The biology of HIFα proteins in cell differentiation and disease

HIF-1alpha Deficiency Attenuates the Cardiomyogenesis of Mouse Embryonic Stem Cells

Cardiac cell formation, cardiomyogenesis, is critically dependent on oxygen availability. It is known that hypoxia, a reduced oxygen level, modulates the in vitro differentiation of pluripotent cells into cardiomyocytes via hypoxia inducible factor-1alpha (HIF-1α)-dependent mechanisms. However, the direct impact of HIF-1α deficiency on the formation and maturation of cardiac-like cells derived from mouse embryonic stem cells (mESC) in vitro remains to be elucidated. In the present study, we demonstrated that HIF-1α deficiency significantly altered the quality and quantity of mESC-derived cardiomyocytes. It was accompanied with lower mRNA and protein levels of cardiac cell specific markers (myosin heavy chains 6 and 7) and with a decreasing percentage of myosin heavy chain α and β, and cardiac troponin T-positive cells. As to structural aspects of the differentiated cardiomyocytes, the localization of contractile proteins (cardiac troponin T, myosin heavy chain α and β) and the organization of myofibrils were also different. Simultaneously, HIF-1α deficiency was associated with a lower percentage of beating embryoid bodies. Interestingly, an observed alteration in the in vitro differentiation scheme of HIF-1α deficient cells was accompanied with significantly lower expression of the endodermal marker (hepatic nuclear factor 4 alpha). These findings thus suggest that HIF-1α deficiency attenuates spontaneous cardiomyogenesis through the negative regulation of endoderm development in mESC differentiating in vitro.

Vascular endothelial growth factors signalling in normal human dental pulp: a study of gene and protein expression

In the well-vascularized dental pulp vascular endothelial growth factor A (VEGF-A) is expressed. Vascular endothelial growth factor A is a member of the VEGF family, which includes VEGFs-B, -C, and -D. The latter three have not been investigated in the pulp. Vascular endothelial growth factors C and D are the only ligands for vascular endothelial growth factor receptor (VEGFR)-3, which is usually expressed in lymphatic endothelium. They can also activate VEGFR-2, the main angiogenic receptor. We aimed to study VEGFs signalling in human dental pulp at the gene level and to identify the cellular source for protein expression using immunolabelling. All VEGFs (-A, -B, -C, and -D) were expressed in the pulp and may exert both autocrine and paracrine effects in blood vessels and immune cells found to be equipped with VEGFRs-2 and -3. Lymphatic vessel endothelial hyaluronan receptor-positive macrophages, known to be involved in angiogenesis, were found in the pulp, whereas lymphatic vessels were not detected. Twenty-six of 84 VEGF signalling genes, including VEGFR-3, were expressed at a significantly higher level in the pulp than in the control periodontal ligament. In conclusion, the normal human pulp represents a tissue with relatively high VEGF signalling involving both immune responses and vascular activity.

Hypoxia-inducible factor 1 alpha contributes to cardiac healing in mesenchymal stem cells-mediated cardiac repair

Mesenchymal stem cells (MSC) are effective in treating myocardial infarction (MI) and previous reports demonstrated that hypoxia improves MSC self-renewal and therapeutics. Considering that hypoxia-inducible factor-1 alpha (HIF-1α) is a master regulator of the adaptative response to hypoxia, we hypothesized that HIF-1α overexpression in MSC could mimic some of the mechanisms triggered by hypoxia and increase their therapeutic potential without hypoxia stimulation. Transduction of MSC with HIF-1α lentivirus vectors (MSC-HIF) resulted in increased cell adhesion and migration, and activation of target genes coding for paracrine factors. When MSC-HIF were intramyocardially injected in infarcted nude rats, significant improvement was found (after treatment of infarcted rats with MSC-HIF) in terms of cardiac function, angiogenesis, cardiomyocyte proliferation, and reduction of fibrotic tissue with no induction of cardiac hypertrophy. This finding provides evidences for a crucial role of HIF-1α on MSC biology and suggests the stabilization of HIF-1α as a novel strategy for cellular therapies.

Advances in understanding mechanisms underlying the antitumor activity of curcumin analogue EF24

Curcumin, a natural polyphenol which was first extracted by Vogel and Pelletier from rhizomes of the plant Curcuma longa L, has potent anticarcinogenic activity and low toxic side effects in a wide variety of tumor cells. It has been listed as a third-generation chemoprophylactic drug by the US National Cancer Institute. However, the therapeutic benefit is hampered by its low absorption after transdermal or oral application. Ames et al. have developed a series of novel synthetic curcumin analogs that are more potent and have better water solubility than curcumin. One of these leading compounds, EF24, exhibits about 10-fold greater cytotoxic activity against various cancer cell lines in relation to curcumin. This article will review the recent advances in understanding mechanisms underlying the antitumor activity of EF24.