Copper-Containing Alloy as Immunoregulatory Material in Bone Regeneration via Mitochondrial Oxidative Stress

Abstract

In the mammalian skeletal system, osteogenesis and angiogenesis are closely linked by type H vessels during bone regeneration and repair. Our previous studies confirmed the promotion of these processes by copper-containing metal (CCM) in vitro and in vivo. However, whether and how the coupling of angiogenesis and osteogenesis participates in the promotion of bone regeneration by CCM in vivo is unknown. In this study, M2a macrophages but not M2c macrophages were shown to be immunoregulated by CCM. A CCM, 316L−5Cu, was applied to drilling hole injuries of the tibia of C57/6 mice for comparison. We observed advanced formation of cortical bone and type H vessels beneath the new bone in the 316L−5Cu group 14 and 21 days postinjury. Moreover, the recruitment of CD206-positive M2a macrophages, which are regarded as the primary source of platelet-derived growth factor type BB (PDGF-BB), was significantly promoted at the injury site at days 14 and 21. Under the stimulation of CCM, mitochondria-derived reactive oxygen species were also found to be upregulated in CD206hi M2a macrophages in vitro, and this upregulation was correlated with the expression of PDGF-BB. In conclusion, our results indicate that CCM promotes the evolution of callus through the generation of type H vessels during the process of bone repair by upregulating the expression of PDGF-BB derived from M2a macrophages.

The role of macrophages in fracture healing: a narrative review of the recent updates and therapeutic perspectives

“…Applying a biomimetic polysaccharide hydrogel-metal scaffold composite loaded with IL-4 and BMP-2 within femoral defects in rats, Wang et al observed an increase in the number of M2 macrophages and in the proliferation and differentiation of skeletal progenitors into osteoblasts, which significantly improved bone regeneration (69). In another study, Xu et al (70) developed an intramedullary nail composed of a copper-containing stainless steel as a strategy to deliver copper ions at the injury site, as this ion had been previously shown to considerably induce M2 macrophage polarization in vitro (71). Using the drill-hole injury model in the tibia of mice, the authors reported an accelerated formation of new cortical bone in the animals that received the copper-enriched intramedullary nail.…”

“…Using the drill-hole injury model in the tibia of mice, the authors reported an accelerated formation of new cortical bone in the animals that received the copper-enriched intramedullary nail. When the callus was evaluated, it was observed an increased infiltration of CD206 + M2a macrophages, which located close to the newly formed type-H vessels and around the surface of the neoformed osseous tissue (70).…”

Early osteoimmunomodulation by mucin hydrogels augments the healing and revascularization of rat critical-size calvarial bone defects

“…M2 macrophages can produce regenerative factors such as osteogenic and angiogenic molecules, thus promoting neobone formation and revascularization [ 22 ]. CD206-expressing macrophages (M2a) express abundant platelet-derived growth factor type BB and promote the formation of blood vessels [ 49 ]. CD163-expressing macrophages (M2c) secrete high levels of matrix metalloproteinases 9 (MMP9) to promote vascular remodeling.…”

Differently Charged P (VDF-TrFE) Membranes Influence Osteogenesis Through Differential Immunomodulatory Function of Macrophages

“…During the early stages after implantation of biomaterials, the macrophages migrate to the implant area and differentiate into the pro-inflammatory M1 phenotype (classical type), triggering the defensive inflammation by the release of pro-inflammatory molecules, such as interleukin (IL)-1, tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS) (Wu et al, 2020). The phenotype plasticity allows macrophages to switch into different phenotypes in response to distinct material signals (Miron and Bosshardt, 2016;Xu et al, 2020). Subsequently, antiinflammatory M2 macrophages (alternative type) participate in bone reconstruction by the production of antiinflammatory molecules, including arginase-1 (Arg-1), IL-10, and IL-4 (Wei et al, 2018).…”