Abstract
Effective communication between immune and bone-forming cells is crucial for the successful healing of bone defects. This study aimed to assess the potential of a decellularized placental sponge (DPS) as a coculture system for inducing M1/M2 polarization in macrophages and promoting osteogenic differentiation in adipose-derived mesenchymal stem cells (AD-MSCs), both in vitro and in vivo. We prepared the DPS and conducted a comprehensive characterization of its biomechanical properties, antibacterial activity, and biocompatibility. In vitro, we examined the influence of the DPS on the polarization of macrophages cocultured with AD-MSCs through nitric oxide assays, cytokine assays, phagocytosis tests, and real-time polymerase chain reaction (PCR). For in vivo assessment, we utilized micro-CT imaging, histological evaluations, and real-time PCR to determine the impact of the DPS seeded with Wharton's jelly mesenchymal stem cells (WJ-MSCs) on bone regeneration in a calvarial bone defect model. The coculture of AD-MSCs and macrophages on the DPS led to increased production of IL-10, upregulation of CD206, Arg1, and YM1 gene expression, and enhanced phagocytic capacity for apoptotic thymocytes. Concurrently, it reduced the secretion of TNF-α and nitric oxide (NO), downregulated the expression of CD86, NOS2, and IRF5 genes, and decreased macrophage phagocytosis of yeast. These results indicated polarization of macrophages toward an M2-like phenotype. In vivo, the presence of the DPS resulted in enhanced bone formation at the defect site. Immunostaining demonstrated that both the DPS and DPS + WJ-MSC constructs induced macrophage polarization toward an M2 phenotype, as compared to the control defect. In conclusion, this immunomodulatory effect, coupled with its biocompatibility and biomechanical properties resembling natural bone, positions the DPS as an attractive candidate for further exploration in the field of bone tissue engineering and regenerative medicine.