Polydopamine-Laced Biomimetic Material for Enhanced Osteogenic Effects and Bone Repair

Objectives: Bone grafting is the second most frequently performed tissue transplantation worldwide, yet there is ongoing concern regarding limited availability. Development of synthetic bone graft substitutes is critical to meet patient demand while circumventing the drawbacks of autografts and allografts. Using a hydroxyapatite-collagen (HC) composite material can mimic the composition and ultra-structures of natural bone and provide adequate bioactive material-tissue interactions. Incorporation of dopamine (DA) into the HC composite is key to attain a mechanical strength profile comparable to that of cortical bone. Here, we examine the osteogenic effects of polydopamine-laced hydroxyapatite collagen calcium silicate biomaterial (HCCS-PDA) particulates with rat bone marrow derived mesenchymal stem cells (rMSCs) to repair rat critical-sized calvarial defects (CSD).
Methods: The in vitro osteogenic effects of HCCS-PDA were examined by culturing rMSCs on material-coated plates and evaluating cellular attachment, proliferation, and mineral nodule formation. To evaluate in vivo bone regeneration, HCCS-PDA and HCCS with or without rMSCs were implanted into CSD. After 12 weeks, calvarial bone regeneration was evaluated radiographically, histologically, and histomorphometrically.
Results: The HCCS-PDA group demonstrated higher cellular attachment, proliferation, and mineralization than the HCCS group in vitro. Micro-CT analysis revealed HCCS-PDA seeded with rMSCs led to in vivo bone formation at 12 weeks post-implantation, while the other biomaterial groups failed to bridge the CSD and displayed limited osteoconductivity. The newly formed bone volume of the HCCS-PDA with rMSCs group (59.01 ± 7.21 mm³) was significantly higher than the HCCS with rMSCs group (43.22 ± 5.99 mm³) (p<0.05). Analysis of the autograft group indicated 23.35 ± 2.48 mm³ bone volume.
Conclusions: The HCCS-PDA particles with rMSC aggregates showed superior bone regeneration in the defect site compared to the other biomaterial groups and the autograft. This biomimetic biomaterial with rMSC incorporation shows promise for development of future therapeutic strategies in bone tissue engineering.