Enhanced bone regeneration in critical-size defects using novel ultralong hydroxyapatite microtubes/chitosan...

This study evaluated the effects of hydroxyapatite microtubes and chitosan composite scaffold (HMTs-CHS) on bone regeneration in rat calvarial critical-size defects (CSDs).

HMTs-CHS composites were fabricated through hydrothermal synthesis and atmospheric pressure sintering. The scaffolds were analyzed using SEM, XRD, and FTIR to verify their structural and chemical characteristics. In vitro studies assessed cell proliferation, cytotoxicity, and osteogenic differentiation using bone marrow mesenchymal stem cells (BMSCs). For in vivo evaluation, 24 rats with 8-mm critical-size calvarial defects were divided into three groups: blank, CHS, and HMTs-CHS. Bone regeneration was evaluated at 30 and 60 days using micro-CT and histological analysis.

The HMTs-CHS scaffold exhibited a well-organized honeycomb-like structure with optimal pore size distribution (100-160 μm). The scaffold significantly enhanced BMSC proliferation and osteogenic differentiation, with increased EdU-positive cells, elevated ALP activity, and enhanced matrix mineralization. Osteogenic markers (RUNX2, COL1, OPN, OCN, BSP) were significantly upregulated in the HMTs-CHS group at both gene and protein levels. In vivo, the HMTs-CHS group showed superior bone regeneration with higher bone volume fraction (BV/TV: 14.07 ± 0.84% at 60 days, representing a - 44% relative improvement over the CHS group at 9.74 ± 1.36%) and better trabecular architecture (p < 0.05). Histological examination confirmed enhanced bone formation and maturation.

The HMTs-CHS composite significantly improved bone regeneration in CSDs compared to CHS alone or no treatment. These findings suggest HMTs-CHS could be a promising biomaterial for treating cranial bone defects, offering an alternative to traditional bone grafts.