Histone modification landscape and the key significance of H3K27me3 in myocardial ischaemia/reperfusion injury.

Histone modifications play crucial roles in the pathogenesis of myocardial ischaemia/reperfusion (I/R) injury. However, a genome-wide map of histone modifications and the underlying epigenetic signatures in myocardial I/R injury have not been established. Here, we integrated transcriptome and epigenome of histone modifications to characterize epigenetic signatures after I/R injury. Disease-specific histone mark alterations were mainly found in H3K27me3-, H3K27ac-, and H3K4me1-marked regions 24 and 48 h after I/R. Genes differentially modified by H3K27ac, H3K4me1 and H3K27me3 were involved in immune response, heart conduction or contraction, cytoskeleton, and angiogenesis. H3K27me3 and its methyltransferase polycomb repressor complex 2 (PRC2) were upregulated in myocardial tissues after I/R. Upon selective inhibition of EZH2 (the catalytic core of PRC2), the mice manifest improved cardiac function, enhanced angiogenesis, and reduced fibrosis. Further investigations confirmed that EZH2 inhibition regulated H3K27me3 modification of multiple pro-angiogenic genes and ultimately enhanced angiogenic properties in vivo and in vitro. This study delineates a landscape of histone modifications in myocardial I/R injury, and identifies H3K27me3 as a key epigenetic modifier in I/R process. The inhibition of H3K27me3 and its methyltransferase might be a potential strategy for myocardial I/R injury intervention.

PKM2 deficiency exacerbates gram-negative sepsis-induced cardiomyopathy via disrupting cardiac calcium homeostasis.

Sepsis is a life-threatening syndrome with multi-organ dysfunction in critical care medicine. With the occurrence of sepsis-induced cardiomyopathy (SIC), characterized by reduced ventricular contractility, the mortality of sepsis is boosted to 70-90%. Pyruvate kinase M2 (PKM2) functions in a variety of biological processes and diseases other than glycolysis, and has been documented as a cardioprotective factor in several heart diseases. It is currently unknown whether PKM2 influences the development of SIC. Here, we found that PKM2 was upregulated in cardiomyocytes treated with LPS both in vitro and in vivo. Pkm2 inhibition exacerbated the LPS-induced cardiac damage to neonatal rat cardiomyocytes (NRCMs). Furthermore, cardiomyocytes lacking PKM2 aggravated LPS-induced cardiomyopathy, including myocardial damage and impaired contractility, whereas PKM2 overexpression and activation mitigated SIC. Mechanism investigation revealed that PKM2 interacted with sarcoplasmic/endoplasmic reticulum calcium ATPase 2a (SERCA2a), a key regulator of the excitation-contraction coupling, to maintain calcium homeostasis, and PKM2 deficiency exacerbated LPS-induced cardiac systolic dysfunction by impairing SERCA2a expression. In conclusion, these findings highlight that PKM2 plays an essential role in gram-negative sepsis-induced cardiomyopathy, which provides an attractive target for the prevention and treatment of septic cardiomyopathy.

Pyruvate Kinase M2 Protects Heart from Pressure Overload-Induced Heart Failure by Phosphorylating RAC1.

Background Heart failure, caused by sustained pressure overload, remains a major public health problem. PKM (pyruvate kinase M) acts as a rate-limiting enzyme of glycolysis. PKM2 (pyruvate kinase M2), an alternative splicing product of PKM, plays complex roles in various biological processes and diseases. However, the role of PKM2 in the development of heart failure remains unknown. Methods and Results Cardiomyocyte-specific Pkm2 knockout mice were generated by crossing the floxed Pkm2 mice with α-MHC (myosin heavy chain)-Cre transgenic mice, and cardiac specific Pkm2 overexpression mice were established by injecting adeno-associated virus serotype 9 system. The results showed that cardiomyocyte-specific Pkm2 deletion resulted in significant deterioration of cardiac functions under pressure overload, whereas Pkm2 overexpression mitigated transverse aortic constriction-induced cardiac hypertrophy and improved heart functions. Mechanistically, we demonstrated that PKM2 acted as a protein kinase rather than a pyruvate kinase, which inhibited the activation of RAC1 (rho family, small GTP binding protein)-MAPK (mitogen-activated protein kinase) signaling pathway by phosphorylating RAC1 in the progress of heart failure. In addition, blockade of RAC1 through NSC23766, a specific RAC1 inhibitor, attenuated pathological cardiac remodeling in Pkm2 deficiency mice subjected to transverse aortic constriction. Conclusions This study revealed that PKM2 attenuated overload-induced pathological cardiac hypertrophy and heart failure, which provides an attractive target for the prevention and treatment of cardiomyopathies.

Various administration forms of decellularized amniotic membrane extract towards improving corneal repair.

Amniotic membrane (AM) transplantation is often used as a treatment for corneal repair, but AM is prone to dissolving and shedding after surgery; multiple transplants will cause pain and financial burden. In this work, human amniotic membrane was firstly decellularized to obtain an AM extracellular matrix (dAM). This dAM was homogenized and extracted to obtain the dAM extract (simplified as dAME). Different forms of administration for corneal injury were performed as liquid drops (diluted dAME), in situ gels (using temperature-dependent Poloxamer 407 as the matrix), and tablets (poly(vinyl alcohol) as the matrix). The cytocompatibility of dAME was evaluated using corneal epithelial cells, corneal stromal cells and fibroblasts as cell models. The results showed that dAME is biocompatible to all these cells. Cells exhibited normal morphology and growth state at a dAME concentration of up to 160 µg mL-1. In vivo, dAME exhibited increased wound healing efficiency in severe corneal injury, being characterized with a shorter healing time for epithelium and a faster recovery for stromal opacity and thickness, compared with those of the control eyes. Different forms of administration have different effects on corneal repair; among them, in situ gels achieved the best therapeutic efficiency. Their biological mechanism was detected via quantitative real-time polymerase chain reaction (qRT-PCR) technology. It was confirmed that dAME plays important roles in promoting the mRNA expression of leucine-rich and immunoglobulin-like domains 1 (LRIG1) and in inhibiting the mRNA of transforming growth factor-ß1 (TGF-ß1).

Hyaluronic acid (HA)-based hydrogels for full-thickness wound repairing and skin regeneration.

In this work, two kinds of hyaluronic acid (HA)-based hydrogels were fabricated: one is made from physical freezing-thawing of HA solution (HA1), and the other is from chemical cross-linking of HA and polysaccharide (HA2). They were applied to repair full-thickness skin defects with New Zealand rabbits as the test animals, using powder HA and cotton dress as the references. The wound starts to heal after wounds were disinfected with iodine followed by coating with HA2, HA1, HA and cotton dress (the control), respectively. They were recorded as 4 treatments (groups), HA2, HA1, HA and the control. The healing progress was followed and tested in the duration of 56 days, and the biological repairing mechanism was explored. From the wound area alteration, white blood cell (WBC) measurements and H&E staining, HA2 was the most promising treatment in promoting the wound healing with least serious scar formation. Immunochemistry analyses and real-time PCR tests of the bio-factors involved in the wound healing, vascular endothelial growth factor (VEGF), alpha-smooth muscle actin (α-SMA) and transforming growth factor beta-1 (TGF-ß1), exhibited that HA2 enhanced VEGF and α-SMA secretion but reduced TGF-ß1 expression at early stage, which alleviated the wound inflammation, improved the skin regeneration and relieved the scar formation.