Integrating melt electrowriting (MEW) PCL scaffolds with fibroblast-laden hydrogel toward vascularized skin tissue engineering

Three-dimensional (3D) skin equivalents (SEs) are promising platforms for studying skin disease or assessing the safety of skin-relevant products. Vascularization, which improves the functionality of reconstructed skin, is one of the remaining hurdles in SE production that, when successfully introduced, can widen SE applications. Here, combining porous polycaprolactone (PCL) melt electrowritten (MEW) scaffolds with fibroblast-laden methacrylated gelatin hydrogel (GelMA), we developed SEs with cellular vascular structure. The MEW scaffolds were composed of two layers: random fibers for culturing the keratinocytes to fabricate the epidermis; and well-aligned shapes filled with fibroblast-laden GelMA to mimic the dermis. Three dermal designs varying in porosities and pore sizes were compared to optimize the dermis reconstruction. Within one week, the design with bigger pore sizes achieved optimal cell distribution, penetration, and extracellular matrix (ECM) deposition. Additionally, Retinoic acid (RTA) was tested for improving ECM deposition. To mimic vasculature, we incorporated vascular grafts into the optimized SEs. These were fabricated by casting endothelial fibroblast-laden Matrigel onto small-diameter MEW-tubular structures. The versatility and reproducibility of the obtained SEs offer a robust new tool for in vitro testing and exploration of fundamental biological processes of skin tissue.