Hypoxia increases the expression of enamel genes and cytokines in an ameloblast‐derived cell line

The aim of this study was to investigate the effect of hypoxic conditions on the expression of enamel genes and on the secretion of alkaline phosphatase (ALP), lactate dehydrogenase (LDH), cytokines, and interleukins by an ameloblast‐derived cell line. Murine ameloblast‐derived cells (LS‐8 cells) were exposed to 1% oxygen for 24 and 48 h and harvested after 1, 2, 3, and 7 d. The effect of culture in hypoxic conditions on the expression of structural enamel matrix genes and on the secretion of cytokines and interleukins, as well as ALP and LDH, into the cell‐culture medium was calculated relative to the expression and secretion of these factors by untreated cells (controls) at each time point. Hypoxia increased expression of the structural enamel matrix genes amelogenin (Amelx), ameloblastin (Ambn), and enamelin (Enam), and the enamel protease matrix metalloproteinase‐20 (Mmp20). Expression of hypoxia‐inducible factor 1‐alpha (Hif1α), and secretion of several vascularization factors and pro‐inflammatory factors, were increased after 24 and 48 h of hypoxia. The ALP activity was reduced after 24 and 48 h of hypoxia, whereas the LDH level in the cell‐culture medium was higher after 24 h of hypoxic conditions compared with 48 h. In conclusion, hypoxic exposure may disrupt the controlled fine‐tuned expression and processing of enamel genes, and promote the secretion of pro‐inflammatory factors.     

Cor-triatriatum sinister presenting in the adult as mitral stenosis: an analysis of factors which may be relevant in late presentation

BACKGROUND: Cor-triatriatum sinister is a rare congenital heart defect resulting from the division of the left atrium by a fibro-muscular membrane. It is usual for patients to present in infancy and early childhood, although some cases remain undetected until adult life. As a consequence of trans-membrane flow obstruction, the clinical features often mimic mitral stenosis. At present, the reasons for late presentation are poorly understood. METHODS: A complete review of all cases of cor-triatriatum sinister published in the English literature from 1966 to date as mitral stenosis was performed. Statistical analysis was carried out to determine associations between measurements reflecting the communicating membrane fenestration area, the presence of several clinical variables and patient age at initial presentation. RESULTS: Both pulmonary capillary wedge pressure and mean pressure gradient were significantly higher in younger adults. In addition, the incidence of atrial fibrillation and mitral regurgitation was found to rise with advancing age. CONCLUSIONS: Cor-triatriatum sinister remains an uncommon form of congenital heart disease although it is being diagnosed with increasing frequency in adults due to improvements in diagnostic imaging. This diagnosis should be considered in all patients presenting with signs or symptoms of mitral stenosis.