Modular, Vascularized Hypertrophic Cartilage Constructs for Bone Tissue Engineering Applications.

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Regenerative Medicine

Background:

• Vascularization is a critical challenge for engineered bone grafts, especially for large or ischemic defects.
• Direct bone formation strategies struggle to balance osteogenesis and vascularization, as vasculogenic cues can impede mineralization.

Purpose of the Study:

• To develop a multiphase tissue engineering strategy using endochondral ossification to achieve simultaneous bone mineralization and vascularization.
• To create engineered bone constructs that support both blood vessel formation and sustained mineralization in vitro.

Main Methods:

• Mesenchymal stromal cells were differentiated into hypertrophic chondrocytes to create hypertrophic pellets (HPs).
• HPs were combined with vascularizing microtissues to form multiphase constructs.
• Constructs were cultured in basal medium without exogenous osteogenic or vasculogenic supplements.

Main Results:

• Hypertrophic pellets demonstrated increased alkaline phosphatase activity, calcium deposition, and osteogenic gene expression compared to chondrogenic pellets.
• HPs secreted angiogenic factors, supporting new blood vessel formation in cocultures.
• The resulting multiphase constructs exhibited robust vascularization and sustained tissue mineralization.

Conclusions:

• Endochondral ossification provides a viable strategy for creating multiphase bone tissue constructs.
• This approach enables concomitant mineralization and vascularization, addressing key limitations in bone tissue engineering.
• The developed in vitro method offers a promising pathway for generating vascularized and mineralized engineered bone grafts.