ObjectiveTo investigate the effects of high-concentration of vancomycin and meropenem on the viability and osteogenic differentiation of rat bone marrow mesenchymal stem cells (BMSCs), and to provide experimental evidence for local antibiotic treatment of periprosthetic joint infection (PJI). Methods Rat BMSCs were cultured with vancomycin and meropenem at different concentrations (10-10 000 μg/mL). A cell counting kit 8 assay was used to assess the effects of the antibiotics on cell viability. The antibiotic concentration at which cell viability began to decrease by more than 50% compared to the control group (cells cultured without antibiotics) after 7 days was selected as the upper concentration limit for subsequent experiments. The lowest concentration at which cell viability significantly decreased compared to the control group after 7 days (P<0.05) was selected as the lower concentration limit. The cells were then further cultured in osteogenic induction medium. After 7 days, the proportion of late apoptotic cells was measured by flow cytometry, and the protein expression of Runt-related transcription factor 2 (Runx2), osteopontin (OPN), and Osterix (Osx) was detected by Western blot. After 21 days, Alizarin red staining was performed to evaluate the effects of the antibiotics on BMSCs mineralization and osteogenic differentiation. ResultsThe inhibitory effects of vancomycin and meropenem on BMSCs viability gradually increased with prolonged intervention. After 7 days, the threshold concentration for a significant decrease in BMSCs viability was 500 μg/mL for both antibiotics (P<0.05). Concentrations of 500, 1 000, and 3 000 μg/mL were selected for subsequent experiments. After 7 days of osteogenic induction, flow cytometry showed that the proportions of late apoptotic cells were significantly higher in the all antibiotics groups than in the control group (P<0.05). Western blot showed that low-concentration vancomycin (500 μg/mL) promoted Runx2 expression but inhibited OPN and Osx expressions (P<0.05), whereas high-concentration vancomycin (3 000 μg/mL) inhibited Runx2, OPN, and Osx expressions (P<0.05). Low-concentration meropenem (500 μg/mL) promoted Runx2, OPN, and Osx expressions (P<0.05), whereas high-concentration meropenem (3 000 μg/mL) inhibited the expressions of these osteogenesis-related proteins (P<0.05). After 21 days, the percentage of mineralized area in the 3 000 μg/mL vancomycin and meropenem groups was significantly lower than that in the control group (P<0.05). ConclusionHigh-concentration (3 000 μg/mL) of vancomycin and meropenem administered for more than 7 days may inhibit the viability and osteogenic differentiation of rat BMSCs.