DEVELOPMENT OF A MICROFLUIDICS INTEGRATED MICROVASCULARISED HUMAN SKIN-ON-A-CHIP TISSUE MODEL

Tissue engineered skin constructs have been under development since the 1980s as a replacement for cadaverous human skin and animal models. These have evolved from simple confluent single cell-type arrangements to models with integrated dermal equivalents and often multiple cell types. Concomitantly, formation of stable self-assembled nanofibrous peptide amphiphile (PA) membranes upon contact with hyaluronic acid (HA) in aqueous solution, with comparable ultrastructure to the apical skin basement membrane (BM) have been reported. With the rise of microfluidic cell culture, scientists have scaled down these technologies; however no group to our knowledge has yet published a full thickness microfluidic skin equivalent with a physiologically mimetic tubular microvasculature or investigated integration of a skin model PA-based BM equivalent. This project aimed to integrate these features into a full thickness human skin-on-a-chip model, with a focus on microvasculature. We report the formation of interfacial self-assembled nanofibrous membranes between fibrin and collagen hydrogels and various PAs including C16V3A3K3. We exploit this in the stabilisation of the dermoepidermal interface in a macroscale fibrin-based skin equivalent model. We then design a novel skin-on-a-chip model integrating human-derived cells in a full-thickness arrangement. The model features a stratified epidermal equivalent featuring correct spatial localisation of keratinocyte basal and differentiation markers, dermoepidermal interfacial deposition of laminin 332 and a dermal compartment populated with human fibroblasts expressive of vimentin. The extent of expression of basal and corneal keratinocyte markers, and the sizes of dermally localised vimentin positive bodies, are comparable between our model and ex vivo human skin. The vascularised model incorporates either HUVECs alone or alongside primary pericytes and displays formation of tubular microvessels positive for CD31 surrounded by a laminin positive basement membrane. Microvessel diameters are comparable to those reported in literature for ex vivo human skin vasculature. The skin-equivalent is also tested in 3D extrusion bioprinted devices. We believe that this is a novel development in the field of microfluidic skin models, with a complex microvascular component displaying anastomosis and lumen formation unlike other vascularised skin-chip models. This model has potential utility in the fields of preclinical drugs testing and disease modellin