(a), Effects of IGF-1 (n = 3), cGP (n = 3), combined treatment of cGP + IGF-1 (n = 3) and PBS control, (n = 3) on endothelial cell growth in serum. Combination treatment of cGP + IGF-1 significantly inhibited IGF-1-induced cell growth only when it was elevated at day 6. Treatment with cGP did not alter the growth compared to control group. ##/**p < 0.01 by two-way ANOVA. The experiments were repeated 8 times. (b), The effects of IGF-1 (n = 15), combined treatment of cGP + IGF-1 (n = 15) and PBS (n = 10) on tube formation. Similarly, the combination treatment (cGP + IGF-1) reduced IGF-1-induced tube formation. ##/**p < 0.01 by one way ANOVA. The experiments were repeated 3 times. (c), The effects of IGF-1 (n = 3), combined treatment of cGP + IGF-1 (n = 3) and PBS control (n = 3) on endothelial cell growth after serum withdrawal. The combination treatment increased total cell counts when IGF-1 failed to be effective. **p < 0.01, ***p < 0.001 by two-way ANOVA. The experiments were repeated 4 times. (d, e, f), The effects of IGF-1 alone (black bar, n = 6), combined treatments of cGP + IGF-1 (grey bars, n = 6) and PBS (while bars, n = 6) on cell viability. Compared to IGF-1 alone treatment the combined treatment of cGP + IGF-1 either inhibited (d), or remained (e) or stimulated (f) IGF-1 function. One-way ANOVA with repeated measures were used for analysing the data. Data are presented as mean ± SEM, where #p < 0.05, ##p < 0.01 indicate the difference between the Controls and IGF-1; *p < 0.05, **p < 0.01, indicate the differences between IGF-1 alone and the combination treatments. These experiments were repeated 3 times.