Abstract:

BACKGROUND: In endodontics, revascularization and effective control of bacterial infection are prerequisite for regenerative repair of tissues and further development of the root apex. Ornidazole, carried in pulp-capping materials or vascularized scaffolding materials may control pulpal infections, but its effect on vascularization need to be investigated.

OBJECTIVE: To investigate the residual concentration pattern of ornidazole in root canals and to evaluate the effects of ornidazole on endothelial cell proliferation, migration, and differentiation, as well as on vascular irritation.

METHODS: (1) Ornidazole was encapsulated in the isolated pulp cavity and then immersed in Hank’s balanced salt solution for 7 days. Ornidazole was then removed from the pulp cavity, reencapsulated in sterile water, and again immersed in Hank’s balanced salt solution. The mass concentration of ornidazole in the pulp cavity fluid was measured periodically by colorimetric method. (2) Human umbilical vein endothelial cells were inoculated into well plates. Adherent cells were stimulated by the addition of lipopolysaccharide for 24 hours, and then co-cultured by the addition of 0, 1, 2, 5, 8, 10 μg/mL ornidazole, to detect the cellular activity and migratory ability. Human umbilical vein endothelial cells were inoculated in well plates and co-cultured with different mass concentrations (0, 1, 2, 5, 8, 10 μg/mL) of ornidazole or stimulated by lipopolysaccharide for 24 hours followed by the addition of different mass concentrations (0, 1, 2, 5, 8, 10 μg/mL) of ornidazole. The gene expression of vascular endothelial growth factor and basic fibroblast growth factor as well as the protein expression of vascular endothelial growth factor was detected. (3) The chorioallantoic membrane assay was employed to assess the vascular irritation of 2 and 10 μg/mL ornidazole.

RESULTS AND CONCLUSION: (1) Residual ornidazole in exfoliated teeth was rapidly released within the initial 6 days, with a subsequent decrease in release rate, maintaining a concentration of approximately 2 μg/mL at the root apex after 8 days. (2) Under lipopolysaccharide-induced inflammatory conditions, cell counting kit-8 and cell live-dead fluorescence staining showed that ornidazole (1-10 μg/mL) had no significant effect on the activity of human umbilical vein endothelial cells, and the cell scratch assay showed that ornidazole (1-10 μg/mL) had no obvious effect on the migratory ability of human umbilical vein endothelial cells. RT-qPCR assay showed that, after co-cultivation with ornidazole alone, the mRNA expression of vascular endothelial growth factor and basic fibroblast growth factor in human umbilical vein endothelial cells showed an overall decreasing trend. After co-culturing with ornidazole under lipopolysaccharide-induced inflammation, the mRNA expression of the two factors showed a rising trend in human umbilical vein endothelial cells. Western blot assay showed that vascular endothelial growth factor protein expression had an elevating trend in human umbilical vein endothelial cells after co-culture with ornidazole under lipopolysaccharide-induced inflammatory conditions. (3) The chorioallantoic membrane assay showed that 2 and 10 μg/mL ornidazole were non-vascular irritating. To conclude, 1-10 μg/mL ornidazole is non-cytotoxic and non-vascular irritating, promotes the expression of angiogenesis-related genes and proteins in inflammatory endothelial cells, and serves as a potential therapeutic agent for pulpal infection control.

Key words: ornidazole, endothelial cell, angiogenesis, drug residue, pulp infection, intracanal vascularization