Degradation of cardiac myosin light chain kinase by matrix metalloproteinase-2 contributes to myocardial contractile dysfunction during ischemia/reperfusion

Repeat administration of human umbilical cord mesenchymal stem cells improves left ventricular diastolic function in mice with heart failure with preserved ejection fraction

Currently, no therapy is proven to effectively improve heart failure with preserved ejection fraction (HFpEF). Although stem cell therapy has demonstrated promising results in treating ischemic heart disease, the effectiveness of treating HFpEF with human umbilical cord mesenchymal stem cells (hucMSCs) remains unclear. To answer this question, we administered hucMSCs intravenously (i.v.), either once or repetitively, in a mouse model of HFpEF induced by a high-fat diet and NG-nitroarginine methyl ester hydrochloride. hucMSC treatment improved left ventricular diastolic dysfunction, reduced heart weight and pulmonary edema, and attenuated cardiac modeling (inflammation, interstitial fibrosis, and hypertrophy) in HFpEF mice. Repeat hucMSC administration had better outcomes than a single injection. In vitro, hucMSC culture supernatants reduced maladaptive remodeling in neonatal-rat cardiomyocytes. Ribonucleic acid sequencing and protein level analysis of left ventricle (LV) tissues suggested that hucMSCs activated the protein kinase B (Akt)/forkhead box protein O1 (FoxO1) signaling pathway to treat HFpEF. Inhibition of this pathway reversed the efficacy of hucMSC treatment. In conclusion, these findings indicated that hucMSCs could be a viable therapeutic option for HFpEF.

Oxidative Post-translational Protein Modifications upon Ischemia/Reperfusion Injury

While reperfusion, or restoration of coronary blood flow in acute myocardial infarction, is a requisite for myocardial salvage, it can paradoxically induce a specific damage known as ischemia/reperfusion (I/R) injury. Our understanding of the precise pathophysiological molecular alterations leading to I/R remains limited. In this study, we conducted a comprehensive and unbiased time-course analysis of post-translational modifications (PTMs) in the post-reperfused myocardium of two different animal models (pig and mouse) and evaluated the effect of two different cardioprotective therapies (ischemic preconditioning and neutrophil depletion). In pigs, a first wave of irreversible oxidative damage was observed at the earliest reperfusion time (20 min), impacting proteins essential for cardiac contraction. A second wave, characterized by irreversible oxidation on different residues and reversible Cys oxidation, occurred at late stages (6-12 h), affecting mitochondrial, sarcomere, and inflammation-related proteins. Ischemic preconditioning mitigated the I/R damage caused by the late oxidative wave. In the mouse model, the two-phase pattern of oxidative damage was replicated, and neutrophil depletion mitigated the late wave of I/R-related damage by preventing both Cys reversible oxidation and irreversible oxidation. Altogether, these data identify protein PTMs occurring late after reperfusion as an actionable therapeutic target to reduce the impact of I/R injury.

Exosomes secreted by endothelial cells derived from human induced pluripotent stem cells improve recovery from myocardial infarction in mice

BACKGROUND

Human induced pluripotent stem cell-derived endothelial cells (hiPSC-ECs) exhibit the potential to repair the injured heart after myocardial infarction (MI) by promoting neovascularization and cardiomyocyte survival. However, because of the low cellular retention and poor engraftment efficacy, cell therapy of MI is partly mediated by exosomes secreted from the transplanted cells. In this study, we investigated whether exosomes secreted from hiPSC-ECs could become a promising acellular approach to repair the infarcted heart after MI and elucidated the underlying protective mechanism.

METHODS

The hiPSC-ECs were differentiated, and exosomes were isolated in vitro. Then, hiPSC-EC exosomes were delivered by intramyocardial injection in a murine MI model in vivo. Echocardiography, combined with hemodynamic measurement, histological examination, Ca2+ transient and cell shortening assessment, and Western blot, was used to determine the protective effects of hiPSC-EC exosomes on the infarcted heart. Furthermore, microRNA sequencing, luciferase activity assay, and microRNA gain-loss function experiments were performed to investigate the enriched microRNA and its role in exosome-mediated effects.

RESULTS

In vitro, the hiPSC-EC exosomes enhanced intracellular Ca2+ transients, increased ATP content, and improved cell survival to protect cardiomyocytes from oxygen-glucose deprivation injury. Congruously, hiPSC-EC exosome administration in vivo improved the myocardial contractile function and attenuated the harmful left ventricular remodeling after MI without increasing the frequency of arrhythmias. Mechanistically, the hiPSC-EC exosomes notably rescued the protein expression and function of the sarcoplasmic reticulum Ca2+ ATPase 2a (SERCA-2a) and ryanodine receptor 2 (RyR-2) to maintain intracellular Ca2+ homeostasis and increase cardiomyocyte contraction after MI. The microRNA sequencing showed that miR-100-5p was the most abundant microRNA in exosomes. miR-100-5p could target protein phosphatase 1β (PP-1β) to enhance phospholamban (PLB) phosphorylation at Ser16 and subsequent SERCA activity, which contributes to the hiPSC-EC exosome-exerted cytoprotective effects on maintaining intracellular Ca2+ homeostasis and promoting cardiomyocyte survival.

CONCLUSION

The hiPSC-EC exosomes maintain cardiomyocyte Ca2+ homeostasis to improve myocardial recovery after MI, which may provide an acellular therapeutic option for myocardial injury.

Matrix Metalloproteinases and Heart Transplantation-A Pathophysiological and Clinical View

Heart transplantation is undergoing a continuous development, with rates of success increasing substantially due to advances in immunosuppressive therapy and surgical techniques. The most worrying complication occurring after cardiac transplantation is graft rejection, a phenomenon that is much affected by matrix metalloproteinases (MMPs), with the role of these proteases in the cardiac remodeling process being well established in the literature. A detailed investigation of the association between MMPs and cardiac rejection is necessary for the future development of more targeted therapies in transplanted patients, and to discover prognostic serum and immunohistochemical markers that will lead to more organized therapeutic management in these patients. The aim of this review is therefore to highlight the main MMPs relevant to cardiovascular pathology, with particular emphasis on those involved in complications related to heart transplantation, including cardiac graft rejection.

Involvement of Matrix Metalloproteinases in COVID-19: Molecular Targets, Mechanisms, and Insights for Therapeutic Interventions

MMPs are enzymes involved in SARS-CoV-2 pathogenesis. Notably, the proteolytic activation of MMPs can occur through angiotensin II, immune cells, cytokines, and pro-oxidant agents. However, comprehensive information regarding the impact of MMPs in the different physiological systems with disease progression is not fully understood. In the current study, we review the recent biological advances in understanding the function of MMPs and examine time-course changes in MMPs during COVID-19. In addition, we explore the interplay between pre-existing comorbidities, disease severity, and MMPs. The reviewed studies showed increases in different MMP classes in the cerebrospinal fluid, lung, myocardium, peripheral blood cells, serum, and plasma in patients with COVID-19 compared to non-infected individuals. Individuals with arthritis, obesity, diabetes, hypertension, autoimmune diseases, and cancer had higher MMP levels when infected. Furthermore, this up-regulation may be associated with disease severity and the hospitalization period. Clarifying the molecular pathways and specific mechanisms that mediate MMP activity is important in developing optimized interventions to improve health and clinical outcomes during COVID-19. Furthermore, better knowledge of MMPs will likely provide possible pharmacological and non-pharmacological interventions. This relevant topic might add new concepts and implications for public health in the near future.

Impaired regulation of MMP2/16-MLCK3 by miR-146a-5p increased susceptibility to myocardial ischemic injury in aging mice

AIMS

Aging impairs cardiac function and increases susceptibility to myocardial ischemic injury. Cardiac myosin light chain kinase (MLCK3) phosphorylates cardiac myosin regulatory light chain (MLC2), controlling sarcomere organization and cardiomyocyte contraction. Dysregulation of MLCK3 and phosphorylated MLC2 (p-MLC2) contributes to heart failure after myocardial infarction (MI). We aimed at exploring how the MLCK3-p-MLC2 axis changes in aging hearts post MI and at investigating the underlying regulatory mechanisms.

METHODS AND RESULTS

We generated adult (3 months) and aged (30 months) MI mouse models to compare their cardiac performance, and then detected MLCK3 expression and MLC2 activity. Aging increased the size of MI-induced infarctions and promoted cardiac contractile dysfunction. Furthermore, MLCK3 expression and MLC2 activity increased in adult hearts after MI, but not in aged hearts. miR-146a was found consistently increased in adult and aged hearts post-MI. Mechanistic analyses performed in vitro demonstrated that miR-146a-5p downregulated matrix metalloprotease (MMP)2/16 expression in cardiomyocytes. This downregulation in turn increased MLCK3 expression and MLC2 activity. However, miR-146a-5p failed to regulate the MMP2/16-MLCK3-p-MLC2 axis in senescent cardiomyocytes or in cardiac miR-146a conditional knockout mice, with the latter experiencing an exacerbated deterioration of cardiac function post-MI.

CONCLUSION

These results suggest that increase of MLCK3 and p-MLC2 contents through decreasing MMP2/16 by miR-146a-5p represents a compensatory mechanism that can protect cardiac contractile function after MI. Aging impairs this miR-146a-5p-regulated MMP2/16-MLCK3-p-MLC2 contractile axis, leading to compromised contractile function and increased susceptibility to heart failure.

Exosomes secreted by hiPSC-derived cardiac cells improve recovery from myocardial infarction in swine

Cell therapy treatment of myocardial infarction (MI) is mediated, in part, by exosomes secreted from transplanted cells. Thus, we compared the efficacy of treatment with a mixture of cardiomyocytes (CMs; 10 million), endothelial cells (ECs; 5 million), and smooth muscle cells (SMCs; 5 million) derived from human induced pluripotent stem cells (hiPSCs), or with exosomes extracted from the three cell types, in pigs after MI. Female pigs received sham surgery; infarction without treatment (MI group); or infarction and treatment with hiPSC-CMs, hiPSC-ECs, and hiPSC-SMCs (MI + Cell group); with homogenized fragments from the same dose of cells administered to the MI + Cell group (MI + Fra group); or with exosomes (7.5 mg) extracted from a 2:1:1 mixture of hiPSC-CMs:hiPSC-ECs:hiPSC-SMCs (MI + Exo group). Cells and exosomes were injected into the injured myocardium. In vitro, exosomes promoted EC tube formation and microvessel sprouting from mouse aortic rings and protected hiPSC-CMs by reducing apoptosis, maintaining intracellular calcium homeostasis, and increasing adenosine 5'-triphosphate. In vivo, measurements of left ventricular ejection fraction, wall stress, myocardial bioenergetics, cardiac hypertrophy, scar size, cell apoptosis, and angiogenesis in the infarcted region were better in the MI + Cell, MI + Fra, and MI + Exo groups than in the MI group 4 weeks after infarction. The frequencies of arrhythmic events in animals from the MI, MI + Cell, and MI + Exo groups were similar. Thus, exosomes secreted by hiPSC-derived cardiac cells improved myocardial recovery without increasing the frequency of arrhythmogenic complications and may provide an acellular therapeutic option for myocardial injury.

A Global Profile of Reversible and Irreversible Cysteine Redox Post-Translational Modifications During Myocardial Ischemia/Reperfusion Injury and Antioxidant Intervention

Aims: Cysteine (Cys) is a major target for redox post-translational modifications (PTMs) that occur in response to changes in the cellular redox environment. We describe multiplexed, peptide-based enrichment and quantitative mass spectrometry (MS) applied to globally profile reversible redox Cys PTM in rat hearts during ischemia/reperfusion (I/R) in the presence or absence of an aminothiol antioxidant, N-2-mercaptopropionylglycine (MPG). Parallel fractionation also allowed identification of irreversibly oxidized Cys peptides (Cys-SO₂H/SO₃H). Results: We identified 4505 reversibly oxidized Cys peptides of which 1372 were significantly regulated by ischemia and/or I/R. An additional 219 peptides (247 sites) contained Cys-SO₂H/Cys-SO₃H modifications, and these were predominantly identified from hearts subjected to I/R (n = 168 peptides). Parallel reaction monitoring MS (PRM-MS) enabled relative quantitation of 34 irreversibly oxidized Cys peptides. MPG attenuated a large cluster of I/R-associated reversibly oxidized Cys peptides and irreversible Cys oxidation to less than nonischemic controls (n = 24 and 34 peptides, respectively). PRM-MS showed that Cys sites oxidized during ischemia and/or I/R and "protected" by MPG were largely mitochondrial, and were associated with antioxidant functions (peroxiredoxins 5 and 6) and metabolic processes, including glycolysis. Metabolomics revealed I/R induced changes in glycolytic intermediates that were reversed in the presence of MPG, which were consistent with irreversible PTM of triose phosphate isomerase and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), altered GAPDH enzyme activity, and reduced I/R glycolytic payoff as evidenced by adenosine triphosphate and NADH levels. Innovation: Novel enrichment and PRM-MS approaches developed here enabled large-scale relative quantitation of Cys redox sites modified by reversible and irreversible PTM during I/R and antioxidant remediation. Conclusions: Cys sites identified here are targets of reactive oxygen species that can contribute to protein dysfunction and the pathogenesis of I/R.

The Roles of Matrix Metalloproteinases and Their Inhibitors in Human Diseases

Matrix metalloproteinases (MMPs) are a family of zinc-dependent extracellular matrix (ECM) remodeling endopeptidases that have the capacity to degrade almost every component of the ECM. The degradation of the ECM is of great importance, since it is related to embryonic development and angiogenesis. It is also involved in cell repair and the remodeling of tissues. When the expression of MMPs is altered, it can generate the abnormal degradation of the ECM. This is the initial cause of the development of chronic degenerative diseases and vascular complications generated by diabetes. In addition, this process has an association with neurodegeneration and cancer progression. Within the ECM, the tissue inhibitors of MMPs (TIMPs) inhibit the proteolytic activity of MMPs. TIMPs are important regulators of ECM turnover, tissue remodeling, and cellular behavior. Therefore, TIMPs (similar to MMPs) modulate angiogenesis, cell proliferation, and apoptosis. An interruption in the balance between MMPs and TIMPs has been implicated in the pathophysiology and progression of several diseases. This review focuses on the participation of both MMPs (e.g., MMP-2 and MMP-9) and TIMPs (e.g., TIMP-1 and TIMP-3) in physiological processes and on how their abnormal regulation is associated with human diseases. The inclusion of current strategies and mechanisms of MMP inhibition in the development of new therapies targeting MMPs was also considered.

Cardioprotective Effect of Novel Matrix Metalloproteinase Inhibitors

Background: We recently developed novel matrix metalloproteinase-2 (MMP-2) inhibitor small molecules for cardioprotection against ischemia/reperfusion injury and validated their efficacy in ischemia/reperfusion injury in cardiac myocytes. The aim of the present study was to test our lead compounds for cardioprotection in vivo in a rat model of acute myocardial infarction (AMI) in the presence or absence of hypercholesterolemia, one of the major comorbidities affecting cardioprotection. Methods: Normocholesterolemic adult male Wistar rats were subjected to 30 min of coronary occlusion followed by 120 min of reperfusion to induce AMI. MMP inhibitors (MMPI)-1154 and -1260 at 0.3, 1, and 3 µmol/kg, MMPI-1248 at 1, 3, and 10 µmol/kg were administered at the 25th min of ischemia intravenously. In separate groups, hypercholesterolemia was induced by a 12-week diet (2% cholesterol, 0.25% cholic acid), then the rats were subjected to the same AMI protocol and single doses of the MMPIs that showed the most efficacy in normocholesterolemic animals were tested in the hypercholesterolemic animals. Infarct size/area at risk was assessed at the end of reperfusion in all groups by standard Evans blue and 2,3,5-triphenyltetrazolium chloride (TTC) staining, and myocardial microvascular obstruction (MVO) was determined by thioflavine-S staining. Results: MMPI-1154 at 1 µmol/kg, MMPI-1260 at 3 µmol/kg and ischemic preconditioning (IPC) as the positive control reduced infarct size significantly; however, this effect was not seen in hypercholesterolemic animals. MVO in hypercholesterolemic animals decreased by IPC only. Conclusions: This is the first demonstration that MMPI-1154 and MMPI-1260 showed a dose-dependent infarct size reduction in an in vivo rat AMI model; however, single doses that showed the most efficacy in normocholesterolemic animals were abolished by hypercholesterolemia. The further development of these promising cardioprotective MMPIs should be continued with different dose ranges in the study of hypercholesterolemia and other comorbidities.

β-adrenergic activation may promote myosin light chain kinase degradation through calpain in pressure overload-induced cardiac hypertrophy: β-adrenergic activation results in MLCK degradation

BACKGROUND

β-adrenergic activation is able to exacerbate cardiac hypertrophy. Myosin light chain kinase (MLCK) and its phosphorylated substrate, phospho-myosin light chain 2 (p-MLC2), play vital roles in regulating cardiac hypertrophy. However, it is not yet clear whether there is a relationship between β-adrenergic activation and MLCK in the progression of cardiac hypertrophy. Therefore, we explored this relationship and the underlying mechanisms in this work.

METHODS

Cardiac hypertrophy and cardiomyocyte hypertrophy were induced by pressure overload and isoproterenol (ISO) stimulation, respectively. Echocardiography, histological analysis, immunofluorescence and qRT-PCR were used to confirm the successful establishment of the models. A β-blocker (metoprolol) and a calpain inhibitor (calpeptin) were administered to inhibit β-adrenergic activity in rats and calpain in cardiomyocytes, respectively. The protein expression levels of MLCK, myosin light chain 2 (MLC2), p-MLC2, myosin phosphatase 2 (MYPT2), calmodulin (CaM) and calpain were measured using western blotting. A cleavage assay was performed to assess the degradation of recombinant human MLCK by recombinant human calpain.

RESULTS

The β-blocker alleviated cardiac hypertrophy and dysfunction, increased MLCK and MLC2 phosphorylation and decreased calpain expression in pressure overload-induced cardiac hypertrophy. Additionally, the calpain inhibitor calpeptin attenuated cardiomyocyte hypertrophy, upregulated MLCK and p-MLC2 and reduced MLCK degradation in ISO-induced cardiomyocyte hypertrophy. Recombinant human calpain degraded recombinant human MLCK in vitro in concentration- and time-dependent manners, and this degradation was inhibited by the calpain inhibitor calpeptin.

CONCLUSION

Our study suggested that β-adrenergic activation may promote the degradation of MLCK through calpain in pressure overload-induced cardiac hypertrophy.

Cardioprotective Effects of Metalloproteinase Inhibitor 1-({4-[(4-Chlorobenzoyl)amino]phenyl}sulfonyl-L-Proline in Modeled Acute Myocardial Infarction

Cardioprotective effect of 1-({4 [(4 chlorobenzoyl)amino]phenyl}sulfonyl-L-proline (compound AL-828) was studied in rats with modeled acute myocardial infarction. The test compound was administered intragastrically in a dose of 30 mg/kg/day for 3 days prior to infarction modeling. Metalloproteinase inhibitor antibiotic doxycycline served as the reference drug and was administered in a dose of 40 mg/kg/day by the same schedule. It was shown that AL-828 similar to doxycycline significantly reduced the intensity of myocardial remodeling and maintained the inotropic function of the myocardium in the acute phase of myocardial infarction. By the 20th minute of ischemia, the end-systolic dimension of the left ventricle in control animals increased from 1.98±0.12 to 3.84±0.16 mm, while in animals treated with AL-828, this increase was significantly (p=0.007) less pronounced (from 1.84±0.07 and 2.87±0.21 mm, respectively). The ejection fraction characterizing the inotropic status of the left ventricle in animals treated with AL-828 was significantly higher (p=0.02). By its cardioprotective activity, AL-828 was not inferior to the reference drug doxycycline. It can be assumed that the cardioprotective activity of compound AL-828 is related to suppression of MMP-9 expression and/or inhibition of its activity as was previously demonstrated by us.

Aging Attenuates Cardiac Contractility and Affects Therapeutic Consequences for Myocardial Infarction

Cardiac function of the human heart changes with age. The age-related change of systolic function is subtle under normal conditions, but abrupt under stress or in a pathogenesis state. Aging decreases the cardiac tolerance to stress and increases susceptibility to ischemia, which caused by aging-induced Ca2+ transient impairment and metabolic dysfunction. The changes of contractility proteins and the relative molecules are in a non-linear fashion. Specifically, the expression and activation of cMLCK increase first then fall during ischemia and reperfusion (I/R). This change is responsible for the nonmonotonic contractility alteration in I/R which the underlying mechanism is still unclear. Contractility recovery in I/R is also attenuated by age. The age-related change in cardiac contractility influences the therapeutic effect and intervention timepoint. For most cardiac ischemia therapies, the therapeutic result in the elderly is not identical to the young. Anti-aging treatment has the potential to prevent the development of ischemic injury and improves cardiac function. In this review we discuss the mechanism underlying the contractility changes in the aged heart and age-induced ischemic injury. The potential mechanism underlying the increased susceptibility to ischemic injury in advanced age is highlighted. Furthermore, we discuss the effect of age and the administration time for intervention in cardiac ischemia therapies.

Multifunctional Role of Chymase in Acute and Chronic Tissue Injury and Remodeling

Chymase is the most efficient Ang II (angiotensin II)-forming enzyme in the human body and has been implicated in a wide variety of human diseases that also implicate its many other protease actions. Largely thought to be the product of mast cells, the identification of other cellular sources including cardiac fibroblasts and vascular endothelial cells demonstrates a more widely dispersed production and distribution system in various tissues. Furthermore, newly emerging evidence for its intracellular presence in cardiomyocytes and smooth muscle cells opens an entirely new compartment of chymase-mediated actions that were previously thought to be limited to the extracellular space. This review illustrates how these multiple chymase-mediated mechanisms of action can explain the residual risk in clinical trials of cardiovascular disease using conventional renin-angiotensin system blockade.

Is there an effect of ischemic conditioning on myocardial contractile function following acute myocardial ischemia/reperfusion injury?

Ischemic conditioning induces cardioprotection; the final infarct size following a myocardial ischemic event is reduced. However, whether ischemic conditioning has long-term beneficial effects on myocardial contractile function following such an ischemic event needs further elucidation. To date, ex vivo studies have shown that ischemic conditioning improves the contractile recovery of isolated ventricular papillary muscle or atrial trabeculae following simulated ischemia. However, in vivo animal studies and studies in patients undergoing elective cardiac surgery show conflicting results. At the subcellular level, it is known that ischemic conditioning improved energy metabolism, preserved mitochondrial respiration, ATP production, and Ca²⁺ homeostasis in isolated mitochondria from the myocardium. Ischemic conditioning also presents with post-translational modifications of proteins in the contractile machinery of the myocardium. The beneficial effects on myocardial contractile function need further elucidation. This article is part of a Special Issue entitled: The power of metabolism: Linking energy supply and demand to contractile function edited by Torsten Doenst, Michael Schwarzer and Christine Des Rosiers.

Effects of milrinone on inflammatory response-related gene expressions in cultured rat cardiomyocytes

Congestive heart failure (CHF) is defined as a cardiac dysfunction leading to low cardiac output and inadequate tissue perfusion. Intravenous positive inotropes are used to increase myocardial contractility in hospitalized patients with advanced heart failure. Milrinone is a phosphodiesterase Ⅲ inhibitor and used most commonly for inotropic effect. The well-known PROMISE study investigated the effects of milrinone on mortality in patients with severe CHF, and concluded that long-term therapy with milrinone increased morbidity and mortality among patients with advanced CHF. Previous studies have suggested that phosphodiesterase inhibitors can have potential effects on inflammatory pathways. Hence, we hypothesized that milrinone may alter inflammatory gene expressions in cardiomyocytes, thus leading to adverse clinical outcomes. We used rat cardiomyocyte cell line H9C2 and studied the impact of exposing cardiomyocytes to milrinone (10 μmol/L) for 24 hours on inflammatory gene expressions. RNA extracted from cultured cardiomyocytes was used for whole rat genome gene expression assay (41,000 genes). The following changes in inflammatory response-related gene expressions were discovered. Genes with increased expressions included: THBS2 (+9.98), MMP2 (+3.47), DDIT3 (+2.39), and ADORA3 (+3.5). Genes with decreased expressions were: SPP1 (-5.28) and CD14 (-2.05). We found that the above mentioned gene expression changes seem to indicate that milrinone may hinder the inflammatory process which may potentially lead to adverse clinical outcomes. However, further in vivo and clinical investigations will be needed to illustrate the clinical relevance of these gene expression changes induced by milrinone.

Role of Matrix Metalloproteinase-2 in the Development of Cyclophosphamide-Induced Cardiomyopathy

Immunohistochemical assay was employed to determine localization of MMP-2 in cardiomyocytes of WAG rats and changes in MMP-2 expression during modeled cardiomyopathy induced by single intraperitoneal injection of cyclophosphamide (125 mg/kg) alone or in combination with preventive intraperitoneal administration of an equal dose of asparcam-L (potassium-magnesium asparaginate) 30 min prior to the cytostatic. In the myocardium of control and experimental rats, MMP-2 was mostly located in cardiomyocyte nuclei. During the development of cyclophosphamide-induced cardiomyopathy (in 3 days after injection), the index of MMP-2-positive cardiomyocyte nuclei increased by 76%. In contrast to control hearts, MMP-2 was also expressed in the cardiomyocyte sarcoplasm. Preventive injection of asparcam-L moderated the cardiotoxic effect of cyclophosphamide, which manifested in less pronounced increase in the volume density of cardiomyocytes with lytic changes (by 42%) and index of MMP-2⁺ cardiomyocyte nuclei (by 23%) in comparison with the rats exposed to cyclophosphamide alone.

31P NMR 2D Mapping of Creatine Kinase Forward Flux Rate in Hearts with Postinfarction Left Ventricular Remodeling in Response to Cell Therapy

Utilizing a fast ³¹P magnetic resonance spectroscopy (MRS) 2-dimensional chemical shift imaging (2D-CSI) method, this study examined the heterogeneity of creatine kinase (CK) forward flux rate of hearts with postinfarction left ventricular (LV) remodeling. Immunosuppressed Yorkshire pigs were assigned to 4 groups: 1) A sham-operated normal group (SHAM, n = 6); 2) A 60 minutes distal left anterior descending coronary artery ligation and reperfusion (MI, n = 6); 3) Open patch group; ligation injury plus open fibrin patch over the site of injury (Patch, n = 6); and 4) Cell group, hiPSCs-cardiomyocytes, -endothelial cells, and -smooth muscle cells (2 million, each) were injected into the injured myocardium pass through a fibrin patch (Cell+Patch, n = 5). At 4 weeks, the creatine phosphate (PCr)/ATP ratio, CK forward flux rate (Flux _PCr→ATP), and k constant of CK forward flux rate (k_PCr→ATP) were severely decreased at border zone myocardium (BZ) adjacent to MI. Cell treatment results in significantly increase of PCr/ATP ratio and improve the value of k_PCr→ATP and Flux _PCr→ATP in BZ myocardium. Moreover, the BZ myocardial CK total activity and protein expression of CK mitochondria isozyme and CK myocardial isozyme were significantly reduced, but recovered in response to cell treatment. Thus, cell therapy results in improvement of BZ bioenergetic abnormality in hearts with postinfarction LV remodeling, which is accompanied by significantly improvements in BZ CK activity and CK isozyme expression. The fast 2D ³¹P MR CSI mapping can reliably measure the heterogeneity of bioenergetics in hearts with post infarction LV remodeling.