Effects of Metal Ions from Implantable Biomaterials on Glycolytic Flux in Murine Bone Marrow-Derived Macrophages

Abstract

Total joint replacement surgeries are currently the most cost effective method for joint restoration. However, approximately 10% are expected to fail in the first 10-15 years post-implantation. Failure occurs primarily due to aseptic loosening resulting from bone loss around the implant (i.e., periprosthetic osteolysis), which, itself, is caused primarily by an inflammatory response to implant wear and corrosion products. Some metal ions from implant wear and corrosion have been shown to decrease oxidative phosphorylation (OXPHOS) and alter redox status in macrophages. This metal ion-induced decrease in OXPHOS may be associated with increased glycolytic flux to help maintain energy homeostasis and cellular redox status. Consequently, the primary objective of this thesis was to analyze the effects of Co²⁺, Cr³⁺ and Ni²⁺ on glycolytic flux parameters in BMDMs. Additionally, BMDM harvest after exposure to Co²⁺, Cr³⁺ and Ni²⁺ was optimized to ultimately measure reduced and oxidized glutathione by HPLC to evaluate cellular redox status. Murine BMDMs prepared from C57BL/6NCrl mice were exposed to various concentrations of Co²⁺, Cr³⁺ or Ni²⁺, and glycolytic flux was measured using an extracellular flux analyzer. Overall, results demonstrate that Co²⁺ and Ni²⁺, but not Cr³⁺, lead to an increase in glycolytic flux in BMDMs. These results, together with a previous study showing that Co²⁺ and Ni²⁺ decrease OXPHOS in murine BMDM, suggest that Co²⁺ and Ni²⁺ (but not Cr³⁺) can induce a metabolic shift away from OXPHOS towards glycolysis in macrophages. This metabolic shift may play a critical role in the inflammatory response induced by Co²⁺ and Ni²⁺ in the periprosthetic environment. This research will improve our understanding of the mechanisms underlying implant failure, and potentially facilitate the development of therapeutic approaches to increase implant longevity in the future.