Isolated platelets increase proliferation of hepatocytes. (A) Resting or activated platelets (plt) or microparticles (MP) isolated from these platelet preparations were added to HepG2 cells and incubated under serum-free conditions. After 48 hours, the cell proliferation rate was estimated by quantifying BrdU incorporation. Control groups represent HepG2 cells cultured in presence or absence of FCS. *P < .05 compared with −FCS. Data represent the mean of 3 independent triplicate experiments. Error bars indicate SD. (B) Resting platelets were added to HepG2 cells and incubated under serum free conditions. After various time points, platelets were removed by gentle washing and replaced by serum-free medium. After 48 hours, the cell proliferation rate was estimated by quantifying BrdU incorporation. Control groups represent HepG2 cells cultured in the presence or absence of FCS. *P < .05 compared with −FCS. Data represent the mean of 3 independent triplicate experiments. Error bars indicate SD. OD, optical density.