Myocyte Proliferation Research Articles

Identification and analysis of differentially expressed lncRNAs and their ceRNA networks in DMD/mdx primary myoblasts

This study explored the significance of long non-coding RNAs (lncRNAs), particularly their role in maintaining dystrophin protein stability and regulating myocyte proliferation and differentiation. The investigation focused on DMD/mdx mouse skeletal muscle primary myoblasts, aiming to identify lncRNAs potential as biomarkers and therapeutic targets for Duchenne muscular dystrophy (DMD). Utilizing CLC Genomics Workbench software, 554 differentially expressed lncRNAs were identified in DMD/mdx mice compared to wild-type (WT) control. Among them, 373 were upregulated, and 181 were downregulated. The study highlighted specific lncRNAs (e.g., 5930430L01Rik, Gm10143, LncRNA1490, LncRNA580) and their potential regulatory roles in DMD key genes like IGF1, FN1, TNNI1, and MYOD1. By predicting miRNA and their connections with lncRNA and mRNA (ceRNA network) using tools such as miRNet, miRSYSTEM and miRCARTA, the study revealed potential indirect regulation of Dystrophin, IGF1R and UTRN genes by identified lncRNAs (e.g. 2310001H17Rik-203, C130073E24Rik-202, LncRNA2767, 5930430L01Rik and LncRNA580). These findings suggest that the identified lncRNAs may play crucial roles in the development and progression of DMD through their regulatory influence on key gene expression, providing valuable insights for potential therapeutic interventions.

Morphological, electrophysiological, and molecular alterations in foetal noncompacted cardiomyopathy induced by disruption of ROCK signalling.

Left ventricular noncompaction cardiomyopathy is associated with heart failure, arrhythmia, and sudden cardiac death. The developmental mechanism underpinning noncompaction in the adult heart is still not fully understood, with lack of trabeculae compaction, hypertrabeculation, and loss of proliferation cited as possible causes. To study this, we utilised a mouse model of aberrant Rho kinase (ROCK) signalling in cardiomyocytes, which led to a noncompaction phenotype during embryogenesis, and monitored how this progressed after birth and into adulthood. The cause of the early noncompaction at E15.5 was attributed to a decrease in proliferation in the developing ventricular wall. By E18.5, the phenotype became patchy, with regions of noncompaction interspersed with thick compacted areas of ventricular wall. To study how this altered myoarchitecture of the heart influenced impulse propagation in the developing and adult heart, we used histology with immunohistochemistry for gap junction protein expression, optical mapping, and electrocardiography. At the prenatal stages, a clear reduction in left ventricular wall thickness, accompanied by abnormal conduction of the ectopically paced beat in that area, was observed in mutant hearts. This correlated with increased expression of connexin-40 and connexin-43 in noncompacted trabeculae. In postnatal stages, left ventricular noncompaction was resolved, but the right ventricular wall remained structurally abnormal through to adulthood with cardiomyocyte hypertrophy and retention of myocardial crypts. Thus, this is a novel model of self-correcting embryonic hypertrabeculation cardiomyopathy, but it highlights that remodelling potential differs between the left and right ventricles. We conclude that disruption of ROCK signalling induces both morphological and electrophysiological changes that evolve over time, highlighting the link between myocyte proliferation and noncompaction phenotypes and electrophysiological differentiation.

Abstract We021: Connexin 43 mediates macrophage induced cardiomyocyte proliferation and heart regeneration

Background: Heart regeneration is a potential strategy to recover pumping function after cardiac injury and protect against heart failure. Macrophages have been demonstrated to promote heart regeneration, while its mechanism has not been addressed. Modulating the interaction between macrophages and cardiomyocytes through connexin 43 (CX43) may provide a clinical therapy for preventing further deterioration of patients with heart injury and restoring the lost myocardium. Hypothesis: We hypothesize that macrophages can interact with cardiomyocytes via CX43, leading to promotion of cardiac proliferation and heart regeneration. Aims: Our study aims to provide the evidence of macrophages contacting cardiomyocytes through CX43 and promoting heart regeneration. Methods and Results: Through cell co-culture experiments, we found that macrophages attache to cardiomyocytes via CX43, subsequently promoting myocyte proliferation as evidenced by proliferative markers. Blocking the CX43 connection by SiRNA between two cells suspended cardiomyocyte proliferation in vitro. We generated macrophage-specific CX43 deficient mice (CX43 Mφ/- ) by crosing CD11b-Cre mice and CX43-flox mice. We performed apical resection operation on 1 day-old CX43 Mφ/- mice and harvested the hearts at 21 day-post-resection. CX43 Mφ/- mice demonstrated either the heart regeneration ability nor pumping function. Applying single-cell RNA sequencing in CX43 Mφ/- hearts, we illustrated the unique transcriptional signature of macrophage and cardiomyocyte in macrophage-specific CX43 deficient mice. Conclusion: Our study provides the evidence that macrophages attache to cardiomyocyte via CX43 after cardiac injury, promote cardiomyocyte proliferation and heart regeneration. This discovery may offer a new target for clinical treatment of myocardial infarction.

POLB Regulates Proliferation and Apoptosis of Bovine Primary Myocytes.

DNA polymerase β (DNA polymerase beta (POLB)) belongs to a member of the DNA polymerase X family, mainly involved in various biological metabolic processes, such as eukaryotic DNA replication, DNA damage repair, gene recombination, and cell cycle regulation. In this study, the muscle development-related gene POLB was screened by selection signature and RNA-seq analysis and then validated for the proliferation and apoptosis of bovine primary myocytes. It was also found that overexpression of the POLB gene had a pro-apoptosis effect, but interfering with the expression of the gene had no significant effect on cells. Then, the analysis of related apoptotic genes revealed that POLB overexpression affected CASP9 gene expression.

Gene expression and cellular changes in injured myocardium of Ciona intestinalis.

Ciona intestinalis is an invertebrate animal model system that is well characterized and has many advantages for the study of cardiovascular biology. The regulatory mechanisms of cardiac myocyte proliferation in Ciona are intriguing since regeneration of functional tissue has been demonstrated in other organs of Ciona in response to injury. To identify genes that are differentially expressed in response to Ciona cardiac injury, microarray analysis was conducted on RNA from adult Ciona hearts with normal or damaged myocardium. After a 24- or 48-h recovery period, total RNA was isolated from damaged and control hearts. Initial results indicate significant changes in gene expression in hearts damaged by ligation in comparison to control hearts. Ligation injury shows differential expression of 223 genes as compared to control with limited false discovery (5.8%). Among these 223 genes, 117 have known human orthologs of which 68 were upregulated and 49 were downregulated. Notably, Fgf9/16/20, insulin-like growth factor binding protein and Ras-related protein Rab11b were significantly upregulated in injured hearts, whereas expression of a junctophilin ortholog was decreased. Histological analyses of injured myocardium were conducted in parallel to the microarray study which revealed thickened myocardium in injured hearts. Taken together, these studies will connect differences in gene expression to cellular changes in the myocardium of Ciona, which will help to promote further investigations into the regulatory mechanisms of cardiac myocyte proliferation across chordates.

Identification of FDA-approved drugs that induce heart regeneration in mammals.

Targeting Meis1 and Hoxb13 transcriptional activity could be a viable therapeutic strategy for heart regeneration. In this study, we performd an in silico screening to identify FDA-approved drugs that can inhibit Meis1 and Hoxb13 transcriptional activity based on the resolved crystal structure of Meis1 and Hoxb13 bound to DNA. Paromomycin (Paro) and neomycin (Neo) induced proliferation of neonatal rat ventricular myocytes in vitro and displayed dose-dependent inhibition of Meis1 and Hoxb13 transcriptional activity by luciferase assay and disruption of DNA binding by electromobility shift assay. X-ray crystal structure revealed that both Paro and Neo bind to Meis1 near the Hoxb13-interacting domain. Administration of Paro-Neo combination in adult mice and in pigs after cardiac ischemia/reperfusion injury induced cardiomyocyte proliferation, improved left ventricular systolic function and decreased scar formation. Collectively, we identified FDA-approved drugs with therapeutic potential for induction of heart regeneration in mammals.

MBNL1 Regulates Programmed Postnatal Switching Between Regenerative and Differentiated Cardiac States.

Discovering determinants of cardiomyocyte maturity is critical for deeply understanding the maintenance of differentiated states and potentially reawakening endogenous regenerative programs in adult mammalian hearts as a therapeutic strategy. Forced dedifferentiation paired with oncogene expression is sufficient to drive cardiac regeneration, but elucidation of endogenous developmental regulators of the switch between regenerative and mature cardiomyocyte cell states is necessary for optimal design of regenerative approaches for heart disease. MBNL1 (muscleblind-like 1) regulates fibroblast, thymocyte, and erythroid differentiation and proliferation. Hence, we examined whether MBNL1 promotes and maintains mature cardiomyocyte states while antagonizing cardiomyocyte proliferation. MBNL1 gain- and loss-of-function mouse models were studied at several developmental time points and in surgical models of heart regeneration. Multi-omics approaches were combined with biochemical, histological, and in vitro assays to determine the mechanisms through which MBNL1 exerts its effects. MBNL1 is coexpressed with a maturation-association genetic program in the heart and is regulated by the MEIS1/calcineurin signaling axis. Targeted MBNL1 overexpression early in development prematurely transitioned cardiomyocytes to hypertrophic growth, hypoplasia, and dysfunction, whereas loss of MBNL1 function increased cardiomyocyte cell cycle entry and proliferation through altered cell cycle inhibitor transcript stability. Moreover, MBNL1-dependent stabilization of estrogen-related receptor signaling was essential for maintaining cardiomyocyte maturity in adult myocytes. In accordance with these data, modulating MBNL1 dose tuned the temporal window of neonatal cardiac regeneration, where increased MBNL1 expression arrested myocyte proliferation and regeneration and MBNL1 deletion promoted regenerative states with prolonged myocyte proliferation. However, MBNL1 deficiency was insufficient to promote regeneration in the adult heart because of cell cycle checkpoint activation. Here, MBNL1 was identified as an essential regulator of cardiomyocyte differentiated states, their developmental switch from hyperplastic to hypertrophic growth, and their regenerative potential through controlling an entire maturation program by stabilizing adult myocyte mRNAs during postnatal development and throughout adulthood. Targeting loss of cardiomyocyte maturity and downregulation of cell cycle inhibitors through MBNL1 deletion was not sufficient to promote adult regeneration.

Fueling cardiac myocyte proliferation.

Fueling cardiac myocyte proliferation.

Nonsense Variant PRDM16-Q187X Causes Impaired Myocardial Development and TGF-β Signaling Resulting in Noncompaction Cardiomyopathy in Humans and Mice.

PRDM16 plays a role in myocardial development through TGF-β (transforming growth factor-beta) signaling. Recent evidence suggests that loss of PRDM16 expression is associated with cardiomyopathy development in mice, although its role in human cardiomyopathy development is unclear. This study aims to determine the impact of PRDM16 loss-of-function variants on cardiomyopathy in humans. Individuals with PRDM16 variants were identified and consented. Induced pluripotent stem cell-derived cardiomyocytes were generated from a proband hosting a Q187X nonsense variant as an in vitro model and underwent proliferative and transcriptional analyses. CRISPR (clustered regularly interspaced short palindromic repeats)-mediated knock-in mouse model hosting the Prdm16Q187X allele was generated and subjected to ECG, histological, and transcriptional analysis. We report 2 probands with loss-of-function PRDM16 variants and pediatric left ventricular noncompaction cardiomyopathy. One proband hosts a PRDM16-Q187X variant with left ventricular noncompaction cardiomyopathy and demonstrated infant-onset heart failure, which was selected for further study. Induced pluripotent stem cell-derived cardiomyocytes prepared from the PRDM16-Q187X proband demonstrated a statistically significant impairment in myocyte proliferation and increased apoptosis associated with transcriptional dysregulation of genes implicated in cardiac maturation, including TGF-β-associated transcripts. Homozygous Prdm16Q187X/Q187X mice demonstrated an underdeveloped compact myocardium and were embryonically lethal. Heterozygous Prdm16Q187X/WT mice demonstrated significantly smaller ventricular dimensions, heightened fibrosis, and age-dependent loss of TGF-β expression. Mechanistic studies were undertaken in H9c2 cardiomyoblasts to show that PRDM16 binds TGFB3 promoter and represses its transcription. Novel loss-of-function PRDM16 variant impairs myocardial development resulting in noncompaction cardiomyopathy in humans and mice associated with altered TGF-β signaling.

Abstract P1081: Inhibition Of Mir-200c Abrogates Post-infarction LV Remodeling Following A Myocardial Infarct.

Ischemic injury and adverse post-infarction myocardial remodeling are major causes of heart failure worldwide. Strategies designed to offset cell death with cardiomyocyte regeneration have, to date, not translated to routine clinical practice. m ir-200c modulates the transcripts of cardiogenic transcription factors (TFs) Tbx5 and Gata4 to promote myocyte maturation. We hypothesized that inhibition of mir-200c activity would result in postnatal myocyte de-differentiation and replication sufficient to ameliorate post-infarction decompensation after ischemic injury. To test this hypothesis, we preformed left coronary ligation on Wild-Type (WT) and transgenic mice expressing an RNA inhibitor against miR-200c (I-200c). Echocardiographic left ventricular (LV) ejection fraction (EF) fell from 88.41 ± 1.08% (WT) and 90% ± 1.42% (I-200c) (p=NS) to 28% ± 11.55% (WT) and 36% ± 9.35% at 1 day post injury (DPI) (p =NS). At 21DPI, LVEF was 27% ± 4.31% (WT) and 64% ± 4.25% (I-200c) [p ≤ 0.0001]. Post-infarction LV chamber dilation was inhibited in I-200c mice (1.136 ± 0.19 v 0.67 ± 0.06 p ≤ 0.004 LV Vol/mass). These results indicated that inhibiting miR-200c following ischemic injury can recover cardiac function and prevent LV dilation. Moreover, trichrome stain showed a decrease in fibrosis 21 DPI (WT: 57% ± 17.46 v I-200c: 12% ± 3.01 p ≤ 0.001). To understand the mechanism causing this phenomenon, we analyzed expression of cardiac progenitor markers Tbx5 and Gata4 . Fold change in expression of both TFs were increased at 21 DPI (WT: 1.02 ± 0.09 v I-200c: 2.86 ± 0.76 p ≤ 0.05; WT: 1.00 ± 0.02 v I-200c: 3.08 ± 0.64 p ≤ 0.05). Additionally, I-200c mice have increased fold change of the cardiac progenitor factor Nkx2.5 (1.01 ± 0.07 v 4.16 ± 1.08 p ≤ 0.05). Tbx5, Gata4, Nkx2.5, in the context of ischemic injury, are thought to perturb post-infarct remodeling and promote CM survival. Conclusions: I-200c treatment abrogates post-infarction LV remodeling and significantly restores LV systolic function, which are associated with increased myocyte expression of cardiogenic progenitor markers. Future studies will determine the importance of myocyte proliferation vs. humoral modulation of surviving myocyte phenotype, toward protection of post-infarction LVs.

Effects of maternal hypothyroidism on postnatal cardiomyocyte proliferation and cardiac disease responses of the progeny.

Maternal hypothyroidism (MH) could adversely affect the cardiac disease responses of the progeny. This study tested the hypothesis that MH reduces early postnatal cardiomyocyte (CM) proliferation so that the adult heart of MH progeny has a smaller number of larger cardiac myocytes, which imparts adverse cardiac disease responses following injury. Thyroidectomy (TX) was used to establish MH. The progeny from mice that underwent sham or TX surgery were termed Ctrl (control) or MH (maternal hypothyroidism) progeny, respectively. MH progeny had similar heart weight (HW) to body weight (BW) ratios and larger CM size consistent with fewer CMs at postnatal day 60 (P60) compared with Ctrl (control) progeny. MH progeny had lower numbers of EdU+, Ki67+, and phosphorylated histone H3 (PH3)+ CMs, which suggests they had a decreased CM proliferation in the postnatal timeframe. RNA-seq data showed that genes related to DNA replication were downregulated in P5 MH hearts, including bone morphogenetic protein 10 (Bmp10). Both in vivo and in vitro studies showed Bmp10 treatment increased CM proliferation. After transverse aortic constriction (TAC), the MH progeny had more severe cardiac pathological remodeling compared with the Ctrl progeny. Thyroid hormone (T4) treatment for MH mothers preserved their progeny's postnatal CM proliferation capacity and prevented excessive pathological remodeling after TAC. Our results suggest that CM proliferation during early postnatal development was significantly reduced in MH progeny, resulting in fewer CMs with hypertrophy in adulthood. These changes were associated with more severe cardiac disease responses after pressure overload.NEW & NOTEWORTHY Our study shows that compared with Ctrl (control) progeny, the adult progeny of mothers who have MH (MH progeny) had fewer CMs. This reduction of CM numbers was associated with decreased postnatal CM proliferation. Gene expression studies showed a reduced expression of Bmp10 in MH progeny. Bmp10 has been linked to myocyte proliferation. In vivo and in vitro studies showed that Bmp10 treatment of MH progeny and their myocytes could increase CM proliferation. Differences in CM number and size in adult hearts of MH progeny were linked to more severe cardiac structural and functional remodeling after pressure overload. T4 (synthetic thyroxine) treatment of MH mothers during their pregnancy, prevented the reduction in CM number in their progeny and the adverse response to disease stress.

Comprehensive analysis of metabolomics on flesh quality of yellow catfish (Pelteobagrus fulvidraco) fed plant-based protein diet.

To investigate the mechanism of plant protein components on nutritional value, growth performance, flesh quality, flavor, and proliferation of myocytes of yellow catfish (Pelteobagrus fulvidraco). A total of 540 yellow catfish were randomly allotted into six experimental groups with three replicates and fed six different diets for 8 weeks. The replacement of fish meal with cottonseed meal (CM), sesame meal (SEM), and corn gluten meal (CGM) in the diet significantly reduced growth performance, crude protein, and crude lipid, but the flesh texture (hardness and chewiness) was observably increased. Moreover, the flavor-related amino acid (glutamic acid, glycine, and proline) contents in the CM, SEM, and CGM groups of yellow catfish muscle were significantly increased compared with the fish meal group. The results of metabolomics showed that soybean meal (SBM), peanut meal (PM), CM, SEM, and CGM mainly regulated muscle protein biosynthesis by the variations in the content of vitamin B6, proline, glutamic acid, phenylalanine, and tyrosine in muscle, respectively. In addition, Pearson correlation analysis suggested that the increased glutamic acid content and the decreased tyrosine content were significantly correlated with the inhibition of myocyte proliferation genes. This study provides necessary insights into the mechanism of plant proteins on the dynamic changes of muscle protein, flesh quality, and myocyte proliferation in yellow catfish.

Development of Biodegradable Small Diameter Vascular Graft

Coronary heart disease (CHD) is a major cause of death on a global scale. Treatment options include revascularisation, but achieving a successful vascular graft requires using one with a diameter of less than 4mm and there is no artificial vascular graft at such a small diameter available. Scientists are interested in developing biodegradable artificial vascular grafts that can help overcome challenges associated with CHD. Associate Professor Kyohei Oyama and his team in the Department of Cardiac Surgery, Asahikawa Medical University, Japan, are currently working on two main projects: Creating a biodegradable small diameter vascular graft; and developing a heart regeneration treatment via endogenous cardiac myocyte proliferation. In developing a biodegradable small diameter vascular graft, the researchers hope to benefit patients that require the revascularisation of small vessels and also positively impact young patients who are still growing. The team also hope that the discoveries made through this research might lead to advances in other organ regeneration. When it comes to the need to recover lost cardiac tissue, this is unable to regenerate as cardiac myocytes (muscle cells) have no ability to proliferate. Oyama and the team are investigating the mechanism that limits this proliferation ability with a view to activating it. If cardiac myocyte proliferation can be activated during the revascularisation of CHD, then the damaged heart can be completely cured and the possibility of heart failure eliminated.

Jak inhibitors in vitiligo: a meta analysis.

Jak inhibitors in vitiligo: a meta analysis.

Systemic Hypoxemia Induces Cardiomyocyte Hypertrophy and Right Ventricular Specific Induction of Proliferation.

A recent study suggests that systemic hypoxemia in adult male mice can induce cardiac myocytes to proliferate. The goal of the present experiments was to confirm these results, provide new insights on the mechanisms that induce adult cardiomyocyte cell cycle reentry, and to determine if hypoxemia also induces cardiomyocyte proliferation in female mice. EdU-containing mini pumps were implanted in 3-month-old, male and female C57BL/6 mice. Mice were placed in a hypoxia chamber, and the oxygen was lowered by 1% every day for 14 days to reach 7% oxygen. The animals remained in 7% oxygen for 2 weeks before terminal studies. Myocyte proliferation was also studied with a mosaic analysis with double markers mouse model. Hypoxia induced cardiac hypertrophy in both left ventricular (LV) and right ventricular (RV) myocytes, with LV myocytes lengthening and RV myocytes widening and lengthening. Hypoxia induced an increase (0.01±0.01% in normoxia to 0.11±0.09% in hypoxia) in the number of EdU+ RV cardiomyocytes, with no effect on LV myocytes in male C57BL/6 mice. Similar results were observed in female mice. Furthermore, in mosaic analysis with double markers mice, hypoxia induced a significant increase in RV myocyte proliferation (0.03±0.03% in normoxia to 0.32±0.15% in hypoxia of RFP+ myocytes), with no significant change in LV myocyte proliferation. RNA sequencing showed upregulation of mitotic cell cycle genes and a downregulation of Cullin genes, which promote the G1 to S phase transition in hypoxic mice. There was significant proliferation of nonmyocytes and mild cardiac fibrosis in hypoxic mice that did not disrupt cardiac function. Male and female mice exhibited similar gene expression following hypoxia. Systemic hypoxia induces a global hypertrophic stress response that was associated with increased RV proliferation, and while LV myocytes did not show increased proliferation, our results minimally confirm previous reports that hypoxia can induce cardiomyocyte cell cycle activity in vivo.

Butyrate promotes C2C12 myoblast proliferation by activating ERK/MAPK pathway.

Sarcopenia has garnered considerable interest in recent years as ageing-associated diseases constitute a significant worldwide public health burden. Nutritional supplements have received much attention as potential tools for managing sarcopenia. However, the specific nutrients responsible are still under-investigated. In the current study, we first determined the levels of short chain fatty acids (SCFAs) and intestinal flora in the feces of elderly sarcopenia subjects and elderly healthy individuals by ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS). Then cell viability detection, flow cytometry and transcriptome analysis were adopted to experimentally evaluate the effect and the underlying mechanism of SCFA on C2C12 cells proliferation in vitro. The results suggested that patients with sarcopenia exhibited decreased levels of butyrate. And butyrate may stimulate C2C12 myocyte proliferation via promoting G1/S cell cycle transition. Transcriptomic analyses pointed to upregulation of the Mitogen-activated protein kinase (MAPK) signaling pathway in butyrate-treated cells. In addition, the above proliferative phenotypes could be suppressed by the combination of ERK/MAPK inhibitor. A combined transcriptomic and metabolomic approach was applied in our study to investigate the potential effect of microbiota-derived butyrate yield on muscular proliferation which may indicate a protective effect of nutritional supplements.

Myocardial injection of thermosensitive HADOPA/Ca-FVI/Alg hydrogels improves cardiac repair after myocardial infarction

Myocardial infarction (MI) is a common heart emergency that potentially causes death. Injectable hydrogels with excellent malleability and filling properties are suitable for myocardial injection and can avoid the need for open surgery. In this study, dopamine grafted hyaluronic acid (HADOPA) was synthesized and combined with sodium alginate (Alg) and Ca2+-loaded liposomes (Ca-FVI) to prepare a series of injectable thermosensitive sodium hyaluronate/sodium alginate hydrogels (HADOPA/Ca-FVI/Alg). At 37 °C, the HADOPA/Ca-FVI/Alg solution rapidly changed from liquid to hydrogel because of the crosslinking between sodium alginate and the Ca2+ released from Ca-FVI at a phase transition time of 100–200 s. The HADOPA/Ca-FVI/Alg scaffolds exhibited a porous 3D network structure, controlled porosity, and connected pore properties. Increasing the proportion of HADOPA increases the elasticity and absorbance of hydrogels. Experimental assessment showed that the hydrogels have good biocompatibility and that Alg1-HADOPA is more conducive to the adhesion, proliferation, and spreading of mouse cardiac myocytes while maintaining the best cell state. These findings suggest that HADOPA/Ca-FVI/Alg hydrogels improve cell proliferation and tissue repair, and that they are a promising therapeutic option for cardiac repair after MI.

Abstract 10618: Modified Rna Ccnd2 Promotes Myocardial Remuscularizationin Lv Infarct by Regulating Cardiomyocyte Cell Cycle

The adult mammalian heart has limited capacity to regenerate, due to postnatal cardiomyocyte cell cycle arrest. This study examined whether the cardiomyocyte cell-cycle reactivation can enhance myocardial remuscularization in hearts with acute myocardial infarction (AMI). Because the G1-to-S phase transition of the cell cycle is critically regulated by cyclin D proteins, and the expression of cyclin D2 (CCND2) could regenerate injured myocardium, we hypothesized that a transient and exclusive overexpression of CCND2 in cardiomyocytes can result in myocytes proliferation and therefore, remuscularize myocardial infarct. The transient and exclusive myocyte overexpression of CCND2 was achieved by Specific ModRNA Translation system (SMRTs) 1 . In vitro assessments were performed in hiPSC-derived cardiomyocytes (hiPSC-CMs) by immunofluorescence staining of cell proliferation markers (Ki67, BrdU, PH3, and Aurora B) to evaluate whether cardiomyocyte-specific modified RNA CCND2 ( CMS modRNA-CCND2) could reactivate cell cycle. Using a mouse model of AMI, normal and infarcted mice were compared 4 weeks after AMI to assess the structural and functional outcomes of myocardial injection 100μg CMS modRNA-CCND2. In vitro , the, CMS modRNA-CCND2 resulted in significantly higher CMs cell cycle activity as evidenced by significantly higher percentage of hiPSC-CMs that expressed Ki67 (8.68 ± 1.64 VS 36.68 ± 2.61 , p<0.01), BrdU (8.44 ± 1.14% VS 17.59 ± 0.84%, p<0.01), PH3 (0.51 ± 0.04% VS 1.68 ± 0.09%, p<0.01), and Aurora B (0.47 ± 0.03% VS 1.59 ± 0.07%, P<0.01), CMS modRNA-Luciferase vs CMS modRNA-CCND2, respectively. In vivo, CMs cell cycle activity was significantly increased in SMRT treated hearts 4 weeks post AMI as evidenced by: Ki67 (0.41 ± 0.04% VS 2.00 ± 0.17%, p<0.01), PH3 (0.039 ± 0.004% VS 0.30 ± 0.006%, p<0.01), AMI VS AMI + SMRT, respectively. LV Infarct size also decreased significantly 4 weeks after AMI in AMI + SMRT group of hearts (50.04 ± 1.42% VS 31.28 ± 1.28%, p<0.01). Thus, CMS modRNA-CCND2 could induce myocardial remuscularization by re-activating CM cell- cycle in hearts with AMI. *, equal contribution first author

Neutrophil Extracellular Vesicles and Airway Smooth Muscle Proliferation in the Natural Model of Severe Asthma in Horses.

Extracellular vesicles (EVs) contribute to intercellular communication through the transfer of their rich cargo to recipient cells. The EVs produced by LPS-stimulated neutrophils from healthy humans and horses increase airway smooth muscle (ASM) proliferation, but the roles of neutrophil EVs in asthma are largely unexplored. The aim of this study was to determine whether neutrophil-derived EVs isolated during the remission or exacerbation of asthma influence ASM proliferation differentially. Peripheral blood neutrophils were collected during remission and exacerbation in eight horses affected by severe asthma. The cells were cultured (±LPS), and their EVs were isolated by ultracentrifugation and characterized by laser scattering microscopy and proteomic analysis. The proliferation of ASM co-incubated with EVs was monitored in real time by electrical impedance. Two proteins were significantly upregulated during disease exacerbation in neutrophil EVs (MAST4 and Lrch4), while LPS stimulation greatly altered the proteomic profile. Those changes involved the upregulation of neutrophil degranulation products, including proteases known to induce myocyte proliferation. In agreement with the proteomic results, EVs from LPS-stimulated neutrophils increased ASM proliferation, without an effect of the disease status. The inhalation of environmental LPS could contribute to asthma pathogenesis by activating neutrophils and leading to ASM hyperplasia.

Widespread intracoronary allogeneic cardiosphere-derived cell therapy with and without cyclosporine in reperfused myocardial infarction.

Allogeneic cardiosphere-derived cell (CDC) therapy has been demonstrated to improve myocardial function when administered to reperfused myocardial infarcts. We previously pretreated animals with low-dose cyclosporine immunosuppression to limit allogeneic CDC rejection, but whether it is necessary and, if so, can be initiated at the time of reperfusion remains uncertain. Closed-chest swine (n = 29 animals) were subjected to a 90-min left anterior descending (LAD) coronary artery occlusion. Using a three-way blinded design, we randomized two groups to receive global intracoronary infusions of 20 × 106 CDCs 30 min after reperfusion. A third control group was treated with saline. One CDC group received cyclosporine 10 min before reperfusion (2.5 mg/kg iv and 100 mg/day po), whereas the other groups received placebos. After 1 mo, neither chronic infarct size relative to area at risk (saline control, 46.2 ± 4.0%; CDCs, 46.4 ± 2.1%; and CDCs + cyclosporine, 49.2 ± 3.1%; P = 0.79) nor ejection fraction (saline control, 51 ± 2%; CDCs, 51 ± 2%; and CDC + cyclosporine, 48 ± 2%; P = 0.42) were different among treatment groups. Multiple histological measures of cellular remodeling, myocyte proliferation, and apoptosis were also not different among treatment groups. In contrast to previous studies, we were unable to reproduce the cardioprotective effects demonstrated by allogeneic CDCs without cyclosporine. Furthermore, initiation of intravenous cyclosporine at the time of reperfusion followed by oral therapy was not sufficient to elicit the functional improvement observed in studies where cyclosporine was started 72 h before CDC therapy. This suggests that oral cyclosporine pretreatment may be necessary to effect cardiac repair with allogeneic CDCs.NEW & NOTEWORTHY In a three-way blinded, randomized design, we determined whether allogeneic CDCs administered at reperfusion improved myocardial function and whether intravenous cyclosporine enhanced their efficacy. In contrast to prior studies using oral cyclosporine, CDCs with or without intravenous cyclosporine had no effect on function or infarct size. This indicates that CDCs may be most efficacious for treating chronic LV dysfunction where cyclosporine can be initiated at least 72 h before cell therapy.