How the Hydrogel Scaffold's Porous Structure and Composition Control the Formation of Spheroids for Bone Tissue...

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Regenerative Medicine

Background:

• Traditional scaffold-based tissue regeneration involves separate spheroid fabrication and scaffold incorporation steps.
• This study explores a streamlined approach integrating spheroid formation directly within a scaffold.
• The focus is on developing vascularized bone tissue using mesenchymal stem cells (MSCs) and human umbilical vein endothelial cells (HUVECs).

Purpose of the Study:

• To develop and characterize a novel "two-step-in-one" method for spheroid formation within a porous biomaterial scaffold.
• To investigate the spontaneous spheroidization of MSCs/HUVECs within a cross-linked pullulan/dextran hydrogel.
• To evaluate the osteoinductive potential of hydroxyapatite (HA)-supplemented scaffolds for vascularized bone tissue engineering.

Main Methods:

• Utilized a freeze-dried, cross-linked pullulan/dextran hydrogel scaffold containing dispersed hydroxyapatite (HA) particles.
• Seeded cell suspensions (MSCs/HUVECs) directly onto the dry hydrogel scaffold, allowing simultaneous swelling and spheroid formation.
• Characterized pore morphology, spheroid formation, and cell condensation using 3D tomographic techniques and assessed in vitro osteogenic differentiation.

Main Results:

• The "two-step-in-one" method successfully induced spontaneous spheroid formation within the hydrogel pores.
• Scaffold pore characteristics changed significantly upon swelling, influencing cell condensation and spheroid shape.
• HA-supplemented scaffolds promoted early-stage bone differentiation and osteogenic maturation under dynamic culture conditions, unlike pristine scaffolds.

Conclusions:

• The developed method offers an efficient, high-throughput alternative for producing mature spheroids for tissue engineering.
• The integration of HA particles within the scaffold is crucial for inducing osteogenic differentiation and extracellular matrix mineralization.
• This approach advances scaffold-based strategies for vascularized bone tissue regeneration.