Pulp Cell Response in the Condition of Hypoxia

Objectives: Previous report showed that vasoconstrictor-containing local anesthetics made pulpal blood flow decrease (28.5% of the control value) and intraseptal injection caused severe reduction of the blood flow (9.6% of the control value). However, pulp cell activity in hypoxia has still been unknown. We examined pulp cell activity in the condition of hypoxia in vitro. Methods: Pulp tissues obtained from dogs were cultured in MEM supplemented with 10% FBS and antibiotic solution. After subculture, cells were plated in 35mm cell culture dishes at a concentration of 1~105cells per dish. Then the dishes were divided into two groups; hypoxia group were cultured in a humidified hypoxic environment (2“O2+93“N2O+5“CO2) for 1 to 4d, and in the control group, cells were incubated normoxia condition (95“room air+5“CO2) for 1 to 4d. Cell viability, Cell growth curve, MTT cell growth assay, alkaline phosphatase (ALP) activity, heat shock protein 70 (HSP70) and vascular endothelial growth factor (VEGF) expression were analyzed. Results: Either the cell proliferation ratio or ALP activity were significantly increase compared with the control group (pƒ0.05). HSP70 expression was not significant difference between both groups, but VEGF expression in the hypoxia group was significantly higher compared with control group. Conclusions: These results suggest that hypoxic environment may increase the VEGF of pulp cell in gene level and promote proliferation and differentiation of pulp cell to the osteogenic cells, but cause to cell death or apoptosis. This study was supported by TDCHRC982A01.