Impact of bone marrow mesenchymal stem cell immunomodulation on the osteogenic effects of laponite

Background: With the development of osteoimmunology and bone tissue engineering (BTE), it has been recognized that the immunomodulatory properties of bone biomaterials have considerable impact in determining their fate after implantation. In this regard, the polarization of macrophages secondary to biomaterials is postulated to play a crucial role in modulating their osteogenesis; thus, strategies that may facilitate this process engender increasing levels of attention. Whereas a variety of reports highlight the immunomodulation of bone marrow mesenchymal stem cells (BMSCs) in cell therapy or their osteogenesis in BTE, few have focused on the effect of BMSCs in promoting osteogenesis in BTE through regulating the phenotype of macrophages. Accordingly, there is an urgent need to clarify the immunomodulatory properties of agents such as laponite (Lap), which is comprised of bioactive silicate nanoplatelets with excellent osteogenesis-inducing potential, to enhance their use in BTE. Methods: In the present study, we analyzed the osteoimmunomodulatory properties of Lap alone, as well as following the introduction of BMSCs into Lap, to determine whether BMSCs could modulate its immunomodulatory properties and promote osteogenesis. Results: It was found that the BMSCs reversed the polarization of murine-derived macrophage RAW 264.7 cells from M1 as induced by pure Lap to M2 and promoted osteogenesis. In vivo study confirmed that BMSCs combined with Lap initiated a less severe immune response and had an improved effect on bone regeneration compared with Lap alone, which corresponded with the in vitro evaluation. Conclusion: These results suggest that BMSCs could ameliorate the inflammation induced by Lap and enhance its bone formation. The immunomodulatory characteristics of BMSCs suggest that these might be tailored as a new strategy to promote the osteogenic capacity of biomaterials.