(138c) Dense Cell Bioprinting within Cell-Instructive Hydrogels to Create Complex Tissue Interfaces

Native tissue is composed of a dense cellular structure supported by an extracellular matrix (ECM), which provides mechanical, topographical, and biochemical cues to regulate cellular function. Successful replication of a functional tissue requires biomanufacturing strategies that can recapitulate the developmentally relevant cell-cell and cell-matrix interactions. When tissue interfaces are considered, local changes in ECM composition and cellular make up are crucial. One such tissue is the osteochondral interface, in which the tissue gradually progresses from highly vascular, stiff, and mineralized stiff bone tissue to avascular and elastic cartilage tissue. Although 3D bioprinting strategies have been developed to create this highly complex tissue, none focused on dense cell bioprinting. Compared to cell-laden hydrogels, dense cell bioprinting approaches enable patterning of multi-cellular structures with high cell densities to mimic densely packed native tissue as well as promote much needed cell-cell interactions. In this study, we present a novel bioprinting strategy to create dense cellular structures within cell-instructive hydrogels and demonstrate our ability to control hydrogel heterogeneity spatially and temporally to modulate stem cell definition. Our approach enables the use of a wide range of photocurable polymers, including methacrylate hyaluronic acid (MeHA), which allow tethering of bioactive cues to control stem cell behavior. We fist demonstrate the use of extrusion bioprinting to create multi-cellular dense cellular structures including fibroblasts, endothelial cells, and stem cells. Then, we present our long-term culture results using stem cells and show the effect of cell-adhesive cues on stem cell behavior and differentiation. In this talk, the focus is on stem cell osteogenesis. We show our ability to control hydrogel properties spatially to control stem cell differentiation. We show dense cell bioprinting within biphasic structures containing cues to enhance stem cell osteogenesis and confirm spatial control of osteogenesis using these tissues. Finally, we demonstrate our ability to deliver BMP-2 spatiotemporally to enhance osteogenesis. To finish, we present our ongoing work on spatial control of chondrogenesis and osteogenesis within same tissue constructs.