Evolution of an in vivo bioreactor

Area of Science:

• Biomaterials Science
• Tissue Engineering
• Regenerative Medicine

Background:

• Ideal bone graft substitutes need osteoconductive, osteoinductive, and osteogenic properties.
• Current bone graft substitutes face limitations in achieving all three essential components for effective bone regeneration.

Purpose of the Study:

• To introduce and validate a novel "in vivo bioreactor" model for generating ectopic host bone.
• To assess the efficacy of a vascularized coralline scaffold supplemented with bone morphogenetic protein-2 (BMP-2) in bone formation.

Main Methods:

• A hydroxyapatite coral scaffold (ProOsteon 500) was implanted in a rat model, incorporating a vascular pedicle and/or BMP-2.
• Scaffolds were harvested after 6 weeks, sectioned, and stained for histological analysis, including CD31/PECAM-1 for vascularization.
• Bone formation was quantified histologically as a percentage of scaffold cross-sectional area.

Main Results:

• Vascular pedicle incorporation was essential for both vascular ingrowth and bone formation.
• Scaffolds with a vascular pedicle demonstrated significant neo-vascularization, regardless of BMP-2 supplementation.
• Mean bone formation measured 11.30% +/- 1.19% in vascularized scaffolds.

Conclusions:

• The developed "in vivo bioreactor" model successfully generates vascularized ectopic bone.
• This model holds significant potential for clinical applications in treating skeletal defects and for research into bone cancers.
• Vascularization is a critical factor for successful bone regeneration within the bioreactor system.