A Sacrificial 3D Printed Vessel-on-Chip Demonstrates a Versatile Approach to Model Connective Tissue Pathology

For in vitro organ models, perfused vasculature is crucial to overcome nutrient diffusion limits and to generate immunocompetent models by allowing trans-endothelial migration of immune cells in and out of the tissue. However, vasculature is often disregarded due to its complexity to generate and the necessity to integrate flow. The aim here was to overcome these limitations by combining 3D printing and multi-organ-chip technology to generate a vascularized, fibroblast-populated connective tissue matrix on-chip. A 3D printed, sacrificial, water-dissolvable structure was incorporated into a multi-organ-chip during its fabrication and hollow channels within a collagen/fibrin hydrogel were generated. Subsequently, channels were populated with endothelial cells and varying hydrogel concentrations (F _high /C _high ) used to mimic healthy and diseased connective tissue. The vessels were perfused and stable metabolic/viability conditions (lactate dehydrogenase, glucose, lactate) acquired after 3 days for at least 7 days. Angiogenic sprouting and secretion of angiogenic cytokines were increased in F _high hydrogels. Perfusion with monocytes revealed differentiation into macrophages and migration across the endothelium into the tissue. In conclusion, this versatile, easy method to pattern hydrogels in a multi-organ-chip can serve as the basis to build the next generation of vascularized, immunocompetent human organ models, and opens new possibilities to study health and disease.