Parvalbumin targeted to the cytoplasm specifically inhibits MSC proliferation. (A) MTT assay of MSCs after 48 hours of transduction with Ad-PV-NES-DsRed. The metabolization of MTT was reduced in cells that were transduced with Ad-PV-NES-DsRed compared with cells grown with serum (P < 0.01), whereas no reduction in the metabolization of MTT was observed in cells that expressed the adenoviral transduction control Ad-DsRed compared with cells grown with serum (P > 0.05) (n = 3). (B) Flow-cytometric assays were used to measure cell death quantitatively after cells were stained with PI. The cells were examined 48 hours after transduction. The results are expressed as the percentage of events from a total of 20,000 events (n = 3). *P < 0.01 compared with cells grown in 10% serum. **P < 0.05 cells grown without serum compared with cells treated with 200 nM staurosporine.