RESUMO
BACKGROUND: The diagnosis of periprosthetic joint infection (PJI) is a major challenge in clinical practice. The role of neutrophils in fighting infection has been increasingly understood, and one mechanism of action of these cells is neutrophil extracellular traps. However, little is known about this process in PJI. QUESTIONS/PURPOSES: (1) Are the biomarkers of neutrophil extracellular trap formation (citrullinated histone H3 [H3Cit], cell-free DNA [cf-DNA], and myeloperoxidase [MPO]) increased in the synovial fluid of patients with PJI? (2) What is the diagnostic accuracy of biomarkers of neutrophil extracellular trap formation for PJI? METHODS: Between May 2020 and March 2021, 43 patients who underwent revision THA or TKA were enrolled in this study. Eleven patients were excluded and 32 patients were categorized into the PJI group (n = 16) or non-PJI group (n = 16) according to the 2018 Second International Consensus Meeting on Musculoskeletal Infection criteria. There were 15 men and 17 women in this study, with a median (range) age of 70 years (60 to 80 years). Twenty-seven patients had TKA and five had THA. We measured cf-DNA, MPO, and H3Cit in synovial fluid. The sensitivity, specificity, and receiver operating characteristic curve were calculated for each biomarker using the Musculoskeletal Infection Society criteria as the gold standard for diagnosis and considering a clinical surveillance of 2 years for patients in the non-PJI group. RESULTS: Patients with PJI had higher levels of synovial fluid cf-DNA (median [range] 130 ng/µL [18 to 179] versus 2 ng/µL [0 to 6]; p < 0.001), MPO (1436 ng/µL [55 to 3996] versus 0 ng/µL [0 to 393]; p < 0.001), and H3Cit (2115 ng/µL [5 to 2885] versus 3 ng/µL [0 to 87]; p < 0.001) than those in the non-PJI group. In receiver operating characteristic curve analyses, we observed near-perfect performance for all biomarkers evaluated, with an area under the curve of 1 (95% CI 0.9 to 1), 0.98 (95% CI 0.9 to 1), and 0.94 (95% CI 0.8 to 0.99) for cf-DNA, MPO, and H3Cit, respectively. The sensitivity for detecting PJI using synovial fluid was 100% for cf-DNA, 94% for MPO, and 88% for H3Cit. The specificity was 100% for cf-DNA and MPO, and 88% for H3Cit. CONCLUSION: Our results show that neutrophils in the periprosthetic microenvironment release neutrophil extracellular traps as part of the bactericidal arsenal to fight infection. These results allow a better understanding of the cellular and molecular processes that occur in this microenvironment, enabling the design of more assertive strategies for identifying new biomarkers and improving the available ones. Novel studies are needed to define whether and how neutrophil extracellular trap-related biomarkers can be useful for diagnosing PJI. LEVEL OF EVIDENCE: Level II, diagnostic study.
RESUMO
Osteosarcoma is the most common primary bone tumor in children and young adults. The median survival of osteosarcoma patients has not significantly improved since 1990, despite administration of different classes of chemotherapy agents, such as methotrexate, cisplatin and doxorubicin. Cancer stem cells (CSCs) are responsible for the resistance of osteosarcoma to chemotherapy and OCT4, SOX2 and SSEA4 have been used to identify CSCs in osteosarcoma. Here, we used low-passage patient-derived osteosarcoma cells and osteosarcoma cells directly isolated from patients before and after chemotherapy treatments to evaluate the effects of chemotherapy on stem cell markers expression. We demonstrate that primary osteosarcoma cells are resistant to methotrexate treatment and sensitive to cisplatin and doxorubicin in vitro. We also verified that cisplatin and doxorubicin reduce the expression of SOX2 and OCT4 in primary osteosarcoma cells whereas methotrexate does not alter SOX2 and OCT4 expression, however it increases SSEA4 expression in primary osteosarcoma cells. Finally, we found that, although the combination treatment cisplatin plus doxorubicin inhibited the in vivo growth of osteosarcoma cells in NOD-SCID gamma mice subcutaneously injected with SaOs2, the combination treatment cisplatin plus doxorubicin plus methotrexate did not inhibit the in vivo growth of these cells. These observations may provide an explanation for the poor response of osteosarcomas to chemotherapy and point to the need of reevaluating the therapeutic strategies for human osteosarcomas.