biostudies-literatureUnknown11(5)Alagboso FI<h4>Aims</h4>Bone regeneration during treatment of staphylococcal bone infection is challenging due to the ability of <i>Staphylococcus aureus</i> to invade and persist within osteoblasts. Here, we sought to determine whether the metabolic and extracellular organic matrix formation and mineralization ability of <i>S. aureus</i>-infected human osteoblasts can be restored after rifampicin (RMP) therapy.<h4>Methods</h4>The human osteoblast-like Saos-2 cells infected with <i>S. aureus</i> EDCC 5055 strain and treated with 8 µg/ml RMP underwent osteogenic stimulation for up to 21 days. Test groups were Saos-2 cells + <i>S. aureus</i> and Saos-2 cells + <i>S. aureus</i> + 8 µg/ml RMP, and control groups were uninfected untreated Saos-2 cells and uninfected Saos-2 cells + 8 µg/ml RMP.<h4>Results</h4>The <i>S. aureus</i>-infected osteoblasts showed a significant number of intracellular bacteria colonies and an unusual higher metabolic activity (p < 0.005) compared to uninfected osteoblasts. Treatment with 8 µg/ml RMP significantly eradicated intracellular bacteria and the metabolic activity was comparable to uninfected groups. The RMP-treated infected osteoblasts revealed a significantly reduced amount of mineralized extracellular matrix (ECM) at seven days osteogenesis relative to uninfected untreated osteoblasts (p = 0.007). Prolonged osteogenesis and RMP treatment at 21 days significantly improved the ECM mineralization level. Ultrastructural images of the mineralized RMP-treated infected osteoblasts revealed viable osteoblasts and densely distributed calcium crystal deposits within the extracellular organic matrix. The expression levels of prominent bone formation genes were comparable to the RMP-treated uninfected osteoblasts.<h4>Conclusion</h4>Intracellular <i>S. aureus</i> infection impaired osteoblast metabolism and function. However, treatment with low dosage of RMP eradicated the intracellular <i>S. aureus</i>, enabling extracellular organic matrix formation and mineralization of osteoblasts at later stage. Cite this article: <i>Bone Joint Res</i> 2022;11(5):327-341.Bone & joint research327-341https://www.ebi.ac.uk/biostudies/studies/S-EPMC9130678biostudies-literatureRifampicin restores extracellular organic matrix formation and mineralization of osteoblasts after intracellular <i>Staphylococcus aureus</i> infection.PMC9130678Alagboso FIRupp MDocheva DBrochhausen CAlt VMannala GKWalter NfalseRifampicin restores extracellular organic matrix formation and mineralization of osteoblasts after intracellular <i>Staphylococcus aureus</i> infection.<h4>Aims</h4>Bone regeneration during treatment of staphylococcal bone infection is challenging due to the ability of <i>Staphylococcus aureus</i> to invade and persist within osteoblasts. Here, we sought to determine whether the metabolic and extracellular organic matrix formation and mineralization ability of <i>S. aureus</i>-infected human osteoblasts can be restored after rifampicin (RMP) therapy.<h4>Methods</h4>The human osteoblast-like Saos-2 cells infected with <i>S. aureus</i> EDCC 5055 strain and treated with 8 µg/ml RMP underwent osteogenic stimulation for up to 21 days. Test groups were Saos-2 cells + <i>S. aureus</i> and Saos-2 cells + <i>S. aureus</i> + 8 µg/ml RMP, and control groups were uninfected untreated Saos-2 cells and uninfected Saos-2 cells + 8 µg/ml RMP.<h4>Results</h4>The <i>S. aureus</i>-infected osteoblasts showed a significant number of intracellular bacteria colonies and an unusual higher metabolic activity (p < 0.005) compared to uninfected osteoblasts. Treatment with 8 µg/ml RMP significantly eradicated intracellular bacteria and the metabolic activity was comparable to uninfected groups. The RMP-treated infected osteoblasts revealed a significantly reduced amount of mineralized extracellular matrix (ECM) at seven days osteogenesis relative to uninfected untreated osteoblasts (p = 0.007). Prolonged osteogenesis and RMP treatment at 21 days significantly improved the ECM mineralization level. Ultrastructural images of the mineralized RMP-treated infected osteoblasts revealed viable osteoblasts and densely distributed calcium crystal deposits within the extracellular organic matrix. The expression levels of prominent bone formation genes were comparable to the RMP-treated uninfected osteoblasts.<h4>Conclusion</h4>Intracellular <i>S. aureus</i> infection impaired osteoblast metabolism and function. However, treatment with low dosage of RMP eradicated the intracellular <i>S. aureus</i>, enabling extracellular organic matrix formation and mineralization of osteoblasts at later stage. Cite this article: <i>Bone Joint Res</i> 2022;11(5):327-341.2022-01-01T00:00:00Z2022 May2024-11-15T12:48:43.333Z2024-11-15T12:48:43.333ZS-EPMC91306783560442210.1302/2046-3758.115.BJR-2021-0395.R1