Optimized construction of a full thickness human skin equivalent using 3D bioprinting and a PCL/collagen dermal scaffold

Skin regeneration through tissue engineering combines biomaterials compatible with living cells to build a niche of limited duration that can support recapitulating reconstruction of the key features of native human skin. Reconstructed full thickness human skin is a promising platform for studying skin biology and assessing the safety and efficacy of cosmeceutical and clinical skin care products. Yet, as a target tissue for synthetic reconstruction, skin still carries a unique set of challenges, in spite of its well-defined 3D architecture, cell composition, and the constantly improving biocompatible synthetic materials now available to bioengineers. Commercial in vitro skin models are mostly prepared via manual deposition of cells into and onto a suitable extracellular matrix, which is usually difficult to mold into irregular shapes. There is an unmet need to develop a process for systematic 3D bioprinting of biomimetic skin that demonstrates full and efficient differentiation with high reproducibility and good viability, within a practical time frame. This study presents a full-thickness biomimetic skin equivalent fabricated by extrusion-based bioprinting. The 3D bioprinted full thickness skin model has cellular collagen dermal layer that rests on an acellular PCL/collagen scaffold, and is overlaid by sequential extrusion of bioprinted keratinocytes before airlifting for stratification and differentiation. The bioprinted skin constructs are compared with full-thickness human skin constructs produced by manual seeding of cells, in terms of cell proliferation, viability, histology, immunostaining, and barrier properties, to identify quantitative and qualitative differences. This study identifies an opportunity to streamline specific 3D bioprinting approaches to deliver full thickness reconstructed human skin in a reproducible, consistent and potentially scalable manner.