Engineering Bone Regeneration with Bioabsorbable Scaffolds with Novel Microarchitecture

TLDR

Critical‑sized defects were created in rat calvaria to test whether a bioabsorbable polymer scaffold with unique microarchitecture can induce bone formation by stabilizing the hematoma. Scaffolds were fabricated by emulsion freeze‑drying to achieve 90 % porosity, ~10 m²/g surface area, and median pore sizes of 16 µm and 32 µm. Radiography and histology showed that the scaffolds reduced defect size, increased de novo bone and osteoid compared to controls, and contained small mineralized masses, supporting a paradigm shift toward hematoma‑stabilizing microarchitecture.

Abstract

Critical-sized defects (CSDs) were introduced into rat calvaria to test the hypothesis that absorption of surrounding blood, marrow, and fluid from the osseous wound into a bioabsorbable polymer matrix with unique microarchitecture can induce bone formation via hematoma stabilization. Scaffolds with 90% porosity, specific surface areas of approximately 10 m2/g, and median pore sizes of 16 and 32 µm, respectively, were fabricated using an emulsion freeze-drying process. Contact radiography and radiomorphometry revealed the size of the initial defects (50 mm2) were reduced to 27 ± 11 mm2 and 34 ± 17 mm2 for CSDs treated with poly(D,L-lactide-co-glycolide). Histology and histomorphometry revealed scaffolds filled with significantly more de novo bone than negative controls (p < 0.007), more osteoid than both the negative and autograft controls (p < 0.002), and small masses of mineralized tissue (<15 µm in diameter) observed within the scaffolds. Based on these findings, we propose a change in the current paradigm regarding the microarchitecture of scaffolds for in vivo bone regeneration to include mechanisms based on hematoma stabilization.