3D Bioprinting of Functional Cartilage Tissue Constructs

Abstract

Articular cartilage's avascular, aneural architecture and intrinsically limited regenerative capacity make it among the most challenging tissues to repair, motivating the development of engineered cartilage constructs that recapitulate the zonal organisation, biomechanical properties, and extracellular matrix (ECM) composition of native tissue. This study investigated three bioink formulations -- gelatin methacrylate/hyaluronic acid methacrylate (GelMA/HAMA), nanocellulose/alginate (NCA), and decellularised cartilage ECM-based bioink (dECM) -- for extrusion-based 3D bioprinting of cartilage constructs seeded with human adipose-derived mesenchymal stem cells (hAD-MSCs). Constructs were printed at 4degC using a pneumatic extrusion bioprinter, crosslinked by dual UV/ionic methods, and cultured for 28 days in chondrogenic differentiation medium (TGF-beta3, BMP-6). Mechanical, biochemical, and histological analyses characterised construct maturation. GelMA/HAMA constructs exhibited compressive moduli of 284 +- 34 kPa at day 28 - the highest among the three bioinks and approaching the range of native articular cartilage (200-800 kPa) -- with significantly higher glycosaminoglycan (GAG) deposition (84.2 +- 8.4 µg/µg DNA vs 62.4 +- 6.8 for NCA; p < 0.001). dECM bioink produced the highest type II collagen expression (4.84-fold over undifferentiated controls) consistent with the biochemical cues of native cartilage ECM. Cell viability at day 1 post-printing was > 88% across all formulations. These results establish GelMA/HAMA as the most mechanically competent bioink for cartilage bioprinting and identify dECM bioink as the preferred platform for maximising chondrogenic differentiation fidelity.