Systemic Dosing of Thymosin Beta 4 before and after Ischemia Does Not Attenuate Global Myocardial Ischemia-Reperfusion Injury in Pigs

The use of cardiopulmonary bypass (CPB) and aortic cross-clamping causes myocardial ischemia-reperfusion injury (I-RI) and can lead to reduced postoperative cardiac function. We investigated whether this injury could be attenuated by thymosin beta 4 (TB4), a peptide which has showed cardioprotective effects. Pigs received either TB4 or vehicle and underwent CPB and aortic cross-clamping for 60 min with cold intermittent blood-cardioplegia and were then followed for 30 h. Myocardial function and blood flow was studied by cardiac magnetic resonance and PET imaging. Tissue and plasma samples were analyzed to determine the amount of cardiomyocyte necrosis and apoptosis as well as pharmacokinetics of the peptide. In vitro studies were performed to assess its influence on blood coagulation and vasomotor tone. Serum levels of the peptide were increased after administration compared to control samples. TB4 did not decrease the amount of cell death. Cardiac function and global myocardial blood flow was similar between the study groups. At high doses a vasoconstrictor effect on mesentery arteries and a vasodilator effect on coronary arteries was observed and blood clot firmness was reduced when tested in the presence of an antiplatelet agent. Despite promising results in previous trials the cardioprotective effect of TB4 was not demonstrated in this model for global myocardial I-RI

Loss of PPAR gamma in endothelial cells leads to impaired angiogenesis

Tie2-promoter-mediated loss of peroxisome proliferator-activated receptor gamma (PPAR gamma, also known as PPARG) in mice leads to osteopetrosis and pulmonary arterial hypertension. Vascular disease is associated with loss of PPAR gamma in pulmonary microvascular endothelial cells (PMVEC); we evaluated the role of PPAR gamma in PMVEC functions, such as angiogenesis and migration. The role of PPAR gamma in angiogenesis was evaluated in Tie2CrePPAR gamma(flox/flox) and wild-type mice, and in mouse and human PMVECs. RNA sequencing and bioinformatic approaches were utilized to reveal angiogenesisassociated targets for PPAR gamma. Tie2CrePPAR gamma(flox/flox) mice showed an impaired angiogenic capacity. Analysis of endothelial progenitor-like cells using bone marrow transplantation combined with evaluation of isolated PMVECs revealed that loss of PPAR gamma attenuates the migration and angiogenic capacity of mature PMVECs. PPAR gamma-deficient humanPMVECs showed a similar migration defect in culture. Bioinformatic and experimental analyses newly revealed E2F1 as a target of PPAR gamma in the regulation of PMVEC migration. Disruption of the PPAR gamma-E2F1 axis was associated with a dysregulated Wnt pathway related to the GSK3B interacting protein (GSKIP). In conclusion, PPAR gamma plays an important role in sustaining angiogenic potential in mature PMVECs through E2F1-mediated gene regulation.</p

HSFs and regulation of Hsp70.1 (Hspa1b) in oocytes and preimplantation embryos: new insights brought by transgenic and knockout mouse models

Gene encoding heat shock protein (Hsps) are induced following a thermal stress thanks to the activation of heat shock transcription factor (HSF) which interacts with heat shock elements (HSE) located within the sequence of Hsp promoters. This cellular and protective response (heat shock response (HSR)) is well known and evolutionarily conserved. Nevertheless, HSR does not function in all the cells produced during the life of a multicellular organism, e.g., early mouse embryos. Taking advantage of mouse transgenic and knockout models, we investigated the roles of trans (HSF 1 and 2) and cis (HSE) regulatory elements in the control of Hsp70.1 (Hspa1b) through several developmental steps from oocytes to blastocysts. Our studies confirm that, even in absence of any stress, HSF1 regulates Hsp70.1 in oocytes and early embryos. Our data emphasize the role of maternal and paternal HSFs in the developmentally regulated expression of Hsp70.1 observed when the zygotic genome activation occurs. Furthermore, in this unstressed developmental condition, affinity and binding to HSEs might be more permissive than in the stress response. Finally, submitting blastocyst to different stress conditions, we show that HSF2 is differentially required for Hsp expression and cell survival. Taken together, our findings indicate that the role of heat shock trans and cis regulatory elements evolve along the successive steps of early embryonic development