Composite Spheroid-Laden Bilayer Hydrogel for Engineering Three-Dimensional Osteochondral Tissue.

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Regenerative Medicine

Background:

• Engineering three-dimensional (3D) osteochondral tissue using hydrogels and stem cell spheroids is promising but lacks precise zonal control over cell differentiation.
• Challenges include directing stem cell fate within the hydrogel matrix to mimic native tissue architecture.

Purpose of the Study:

• To develop a composite spheroid-laden bilayer hydrogel system for spatially controlled differentiation of human adipose-derived stem cells (hADSCs) to mimic osteochondral tissue.
• To investigate the role of immobilized growth factors in directing chondrogenic and osteogenic lineages within the engineered construct.

Main Methods:

• Fabrication of a bilayer hydrogel using gelatin methacryloyl (GelMA) with optimized spheroid size and mechanical properties.
• Incorporation of fibers loaded with transforming growth factor beta-1 (TGF-β1) or bone morphogenetic protein-2 (BMP-2) within spheroids to induce specific cell differentiation.
• Assessment of hydrogel interfacial adhesion, cell sprouting, and gene expression profiles post-culture.

Main Results:

• Optimized GelMA hydrogels facilitated homogeneous cell sprouting within the spheroids.
• The bilayer hydrogel exhibited strong interfacial adhesion, with tensile strength increasing after 14 days of culture.
• Spatially confined BMP-2 delivery significantly enhanced osteogenic differentiation and mineral deposition in the bone layer.
• TGF-β1 induced chondrogenic differentiation, with cells forming distinct cartilage and bone layers.

Conclusions:

• The developed composite spheroid-laden hydrogel system enables precise spatial control over stem cell differentiation for osteochondral tissue biofabrication.
• This platform holds potential for engineering other complex tissues by incorporating targeted delivery of specific biomolecules.