The adult mammalian heart is non-regenerative owing to the post-mitotic nature of cardiomyocytes. The neonatal mouse heart can regenerate, but only during the first week of life. Here we show that ...changes in the composition of the extracellular matrix during this week can affect cardiomyocyte growth and differentiation in mice. We identify agrin, a component of neonatal extracellular matrix, as required for the full regenerative capacity of neonatal mouse hearts. In vitro, recombinant agrin promotes the division of cardiomyocytes that are derived from mouse and human induced pluripotent stem cells through a mechanism that involves the disassembly of the dystrophin-glycoprotein complex, and Yap- and ERK-mediated signalling. In vivo, a single administration of agrin promotes cardiac regeneration in adult mice after myocardial infarction, although the degree of cardiomyocyte proliferation observed in this model suggests that there are additional therapeutic mechanisms. Together, our results uncover a new inducer of mammalian heart regeneration and highlight fundamental roles of the extracellular matrix in cardiac repair.
Cardiomyocyte loss after injury results in adverse remodelling and fibrosis, inevitably leading to heart failure. The ERBB2-Neuregulin and Hippo-YAP signalling pathways are key mediators of heart ...regeneration, yet the crosstalk between them is unclear. We demonstrate that transient overexpression of activated ERBB2 in cardiomyocytes (OE CMs) promotes cardiac regeneration in a heart failure model. OE CMs present an epithelial-mesenchymal transition (EMT)-like regenerative response manifested by cytoskeletal remodelling, junction dissolution, migration and extracellular matrix turnover. We identified YAP as a critical mediator of ERBB2 signalling. In OE CMs, YAP interacts with nuclear-envelope and cytoskeletal components, reflecting an altered mechanical state elicited by ERBB2. We identified two YAP-activating phosphorylations on S352 and S274 in OE CMs, which peak during metaphase, that are ERK dependent and Hippo independent. Viral overexpression of YAP phospho-mutants dampened the proliferative competence of OE CMs. Together, we reveal a potent ERBB2-mediated YAP mechanotransduction signalling, involving EMT-like characteristics, resulting in robust heart regeneration.
Irreversible electroporation (IRE) is a non-thermal cell ablation approach that induces selective damage to cell membranes only. The purpose of the current study was to evaluate and optimize its use ...for in-vivo myocardial decellularization.
Forty-two Sprague-Dawley rats were used to compare myocardial damage of seven different IRE protocols with anterior myocardial infarction damage. An in-vivo open thoracotomy model was used, with two-needle electrodes in the anterior ventricular wall. IRE protocols included different combinations of pulse lengths (70 vs. 100 μseconds), frequency (1, 2, 4 Hz), and number (10 vs. 20 pulses), as well as voltage intensity (50, 250 and 500 Volts). All animals underwent baseline echocardiographic evaluation. Degree of myocardial ablation was determined using repeated echocardiography measurements (days 7 and 28) as well as histologic and morphometric analysis at 28 days.
All animals survived 28 days of follow-up. Compared with 50V and 250V, electroporation with 500V was associated with significantly increased myocardial scar and reduction in ejection fraction (67.4%±4% at baseline vs. 34.6%±20% at 28 days; p <0.01). Also, compared with pulse duration of 70 μsec, pulses of 100 μsec were associated with markedly reduced left ventricular function and markedly increased relative scar area ratio (28%±9% vs. 16%±3%, p = 0.02). Decreasing electroporation pulse frequency (1Hz vs. 2Hz, 2Hz vs. 4Hz) was associated with a significant increase in myocardial damage. Electroporation protocols with a greater number of pulses (20 vs. 10) correlated with more profound tissue damage (p<0.05). When compared with myocardial infarction damage, electroporation demonstrated a considerable likeness regarding the extent of the inflammatory process, but with relatively higher levels of extra-cellular preservation.
IRE has a graded effect on the myocardium. The extent of ablation can be controlled by changing pulse length, frequency and number, as well as by changing electric field intensity.
Abstract In Alzheimer's disease (AD), astrocytes undergo morphological changes ranging from atrophy to hypertrophy, but the effect of such changes at the functional level is still largely unknown. ...Here, we aimed to investigate whether alterations in astrocyte activity in AD transient and depend on their microenvironment, or whether are irreversible. We established and characterized a new protocol for the isolation of adult astrocytes and discovered that astrocytes isolated from old 5xFAD mice have higher GFAP expression than astrocytes derived from WT mice, as observed in vivo . We found high C1q levels in brain sections from old 5xFAD mice in close vicinity to amyloid plaques and astrocyte processes. Interestingly, while old 5xFAD astrocytes are impaired in uptake of soluble Aβ42, this effect was reversed upon an addition of exogenous C1q, suggesting a potential role for C1q in astrocyte-mediated Aβ clearance. Our results suggest that scavenger receptor B 1 plays a role in C1q-facilitated Aβ uptake by astrocytes and that expression of scavenger receptor B 1 is reduced in adult old 5xFAD astrocytes. Furthermore, old 5xFAD astrocytes show impairment in support of neuronal growth in co-culture and neurotoxicity concomitant with an elevation in IL-6 expression. Further understanding of the impact of astrocyte impairment on AD pathology may provide insights into the etiology of AD.
Brain metastases are prevalent in various types of cancer and are often terminal, given the low efficacy of available therapies. Therefore, preventing them is of utmost clinical relevance, and ...prophylactic treatments are perhaps the most efficient strategy. Here, we show that systemic prophylactic administration of a toll-like receptor (TLR) 9 agonist, CpG-C, is effective against brain metastases. Acute and chronic systemic administration of CpG-C reduced tumor cell seeding and growth in the brain in three tumor models in mice, including metastasis of human and mouse lung cancer, and spontaneous melanoma-derived brain metastasis. Studying mechanisms underlying the therapeutic effects of CpG-C, we found that in the brain, unlike in the periphery, natural killer (NK) cells and monocytes are not involved in controlling metastasis. Next, we demonstrated that the systemically administered CpG-C is taken up by endothelial cells, astrocytes, and microglia, without affecting blood-brain barrier (BBB) integrity and tumor brain extravasation. In vitro assays pointed to microglia, but not astrocytes, as mediators of CpG- C effects through increased tumor killing and phagocytosis, mediated by direct microglia-tumor contact. In vivo, CpG-C-activated microglia displayed elevated mRNA expression levels of apoptosis-inducing and phagocytosis-related genes. Intravital imaging showed that CpG-C-activated microglia cells contact, kill, and phagocytize tumor cells in the early stages of tumor brain invasion more than nonactivated microglia. Blocking in vivo activation of microglia with minocycline, and depletion of microglia with a colony-stimulating factor 1 inhibitor, indicated that microglia mediate the antitumor effects of CpG-C. Overall, the results suggest prophylactic CpG-C treatment as a new intervention against brain metastasis, through an essential activation of microglia.
Acute MI induces leptin expression in the heart, however the role of myocardial leptin in cardiac ischemia and reperfusion (IR) remains unknown. To shed light on the effects of elevated levels of ...leptin in the myocardium, we overexpressed cardiac leptin and assessed local remodeling and myocardial function in this context.
Cardiac leptin overexpression was stimulated in mice undergoing IR by a single intraperitoneal injection of leptin antagonist (LepA). All mice exhibited a normal pattern of body weight gain. A rapid, long-term upregulation of leptin mRNA was demonstrated in the heart, adipose, and liver tissues in IR/LepA-treated mice. Overexpressed cardiac leptin mRNA extended beyond postoperative day (POD) 30. Plasma leptin peaked 7.5 hours postoperatively, especially in IR/LepA-treated mice, subsiding to normal levels by 24 hours. On POD-30 IR/LepA-treated mice demonstrated cardiomyocyte hypertrophy and perivascular fibrosis compared to IR/saline controls. Echocardiography on POD-30 demonstrated eccentric hypertrophy and systolic dysfunction in IR/LepA. We recorded reductions in Ejection Fraction (p<0.001), Fraction Shortening (p<0.01), and Endocardial Fraction Area Change (p<0.01), and an increase in Endocardial Area Change (p<0.01). Myocardial remodeling in the context of IR and cardiac leptin overexpression was associated with increased cardiac TGFβ ligand expression, activated Smad2, and downregulation of STAT3 activity.
Cardiac IR coinciding with increased myocardial leptin synthesis promotes cardiomyocyte hypertrophy and fibrosis and potentiates myocardial dysfunction. Plasma leptin levels do not reflect cardiac leptin synthesis, and may not predict leptin-related cardiovascular morbidity. Targeting cardiac leptin is a potential treatment for cardiac IR damage.
ABSTRACT Background Inflammation has been implicated in the initiation, progression and manifestation of hypertensive heart disease. We sought to determine the role of monocytes/macrophages in ...hypertension and pressure overload induced left ventricular (LV) remodeling. Methods and results We used two models of LV hypertrophy (LVH). First, to induce hypertension and LVH, we fed Sabra salt-sensitive rats with a high-salt diet. The number of macrophages increased in the hypertensive hearts, peaking at 10 weeks after a high-salt diet. Surprisingly, macrophage depletion, by IV clodronate (CL) liposomes, inhibited the development of hypertension. Moreover, macrophage depletion reduced LVH by 17% ( p < 0.05), and reduced cardiac fibrosis by 75%, compared with controls ( p = 0.001). Second, to determine the role of macrophages in the development and progression of LVH, independent of high-salt diet, we depleted macrophages in mice subjected to transverse aortic constriction and pressure overload. Significantly, macrophage depletion, for 3 weeks, attenuated LVH: a 12% decrease in diastolic and 20% in systolic wall thickness ( p < 0.05), and a 13% in LV mass ( p = 0.04), compared with controls. Additionally, macrophage depletion reduced cardiac fibrosis by 80% ( p = 0.006). Finally, macrophage depletion down-regulated the expression of genes associated with cardiac remodeling and fibrosis: transforming growth factor beta-1 (by 80%) collagen type III alpha-1 (by 71%) and atrial natriuretic factor (by 86%). Conclusions Macrophages mediate the development of hypertension, LVH, adverse cardiac remodeling, and fibrosis. Macrophages, therefore, should be considered as a therapeutic target to reduce the adverse consequences of hypertensive heart disease.
Background
Macrophages and Wnt proteins (Wnts) are independently involved in cardiac development, response to cardiac injury, and repair. However, the role of macrophage‐derived Wnts in the healing ...and repair of myocardial infarction (MI) is unknown. We sought to determine the role of macrophage Wnts in infarct repair.
Methods and Results
We show that the Wnt pathway is activated after MI in mice. Furthermore, we demonstrate that isolated infarct macrophages express distinct Wnt pathway components and are a source of noncanonical Wnts after MI. To determine the effect of macrophage Wnts on cardiac repair, we evaluated mice lacking the essential Wnt transporter Wntless (Wls) in myeloid cells. Significantly, Wntless‐deficient macrophages presented a unique subset of M2‐like macrophages with anti‐inflammatory, reparative, and angiogenic properties. Serial echocardiography studies revealed that mice lacking macrophage Wnt secretion showed improved function and less remodeling 30 days after MI. Finally, mice lacking macrophage‐Wntless had increased vascularization near the infarct site compared with controls.
Conclusions
Macrophage‐derived Wnts are implicated in adverse cardiac remodeling and dysfunction after MI. Together, macrophage Wnts could be a new therapeutic target to improve infarct healing and repair.
The immune system plays a pivotal role in myocardial homeostasis and response to injury. Interleukins-4 and -13 are anti-inflammatory type-2 cytokines, signaling via the common interleukin-13 ...receptor α1 chain and the type-2 interleukin-4 receptor. The role of interleukin-13 receptor α1 in the heart is unknown.
We analyzed myocardial samples from human donors (n=136) and patients with end-stage heart failure (n=177). We found that the interleukin-13 receptor α1 is present in the myocardium and, together with the complementary type-2 interleukin-4 receptor chain
, is significantly downregulated in the hearts of patients with heart failure. Next, we showed that
-deficient mice develop severe myocardial dysfunction and dyssynchrony compared to wild-type mice (left ventricular ejection fraction 29.7±9.9 versus 45.0±8.0;
=0.004, left ventricular end-diastolic diameter 4.2±0.2 versus 3.92±0.3;
=0.03). A bioinformatic analysis of mouse hearts indicated that interleukin-13 receptor α1 regulates critical pathways in the heart other than the immune system, such as extracellular matrix (normalized enrichment score=1.90; false discovery rate q=0.005) and glucose metabolism (normalized enrichment score=-2.36; false discovery rate q=0). Deficiency of
was associated with reduced collagen deposition under normal and pressure-overload conditions.
The results of our studies in humans and mice indicate, for the first time, a role of interleukin-13 receptor α1 in myocardial homeostasis and heart failure and suggests a new therapeutic target to treat heart disease.
Damage to apple (Malus domestica Borkhausen) by Campylomma verbasci (Meyer), has occurred even when effective insecticides are applied against nymphs present at the petal fall stage. However, ...insecticide application at pink bud prevents damage more effectively than when the same insecticides are applied at petal fall. We tested the hypothesis that most mullein bug damage occurs between bloom and petal fall by using two approaches. In the first, we caged naturally occurring nymphs on ‘Red Delicious’ limbs and restricted their possible infestation timing by applying insecticides both before cages were placed and also through the cage at various crop stages from bloom through fruit set. In a second approach, we caged Red Delicious and ‘McIntosh’ fruit clusters and introduced either small or large nymphs at various times from bloom through 3 wk after fruit set. Fruit damage on both varieties was greatest when small nymphs were introduced between bloom and petal fall; damage was uncommon from small nymphs introduced after fruit were ≈6 mm, and absent after the 13 mm size. However, damage was greater in cages into which large nymphs were introduced at 10–13 mm, than in untreated control cages. Fruit damage levels were equivalent on McIntosh and Red Delicious. We compared emergence of nymphs from McIntosh shoots with adjacent plantings of other, more susceptible cultivars by forcing hatch in the laboratory from cuttings collected in late winter. Significantly more nymphs hatched from susceptible varieties than from McIntosh, suggesting possible differences in levels of oviposition.
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