Sustained calcium ion release from bioceramics promotes CaSR-mediated M2 macrophage polarization for osteoinduction. Journal of leukocyte biology Innate immune cells, especially macrophages, play a dual role in tissue repair and the defense against foreign bodies. Although biphasic calcium phosphate (BCP) ceramics have been confirmed as an excellent osteoimmunoregulatory biomaterial, it is unclear whether the ions release of BCP directly affects macrophage polarization and the mechanism by which the ions release is involved in osteoimmunomodulation. Herein, we verified the superior osteoinductive capacity of BCP in wild-type mice and showed its inability to promote this process in macrophage-deficient (LysM ) mice. Moreover, scanning electron microscopy, ion release curve, and calcein AM-staining results confirmed that BCP-released Ca in a sustained manner, thereby maintaining the long-term induction of M2 macrophage polarization and promoting the differentiation of mesenchymal stem cells into osteoblasts during osteogenesis. Furthermore, Ca targeted the Wnt/β-catenin signaling pathway and activated Arg1 and IL-10 (M2 marker genes) transcription through the calcium-sensing receptor (CaSR) in macrophages. Under treatment with a CaSR antagonist, macrophages cultured with the BCP fluid extract exhibited lower Ca intake and weaker M2 macrophage polarization. These findings underscore the critical role of macrophages in bone regeneration and clarify the molecular mechanisms of Ca -mediated osteoinduction by biomaterials, which is of great significance for the future design of biomaterial-oriented tissue regeneration engineering. 10.1002/JLB.3MA0321-739R

The CaSR/TRPV4 coupling mediates pro-inflammatory macrophage function. Acta physiologica (Oxford, England) AIM:Although calcium-sensing receptor (CaSR) and transient receptor potential vanilloid 4 (TRPV4) channels are functionally expressed on macrophages, it is unclear if they work coordinately to mediate macrophage function. The present study investigates whether CaSR couples to TRPV4 channels and mediates macrophage polarization via Ca signaling. METHODS:The role of CaSR/TRPV4/Ca signaling was assessed in lipopolysaccharide (LPS)-treated peritoneal macrophages (PMs) from wild-type (WT) and TRPV4 knockout (TRPV4 KO) mice. The expression and function of CaSR and TRPV4 in PMs were analyzed by immunofluorescence and digital Ca imaging. The correlation factors of M1 polarization, CCR7, IL-1β, and TNFα were detected using q-PCR, western blot, and ELISA. RESULTS:We found that PMs expressed CaSR and TRPV4, and CaSR activation-induced marked Ca signaling predominately through extracellular Ca entry, which was inhibited by selective pharmacological blockers of CaSR and TRPV4 channels. The CaSR activation-induced Ca signaling was significantly attenuated in PMs from TRPV4 KO mice compared to those from WT mice. Moreover, the CaSR activation-induced Ca entry via TRPV4 channels was inhibited by blocking phospholipases A2 (PLA2)/cytochromeP450 (CYP450) and phospholipase C (PLC)/Protein kinase C (PKC) pathways. Finally, CaSR activation promoted the expression and release of M1-associated cytokines IL-1β and TNFɑ, which were attenuated in PMs from TRPV4 KO mice. CONCLUSION:We reveal a novel coupling of the CaSR and TRPV4 channels via PLA2/CYP450 and PLC/PKC pathways, promoting a Ca -dependent M1 macrophage polarization. Modulation of this coupling and downstream pathways may become a potential strategy for the prevention/treatment of immune-related disease. 10.1111/apha.13926