Replicating the zonal structure of osteochondral tissue in engineered constructs remains challenging. This study explores 3D bioprinting of osteochondral units using human nasal chondrocytes (hNCs). While hNCs are effective for fabricating hyaline cartilage layers, their interaction with hydroxyapatite (HAp) remains poorly understood. HAp, known to promote hypertrophic and osteogenic differentiation of mesenchymal stem cells, may similarly induce hypertrophic differentiation in hNCs. To test this, we developed a bioprintable granular hydrogel composite incorporating HAp, enabling simultaneous deposition of bioink and hNCs. High molecular weight hyaluronic-acid functionalized with tyramine (THA) was combined with collagen fibrils and HAp particles then crosslinked enzymatically with a combination of horseradish peroxidase and hydrogen peroxide. The bulk hydrogel was fragmented via extrusion through a cell strainer. The resulting granular gel was supplemented by a solution of low molecular weight THA, hNCs and a photoinitiator system based on ruthenium/sodium persulfate. Constructs were extruded into cylindrical molds using a pneumatic bioprinter and crosslinked using blue light. The printed constructs were cultured in chondrogenic medium for 28 days. We have successfully 3D bioprinted composites with homogeneously distributed HAp particles and hNCs. The cell viability was preserved throughout encapsulation and printing, as shown by an initial assessment with trypan blue before printing and Live/Dead staining on days 1, 3, and 7. The constructs maintained their shape throughout the 28-day culture period and exhibited various cell morphologies within and around the constructs. By day 28, a proliferative layer of hNCs was observed surrounding the constructs. We developed a composite bioink for joint encapsulation of HAp particles and hNCs in biofabricated constructs, demonstrating promising cell viability, shape retention, and printability. Combining this granular system with bioactive factors and multi-material 3D bioprinting could enable the fabrication of multizonal tissues, providing a potential solution for osteochondral defect repair.
Tankus et al. (Mon,) studied this question.