Regulatory role of B-cell maturation antigen on the toxic effect of chromium ions on human SaOS-2 osteoblasts

Interaction pathways of implant metal localized corrosion and macrophage inflammatory reactions

Macrophages play a central role in immunological responses to metallic species associated with the localized corrosion of metallic implants, and mediating in peri-implant inflammations. Herein, the pathways of localized corrosion-macrophage interactions were systematically investigated on 316L stainless steel (SS) implant metals. Electrochemical monitoring under macrophage-mediated inflammatory conditions showed a decreased pitting corrosion resistance of 316L SSs in the presence of RAW264.7 cells as the cells would disrupt biomolecule adsorbed layer on the metal surface. The pitting potentials were furtherly decreased when the RAW264.7 cells were induced to the M1 pro-inflammatory phenotype by the addition of lipopolysaccharide (LPS), and pitting corrosion preferentially initiated at the peripheries of macrophages. The overproduction of aggressive ROS under inflammatory conditions would accelerate the localized corrosion of 316L SS around macrophages. Under pitting corrosion condition, the viability and pro-inflammatory polarization of RAW264.7 cells were region-dependent, lower viability and more remarkable morphology transformation of macrophages in the pitting corrosion region than the pitting-free region. The pitting corrosion of 316L SS induced high expression of CD86, TNF-α, IL-6 and high level of intracellular ROS in macrophages. Uneven release of metallic species (Fe2+, Cr3+, Ni2+, etc) and uneven distribution of surface overpotential stimulated macrophage inflammatory responses near the corrosion pits. A synergetic effect of localized corrosion and macrophages was revealed, which could furtherly promote localized corrosion of 316L SS and macrophage inflammatory reactions. Our results provided direct evidence of corrosion-macrophage interaction in metallic implants and disclosed the pathways of this mutual stimulation effect.

Regulation of localized corrosion of 316L stainless steel on osteogenic differentiation of bone morrow derived mesenchymal stem cells

Localized corrosion has become a concerning issue in orthopedic implants as it is associated with peri-implant adverse tissue reactions and implant failure. Here, the pitting corrosion of 316 L stainless steels (316 L SSs) was initiated by electrochemical polarization to simulate the in vivo localized corrosion of orthopedic implants. The effect of localized corrosion on osteogenic differentiation of bone marrow derived mesenchymal stem cells (BMSCs) was systematically studied. The results suggest that pitting corrosion of 316 L SS reduced the viability, adhesion, proliferation, and osteogenic differentiation abilities of BMSCs, especially for the cells around the corrosion pits. The relatively high concentrations of metallic ions such as Cr3+ and Ni2+ released by pitting corrosion could cause cytotoxicity to the BMSCs. The inhomogeneous electrochemical environment resulted from localized corrosion could promote reactive oxygen species (ROS) generation around the corrosion pits and cause oxidative stress of BMSCs. In addition, localized corrosion could also electrochemically interact with the cells and lead to cell membrane depolarization. The depolarized cell membranes and relatively high levels of ROS mediated the degradation of the osteogenic capacity of BMSCs. This work provides new insights into corrosion-mediated cell function degeneration as well as the material-cell interactions.

Sodium hydrosulfide mitigates dexamethasone-induced osteoblast dysfunction by interfering with mitochondrial function

Osteoporosis is one of the clinical complications of long-term treatment with glucocorticoids (GCs), characterized by systemic damage of bone mass and osteoblast dysfunction. Hydrogen sulfide was found to be involved in GCs-induced osteoblast dysfunction. Osteoblastic MC3T3-E1 cell and mitochondrial function were determined by cell viability, M-CSF level, and ALP activity and superoxide production, membrane potential, and ATP level, respectively. The purpose of this research was to explore the impact of NaHS on osteoblastic MC3T3-E1 cell function as well as on Sirt1 and PGC1α expression in dexamethasone (DEX)-treated osteoblast cells. DEX-treated MC3T3-E1 cells exhibited decreased cell viability and ALP activity, as well as increased M-CSF level; all these changes were dramatically attenuated by NaHS. DEX-treated cells also displayed mitochondrial dysfunction, namely decreased mitochondrial membrane potential and ATP generation and increased superoxide generation, which were partly reversed by NaHS. We confirmed decreased Sirt1 and PGC1α protein expression in DEX-treated MC3T3-E1 cells by Western blot, which was also partly reversed by NaHS. Silencing of Sirt1 abrogated the protective effect of NaHS against DEX-induced cell damage and mitochondrial dysfunction. NaHS alleviates DEX-induced osteoblastic MC3T3-E1 cell injury by improving mitochondrial function.