffolds showed a decrease in pro-inflammatory IL-1β, an increase in the pro-angiogenic CD31 and a decrease in pro-fibrotic α-SMA protein expression. We showed enhanced pro-angiogenic and reduced pro-fibrotic expression with the addition of SDF and Klotho plasmids respectively (p < 0.01); however, the rate of wound healing was reduced with gene activation. Discussion: While the chitosan layer of the bilayer scaffold does not integrate into the wound bed it does form a protective covering with enhanced anti-inflammatory cues that support the lower integrating dermal collagen layer yielding optimal anti-fibrotic wound healing. These properties highlight the potential of this chitosan-collagen bi-layered scaffold, suggesting its suitability for promoting enhanced healing of chronic wounds in clinical settings.