Updated pathophysiological overview of functional MR (ventricular and atrial).

Basic mechanism of ventricular functional mitral regurgitation (FMR) is subvalvular tethering. Left ventricular (LV) dilatation, in association with mitral valve (MV) annular dilatation, causes outward displacement of papillary muscles (PMs), which abnormally pulls or tethers MV leaflets, resulting in MV tenting, reduction in leaflets coaptation and MR. Because surgical annuloplasty does shorten distance between anterior and posterior MV annuli to improve coaptation but does not address this subvalvular tethering, ventricular FMR frequently persists or recurs in the chronic stage after surgical annuloplasty. This high incidence of persistent/recurrent MR requires additional procedures to reduce subvalvular tethering. Although patients occasionally show marked improvements after annuloplasty with surgical tethering reduction procedures such as PM approximation, evidence to support benefits of such surgery is limited, requiring further trials. Recently, MV adaptation or MV leaflets tissue growth associated with LV dilatation attracts attention. Patients with larger MV leaflets with significant LV dilatation/dysfunction show less MV tethering and MR compared to those with smaller MV leaflets but with similar LV remodeling, suggesting the protective or beneficial role of MV leaflets tissue growth against LV remodeling. The MV leaflets tissue growth has the potential to lead to novel strategies of treatment for ventricular FMR. It is well known that atrial FMR is frequent in patients with left atrial dilatation, typically in those with isolated atrial fibrillation. The degree of atrial FMR is usually mild, even when it is present, and occasionally moderate, and severe atrial FMR is really rare. It is known that only severe regurgitation causes heart failure in primary MR, resulting in description on indications of surgery or intervention for only severe MR in current guidelines. Therefore, this atrial FMR up to moderate degree did not attract attention for a long time. However, recent studies have shown that patients with only moderate atrial FMR develop severe heart failure, suggesting more aggressive indication of MV surgery or intervention for "moderate" regurgitation in patients with atrial FMR. Therefore, atrial FMR is now recognized highly important. The unveiled malignant nature of atrial FMR arises many questions, including (1) why patients with only moderate atrial FMR develop heart failure? (2) do patients with mild atrial FMR develop heart failure or not?, and many others. Atrial FMR seems even more mysterious after the unveiling of its significance.

Genetic Testing Enables the Diagnosis of Familial Hypercholesterolemia Underdiagnosed by Clinical Criteria: Analysis of Japanese Early-Onset Coronary Artery Disease Patients.

Definitive diagnosis of familial hypercholesterolemia (FH) is paramount for the risk management of patients and their relatives. The present study aimed to investigate the frequency of gene variants contributing to low-density lipoprotein cholesterol (LDL-C) metabolism and their clinical relevance in patients with early-onset coronary artery disease (EOCAD). Among 63 consecutive patients with EOCAD (men <55 years or women <65 years) who underwent percutaneous coronary intervention (PCI) from 2013 to 2019 at Keio University Hospital, 52 consented to participate in this retrospective study. Targeted sequencing of LDLR, PCSK9, APOB, and LDLRAP1 was performed. Of the 52 patients enrolled (42 men; mean age: 50 ± 6 years), one (LDLR, c.1221_1222delCGinsT) harbored a pathogenic mutation, and one (APOB, c.10591A>G) harbored variants of uncertain significance. Both the patients harboring the variants were male, showing no history of diabetes mellitus or chronic kidney disease, no family history of EOCAD, and no physical findings of FH (i.e., tendon xanthomas or Achilles tendon thickening). Patients harboring the LDLR variant had three-vessel disease, were on a statin prescription at baseline, and had stable LDL-C levels; however, the case showed a poor response to the intensification of medication after PCI. Approximately 3.8% of patients with EOCAD harbored variants of gene related to LDL-C metabolism; there were no notable indicators in the patients' background or clinical course to diagnose FH. Given the difficulty in diagnosing FH based on clinical manifestations and family history, genetic testing could enable the identification of hidden risk factors and provide early warnings to their relatives.

Preoperative decline in skeletal muscle strength of patients with cardiovascular disease affects postoperative pulmonary complication occurrence: a single-center retrospective study.

BACKGROUND: Dynapenia, defined as age-related skeletal muscle strength decline, has been reported as a poor prognostic factor in patients with cardiovascular disease. Decline in skeletal muscle strength (DS), the main symptom of dynapenia, may be an important clinical indicator in patients undergoing cardiac surgery. However, the relationship between DS and postoperative pulmonary complication occurrence is unclear. Herein, we investigated the relationship between preoperative DS and postoperative pulmonary complication occurrence in patients undergoing cardiac surgery. METHODS: We enrolled 125 patients who underwent cardiac surgery. DS was determined by low grip strength and quadriceps isometric strength. The patients were divided into DS and non-DS groups. The relationship between the clinical characteristics and preoperative physical function was compared, and factors associated with postoperative pulmonary complication occurrence were investigated using multivariate logistic regression analysis. RESULTS: There were 42 (33.6%) patients in the DS group and 83 (66.4%) patients in the non-DS group. Compared with the non-DS group, the DS group was significantly older and had a higher body mass index and Japan SCORE (operative mortality rate and major complication rate). The DS group also had a lower estimated glomerular filtration rate and preoperative Barthel index than the non-DS group. Furthermore the DS group had a significantly higher incidence of postoperative pulmonary complications and length of intensive care unit stay, and their postoperative rehabilitation was prolonged compared to the non-DS group. Multivariate logistic regression analysis revealed that DS was a determinant of postoperative pulmonary complications (odds ratio 4.26, 95% confidence interval 1.63‒11.14). CONCLUSIONS: We showed that preoperative DS was an independent risk factor for postoperative pulmonary complications in patients undergoing cardiac surgery. Skeletal muscle strength before cardiac surgery may be an important clinical indicator for predicting the prognosis of patients from post-surgery to discharge and for planning postoperative rehabilitation programs.

Relationship between device displacement distance toward the caudal side during standing and pocket position laterality.

BACKGROUND: The displacement of cardiac implantable electronic devices (CIEDs) toward the caudal side during standing after CIED implantation could cause lead dislodgement. This study investigated the relationship between supine pocket position and standing CIEDs' displacement distance after the implantation. METHODS: After CIED surgeries performed at 2 hospitals between 2012 and 2020, 134 patients underwent postoperative chest x-rays in the supine and standing positions during hospitalization. To measure the displacement distance of CIEDs from the supine to the standing position, we identified the first thoracic vertebrae (Th1) in the supine position using the first rib as an index, drew a horizontal line at the lower edge of the Th1, and calculated the distance from that point to the upper edge of the CIED. The difference between measures for the two positions was compared. At the position of the pocket in the thorax in the supine position, the ratio of the distance between the thorax and the device is defined as the device thorax ratio (DTR). We examined the relationship between DTR and CIED displacement distance. RESULTS: In this study, we included 134 patients (53% men; median age, 79 years, body mass index, 22.3 ± 3.4; pacemaker 93%, left implantation 96%). We found that the more lateral the position of the CIED pocket, the more the CIED fell when standing (confidence interval = 0.34-0.60, P < .001). CONCLUSIONS: The farther the CIED was implanted outside the thorax in the supine position, the more significantly the CIED was displaced in the standing position.

AVP-eGFP was significantly upregulated by hypovolemia in the parvocellular division of the paraventricular nucleus in the transgenic rats.

Arginine vasopressin (AVP) is produced in the paraventricular (PVN) and supraoptic nuclei (SON). Peripheral AVP, which is secreted from the posterior pituitary, is produced in the magnocellular division of the PVN (mPVN) and SON. In addition, AVP is produced in the parvocellular division of the PVN (pPVN), where corticotrophin-releasing factor (CRF) is synthesized. These peptides synergistically modulate the hypothalamic-pituitary-adrenal (HPA) axis. Previous studies have revealed that the HPA axis was activated by hypovolemia. However, the detailed dynamics of AVP in the pPVN under hypovolemic state has not been elucidated. Here, we evaluated the effects of hypovolemia and hyperosmolality on the hypothalamus, using AVP-enhanced green fluorescent protein (eGFP) transgenic rats. Polyethylene glycol (PEG) or 3% hypertonic saline (HTN) was intraperitoneally administered to develop hypovolemia or hyperosmolality. AVP-eGFP intensity was robustly upregulated at 3 and 6 h after intraperitoneal administration of PEG or HTN in the mPVN. While in the pPVN, eGFP intensity was significantly increased at 6 h after intraperitoneal administration of PEG with significant induction of Fos-immunoreactive (-ir) neurons. Consistently, eGFP mRNA, AVP hnRNA, and CRF mRNA in the pPVN and plasma AVP and corticosterone were significantly increased at 6 h after intraperitoneal administration of PEG. The results suggest that AVP and CRF syntheses in the pPVN were activated by hypovolemia, resulting in the activation of the HPA axis.

Adenosine revives catheter-induced mechanical blocks in radiofrequency ablation.

Adenosine can hyperpolarize the atrial action potential, which helps rapidly re-establish the membrane potential in ablated sites and unmask "dormant conduction." It has been reported that pharmacological agents, including adenosine, were unable to revive traumatized tissues. We present the first case of the catheter-induced mechanical block ("bump" phenomenon) that was unmasked with adenosine administration in the working myocardium of the superior vena cava. This result may be because, unlike before, we could determine the force of contact between the tip of the ablation catheter and the myocardial tissue. This case suggests the clinical usefulness of adenosine for unmasking bumped sites.

MITOL/MARCH5 determines the susceptibility of cardiomyocytes to doxorubicin-induced ferroptosis by regulating GSH homeostasis.

MITOL/MARCH5 is an E3 ubiquitin ligase that plays a crucial role in the control of mitochondrial quality and function. However, the significance of MITOL in cardiomyocytes under physiological and pathological conditions remains unclear. First, to determine the significance of MITOL in unstressed hearts, we assessed the cellular changes with the reduction of MITOL expression by siRNA in neonatal rat primary ventricular cardiomyocytes (NRVMs). MITOL knockdown in NRVMs induced cell death via ferroptosis, a newly defined non-apoptotic programmed cell death, even under no stress conditions. This phenomenon was observed only in NRVMs, not in other cell types. MITOL knockdown markedly reduced mitochondria-localized GPX4, a key enzyme associated with ferroptosis, promoting accumulation of lipid peroxides in mitochondria. In contrast, the activation of GPX4 in MITOL knockdown cells suppressed lipid peroxidation and cell death. MITOL knockdown reduced the glutathione/oxidized glutathione (GSH/GSSG) ratio that regulated GPX4 expression. Indeed, the administration of GSH or N-acetylcysteine improved the expression of GPX4 and viability in MITOL-knockdown NRVMs. MITOL-knockdown increased the expression of the glutathione-degrading enzyme, ChaC glutathione-specific γ-glutamylcyclotransferase 1 (Chac1). The knockdown of Chac1 restored the GSH/GSSG ratio, GPX4 expression, and viability in MITOL-knockdown NRVMs. Further, in cultured cardiomyocytes stressed with DOX, both MITOL and GPX4 were reduced, whereas forced-expression of MITOL suppressed DOX-induced ferroptosis by maintaining GPX4 content. Additionally, MITOL knockdown worsened vulnerability to DOX, which was almost completely rescued by treatment with ferrostatin-1, a ferroptosis inhibitor. In vivo, cardiac-specific depletion of MITOL did not produce obvious abnormality, but enhanced susceptibility to DOX toxicity. Finally, administration of ferrostatin-1 suppressed exacerbation of DOX-induced myocardial damage in MITOL-knockout hearts. The present study demonstrates that MITOL determines the cell fate of cardiomyocytes via the ferroptosis process and plays a key role in regulating vulnerability to DOX treatment. (288/300).

Chemogenetic activation of endogenous arginine vasopressin exerts anorexigenic effects via central nesfatin-1/NucB2 pathway.

We examined whether the chemogenetic activation of endogenous arginine vasopressin (AVP) affects central nesfatin-1/NucB2 neurons, using a transgenic rat line that was previously generated. Saline (1 mL/kg) or clozapine-N-oxide (CNO, 1 mg/mL/kg), an agonist for hM3Dq, was subcutaneously administered in adult male AVP-hM3Dq-mCherry transgenic rats (300-370 g). Food and water intake were significantly suppressed after subcutaneous (s.c.) injection of CNO, with aberrant circadian rhythmicity. The percentages of Fos expression in nesfatin-1/NucB2-immunoreactive neurons were significantly increased in the hypothalamus and brainstem at 120 min after s.c. injection of CNO. Suppressed food intake that was induced by chemogenetic activation of endogenous AVP was ablated after intracerebroventricularly administered nesfatin-1/NucB2-neutralizing antibody in comparison with vehicle, without any alteration of water intake nor circadian rhythmicity. These results suggest that chemogenetic activation of endogenous AVP affects, at least in part, central nesfatin-1/NucB2 neurons and may exert anorexigenic effects in the transgenic rats.

Autoimmune hypophysitis as a cause of adrenocorticotropic hormone deficiency in pulmonary arterial hypertension: a case report.

BACKGROUND: Severe pulmonary arterial hypertension (PAH) is generally treated with multiple PAH-specific vasodilators. If these agents are unsuccessful, additional treatment options are scarce, and the prognosis is poor due to right-sided heart failure. Some of these severe cases are also accompanied by endocrinological side effects. The most common side effect of prostacyclin is thyroid dysfunction, but in very few cases, adrenocorticotropic hormone (ACTH) deficiency may occur. CASE SUMMARY: A 35-year-old woman was diagnosed with hereditary PAH 2 years ago. Since her mean pulmonary arterial pressure was high, combination therapy of vasodilators, including prostacyclin, was introduced. Several months later, she was hospitalized with a persistent fever. Laboratory tests showed no findings suggestive of infection. However, hypereosinophilia and decreased secretion of ACTH and cortisol were noted, which led to the diagnosis of ACTH deficiency. A multimodal diagnostic approach, including pituitary magnetic resonance imaging and axillary lymph node biopsy, indicated that the aetiology of the ACTH deficiency was likely autoimmune hypophysitis. She was treated with hydrocortisone supplementation, which significantly relieved her condition. DISCUSSION: Endocrinological side effects in PAH patients using prostacyclin should be carefully addressed. If right-sided heart failure worsens during the administration of prostacyclin, it is essential to determine whether it is due to progression of pulmonary hypertension or endocrinological side effects. Careful diagnosis and treatment are important for managing the haemodynamics and symptoms of PAH patients given prostacyclin.

Time-Series Transcriptome Analysis Reveals the miR-27a-5p-Ppm1l Axis as a New Pathway Regulating Macrophage Alternative Polarization After Myocardial Infarction.

BACKGROUND: Timely differentiation of monocytes into M2-like macrophages is important in the cardiac healing process after myocardial infarction (MI), but molecular mechanisms governing M2-like macrophage differentiation at the transcriptional level after MI have not been fully understood.Methods and Results:A time-series microarray analysis of mRNAs and microRNAs in macrophages isolated from the infarcted myocardium was performed to identify the microRNAs involved in regulating the process of differentiation to M2-like macrophages. Correlation analysis revealed 7 microRNAs showing negative correlations with the progression of polarity changes towards M2-like subsets. Next, correlation coefficients for the changes in expression of mRNAs and miRNAs over time were calculated for all combinations. As a result, miR-27a-5p was extracted as a possible regulator of the largest number of genes in the pathway for the M2-like polarization. By selecting mouse mRNAs and human mRNAs possessing target sequences of miR-27a-5p and showing expression patterns inversely correlated with that of miR-27a-5p, 8 potential targets of miR-27a-5p were identified, includingPpm1l. Using the mouse bone marrow-derived macrophages undergoing differentiation into M2-like subsets by interleukin 4 stimulation, we confirmed that miR-27a-5p suppressed M2-related genes by negatively regulatingPpm1lexpression. CONCLUSIONS: Ppm1land miR-27a-5p may be the key molecules regulating M2-like polarization, with miR-27a-5p inhibiting the M2-like polarization through downregulation ofPpm1lexpression.

TNFRSF13B c.226G>A (p.Gly76Ser) as a Novel Causative Mutation for Pulmonary Arterial Hypertension.

Background Recently, some studies reported the pulmonary artery hypertension (PAH)-associated genes. However, a majority of patients with familial or sporadic PAH lack variants in the known pathogenic genes. In this study, we investigated the new causative gene variants associated with PAH. Methods and Results Whole-exome sequencing in 242 Japanese patients with familial or sporadic PAH identified a heterozygous substitution change involving c.226G>A (p.Gly76Ser) in tumor necrotic factor receptor superfamily 13B gene (TNFRSF13B) in 6 (2.5%) patients. TNFRSF13B controls the differentiation of B cell and secretion of inflammatory cytokines and may be involved in vascular inflammation. In silico structural analysis simulation demonstrated the structural instability of the N-terminal region of the protein synthesized from TNFRSF13B p.Gly76Ser variant. These suggest that the TNFRSF13B p.Gly76Ser variant may be involved in the development of PAH via aberrant inflammation in pulmonary vessels. Conclusions TNFRSF13B p.Gly76Ser variant is a candidate of novel causative gene variant for PAH.

MerTK Expression and ERK Activation Are Essential for the Functional Maturation of Osteopontin-Producing Reparative Macrophages After Myocardial Infarction.

Background We previously reported that osteopontin plays an essential role in accelerating both reparative fibrosis and clearance of dead cells (efferocytosis) during tissue repair after myocardial infarction (MI) and galectin-3hiCD206+ macrophages is the main source of osteopontin in post-MI heart. Interleukin-10- STAT3 (signal transducer and activator of transcription 3)-galectin-3 axis is essential for Spp1 (encoding osteopontin) transcriptional activation in cardiac macrophages after MI. Here, we investigated the more detailed mechanism responsible for functional maturation of osteopontin-producing macrophages. Methods and Results In post-MI hearts, Spp1 transcriptional activation occurred almost exclusively in MerTK (Mer tyrosine kinase)+ galectin-3hi macrophages. The induction of MerTK on galectin-3hi macrophages is essential for their functional maturation including efferocytosis and Spp1 transcriptional activity. MerTK+galectin-3hi macrophages showed a strong activation of both STAT3 and ERK (extracellular signal-regulated kinase). STAT3 inhibition suppressed the differentiation of osteopontin-producing MerTK+galectin-3hi macrophages, however, STAT3 activation was insufficient at inducing Spp1 transcriptional activity. ERK inhibition suppressed Spp1 transcriptional activation without affecting MerTK or galectin-3 expression. Concomitant activation of ERK is required for transcriptional activation of Spp1. In Il-10 knockout enhanced green fluorescent protein-Spp1 knock-in mice subjected to MI, osteopontin-producing macrophages decreased but did not disappear entirely. Interleukin-10 and macrophage colony-stimulating factor synergistically activated STAT3 and ERK and promoted the differentiation of osteopontin-producing MerTK+galectin-3hi macrophages in bone marrow-derived macrophages. Coadministration of anti-interleukin-10 plus anti-macrophage colony-stimulating factor antibodies substantially reduced the number of osteopontin-producing macrophages by more than anti-interleukin-10 antibody alone in post-MI hearts. Conclusions Interleukin-10 and macrophage colony-stimulating factor act synergistically to activate STAT3 and ERK in cardiac macrophages, which in turn upregulate the expression of galectin-3 and MerTK, leading to the functional maturation of osteopontin-producing macrophages.

Poor outcomes in carriers of the RNF213 variant (p.Arg4810Lys) with pulmonary arterial hypertension.

BACKGROUND: A variant of c.14429G>A (p.Arg4810Lys, rs112735431) in the ring finger protein 213 gene (RNF213; NM_001256071.2) has been recently identified as a risk allele for pulmonary arterial hypertension (PAH). PAH can be added as a new member of RNF213-associated vascular diseases, which include Moyamoya disease and peripheral pulmonary stenosis. Our aim was to identify the clinical features and outcomes of PAH patients with this variant. METHODS: Whole-exome sequencing was performed in 139 idiopathic (or possibly heritable) PAH patients. RESULTS: The RNF213 p.Arg4810Lys variant was identified in a heterozygous state in 11 patients (7.9%). Time-course changes in hemodynamics after combination therapy in the patients with the RNF213 p.Arg4810Lys variant were significantly poorer compared with those carrying the bone morphogenic protein receptor type 2 (BMPR2) mutation (n = 36) (comparison of changes in mean pulmonary arterial pressure, p = 0.007). The event-free rate of death or lung transplantation was significantly poorer in RNF213 p.Arg4810Lys variant carriers than in BMPR2 mutation carriers (5-year event-free rate since the introduction of prostaglandin I2 infusion, 0% vs 93%, respectively; p < 0.001). CONCLUSIONS: Idiopathic PAH patients with the RNF213 p.Arg4810Lys variant are associated with poor clinical outcomes even in recent times. Earlier consideration of lung transplantation might be required for RNF213 p.Arg4810Lys variant carriers who are developing PAH. Documentation of the RNF213 p.Arg4810Lys variant, as well as already known pathogenic genes, such as BMPR2, can provide clinically relevant information for therapeutic strategies, leading to a personalized approach for the treatment of PAH.

A microsurgical technique for catheter insertion in the rat femoral artery

Abstract Purpose: To modify a surgical catheterization method using the bent needle introducer in small animals. Methods: Eight-week-old male Lewis rats were used in the study. A needle introducer was created by bending a 21G injection needle at 45°. The bent needle introducer was used for catheter insertion into the left femoral artery of the rats under anesthesia. As a control, a catheter was directly inserted into the blood vessel without the introducer. The insertion time of each method was measured. Blood pressure and heart rate were measured 24 h after catheter insertion using the telemetry system. Results: Using the introducer, the catheter was successfully inserted within a short time in all rats. Without the introducer, a longer duration was required for catheter insertion. The frequency of the insertion with no catheter-based errors with the introducer tended to be higher than that without the introducer. The mean arterial pressure and heart rate 24 h after catheter insertion in each group were almost the same. Conclusions: We developed a surgical catheterization method using the introducer in small animals. This could potentially reduce the frequency of the insertion with catheter-based errors and insertion time.

Balloon pulmonary angioplasty for symptomatic chronic thromboembolic disease without pulmonary hypertension at rest.

BACKGROUND: Patients with chronic thromboembolic disease (CTED) have chronic thromboembolic obstructions of the pulmonary arteries with exercise intolerance, but without signs of pulmonary hypertension at rest. We investigated the efficacy of balloon pulmonary angioplasty (BPA) for CTED patients. METHODS: Fifteen CTED patients (4 males, 11 females) who underwent BPA were enrolled. The inclusion criteria were 1) chronic thromboembolic obstructions of the pulmonary artery identified on ventilation-perfusion scans and pulmonary angiography, 2) WHO functional class II or greater, and 3) mean PAP of <25 mmHg as measured by right heart catheterization. This study excluded patients with CTEPH at diagnosis. RESULTS: At the 6-month follow-up after the final BPA session, hemodynamics and 6-min walk distance were significantly improved. Although more than half of the patients were prescribed home oxygen therapy before BPA due to O2 desaturation with exercise, the use ratio of home oxygen therapy was reduced at the time of follow-up (from 53% to 7%; P = 0.01). Furthermore, cardiopulmonary exercise tests during right heart catheterization demonstrated that BPA could ameliorate an abnormal pulmonary vascular response to exercise. CONCLUSIONS: BPA can produce favorable outcomes in patients with CTED. Prospective, larger randomized clinical trials are needed to further investigate this treatment strategy.

Balloon pulmonary angioplasty attenuates sleep apnea in patients with chronic thromboembolic pulmonary hypertension.

BACKGROUND: Balloon pulmonary angioplasty (BPA) improves pulmonary hemodynamics in chronic thromboembolic pulmonary hypertension (CTEPH) patients. However, whether it affects the severity of sleep apnea (SA) remains unknown. We investigated the effect of BPA on the severity of SA in CTEPH patients. METHODS: We studied 13 patients with CTEPH who had an apnea hypopnea index (AHI) > 10 before BPA and underwent a second polygraph test 6 months after the last BPA session. RESULTS: BPA decreased pulmonary vascular resistance, mean pulmonary artery pressure (PAP), and plasma B-type natriuretic peptide levels, and increased the 6-minute walking distance. BPA decreased the AHI (from 20.9 [13.9-35.7] to 16.3 [7.7-21.8] times/hour, P = 0.023) and hypopnea index (from 13.2 [8.4-22.5] to 6.4 [3.8-10.9] times/hour, P = 0.013), but not the obstructive, central, or mixed apnea index. The change in AHI correlated with that in mean PAP, but not with the change in body mass index or other parameters of hemodynamics. CONCLUSIONS: BPA-induced improvement in hemodynamics was associated with the attenuation of SA in patients with CTEPH and SA. Therefore, close attention should be paid to SA in CTEPH patients, and SA should be re-evaluated after BPA to avoid overestimating its severity.

Therapeutic role of miR-19a/19b in cardiac regeneration and protection from myocardial infarction.

The primary cause of heart failure is the loss of cardiomyocytes in the diseased adult heart. Previously, we reported that the miR-17-92 cluster plays a key role in cardiomyocyte proliferation. Here, we report that expression of miR-19a/19b, members of the miR-17-92 cluster, is induced in heart failure patients. We show that intra-cardiac injection of miR-19a/19b mimics enhances cardiomyocyte proliferation and stimulates cardiac regeneration in response to myocardial infarction (MI) injury. miR-19a/19b protected the adult heart in two distinctive phases: an early phase immediately after MI and long-term protection. Genome-wide transcriptome analysis demonstrates that genes related to the immune response are repressed by miR-19a/19b. Using an adeno-associated virus approach, we validate that miR-19a/19b reduces MI-induced cardiac damage and protects cardiac function. Finally, we confirm the therapeutic potential of miR-19a/19b in protecting cardiac function by systemically delivering miR-19a/19b into mice post-MI. Our study establishes miR-19a/19b as potential therapeutic targets to treat heart failure.

Endothelial-Mesenchymal Transition Drives Expression of CD44 Variant and xCT in Pulmonary Hypertension.

Pulmonary arterial hypertension (PAH) pathogenesis shares similarities with carcinogenesis. One CD44 variant (CD44v) isoform, CD44v8-10, binds to and stabilizes the cystine transporter subunit (xCT), producing reduced glutathione and thereby enhancing the antioxidant defense of cancer stem cells. Pharmacological inhibition of xCT by sulfasalazine suppresses tumor growth, survival, and resistance to chemotherapy. We investigated whether the CD44v-xCT axis contributes to PAH pathogenesis. CD44v was predominantly expressed on endothelial-to-mesenchymal transition (EndMT)-like cells in the neointimal layer of PAH affected pulmonary arterioles. In vitro, CD44 standard form and CD44v were induced as a result of EndMT. Among human pulmonary artery endothelial cells that have undergone EndMT, CD44v+ cells showed high levels of xCT expression on their cell surfaces and high concentrations of glutathione for survival. This made CD44v+ cells the most vulnerable target for sulfasalazine. CD44v+xCThi cells showed the highest expression levels of proinflammatory cytokines, antioxidant enzymes, antiapoptotic molecules, and cyclin-dependent kinase inhibitors. In the Sugen5416/hypoxia mouse model, CD44v+ cells were present in the thickened pulmonary vascular wall. The administration of sulfasalazine started either at the same time as "Sugen5416" administration (a prevention model) or after the development of pulmonary hypertension (a reversal model) attenuated the muscularization of the pulmonary vessels, decreased the expression of markers of inflammation, and reduced the right ventricular systolic pressure, while reducing CD44v+ cells. In conclusion, CD44v+xCThi cells appear during EndMT and in pulmonary hypertension tissues. Sulfasalazine is expected to be a novel therapeutic agent for PAH, most likely targeting EndMT-derived CD44v+xCThi cells.

IL (Interleukin)-10-STAT3-Galectin-3 Axis Is Essential for Osteopontin-Producing Reparative Macrophage Polarization After Myocardial Infarction.

BACKGROUND: Both osteopontin (OPN) and galectin-3 have been implicated in phagocytic clearance of dead cells and reparative fibrosis during wound healing. CD206+ macrophages are involved in tissue repair through phagocytosis and fibrosis after myocardial infarction (MI). However, the relationship among OPN, galectin-3, and macrophage polarization in the context of MI remains unclear. METHODS: The time course of Spp1 (encoding OPN) expression in the heart after MI showed a strong activation of Spp1 on day 3 after MI. To identify where in the body and in which cells the transcriptional activity of Spp1 increased after MI, we analyzed EGFP (enhanced green fluorescent protein)- Spp1 knockin reporter mice on day 3 after MI. RESULTS: The transcriptional activity of Spp1 increased only in CD206+ macrophages in the infarct myocardium, and most of CD206+ macrophages have strong transcriptional activation of Spp1 after MI. The temporal expression pattern of Lgal3 (encoding galectin-3) in cardiac macrophages after MI was similar to that of Spp1, and OPN is almost exclusively produced by galectin-3hiCD206+ macrophages. Although both interleukin (IL)-4 and IL-10 were reported to promote CD206+ macrophage-mediated cardiac repair after MI, IL-10- but not IL-4-stimulated CD11b+Ly6G- cells could differentiate into OPN-producing galectin-3hiCD206+ macrophages and showed enhanced phagocytic ability. Inhibition of STAT3 tyrosine phosphorylation suppressed IL-10-induced expression of intracellular galectin-3 and transcriptional activation of Spp1. Knockdown of galectin-3 suppressed their ability to differentiate into OPN-producing cells, but not STAT3 activation. The tyrosine phosphorylation of STAT3 and the appearance rate of galectin-3hiCD206+ cells on cardiac CD11b+Ly6G- cells in Spp1 knockout mice were the same as those in wild-type mice. Spp1 knockout mice showed vulnerability to developing post-MI left ventricular chamber dilatation and the terminal deoxynucleo-tidyltransferase 2'-Deoxyuridine-5'-triphosphate nick-end labeling (TUNEL)-positive cells in the infarcted myocardium after MI remained higher in number in Spp1 knockout mice than in wild-type mice. CONCLUSIONS: OPN is almost exclusively produced by galectin-3hiCD206+ macrophages, which specifically appear in the infarct myocardium after MI. The IL-10-STAT3-galectin-3 axis is essential for OPN-producing reparative macrophage polarization after myocardial infarction, and these macrophages contribute to tissue repair by promoting fibrosis and clearance of apoptotic cells. These results suggest that galectin-3 may contribute to reparative fibrosis in the infarct myocardium by controlling OPN levels.