High levels of HIF-1α in hypoxic dental pulps associated with teeth with severe periodontitis

In this study we investigated the expression of HIF-1 alpha in dental pulps of the teeth with severe periodontitis. The expression of HIF-1 alpha in dental pulps of the teeth with severe periodontitis was detected by immunohistochemistry, immunofluorescence and real-time PCR. Bone marrow macrophages (BMMs) were cultured under hypoxia in vitro. HIF-1 alpha, osteoclast-specific factors (NFATc1, CTSK and c-fos) and RANKL-induced osteoclastogenesis were evaluated by immunofluorescence, TRAP staining and western blotting. High levels of HIF-1 alpha protein were detected in dental pulps of teeth with severe periodontitis, whereas few positive HIF-1 alpha expressions were detected in healthy dental pulps. Hypoxia occurred in the dental pulps in response to heavy periodontitis. Many HIF-1A-positive infiltratory inflammatory cells were observed around blood vessels. Tooth internal resorption was found in some teeth with severe periodontitis. The HIF-1 alpha levels were upregulated in BMMs under hypoxia, which also promoted osteoclast formation and resorption by NFATc1, CTSK and c-fos. Teeth with severe periodontitis show hypoxic dental pulps and increased potential of osteoclastic differentiation.