Metformin suppresses UHMWPE particle-induced osteolysis in the mouse calvaria by promoting polarization of macrophages to an anti-inflammatory phenotype.

BACKGROUND

Implant failure remains a major obstacle to successful treatment via TJA. Periprosthetic osteolysis and aseptic loosening are considered as proof of wear debris-induced disruption of local regulatory mechanisms related to excessive bone resorption associated with osteolysis and the damage at the bone-prosthesis interface. Therefore, there is an immediate need to explore strategies for limiting and curing periprosthetic osteolysis and aseptic loosening.

METHODS

We analyzed the in vitro cytokine production by primary mouse bone marrow macrophages (BMMs) that were exposed to ultra-high molecular weight polyethylene (UHMWPE) particles and treated with metformin at different concentrations with or without 5-aminoimidazole-4-carboxamide ribonucleoside to activate or inhibit AMPK. A mouse calvarial model was used to examine the in vivo effects of metformin on UHMWPE particle-induced osteolysis.

RESULTS

With particles, primary mouse BMMs secreted more pro-inflammatory cytokines tumor necrosis factor-α and interleukin (IL)-6. Treatment with metformin inhibited these variations and promoted the release of cytokine IL-10 with anti-inflammatory capability. In vivo, metformin reduced the production of pro-inflammatory cytokines, osteoclastogenesis, and osteolysis, increasing IL-10 production. Metformin also promoted the polarization of macrophages to an anti-inflammatory phenotype in vivo via AMPK activation.

DISCUSSION

A crucial point in limiting and correcting the periprosthetic osteolysis and aseptic loosening is the inhibition of inflammatory factor production and osteoclast activation induced by activated macrophages. The ability of metformin to attenuate osteolysis induced in mouse calvaria by the particles was related to a reduction in osteoclast number and polarization of macrophages to an anti-inflammatory functional phenotype.

CONCLUSIONS

Metformin could limit the osteolysis induced by implant debris. Therefore, we hypothesized that metformin could be a potential drug for osteolysis induced by implant debris.