Figure 4. Staphylococcus aureus lacking SpA does not trigger osteoblast apoptosis.
(A) Osteoblasts (5×105 cells/ml) were preincubated with either control buffer or formaldehyde fixed S. aureus Newman (1×109 cells/ml) for 24 hrs. Osteoblasts are removed, lysed and incubated with caspase 3 substrate (DEVD-pNA) for 1 hr at 37°C. Caspase 3 cleavage was measured at 405 nm in a microplate reader. (B+C) To measure Annexin V binding pelleted osteoblasts were re-suspended in 100 µl of FITC-Annexin V antibody. Suspensions were incubated in the dark for 15 min at RT and analysed by flow cytometry. *P<0.01, **P<0.05, n = 5.