Abstract: Zhu Yalin, Hou Wei, Paride Abliz Department of Dermatology, First Affiliated Hospital of Xinjiang Medical University, Urumqi 830054, China Corresponding author: Paride Abliz, Email: palidae@aliyun.com 【Abstract】 Objective To evaluate in vitro effects of propranolol and isoproterenol on proliferation of infantile hemangioma endothelial cells （IHECs） as well as expressions of vascular endothelial growth factors （VEGF and VEGF-2） and human basic fibroblast growth factor （bFGF）. Methods The second - third passage endothelial cells derived from the proliferative phase of infantile hemangioma were divided into propranolol and isoproterenol groups. The propranolol group was further classified into 5 groups to be treated with propranolol solutions at concentrations of 10, 15, 20 mg/L, EGM-2 medium （blank control group 1）, or EGM-2 medium containing 0.16% DMSO （DMSO group）, while the isoproterenol group was classified into 4 groups to be treated with isoproterenol solutions at concentrations of 5, 10, 20 mg/L or EGM-2 medium （blank control group 2）. Methyl thiazolyl tetrazolium （MTT） assay was performed to evaluate cellular proliferative activity in these propranolol groups at 24, 48, 72 and 96 hours separately, enzyme-linked immunosorbent assay （ELISA） to measure VEGF, VEGF-2 and bFGF levels in culture supernatants of IHECs at 24 and 48 hours separately. Results The proliferative activity of IHECs showed no significant differences between 10-, 15- and 20-mg/L propranolol groups at either 24 or 48 hours （H = 1.152, 2.643, respectively, both P > 0.05）, or between the blank control group 1, DMSO group, and 10- and 15-mg/L propranolol groups at either 72 or 96 hours, but significantly decreased in the 20-mg/L propranolol group compared with the blank control group 1 at 72 and 96 hours （both P < 0.05）. The 24-hour treatments with propranolol or isoproterenol at the above concentrations all affected the expressions of VEGF, VEGF-2 and bFGF to different degrees. At 48 hours, there was a significant decrease in VEGF levels in 15- and 20-mg/L propranolol groups, as well as in VEGF-2 and bFGF levels in 10-, 15- and 20-mg/L propranolol groups compared with the blank control group 1 （all P < 0.05）, but a significant increase in VEGF levels in 5-, 10- and 20-mg/L isoproterenol groups compared with the blank control group 2 （all P < 0.05）, as well as in VEGF-2 and bFGF levels in the 20-mg/L isoproterenol group compared with the blank control group 2, 5- and 10-mg/L isoproterenol groups （all P < 0.05）. Conclusions The treatment with propranolol at specific concentrations for specific durations can suppress the growth of, as well as expressions of VEGF, VEGF-2 and bFGF in, endothelial cells derived from the proliferative phase of infantile hemangioma, whereas that with isoproterenol has opposite effects. The therapeutic mechanism of propranolol in infantile hemangioma may be associated with expressions of β-adrenergic receptors and their downstream signal transduction-related cytokines.