Anisotropic mineralized collagen scaffolds accelerate osteogenic response in a glycosaminoglycan-dependent fashion

Abstract

Regeneration of critically-sized craniofacial bone defects requires a template to promote cell activity and bone remodeling. However, induced regeneration becomes more challenging with increasing defect size. Methods of repair using allografts and autografts have inconsistent results, attributed to age-related regenerative capabilities of bone. We are developing a mineralized collagen scaffold to promote craniomaxillofacial bone regeneration as an alternative to repair. Here, we hypothesize modifying the pore anisotropy and glycosaminoglycan content of the scaffold will improve cell migration, viability, and subsequent bone formation. Using anisotropic and isotropic scaffold variants, we test the role of pore orientation on human mesenchymal stem cell (MSC) activity. We subsequently explore the role of glycosaminoglycan content, notably chondroitin-6-sulfate, chondroitin-4-sulfate, and heparin sulfate on mineralization. We find that while short term MSC migration and activity was not affected by pore orientation, increased bone mineral synthesis was observed in anisotropic scaffolds. Further, while scaffold glycosaminoglycan content did not impact cell viability, heparin sulfate and chondroitin-6-sulfate containing variants increased mineral formation at the late stage of in vitro culture, respectively. Overall, these findings show scaffold microstructural and proteoglycan modifications represent a powerful tool to improve MSC osteogenic activity.

Repair of critical-size porcine craniofacial bone defects using a collagen-polycaprolactone composite biomaterial

“…However, the large scale of the defects tested likely require efforts to boost cell recruitment and activity. Key modification include: the use of intraoperative adipose-derived stem cells seeding to boost healing [58]; modifications to the glycosaminoglycan content and pore size or orientation of the mineralized collagen scaffold to promote greater cell migration into the defect [57,59] and the potential to incorporate biomolecular signals (e.g., transiently incorporated BMP2, VEGF) or modify the mineral composition (e.g., inclusion of zinc ions) to promote proliferation, osteogenesis, or angiogenic activity [60][61][62].…”

Glycosaminoglycan content of a mineralized collagen scaffold promotes mesenchymal stem cell secretion of factors to modulate angiogenesis and monocyte differentiation

“…The regeneration of complex CMF bone defects requires the interaction of biomaterial implants with multiple cell types. Previously, mineralized collagen scaffolds fabricated with CS6 glycosaminoglycan content have been shown to promote greater calcium and phosphorous mineral after 28 days of hMSC culture compared to CS4- and Heparin-containing scaffolds [65]. In order to successfully regenerate CMF defects, we must consider not only osteogenesis, but also mature vessel formation, resorption of the implant by osteoclasts, and the immune response.…”

Biomaterial design strategies to address obstacles in craniomaxillofacial bone repair

“…136,137 Additionally, glycosaminoglycans are important constituents of healthy bone and specically glycosaminoglycans chondroitin-6-sulfate and heparin sulfate have been shown to promote mineral formation in mineralized collagen scaffolds. 138 Glycosaminoglycans have dramatic effects on other cells and processes such as angiogenesis and inammation. Studies using chondroitin sulfate have demonstrated an inhibitory effect of this glycosaminoglycan on monocyte migration in vitro and thus a potential anti-angiogenic effect in vivo.…”

“…147 This has also held true for anisotropic pores in mineralized collagen scaffolds, where alignment caused an increase in osteogenic gene expression and mineralization. 138 This alignment may also have benecial effects in directing vessel network formation through channel-like materials and providing guidance for angiogenesis. 148 Pore size and shape can effect multiple cell types, and thus there is some speculation on the best pore size for enhancing osteogenesis due to multiple cell interactions.…”