Slit3 stimulates EC proliferation. The cell number of the cultured mouse lung ECs (A) and HUVECs (B) was measured after the addition of recombinant Slit3 at 0 to 0.40 nmol/L in the culture medium. BSA (1.3 nmol/L) served as a negative control, whereas VEGF (0.50 nmol/L) served as a positive control. The data are presented as -fold increase in cell number relative to the BSA control. The results were from 3 independent experiments in triplicate and are expressed as mean ± SD. Asterisks indicate the treatment that yielded statistically significant differences in comparison with BSA control (*P < .05; **P < .005, Student t test).