| Background and objectivePulpitis is the inflammation of dental pulp tissue, which is mainly caused by bacteria infection. Hypoxia-inducible factor-1 is transcription factors that respond to changes in available oxygen in the cellular environment, to be specific, to decreases in oxygen, or hypoxia. Vascular endothelial growth factor(VEGF), originally known as vascular permeability factor(VPF) is a signal protein produced by cells that stimulates vasculogenesis and angiogenesis. VEGF plays an important role in cancer and inflammation. The conditioning for hypoxia, VEGF is one of the main target genes of HIF- 1α.Whereas HIF-1α is the major VEGF inducer during tumor angiogenesis. The role of HIF-1α and VEGF-c in the pathogenesis of inflamed dental pulp tissue was still ambiguous. The objective of the present study was to investigate the expression and the distribution of HIF-1α and VEGF-c in health and inflamed dental pulp tissue. Results from these studies will provide interpretation into the role of oxygen metabolism in the pathogenesis of pulpitis, leading to further studies in oxygen regulated pathways. The insights will help to develop targeted therapy to cure pulpitis.MethodsThe dental pulp biopsies were randomly obtained from the patients attending the affiliated Huizhou Stomatology Hospital affiliated Medical College of Jinan University from December 2013 to May 2014.Total 40 dental pulp tissue specimens included healthy control group(n=10), deep caries pulp group(n=10), chronic pulpitis group(n=10), acute pulpitis group(n=10).All dental pulp tissue was obtained from tooth extraction which needs orthodontic treatment and wisdom teeth. The histological change of pulp tissues was observed under microscope after HE staining.The HIF-1α and VEGF-c expression in the tissues were analyzed by IHC. All statistical analyses were performed using SPSS 16.0 software(α=0.05,P<0.05).1) Nonparametric tests were chosen for continuous variables since the data were not distributed normally. 2) Differences in pulpal IHC examination data and the density of HIF-1α, VEGF-c of different groups were analyzed using Kruskal-Wallis H test. 3) The relationship between the expression level of HIF-1α, VEGF-c in dental pulp tissues and the inflammation score were analyzed with the Pearson correlation. 4) The relationship between the levels of HIF-1α, VEGF-c in tissue was analyzed with the Pearson correlation.Results1. Histological observations1) Histologically, no inflammatory infiltration and inflammatory cell infiltration was found in clinically healthy pulp tissues and deep caries pulp. 2) Compared with the chronic pulpitis, acute pulpitis group showed acute inflammatory infiltration. 3) Compared with healthy and deep caries, the chronic pulpitis showed moderate inflammatory infiltration. 4) Compared with chronic pulpitis, the inflammation score of pulpal tissues from both chronic pulpitis group and acute pulpitis group were significantly higher(P<0.01); In addition, the inflammation score of periodontal tissues from both acute pulpitis group was significantly higher than that of chronic pulpitis group(P< 0.01).2. HIF-1α, VEGF-c protein immunohistochemical staining resultsHIF-1α protein positive cells were mainly localized in odontoblasts, fibroblasts, endothelial cells and inflammatory cells. Compared with healthy and deep caries pulp group, the density of HIF-1α positive cells significantly increased in chronic pulpitis groups(P<0.01), and the density of HIF-1α positive cells positive cells in acute pulpitis group was significantly higher than those in chronic pulpitis group(P<0.01).VEGF-c positive expressions mainly localized in odontoblasts, fibroblasts, endothelial cells, macrophages and plasma cells. Compared with healthy and deep caries pulp group, the density of VEGF-c positive cells significantly increased in acute pulpitis groups(P<0.01), and the density of HIF-1α positive cells positive cells in chronic pulpitis group was significantly higher than those in acute pulpitis group(P<0.01).3. Correlation analysis between the expression level of HIF-1α,VEGF-c and the inflammation score of pulpal tissues1) There was a positive correlation between the density of HIF-1α positive cells and the inflammation score in pulpal tissues of each group(P<0.01). 2) There was a positive correlation between the density of VEGF-c positive cells and the inflammation score in pulpal tissues of each group(P<0.01).4. Correlation analysis between the expression levels of HIF-1αand VEGF-cThe Pearson correlation analysis showed that there was a positive correlation between the expression level of HIF-1α and VEGF-c in pulpal tissues of each groups(P<0.01).Conclusions1. Compared with healthy and deep caries pulp group, the density of HIF-1α and VEGF-c positive cells significantly increased in human inflamed dental pulp tissue. 2. There was a positive relationship between the expression level of HIF-1α and VEGF-c and the inflammation score of pulpal tissues.HIF-1α and VEGF-c expression may involve in human inflamed dental pulp tissue. HIF-1α and VEGF-c may play a key role in the pathogenesis of dental pulpitis. |
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