Cell-only bioprinting of articular cartilage progenitor cells within a physically constraining support bath to engineer structurally organized grafts

This study demonstrates a scaffold-free, cell-only bioprinting strategy to engineer structurally organized articular cartilage grafts with biomimetic, arcade-like collagen architecture. By introducing spatially defined physical boundaries using agarose molds and a xanthan gum-based support bath, articular cartilage progenitor cells were guided to deposit aligned extracellular matrix. Thinner boundaries promoted greater collagen alignment, while multilayered constructs exhibited zonal organization resembling native cartilage. The engineered tissues showed robust chondrogenesis, high collagen II content, and physiologically relevant tensile properties.