Deciphering dermal fibroblast behavior in 3D bioprinted dermis contructs

In recent years, numerous strategies have emerged to answer the growing demand for graftable tissues. Tissue engineering and in-vitro production are one of them. Among all the engineered tissues, skin is one of the most advanced. Nevertheless, biofabrication of graftable and fully functional skin substitutes is still far from being reached. Skin reconstruction, particularly dermis, necessitates cultivation and maturation for several weeks (> 3 weeks) to recover the tissues composition and functions, which prevent its transfer to clinical applications. Thus, several strategies, including 3D bioprinting, have been explored to accelerate these productions. In the present study, based on the successful application of 3D bioprinting achieved by our group for skin reconstruction in 21 days, we propose to detail the biological behaviors and maturation phases occurring in the bioprinted skin construct thanks to a descriptive approach transferred from the bioprocess field. The aim is to comprehensively characterize dermis construct maturation phases (cell proliferation and ECM secretion) to master later the interdependent and consecutive mechanisms involved in in-vitro production. Thus, standardized quantitative techniques were deployed to describe 3D bioprinted dermis proliferation and maturation phases. Then, in a second step, various parameters potentially impacting the dermis reconstruction phases were evaluated to challenge our methodology and reveal the biological behavior described (fibroblast proliferation and migration, cell death, ECM remodeling with MMP secretion). The parameters studied concern the bioprinting practice including various printed geometries, bioink formulations and cellular physiology in relation with their nutritional supplementation with selected medium additives.