An acute immune response underlies the benefit of cardiac stem cell therapy.

Clinical trials using adult stem cells to regenerate damaged heart tissue continue to this day1,2, despite ongoing questions of efficacy and a lack of mechanistic understanding of the underlying biological effect3. The rationale for these cell therapy trials is derived from animal studies that show a modest but reproducible improvement in cardiac function in models of cardiac ischaemic injury4,5. Here we examine the mechanistic basis for cell therapy in mice after ischaemia-reperfusion injury, and find that-although heart function is enhanced-it is not associated with the production of new cardiomyocytes. Cell therapy improved heart function through an acute sterile immune response characterized by the temporal and regional induction of CCR2+ and CX3CR1+ macrophages. Intracardiac injection of two distinct types of adult stem cells, cells killed by freezing and thawing or a chemical inducer of the innate immune response all induced a similar regional accumulation of CCR2+ and CX3CR1+ macrophages, and provided functional rejuvenation to the heart after ischaemia-reperfusion injury. This selective macrophage response altered the activity of cardiac fibroblasts, reduced the extracellular matrix content in the border zone and enhanced the mechanical properties of the injured area. The functional benefit of cardiac cell therapy is thus due to an acute inflammatory-based wound-healing response that rejuvenates the infarcted area of the heart.

Gata4-Dependent Differentiation of c-Kit+-Derived Endothelial Cells Underlies Artefactual Cardiomyocyte Regeneration in the Heart.

BACKGROUND: Although c-Kit+ adult progenitor cells were initially reported to produce new cardiomyocytes in the heart, recent genetic evidence suggests that such events are exceedingly rare. However, to determine if these rare events represent true de novo cardiomyocyte formation, we deleted the necessary cardiogenic transcription factors Gata4 and Gata6 from c-Kit-expressing cardiac progenitor cells. METHODS: Kit allele-dependent lineage tracing and fusion analysis were performed in mice following simultaneous Gata4 and Gata6 cell type-specific deletion to examine rates of putative de novo cardiomyocyte formation from c-Kit+ cells. Bone marrow transplantation experiments were used to define the contribution of Kit allele-derived hematopoietic cells versus Kit lineage-dependent cells endogenous to the heart in contributing to apparent de novo lineage-traced cardiomyocytes. A Tie2CreERT2 transgene was also used to examine the global impact of Gata4 deletion on the mature cardiac endothelial cell network, which was further evaluated with select angiogenesis assays. RESULTS: Deletion of Gata4 in Kit lineage-derived endothelial cells or in total endothelial cells using the Tie2CreERT2 transgene, but not from bone morrow cells, resulted in profound endothelial cell expansion, defective endothelial cell differentiation, leukocyte infiltration into the heart, and a dramatic increase in Kit allele-dependent lineage-traced cardiomyocytes. However, this increase in labeled cardiomyocytes was an artefact of greater leukocyte-cardiomyocyte cellular fusion because of defective endothelial cell differentiation in the absence of Gata4. CONCLUSIONS: Past identification of presumed de novo cardiomyocyte formation in the heart from c-Kit+ cells using Kit allele lineage tracing appears to be an artefact of labeled leukocyte fusion with cardiomyocytes. Deletion of Gata4 from c-Kit+ endothelial progenitor cells or adult endothelial cells negatively impacted angiogenesis and capillary network integrity.

The caspase-3-p120-RasGAP module generates a NF-κB repressor in response to cellular stress.

The nuclear factor κB (NF-κB) transcription factor is a master regulator of inflammation. Short-term NF-κB activation is generally beneficial. However, sustained NF-κB might be detrimental, directly causing apoptosis of cells or leading to a persistent damaging inflammatory response. NF-κB activity in stressed cells needs therefore to be controlled for homeostasis maintenance. In mildly stressed cells, caspase-3 cleaves p120 RasGAP, also known as RASA1, into an N-terminal fragment, which we call fragment N. We show here that this fragment is a potent NF-κB inhibitor. Fragment N decreases the transcriptional activity of NF-κB by promoting its export from the nucleus. Cells unable to generate fragment N displayed increased NF-κB activation upon stress. Knock-in mice expressing an uncleavable p120 RasGAP mutant showed exaggerated NF-κB activation when their epidermis was treated with anthralin, a drug used for the treatment of psoriasis. Our study provides biochemical and genetic evidence of the importance of the caspase-3-p120-RasGAP stress-sensing module in the control of stress-induced NF-κB activation.

Isolation of Adult Mouse Cardiac Fibroblasts.

Fibroblasts are dynamic cells of mesenchymal origin that regulate tissue homeostasis, extracellular matrix production, and acute wound healing. Fibroblasts respond to tissue injury and inflammation by differentiating into myofibroblasts and secreting extracellular matrix proteins. Fibroblasts are the principal mediators of the fibrotic response in all tissues and organs. Adult primary fibroblasts represent an essential tool for in vitro studies. Although they lack surface markers, fibroblasts are relatively easy to obtain and culture; primary fibroblasts are sensitive heterogeneous cell subpopulations with limited expansion potential and increased differentiation capacity. Adult primary fibroblasts fail to maintain an undifferentiated state ex vivo for long periods and quickly differentiate into myofibroblasts in culture, which necessitates the utilization of these cells either directly after isolation or after a few passages. Herein, we describe a detailed protocol for enzymatic isolation of primary cardiac fibroblasts from adult mouse hearts and their culture and expansion in a serum-containing culture medium. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Preparation of primary adult cardiac fibroblasts for culture and single-cell analysis.

Some stable and closed-shell structures of anticancer drugs by graph theoretical parameters.

The eigenvalues are significant in mathematics, but they are also relevant in other domains like as chemistry, economics, and a variety of others. In terms of our research, eigenvalues are used in chemistry to represent not only the form of energy but also the various physicochemical aspects of a chemical substance. We must comprehend the connection between mathematics and chemistry. The antibonding level is related to positive eigenvalues, the bonding level is associated to negative eigenvalues, and the nonbonding level is linked to zero eigenvalues. In this work, we studied some anticancer drug structures in terms of nullity, matching number, eigenvalues of adjacency matrix, and characteristics polynomials. As a result, Carmustine, Caulibugulone-E, Aspidostomide-E anticancer drug structures are stable, closed-shell molecules since their nullity is equal to zero.

The role of the urban agriculture on food security during armed conflicts in the Gaza Strip.

This study aims to assess the potential of urban agriculture (UA) to secure daily needs during the armed conflicts, in addition to assess the contribution of UA in alleviating poverty levels and unemployment rates for its practitioners. A combination of both quantitative and qualitative research methods were employed in this study. In the quantitative design, 129 randomly selected urban farmers from the area of the survey completed the self-administered close-ended questionnaires, whereas the statistical analysis presents the socio-demographic, economic, and other aspects of the households. The qualitative data collection included interviews with six governmental and nongovernmental officials. The results show that 89.2 percent of the UA practitioners are feeling food security. However, a small percentage of the households who practice UA are still experiencing difficulties with food security. In the meantime, the armed conflict forced most of the urban farmers to evacuate their homes or lands; thus, only 34.9 percent of urban farmers managed to gain food during the 2014 armed conflict. In a nutshell, UA significantly and positively contributes to alleviating household food insecurity in the study area. However, its role was very limited during the 2014 armed conflict.

Overlapping and differential functions of ATF6α versus ATF6ß in the mouse heart.

Hemodynamic stress on the mammalian heart results in compensatory hypertrophy and activation of the unfolded protein response through activating transcription factor 6α (ATF6α) in cardiac myocytes, but the roles of ATF6α or the related transcription factor ATF6ß in regulating this hypertrophic response are not well-understood. Here we examined the effects of loss of ATF6α or ATF6ß on the cardiac response to pressure overload. Mice gene-deleted for Atf6 or Atf6b were subjected to 2 weeks of transverse aortic constriction, and each showed a significant reduction in hypertrophy with reduced expression of endoplasmic reticulum (ER) stress-associated proteins compared with controls. However, with long-term pressure overload both Atf6 and Atf6b null mice showed enhanced decompensation typified by increased heart weight, pulmonary edema and reduced function compared to control mice. Our subsequent studies using cardiac-specific transgenic mice expressing the transcriptionally active N-terminus of ATF6α or ATF6ß revealed that these factors control overlapping gene expression networks that include numerous ER protein chaperones and ER associated degradation components. This work reveals previously unappreciated roles for ATF6α and ATF6ß in regulating the pressure overload induced cardiac hypertrophic response and in controlling the expression of genes that condition the ER during hemodynamic stress.

Inhibition of mitochondrial permeability transition by deletion of the ANT family and CypD.

The mitochondrial permeability transition pore (MPTP) has resisted molecular identification. The original model of the MPTP that proposed the adenine nucleotide translocator (ANT) as the inner membrane pore-forming component was challenged when mitochondria from Ant1/2 double null mouse liver still had MPTP activity. Because mice express three Ant genes, we reinvestigated whether the ANTs comprise the MPTP. Liver mitochondria from Ant1, Ant2, and Ant4 deficient mice were highly refractory to Ca2+-induced MPTP formation, and when also given cyclosporine A (CsA), the MPTP was completely inhibited. Moreover, liver mitochondria from mice with quadruple deletion of Ant1, Ant2, Ant4, and Ppif (cyclophilin D, target of CsA) lacked Ca2+-induced MPTP formation. Inner-membrane patch clamping in mitochondria from Ant1, Ant2, and Ant4 triple null mouse embryonic fibroblasts showed a loss of MPTP activity. Our findings suggest a model for the MPTP consisting of two distinct molecular components: The ANTs and an unknown species requiring CypD.

Thrombospondin-3 augments injury-induced cardiomyopathy by intracellular integrin inhibition and sarcolemmal instability.

Thrombospondins (Thbs) are a family of five secreted matricellular glycoproteins in vertebrates that broadly affect cell-matrix interaction. While Thbs4 is known to protect striated muscle from disease by enhancing sarcolemmal stability through increased integrin and dystroglycan attachment complexes, here we show that Thbs3 antithetically promotes sarcolemmal destabilization by reducing integrin function, augmenting disease-induced decompensation. Deletion of Thbs3 in mice enhances integrin membrane expression and membrane stability, protecting the heart from disease stimuli. Transgene-mediated overexpression of α7ß1D integrin in the heart ameliorates the disease predisposing effects of Thbs3 by augmenting sarcolemmal stability. Mechanistically, we show that mutating Thbs3 to contain the conserved RGD integrin binding domain normally found in Thbs4 and Thbs5 now rescues the defective expression of integrins on the sarcolemma. Thus, Thbs proteins mediate the intracellular processing of integrin plasma membrane attachment complexes to regulate the dynamics of cellular remodeling and membrane stability.

Cell-specific ablation of Hsp47 defines the collagen-producing cells in the injured heart

Collagen production in the adult heart is thought to be regulated by the fibroblast, although cardiomyocytes and endothelial cells also express multiple collagen mRNAs. Molecular chaperones are required for procollagen biosynthesis, including heat shock protein 47 (Hsp47). To determine the cell types critically involved in cardiac injury­induced fibrosis theHsp47 gene was deleted in cardiomyocytes, endothelial cells, or myofibroblasts. Deletion ofHsp47 from cardiomyocytes during embryonic development or adult stages, or deletion from adult endothelial cells, did not affect cardiac fibrosis after pressure overload injury. However, myofibroblast-specific ablation of Hsp47; blocked fibrosis and deposition of collagens type I, III, and V following pressure overload as well as significantly reduced cardiac hypertrophy. Fibroblast-specific Hsp47-deleted mice showed lethality after myocardial infarction injury, with ineffective scar formation and ventricular wall rupture. Similarly, only myofibroblast-specific deletion of Hsp47reduced fibrosis and disease in skeletal muscle in a mouse model of muscular dystrophy. Mechanistically, deletion of Hsp47 from myofibroblasts reduced mRNA expression of fibrillar collagens and attenuated their proliferation in the heart without affecting paracrine secretory activity of these cells. The results show that myofibroblasts are the primary mediators of tissue fibrosis and scar formation in the injured adult heart, which unexpectedly affects cardiomyocyte hypertrophy.

Specialized fibroblast differentiated states underlie scar formation in the infarcted mouse heart.

Fibroblasts are a dynamic cell type that achieve selective differentiated states to mediate acute wound healing and long-term tissue remodeling with scarring. With myocardial infarction injury, cardiomyocytes are replaced by secreted extracellular matrix proteins produced by proliferating and differentiating fibroblasts. Here, we employed 3 different mouse lineage-tracing models and stage-specific gene profiling to phenotypically analyze and classify resident cardiac fibroblast dynamics during myocardial infarction injury and stable scar formation. Fibroblasts were activated and highly proliferative, reaching a maximum rate within 2 to 4 days after infarction injury, at which point they expanded 3.5-fold and were maintained long term. By 3 to 7 days, these cells differentiated into myofibroblasts that secreted abundant extracellular matrix proteins and expressed smooth muscle α-actin to structurally support the necrotic area. By 7 to 10 days, myofibroblasts lost proliferative ability and smooth muscle α-actin expression as the collagen-containing extracellular matrix and scar fully matured. However, these same lineage-traced initial fibroblasts persisted within the scar, achieving a new molecular and stable differentiated state referred to as a matrifibrocyte, which was also observed in the scars of human hearts. These cells express common and unique extracellular matrix and tendon genes that are more specialized to support the mature scar.

Fibroblast-specific TGF-ß-Smad2/3 signaling underlies cardiac fibrosis.

The master cytokine TGF-ß mediates tissue fibrosis associated with inflammation and tissue injury. TGF-ß induces fibroblast activation and differentiation into myofibroblasts that secrete extracellular matrix proteins. Canonical TGF-ß signaling mobilizes Smad2 and Smad3 transcription factors that control fibrosis by promoting gene expression. However, the importance of TGF-ß-Smad2/3 signaling in fibroblast-mediated cardiac fibrosis has not been directly evaluated in vivo. Here, we examined pressure overload-induced cardiac fibrosis in fibroblast- and myofibroblast-specific inducible Cre-expressing mouse lines with selective deletion of the TGF-ß receptors Tgfbr1/2, Smad2, or Smad3. Fibroblast-specific deletion of Tgfbr1/2 or Smad3, but not Smad2, markedly reduced the pressure overload-induced fibrotic response as well as fibrosis mediated by a heart-specific, latency-resistant TGF-ß mutant transgene. Interestingly, cardiac fibroblast-specific deletion of Tgfbr1/2, but not Smad2/3, attenuated the cardiac hypertrophic response to pressure overload stimulation. Mechanistically, loss of Smad2/3 from tissue-resident fibroblasts attenuated injury-induced cellular expansion within the heart and the expression of fibrosis-mediating genes. Deletion of Smad2/3 or Tgfbr1/2 from cardiac fibroblasts similarly inhibited the gene program for fibrosis and extracellular matrix remodeling, although deletion of Tgfbr1/2 uniquely altered expression of an array of regulatory genes involved in cardiomyocyte homeostasis and disease compensation. These findings implicate TGF-ß-Smad2/3 signaling in activated tissue-resident cardiac fibroblasts as principal mediators of the fibrotic response.

Nemo-Like Kinase (NLK) Is a Pathological Signaling Effector in the Mouse Heart.

Nemo-like kinase (NLK) is an evolutionary conserved serine/threonine protein kinase implicated in development, proliferation and apoptosis regulation. Here we identified NLK as a gene product induced in the hearts of mice subjected to pressure overload or myocardial infarction injury, suggesting a potential regulatory role with pathological stimulation to this organ. To examine the potential functional consequences of increased NLK levels, cardiac-specific transgenic mice with inducible expression of this gene product were generated, as well as cardiac-specific Nlk gene-deleted mice. NLK transgenic mice demonstrated baseline cardiac hypertrophy, dilation, interstitial fibrosis, apoptosis and progression towards heart failure in response to two surgery-induced cardiac disease models. In contrast, cardiac-specific deletion of Nlk from the heart, achieved by crossing a Nlk-loxP allele containing mouse with either a mouse containing a ß-myosin heavy chain promoter driven Cre transgene or a tamoxifen inducible α-myosin heavy chain promoter containing transgene driving a MerCreMer cDNA, protected the mice from cardiac dysfunction following pathological stimuli. Mechanistically, NLK interacted with multiple proteins including the transcription factor Stat1, which was significantly increased in the hearts of NLK transgenic mice. These results indicate that NLK is a pathological effector in the heart.

Genetic lineage tracing defines myofibroblast origin and function in the injured heart.

Cardiac fibroblasts convert to myofibroblasts with injury to mediate healing after acute myocardial infarction (MI) and to mediate long-standing fibrosis with chronic disease. Myofibroblasts remain a poorly defined cell type in terms of their origins and functional effects in vivo. Here we generate Postn (periostin) gene-targeted mice containing a tamoxifen-inducible Cre for cellular lineage-tracing analysis. This Postn allele identifies essentially all myofibroblasts within the heart and multiple other tissues. Lineage tracing with four additional Cre-expressing mouse lines shows that periostin-expressing myofibroblasts in the heart derive from tissue-resident fibroblasts of the Tcf21 lineage, but not endothelial, immune/myeloid or smooth muscle cells. Deletion of periostin(+) myofibroblasts reduces collagen production and scar formation after MI. Periostin-traced myofibroblasts also revert back to a less-activated state upon injury resolution. Our results define the myofibroblast as a periostin-expressing cell type necessary for adaptive healing and fibrosis in the heart, which arises from Tcf21(+) tissue-resident fibroblasts.

Caspase-3 and RasGAP: a stress-sensing survival/demise switch.

The final decision on cell fate, survival versus cell death, relies on complex and tightly regulated checkpoint mechanisms. The caspase-3 protease is a predominant player in the execution of apoptosis. However, recent progress has shown that this protease paradoxically can also protect cells from death. Here, we discuss the underappreciated, protective, and prosurvival role of caspase-3 and detail the evidence showing that caspase-3, through differential processing of p120 Ras GTPase-activating protein (RasGAP), can modulate a given set of proteins to generate, depending on the intensity of the input signals, opposite outcomes (survival vs death).

The role of endogenous and exogenous RasGAP-derived fragment N in protecting cardiomyocytes from peroxynitrite-induced apoptosis.

Peroxynitrite (PN) is a potent nitrating and oxidizing agent generated during various pathological situations affecting the heart. The negative effects of PN result, at least in part, from its ability to activate caspases and apoptosis. RasGAP is a ubiquitously expressed protein that is cleaved sequentially by caspase-3. At low caspase-3 activity, RasGAP is cleaved into an N-terminal fragment, called fragment N, that protects cells by activating the Ras/PI3K/Akt pathway. At high caspase-3 activity, fragment N is further cleaved and this abrogates its capacity to stimulate the antiapoptotic Akt kinase. Fragment N formation is crucial for the survival of cells exposed to a variety of stresses. Here we investigate the pattern of RasGAP cleavage upon PN stimulation and the capacity of fragment N to protect cardiomyocytes. PN did not lead to sequential cleavage of RasGAP. Indeed, PN did not allow accumulation of fragment N because it induced its rapid cleavage into smaller fragments. No situations were found in cells treated with PN in which the presence of fragment N was associated with survival. However, expression of a caspase-resistant form of fragment N in cardiomyocytes protected them from PN-induced apoptosis. Our results indicate that the antiapoptotic pathway activated by fragment N is effective at inhibiting PN-induced apoptosis (as seen when cardiomyocytes express a capase-3-resistant form of fragment N) but because fragment N is too transiently generated in response to PN, no survival response is effectively produced. This may explain the marked deleterious consequences of PN generation in various organs, including the heart.

Caspase-3 protects stressed organs against cell death.

The ability to generate appropriate defense responses is crucial for the survival of an organism exposed to pathogenesis-inducing insults. However, the mechanisms that allow tissues and organs to cope with such stresses are poorly understood. Here we show that caspase-3-knockout mice or caspase inhibitor-treated mice were defective in activating the antiapoptotic Akt kinase in response to various chemical and environmental stresses causing sunburns, cardiomyopathy, or colitis. Defective Akt activation in caspase-3-knockout mice was accompanied by increased cell death and impaired survival in some cases. Mice homozygous for a mutation in RasGAP that prevents its cleavage by caspase-3 exhibited a similar defect in Akt activation, leading to increased apoptosis in stressed organs, marked deterioration of their physiological functions, and stronger disease development. Our results provide evidence for the relevance of caspase-3 as a stress intensity sensor that controls cell fate by either initiating a RasGAP cleavage-dependent cell resistance program or a cell suicide response.

RasGAP-derived fragment N increases the resistance of beta cells towards apoptosis in NOD mice and delays the progression from mild to overt diabetes.

The caspase-3-generated RasGAP N-terminal fragment (fragment N) inhibits apoptosis in a Ras-PI3K-Akt-dependent manner. Fragment N protects various cell types, including insulin-secreting cells, against different types of stresses. Whether fragment N exerts a protective role during the development of type 1 diabetes is however not known. Non-obese diabetic (NOD) mice represent a well-known model for spontaneous development of type 1 diabetes that shares similarities with the diseases encountered in humans. To assess the role of fragment N in type 1 diabetes development, a transgene encoding fragment N under the control of the rat insulin promoter (RIP) was back-crossed into the NOD background creating the NOD-RIPN strain. Despite a mosaic expression of fragment N in the beta cell population of NOD-RIPN mice, islets isolated from these mice were more resistant to apoptosis than control NOD islets. Islet lymphocytic infiltration and occurrence of a mild increase in glycemia developed with the same kinetics in both strains. However, the period of time separating the mild increase in glycemia and overt diabetes was significantly longer in NOD-RIPN mice compared to the control NOD mice. There was also a significant decrease in the number of apoptotic beta cells in situ at 16 weeks of age in the NOD-RIPN mice. Fragment N exerts therefore a protective effect on beta cells within the pro-diabetogenic NOD background and this prevents a fast progression from mild to overt diabetes.

Old yellow enzymes, highly homologous FMN oxidoreductases with modulating roles in oxidative stress and programmed cell death in yeast.

In a genetic screen to identify modifiers of Bax-dependent lethality in yeast, the C terminus of OYE2 was isolated based on its capacity to restore sensitivity to a Bax-resistant yeast mutant strain. Overexpression of full-length OYE2 suppresses Bax lethality in yeast, lowers endogenous reactive oxygen species (ROS), increases resistance to H(2)O(2)-induced programmed cell death (PCD), and significantly lowers ROS levels generated by organic prooxidants. Reciprocally, Delta oye2 yeast strains are sensitive to prooxidant-induced PCD. Overexpression and knock-out analysis indicate these OYE2 antioxidant activities are opposed by OYE3, a highly homologous heterodimerizing protein, which functions as a prooxidant promoting H(2)O(2)-induced PCD in wild type yeast. To exert its effect OYE3 requires the presence of OYE2. Deletion of the 12 C-terminal amino acids and catalytic inactivation of OYE2 by a Y197F mutation enhance significantly survival upon H(2)O(2)-induced PCD in wild type cells, but accelerate PCD in Delta oye3 cells, implicating the oye2p-oye3p heterodimer for promoting cell death upon oxidative stress. Unexpectedly, a strain with a double knock-out of these genes (Delta oye2 oye3) is highly resistant to H(2)O(2)-induced PCD, exhibits increased respiratory capacity, and undergoes less cell death during the adaptive response in chronological aging. Simultaneous deletion of OYE2 and other antioxidant genes hyperinduces endogenous levels of ROS, promoting H(2)O(2)-induced cell death: in Delta oye2 glr1 yeast high levels of oxidized glutathione elicited gross morphological aberrations involving the actin cytoskeleton and defects in organelle partitioning. Altering the ratio of reduced to oxidized glutathione by exogenous addition of GSH fully reversed these alterations. Based on this work, OYE proteins are firmly placed in the signaling network connecting ROS generation, PCD modulation, and cytoskeletal dynamics in yeast.