3D bioprinting of methacrylated hyaluronic acid (MeHA) hydrogel with intrinsic osteogenicity

TLDR

Bone regenerative medicine requires suitable bone substitutes, but hydrogels’ viscoelastic properties limit their 3D bioprinting applicability. The study aimed to modify hyaluronic acid into photo‑crosslinkable methacrylated hydrogels with enhanced stiffness and stability for bone tissue engineering and 3D bioprinting. The authors methacrylated HA, crosslinked it with UV light, and incorporated human bone marrow MSCs to assess mechanical properties, cell viability, and osteogenic differentiation. UV‑crosslinked MeHA gels exhibited increased rigidity, supported 64.4 % MSC viability after 21 days, induced spontaneous osteogenic differentiation at high polymer concentrations, and BMP‑2 further enhanced mineralisation, proving suitability for bioprinted bone scaffolds.

Abstract

In bone regenerative medicine there is a need for suitable bone substitutes. Hydrogels have excellent biocompatible and biodegradable characteristics, but their visco-elastic properties limit their applicability, especially with respect to 3D bioprinting. In this study, we modified the naturally occurring extracellular matrix glycosaminoglycan hyaluronic acid (HA), in order to yield photo-crosslinkable hydrogels with increased mechanical stiffness and long-term stability, and with minimal decrease in cytocompatibility. Application of these tailor-made methacrylated hyaluronic acid (MeHA) gels for bone tissue engineering and 3D bioprinting was the subject of investigation. Visco-elastic properties of MeHA gels, measured by rheology and dynamic mechanical analysis, showed that irradiation of the hydrogels with UV light led to increased storage moduli and elastic moduli, indicating increasing gel rigidity. Subsequently, human bone marrow derived mesenchymal stromal cells (MSCs) were incorporated into MeHA hydrogels, and cell viability remained 64.4% after 21 days of culture. Osteogenic differentiation of MSCs occurred spontaneously in hydrogels with high concentrations of MeHA polymer, in absence of additional osteogenic stimuli. Addition of bone morphogenetic protein-2 (BMP-2) to the culture medium further increased osteogenic differentiation, as evidenced by increased matrix mineralisation. MeHA hydrogels demonstrated to be suitable for 3D bioprinting, and were printed into porous and anatomically shaped scaffolds. Taken together, photosensitive MeHA-based hydrogels fulfilled our criteria for cellular bioprinted bone constructs within a narrow window of concentration.