Functional hollow porous microfiber scaffold with BMP-2 for macrophages polarization and bone regeneration

Artificial bone substitutes have garnered significant attention within the field of biomaterials, and the use of tissue engineering technology to repair bone defects has emerged as a promising alternative. However, when artificial bone substitutes are implanted in the body, they can induce many adverse cellular and tissue immune responses. In this study, we use coaxial electrospinning technology to fabricate microfiber with controllable diameter, excellent mechanical properties and surface porous structure. Poly(3-hydroxybutyrate- co -4-hydroxybutyrate) (P34HB) and polyethylene glycol (PEG) were used as shell solutions and polyvinyl alcohol (PVA) and bone morphogenetic protein-2 (BMP-2) peptides as core solutions. Compared to PVA/P34HB-PEG (P/P-P) scaffolds, PVA-BMP-2/P34HB-PEG (P-B/P-P) scaffolds polarized more human monocytic leukemia cell line (THP-1 cells) toward alternatively activated macrophages (M2), as demonstrated by increased M2 and decreased classically activated macrophage (M1) phenotypic marker expression in the cells. P-B/P-P microfibers have the potential to regulate the polarization state of macrophages, induce them to differentiate into an M2 phenotype and inhibit the inflammatory response of surrounding tissues. In addition, microfibers with a hollow porous structure facilitate the controlled release of BMP-2 peptides by regulating the fiber diameter, enhancing the differentiation of pre-osteoblastic cell line derived from mouse calvaria (MC3T3-E1) cells in an osteogenic direction and facilitating the repair of bone defects in vivo. This study presents microfibers essential for modulating the osteoimmune microenvironment, facilitating efficient bone regeneration.