Resorbable Poly-(D,L)-Lactide Anchorage of Nanoparticulate Mineralized Collagen Materials Maximizes In Vivo Skull Regeneration

BackgroundA clinical demand exists for bone biomaterials that mirror tissue-specific extracellular matrix (ECM) properties and regulate progenitor cell fate. Nanoparticulate mineralized collagen glycosaminoglycan (MC-GAG) scaffolds have demonstrated to promote skull regeneration in vivo without addition of growth factors or exogenous progenitor cells, offering a materials-only solution for cranial defect reconstructions. Further enhancement of the safety and regenerative potential of MC-GAG is however necessary for clinical translation. Here, we investigated the regenerative effect of MC-GAG scaffold fixation with a resorbable poly(D,L-lactide) (PDLLA) implant for cerebral protection. MethodsFourteen-millimeter cranial defects were created in New Zealand white rabbits, divided into four groups: 1) defect only, 2) defect with PDLLA, 3) MC-GAG, and 4) MC-GAG with PDLLA. Initial bone healing assessment was conducted at 3 and 9 months using microcomputed tomography (microCT), histology, reference point indentation, and scanning electron microscopy. Long-term effects were evaluated through in vivo microCT imaging at 3, 6, and 9 months, with biomechanical testing of explanted skulls at 9 months. ResultsAt 3 months, MC-GAG significantly enhanced mineralization compared to empty and PDLLA-treated defects, with even greater mineralization observed for MC-GAG-PDLLA. Histologically, MC-GAG demonstrated trabecular mineralization, while MC-GAG-PDLLA had a structural organization resembling native bone. Biomechanical assessment showed enhanced toughness and stiffness for both MC-GAG and MC-GAG-PDLLA. At 6 months, MC-GAG-PDLLA displayed the highest bone mass, and at 9 months, both MC-GAG-containing scaffolds demonstrated superior bone regeneration compared to controls. By 9 months, PDLLA implants were completely resorbed and MC-GAG-PDLLA exhibited mechanical properties surpassing those of all other groups. ConclusionsFixation of MC-GAG scaffolds with PDLLA implants improved mineralization and bone regeneration compared to either material alone for cranial defect reconstruction. Clinical Relevance StatementCranioplasties are essential for cerebral protection and neurological restoration, but current materials have limitations, necessitating alternative bone biomaterials for improved outcomes.