Stimulates Cardiomyocyte Proliferation Research Articles

Cardiac injury modulates critical components of prostaglandin E2 signaling during zebrafish heart regeneration

The inability to effectively stimulate cardiomyocyte proliferation remains a principle barrier to regeneration in the adult human heart. A tightly regulated, acute inflammatory response mediated by a range of cell types is required to initiate regenerative processes. Prostaglandin E2 (PGE2), a potent lipid signaling molecule induced by inflammation, has been shown to promote regeneration and cell proliferation; however, the dynamics of PGE2 signaling in the context of heart regeneration remain underexplored. Here, we employ the regeneration-competent zebrafish to characterize components of the PGE2 signaling circuit following cardiac injury. In the regenerating adult heart, we documented an increase in PGE2 levels, concurrent with upregulation of cox2a and ptges, two genes critical for PGE2 synthesis. Furthermore, we identified the epicardium as the most prominent site for cox2a expression, thereby suggesting a role for this tissue as an inflammatory mediator. Injury also drove the opposing expression of PGE2 receptors, upregulating pro-restorative ptger2a and downregulating the opposing receptor ptger3. Importantly, treatment with pharmacological inhibitors of Cox2 activity suppressed both production of PGE2, and the proliferation of cardiomyocytes. These results suggest that injury-induced PGE2 signaling is key to stimulating cardiomyocyte proliferation during regeneration.

P314Osteopontin stimulates cell cycle in neonatal cardiomyocytes

Abstract Introduction Macrophages control myocardial regeneration in the neonatal heart and repair in the adult heart. Osteopontin (OPN) is a macrophage-derived protein which is upregulated following tissue injury. While OPN regulates cell adhesion, spreading and migration, its role in myocardial regeneration is unknown. Purpose We aimed to test the hypothesis that OPN stimulates cardiomyocyte proliferation. Methods and results Mouse neonatal cardiomyocytes were treated with a serum-free medium for 24 hours. Immunofluorescent staining showed that these cells expressed the OPN receptor CD44 (Fig. 1A). To assess cell expansion, we used MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, colorimetric assay. OPN preserved cardiomyocyte count in a low glucose medium for 24 hours, compared with no OPN treatment (Fig. 1B). Staining for phosphohistone (pH)3, a marker of nucleus division, showed a higher expression of pH3 in cardiomyocytes after OPN treatment (Fig. 1C). Immunoblotting revealed that OPN induced the phosphorylation of cell-cycle activity proteins, known as yes-associated protein (YAP)1, and extracellular signal-regulated kinase (ERK)2, while it decreased the phosphorylation of the YAP1 inhibitor, the large tumor-suppressor kinase (LATS)1/2 (Figs. 1D and 1E). Gene expression analysis revealed that OPN upregulated the transcriptional enhancer factor TEF-1 (TEAD1), which interacts with YAP1 (Fig. 1F), connective tissue growth factor (CTGF) and cyclin-dependent kinase 1 (CDK1), which are YAP downstream targets (Figs. 1G and 1H). Furthermore, OPN significantly upregulated cyclin B1, a regulator of the mitotic (M) phase (Fig. 1I). Moreover, OPN may promote positive feedback by upregulating the expression of CD44, SPP-1 (Figs. 1J and 1K). Finally, administration of OPN to adult mouse improved cardiac remodeling and function after myocardial infarction. Conclusions OPN stimulates cell-cycle activity in neonatal cardiomyocytes through YAP1 activity, independently from the HIPPO-YAP signaling pathway. Because macrophages are a major source of OPN after injury, our findings could explain the essential role of macrophages in neonatal heart regeneration and adult heart repair. Acknowledgement/Funding Israel Science Foundation

Stimulating Cardiogenesis as a Treatment for Heart Failure.

After myocardial injury, cardiomyocyte loss cannot be corrected by using currently available clinical treatments. In recent years, considerable effort has been made to develop cell-based cardiac repair therapies aimed at correcting for this loss. An exciting crop of recent studies reveals that inducing endogenous repair and proliferation of cardiomyocytes may be a viable option for regenerating injured myocardium. Here, we review current heart failure treatments, the state of cardiomyocyte renewal in mammals, and the molecular signals that stimulate cardiomyocyte proliferation. These signals include growth factors, intrinsic signaling pathways, microRNAs, and cell cycle regulators. Animal model cardiac regeneration studies reveal that modulation of exogenous and cell-intrinsic signaling pathways can induce reentry of adult cardiomyocytes into the cell cycle. Using direct myocardial injection, epicardial patch delivery, or systemic administration of growth molecules, these studies show that inducing endogenous cardiomyocytes to self-renew is an exciting and promising therapeutic strategy to treat cardiac injury in humans.

A post-surgical adjunctive hypoxic therapy for myocardial infarction: Initiate endogenous cardiomyocyte proliferation in adults

Myocardial infarction (MI) is a major threat to health worldwide, but today’s methods for recovering heart function are limited, which is due largely to the deficient proliferative capacity of adult cardiomyocytes in the human body. To successfully overwhelm this deficiency, we propose a promising hypoxic therapy and highlight its unique role in directly eliciting endogenous myocardial regeneration in vivo. In the hypothesis, sufficient oxygen could be a restrictive factor of myocardial growth, whereas a moderate hypoxia might stimulate cardiomyocyte proliferation and enhance myocardial regeneration, heart weight and cardiac function recovery. The potential involvements of the hypoxia inducible factor-1 (HIF-1) and its downstream oncogenic signalings were hypothesized and evaluated in detail. Notably, the hypoxic treatment may initiate spontaneous proliferation of pre-existing cardiomyocytes in adult human body, which cannot (or hardly) be achieved by current MI-therapeutic approaches such as cardiovascular drugs, cardiac surgeries and aerobic exercise. The hypoxic therapy will lead to lower surgical risks compared with tissue regeneration in vitro and putative cardiac transplantation. With optimized moderately-low oxygen concentration, available therapeutic frequency and cycles, and controllable side effects, the hypoxic therapy will be a non-invasive, non-surgical, low-cost and low-risk approach to promoting myocardial regeneration in vivo and recovering cardiac function for MI patients who have large-area myocardial necrosis, in addition to other current MI-therapeutic methodologies.

Vitamin D Stimulates Cardiomyocyte Proliferation and Controls Organ Size and Regeneration in Zebrafish

Attaining proper organ size during development and regeneration hinges on the activity of mitogenic factors. Here, we performed a large-scale chemical screen in embryonic zebrafish to identify cardiomyocyte mitogens. Although commonly considered anti-proliferative, vitamin D analogs like alfacalcidol had rapid, potent mitogenic effects on embryonic and adult cardiomyocytes invivo. Moreover, pharmacologic or genetic manipulation of vitamin D signaling controlled proliferation in multiple adult cell types and dictated growth rates in embryonic and juvenile zebrafish. Tissue-specific modulation of vitamin D receptor (VDR) signaling had organ-restricted effects, with cardiac VDR activation causing cardiomegaly. Alfacalcidol enhanced the regenerative response of injured zebrafish hearts, whereas VDR blockade inhibited regeneration. Alfacalcidol activated cardiac expression of genes associated with ErbB2 signaling, while ErbB2 inhibition blunted its effects on cell proliferation. Our findings identify vitamin D as mitogenic for cardiomyocytes and other cell types in zebrafish and indicate a mechanism to regulate organ size and regeneration.

A long noncoding RNA NR_045363 controls cardiomyocyte proliferation and cardiac repair

Long noncoding RNAs (lncRNAs) play important roles in the regulation of genes involved in cell proliferation. We have previously sought to more globally understand the differences of lncRNA expression between human fetal heart and adult heart to identify some functional lncRNAs which involve in the process of heart repair. We found that a highly conserved long noncoding RNA NR_045363 was mainly expressed in cardiomyocytes and rarely in non-cardiomyocytes. NR_045363 overexpression in 7-day-old mice heart could improve cardiac function and stimulate cardiomyocyte proliferation after myocardial infarction. Furthermore, NR_045363 knockdown inhibited proliferation of primary embryonic cardiomyocytes, while NR_045363 overexpression enhanced DNA synthesis and cytokinesis in neonatal cardiomyocytes in vitro. Mechanistic analysis revealed that NR_045363 promoted cardiomyocyte proliferation through interaction with miR-216a, which regulated the JAK2-STAT3 pathway. Our results showed that NR_045363 is a potent lncRNA modulator essential for cardiomyocyte proliferation.

Discovery of a Small Molecule to Increase Cardiomyocytes and Protect the Heart After Ischemic Injury

Accumulating data suggest that new cardiomyocytes in adults are generated from existing cardiomyocytes throughout life. To enhance the endogenous cardiac regeneration, we performed chemical screenings to identify compounds that activate pro-proliferative YES-associated protein and transcriptional enhancer factor domain activities in cardiomyocytes. We synthesized a novel fluorine-containing TT-10 (C11H10FN3OS2) from the biologically hit compound. TT-10 promoted cardiomyocyte proliferation and simultaneously exerted antioxidant and antiapoptotic effects invitro. TT-10 treatment in mice ameliorated myocardial infarction-induced cardiac dysfunction at least in part via enhancing clonal expansion of existing cardiomyocytes with nuclear YES-associated protein expression. Stimulating cardiomyocyte proliferation and/or protection with TT-10 might complement current therapies for myocardial infarction.

Systemic arterial hypertension but not IGF-I treatment stimulates cardiomyocyte enlargement in neonatal lambs.

Although cardiomyocyte terminal differentiation is nearly complete at birth in sheep, as in humans, very limited postnatal expansion of myocyte number may occur. The capacity of newborn cardiomyocytes to respond to growth stimulation by proliferation is poorly understood. Our objective was to test this growth response in newborn lambs with two stimuli shown to be potent inducers of cardiomyocyte growth in fetuses and adults: increased systolic load (Load) and insulin-like growth factor I (IGF-I). Vascular catheters and an inflatable aortic occluder were implanted in lambs. Hearts were collected for analysis at 18 days of age after a 7-day experiment and compared with control hearts. Load hearts, but not IGF-I hearts, were heavier ( P = 0.001) because of increased mass of the left ventricle (LV), septum, and left atrium (40-50%, P = 0.004). Terminal differentiation and cell cycle activity were not different between groups. Myocyte length was 7% greater in Load lamb hearts ( P < 0.05), and binucleated myocytes, which comprise ~90% of LV cells, were 25% larger in volume ( P = 0.03). Myocyte number per gram of myocardium was decreased in all ventricles of Load lambs ( P = 0.01). Cells from the IGF-I group were not different by any comparison. These results suggest that the newborn sheep LV responds to systolic stress with cardiomyocyte hypertrophy, not proliferation. Furthermore, IGF-I is ineffective at stimulating cardiomyocyte proliferation at this age (despite effectiveness when administered before birth). Thus, to expand cardiomyocyte number in the newborn heart, therapies other than systolic pressure load and IGF-I treatment need to be developed.

Abstract 308: Wls Inhibits Fibrosis Through Wnt Secretion From the Cardiomyocytes During Heart Regeneration

Because cardiomyocytes lose their capacity for self-renewal shortly after birth, the heart cannot regenerate muscle lost due to injury or heart failure. Instead, dead myocardium is replaced with a fibrotic scar. Recent studies have demonstrated that blocking the Hippo pathway specifically in cardiomyocytes promotes heart functional recovery after injury, not only by stimulating cardiomyocyte proliferation, but also by preventing fibrosis. The mechanism through which YAP activates the cell cycle is widely studied; however, the mechanism through which it inhibits fibrosis is unknown. Here, we identified Wntless ( Wls ) to be a downstream target of YAP in regenerating cardiomyocytes; Wls plays a role in regulating the secretion of Wnt ligands, which influences interstitial cells through paracrine effects. By using Adeno-Associated Virus 9 (AAV9) to deliver guide RNAs (gRNAs) that target the Wls locus exclusively in cardiomyocytes that express the Cas9 protein, we generated a cardiomyocyte-specific Wls knock out mouse (Wls-Cas9 CKO). After myocardial infarction at the neonatal stage (regenerative stage), cardiomyocyte deletion of Wls detrimental the heart regeneration as showed decreased heart function and increased fibrosis in Wls-Cas9 CKO mice. Mechanistically, by performing nuclear RNA-Seq technology, we revealed that non-canonical Wnt ligands are enriched in cardiomyocytes suggest cardiomyocytes influence fibroblasts through non-canonical signaling during heart regeneration. We will further use the single-cell sequencing technology to investigate the cell to cell communication during heart regeneration.

Dusp6 attenuates Ras/MAPK signaling to limit zebrafish heart regeneration.

Zebrafish regenerate cardiac tissue through proliferation of pre-existing cardiomyocytes and neovascularization. Secreted growth factors such as FGFs, IGF, PDGFs and Neuregulin play essential roles in stimulating cardiomyocyte proliferation. These factors activate the Ras/MAPK pathway, which is tightly controlled by the feedback attenuator Dual specificity phosphatase 6 (Dusp6), an ERK phosphatase. Here, we show that suppressing Dusp6 function enhances cardiac regeneration. Inactivation of Dusp6 by small molecules or by gene inactivation increased cardiomyocyte proliferation, coronary angiogenesis, and reduced fibrosis after ventricular resection. Inhibition of Erbb or PDGF receptor signaling suppressed cardiac regeneration in wild-type zebrafish, but had a milder effect on regeneration in dusp6 mutants. Moreover, in rat primary cardiomyocytes, NRG1-stimulated proliferation can be enhanced upon chemical inhibition of Dusp6 with BCI. Our results suggest that Dusp6 attenuates Ras/MAPK signaling during regeneration and that suppressing Dusp6 can enhance cardiac repair.

Spiny mouse is protected from ischemia induced cardiac injury: leading role of microRNAs

Introduction and hypothesisDespite advances in drug therapy, revascularization and surgical interventions, mortality and morbidity from heart failure in ischemic heart disease remains high and a breakthrough in our understanding of this disorder is needed. Spiny mouse (Acomys cahirinus) has evolved a remarkable capacity to regenerate full thickness skin tissue without scarring. Here we tested the hypothesis that the lack of scarring and resulting regeneration in adult Acomys skin also applies to the heart.Methods and ResultsAdult Acomys and CD1 mice had either left anterior descending coronary artery ligation or sham surgery. Proliferative cells were identified by nuclear incorporation of 5‐bromodeoxyuridine (BrdU, 50mg/kg, daily, i.p.) with injections from 3d post myocardial infarction (MI) for 2wks and cardiac function was assessed by echocardiography. Following MI, Acomys infarct size was one‐fourth (18.6±3.4%) vs CD1 (76.2±3.4%, p&lt;0.05) with 3.2 fold better systolic function (ejection fraction 77.1±6.5 vs CD1 24.6±4.6%, p&lt;0.05). Post‐MI, Acomys had 2.2‐fold more proliferating cardiomyocytes (BrdU+ cells) in their left ventricle vs CD1 mice (Acomys‐sham 16±9.8 vs Acomys‐MI 101.1±30.9: CD1‐sham 11±3.5 vs CD1‐MI 44±9.1, p&lt;0.05). We also measured the expression of miRNAs in the border zone of the infarcted hearts for both CD1 and Acomys and the corresponding zone in sham‐operated animals using small RNA‐Sequencing. We found four miRNAs that have been shown to stimulate/promote cardiomyocyte proliferation and cardiac regeneration were significantly changed in the Acomys‐MI hearts: miR410‐3p (5.2‐fold increase in Acomys‐MI relative to Acomys‐Sham, Q value=&lt;0.03), miR‐199a (miR‐199a‐3p:4.6‐fold increase in Acomys‐MI relative to Acomys‐Sham, Q value=0.0003; miR‐199a‐5p:3.5‐fold increase in Acomys‐MI relative to Acomys‐Sham, Q value=0.0088), miR‐214(miR‐214‐3p: 4.3‐fold increase in Acomys‐MI relative to Acomys‐Sham Q value=0.005; miR‐214‐5p: 4.0‐fold increase in Acomys‐MI relative to Acomys‐Sham, Q value=0.01, and let‐7f‐5p (2.0‐fold decrease in Acomys‐MI relative to Acomys‐Sham, Q value=0.02 &lt;0.05). However, these miRNAs were not different between CD1 groups. Associated with this there was a dramatic increase in coronary microvasculature in the infarct region in Acomys.ConclusionsWe conclude that the Acomys heart responds to severe ischemia‐induced cardiac damage by increasing the number of proliferating cardiomyocytes. A possible mechanism is suggested by the upregulation of expression of microRNAs known to stimulate cardiomyocyte proliferation and cardiac regeneration (miR410, −199a, −214, let‐7f), These processes regenerated cardiac cells and vastly reduced scarring and hence preserved cardiac function.Support or Funding InformationNational Institute of Health grants HL33610(M.K.R), UM1 HL087366 to the Cardiovascular Cell Therapy Research Network (C.J. Pepine). Florida Heart Foundation Stop Heart Disease (Y.F. Qi).

A growing role for the Hippo signaling pathway in the heart.

Heart disease is a major cause of clinical morbidity and mortality, and a significant health and economic burden worldwide. The loss of functional cardiomyocytes, often a result of myocardial infarction, leads to impaired cardiac output and ultimately heart failure. Therefore, efforts to improve cardiomyocyte viability and stimulate cardiomyocyte proliferation remain attractive therapeutic goals. Originally identified in Drosophila, the Hippo signaling pathway is highly conserved from flies to humans and regulates organ size through modulation of both cell survival and proliferation. This is particularly relevant to the heart, an organ with limited regenerative ability. Recent work has demonstrated a critical role for this signaling cascade in determining heart development, homeostasis, injury and the potential for regeneration. Here we review the function of canonical and non-canonical Hippo signaling in cardiomyocytes, with a particular focus on proliferation and survival, and how this impacts the stressed adult heart.

Transplantation of adipose-derived stem cells combined with neuregulin-microparticles promotes efficient cardiac repair in a rat myocardial infarction model

Tissue engineering is a promising strategy to promote heart regeneration after a myocardial infarction (MI). In this study, we investigated the reparative potential of a system that combines adipose-derived stem cells (ADSCs) with microparticles (MPs) loaded with neuregulin (NRG), named ADSC-NRG-MPs, on a rat MI model. First, cells were attached to the surface of MPs encapsulating NRG and coated with a 1:1 mixture of collagen and poly-d-lysine. One week after in vivo administration, the system favored the shift of macrophage expression from a pro-inflammatory to a regenerative phenotype. At long-term, the adhesion of ADSCs to MPs resulted in an increased cell engraftment, with cells being detectable in the tissue up to three months. In consonance, better tissue repair was observed in the animals treated with cells attached to MPs, which presented thicker left ventricles than the animals treated with ADSCs alone. Moreover, the presence of NRG in the system promoted a more complete regeneration, reducing the infarct size and stimulating cardiomyocyte proliferation. Regarding vasculogenesis, the presence of ADSCs and NRG-MPs alone stimulated vessel formation when compared to the control group, but the combination of both induced the largest vasculogenic effect, promoting the formation of both arterioles and capillaries. Importantly, only when ADSCs were administered adhered to MPs, they were incorporated into newly formed vessels. Collectively, these findings demonstrate that the combination of ADSCs, MPs and NRG favored a synergy for inducing a greater and more complete improvement in heart regeneration and provided strong evidence to move forward with preclinical studies with this strategy.

Abstract 370: Hedgehog Signaling Regulates Cardiac Regeneration in vivo

The adult mammalian heart has a limited regenerative capacity due primarily to reduced cardiomyocyte (CM) proliferation. Here, we demonstrated hedgehog (HH) signaling pathway as an essential regulator of heart regeneration and CM proliferation. We undertook genome-wide screening using a novel algorithm, bootstrap, which showed an induction of HH signals in the regenerating newt heart. Blockade of HH signaling in the resected newt heart resulted in complete ablation of cardiac regeneration and scar formation. EdU-labeling revealed that inhibition of the HH pathway significantly reduced CM proliferation by 3-fold (n=4 at each time period post-injury). In mammals, cardiac specific loss- and gain-of-function of HH signals demonstrated its role in CM proliferation and regeneration in the postnatal heart. Genetic deletion of floxed-Smoothened ( Smo L/L ) allele at postnatal day 2 (P2) inhibited neonatal heart regeneration with impaired cardiac function and scarring following injury. Conversely, induction of constitutively active Smoothened (SmoM2) at P7 stimulated CM proliferation by 2.5-fold (n=3) and regeneration after myocardial infarction during the non-regenerative window. Lineage-tracing experiments showed that activation of Smo contributed to heart regeneration by promoting proliferation of the pre-existing cardiomyocytes. Activation of HH signals in the cultured CM at P1 and P7 showed an increased proliferative response by 2- and 3-fold (n=4; 1900 cells evaluated for each condition), respectively. Mechanistically, ChIP-seq analysis revealed that HH signals promoted the proliferative program by directly regulating the expression of cyclin-dependent kinases including cyclinD2, cyclinE1 and Cdc7. Finally, activation of HH signaling in the terminally differentiated hiPSC-derived CM resulted in an increase in the number of α-Actinin + /EdU + and α-Actinin + /Ki67 + cells by 2.5-fold (n=3; 645 cells assessed for each condition) and 3-fold (n=3; 685 cells assessed for each condition), respectively. These studies defined an evolutionarily conserved function of HH signaling from newt to mouse to human, as a key regulator of cardiomyocyte proliferation and regeneration that may serve as a platform for regenerative therapies.

Circulation Research “In This Issue” Anthology

Circulation Research “In This Issue” Anthology

MiR-410 and miR-495 Are Dynamically Regulated in Diverse Cardiomyopathies and Their Inhibition Attenuates Pathological Hypertrophy.

Noncoding RNAs have emerged as important modulators in cardiac development and pathological remodeling. Recently, we demonstrated that regulation of the Gtl2-Dio3 noncoding RNA locus is dependent on the MEF2 transcription factor in cardiac muscle, and that two of its encoded miRNAs, miR-410 and miR-495, induce robust cardiomyocyte proliferation. Given the possibility of manipulating the expression of these miRNAs to repair the damaged heart by stimulating cardiomyocyte proliferation, it is important to determine whether the Gtl2-Dio3 noncoding RNAs are regulated in cardiac disease and whether they function downstream of pathological cardiac stress signaling. Therefore, we examined expression of the above miRNAs processed from the Gtl2-Dio3 locus in various cardiomyopathies. These noncoding RNAs were upregulated in all cardiac disease models examined including myocardial infarction (MI) and chronic angiotensin II (Ang II) stimulation, and in the cardiomyopathies associated with muscular dystrophies. Consistent with these observations, we show that the Gtl2-Dio3 proximal promoter is activated by stress stimuli in cardiomyocytes and requires MEF2 for its induction. Furthermore, inhibiting miR-410 or miR-495 in stressed cardiomyocytes attenuated the hypertrophic response. Thus, the Gtl2-Dio3 noncoding RNA locus is a novel marker of cardiac disease and modulating the activity of its encoded miRNAs may mitigate pathological cardiac remodeling in these diseases.

Epicardial Outgrowth Culture Assay and Ex Vivo Assessment of Epicardial-derived Cell Migration.

A single layer of epicardial cells lines the heart, providing paracrine factors that stimulate cardiomyocyte proliferation and directly contributing cardiovascular progenitors during development and disease. While a number of factors have been implicated in epicardium-derived cell (EPDC) mobilization, the mechanisms governing their subsequent migration and differentiation are poorly understood. Here, we present in vitro and ex vivo strategies to study EPDC motility and differentiation. First, we describe a method of obtaining primary epicardial cells by outgrowth culture from the embryonic mouse heart. We also introduce a detailed protocol to assess three-dimensional migration of labeled EPDC in an organ culture system. We provide evidence using these techniques that genetic deletion of myocardin-related transcription factors in the epicardium attenuates EPDC migration. This approach serves as a platform to evaluate candidate modifiers of EPDC biology and could be used to develop genetic or chemical screens to identify novel regulators of EPDC mobilization that might be useful for cardiac repair.

Bioengineered FSTL1 Patches Restore Cardiac Function Following Myocardial Infarction

Improving the limited ability of the heart to regenerate after infarction is crucial. Researchers now demonstrate that delivery of follistatin-like 1 (FSTL1) into injured hearts via collagen patches stimulates cardiomyocyte proliferation and cardiac functional recovery. These findings highlight the epicardium as a source of novel regenerative factors and biomimetic nanomaterials in cardiac translational medicine.

Activation of FGF1B Promoter and FGF1 Are Involved in Cardiogenesis Through the Signaling of PKC, but Not MAPK.

Heart disease is the leading cause of human death in the 21st century. Heart transplantation is a promising way to treat this. Because donor resources are limited, cell-based therapy has been developed as an alternative. Therefore, genes that trigger cardiogenesis could have potential in the treatment of heart disease. Fibroblast growth factor 1 (FGF1) is reported to stimulate cardiomyocyte proliferation under conditions of myocardial infarction, but little is known about its function during cardiac differentiation. In this study, we established an in vitro cardiogenesis model through a reliable chemical induction protocol to determine whether FGF1 and its gene expression are involved in cardiogenesis. Oxytocin, not only a well-known hormone but also a cardiac differentiation inducer, was used in a mouse embryonic stem cell line, E14Tg2a, to achieve cardiac differentiation. After differentiation, beating cell clusters appeared and the expression of FGF1B mRNA was upregulated in the late differentiation stage (differentiation days 8-14). Interestingly, FGF1B expression patterns during cardiac differentiation were similar to those of a mature cardiomyocyte marker, troponin T2, cardiac. The blockage of FGF1-FGF receptor (FGFR) signaling reduced not only the appearance of beating cluster formation but also the expression levels of cardiomyocyte-associated genes. Moreover, by investigating FGF1 downstream signaling cascades, we observed that the efficiency of beating cluster formation was mainly regulated through the FGF1-FGFR-PKC signaling axis. Taken together, we provide evidence to support that FGF1 could regulate cardiogenesis primarily through the protein kinase C signaling, but not through the mitogen-activated protein kinase signaling, pathway.

RNA Mimics as Therapeutics for Cardiac Regeneration: A Paradigm Shift

RNA Mimics as Therapeutics for Cardiac Regeneration: A Paradigm Shift