Figure 3
Depolarization of ΔΨ m precedes changes in morphology or plasma membrane integrity of bone marrow-derived mesenchymal stem cells (BMMSCs). BMMSC lines 412, 407, and 470 were used to study the early changes in ΔΨm and cell viability as determined by Trypan blue after 4 hours of infection. (a) Trypan blue staining of control cells and response to CCCP (protonophore) that was used as a positive control. (b) Staphylococcus aureus Cowan I caused slight depolarization of ΔΨm. (c) S. aureus KK1089 induced changes in ΔΨm and Trypan blue after 4 hours. (d) Staphylococcus epidermidis ATCC 14990 and (e) S. epidermidis KK1087 induced depolarization of ΔΨm. (f) Depolarization of ΔΨm and Trypan blue staining at 4 hours in Pseudomonas aeruginosa PA01-infected BMMSCs. The fluorescent 595 nm/535 nm ratio of JC-10 was used to determine ΔΨm, and the 595 nm/535 nm ratios of infected BMMSCs were compared with uninfected control cells. Results are indicated as mean ± standard deviation of four independent replicates. Magnification was 200 × in all panels. Red circles indicate Trypan blue-positive nuclei. Black squares indicate the aggregates produced by S. aureus. *P <0.05, **P <0.01, and ***P <0.001 in two-sample t test between control BMMSCs and infected BMMSCs. ΔΨm, mitochondrial inner membrane potential; CCCP, carbonyl cyanide m-chlorophenylhydrazone; JC-10, enhanced 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide.