3D Printing of an immunocompetent, epidermal-dermal model

Project Summary/Abstract Bacteria in biofilms, not individual or free swimming (ie planktonic) are responsible for 80% of all hospital acquired infections, about 1.6 million infections and 80,000 deaths, at an annual cost of $16.8 to $27.2 billion dollars in the US. Translational research for skin infections, like diabetic foot ulcers, burn wounds, and common but increasingly recalcitrant impetigo in children, currently use agar plates, porcine skin extracts, live murine or porcine models before clinical trials. However, porcine and murine models have distinct commensals and immune responses. As part of the parent grant, we recently reported results showing the storage and loss modulus (mechanical viscoelastic properties) of skin commensal biofilms, Cutibacterium acnes and Staphylococcus epidermidis, are dependent on the type of substrate they are grown on: tryptic soy agar versus reconstructed human epidermal tissue. Furthermore, commensal organisms can modulate the immune response, including protecting against pathogenic species. This project seeks to develop 3D bioprinted tissue constructs as a more representative and flexible model than the commercial skin. The preliminary results showing distinct storage and loss modulus in response to being grown on agar versus skin were shown using commercially available reconstructed human epidermal tissue. These are costly, require a 6-week lead time, and are not useful for understanding mechanism as they come pre-assembled. We seek to develop a protocol for rapid production of customizable vascularized human epidermal tissue. This builds on success in the literature for producing reconstructed human epidermal tissue. It also builds on success of a neighboring lab producing functional capillary layers on a chip. The challenges to be addressed are (1) adding macrophages into the system; (2) reproducing these constructs using a 3D bioprinter; (3) validating normal physiological response to temperature stress. Adding macrophages to the system will allow in situ manipulation of the immune system and measurements of macrophage invasion into biofilms. Reproducing these constructs using a 3D bioprinter will allow rapid assembly of the epidermis, dermis, macrophage, and eventual vascular layer. The vascular layer will allow heat flux away from the system which is necessary for studying the impacts of climate change on the system. Even meeting these challenges will not bring the system to the point where it will replace murine and porcine models. The remaining challenges will include functionalizing the skin with human commensal organisms; architecting pores; and inducing the perspiration response.