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Intracellular Staphylococcus aureus induces apoptosis in mouse osteoblasts
K A Tucker1, S S Reilly, C S Leslie
1Department of Biology, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, NC 28223, USA.
Abstract:
Staphylococcus aureus invades osteoblasts and is the primary cause of osteomyelitis. This study examined the ability of S. aureus to induce apoptosis in a mouse osteoblast cell line. The presence of intracellular S. aureus was demonstrated by transmission electron microscopy. Light microscopy was utilized to examine morphological changes in the osteoblasts following killing of extracellular bacteria. Cell rounding was observed, and dark centers due to condensation of chromatin were noted in cells in infected osteoblast cultures. DNA was isolated from infected osteoblast cultures, and electrophoresis revealed the laddering effect characteristic of cells undergoing apoptosis. Additionally, an in situ cell death detection assay was utilized to label apoptosis-induced DNA strand breaks. Apoptotic nuclei were present, providing further evidence that S. aureus induces apoptosis in osteoblasts.
Insights
Staphylococcus aureus infection triggers apoptosis, or programmed cell death, in osteoblasts. This study confirms Staphylococcus aureus induces osteoblast apoptosis, a key factor in osteomyelitis development.
Area of Science:
- Microbiology
- Cell Biology
- Pathology
Background:
- Staphylococcus aureus is a primary pathogen causing osteomyelitis.
- Bacterial invasion of osteoblasts is a critical step in bone infection pathogenesis.
Purpose of the Study:
- To investigate the capacity of Staphylococcus aureus to induce apoptosis in a mouse osteoblast cell line.
- To elucidate the cellular mechanisms by which S. aureus affects osteoblast viability.
Main Methods:
- Transmission electron microscopy to confirm intracellular bacterial presence.
- Light microscopy to observe morphological changes in infected osteoblasts.
- DNA electrophoresis and in situ cell death detection assays to identify apoptosis.
Main Results:
- Intracellular Staphylococcus aureus was visualized within osteoblasts.
- Morphological changes, including cell rounding and chromatin condensation, were observed.
- DNA laddering and positive labeling for DNA strand breaks confirmed apoptosis induction.
Conclusions:
- Staphylococcus aureus actively invades osteoblasts.
- The bacteria induce apoptosis in osteoblasts through distinct cellular pathways.
- Osteoblast apoptosis is a significant mechanism contributing to Staphylococcus aureus-induced osteomyelitis.