Serglycin is a novel adipocytokine highly expressed in epicardial adipose tissue.

Much recent work has highlighted the key role of adipose tissue as an endocrine organ that secretes a number of adipocytokines, linking adiposity, especially intra-abdominal visceral fat, and the pathogenesis of cardiovascular and metabolic diseases. However, the role of epicardial adipose tissue (EAT), another important visceral fat depot situated in close proximity to epicardial coronary arteries and myocardium, has been less well studied. In this study, we sought to characterize EAT by comparing gene expression profiles of EAT, omental adipose tissue (OAT), and subcutaneous adipose tissue (SCAT) in patients who underwent elective coronary artery bypass graft surgery for critical coronary artery disease (CAD) and identify molecules involved in inflammation. A total of 15,304 probes were detected in all depots, and 231 probes were differentially expressed. Significantly higher expression of pro-inflammatory genes such as interleukin-1ß, -6, and -8, and chemokine receptor 2 was observed in EAT, even when compared with OAT. Among them, serglycin was one of the most abundantly expressed genes in EAT. Serglycin expression was induced during adipocytic differentiation of 3T3L1 cells. Serglycin was secreted from adipocytes, and tumor necrosis factor-α stimulated its expression and secretion in adipocytes. Serglycin was also present in human serum samples. These results suggest that human EAT has strong inflammatory properties in patients with CAD and provide novel evidence that serglycin is an adipocytokine highly expressed in EAT.

NFAT5 regulates the canonical Wnt pathway and is required for cardiomyogenic differentiation.

While nuclear factor of activated T cells 5 (NFAT5), a transcription factor implicated in osmotic stress response, is suggested to be involved in other processes such as migration and proliferation, its role in cardiomyogenesis is largely unknown. Here, we examined the role of NFAT5 in cardiac differentiation of P19CL6 cells, and observed that it was abundantly expressed in undifferentiated P19CL6 cells, and its protein expression was significantly downregulated by enhanced proteasomal degradation during DMSO-induced cardiomyogenesis. Expression of a dominant negative mutant of NFAT5 markedly attenuated cardiomyogenesis, which was associated with the inhibition of mesodermal differentiation. TOPflash reporter assay revealed that the transcriptional activity of canonical Wnt signaling was activated prior to mesodermal differentiation, and this activation was markedly attenuated by NFAT5 inhibition. Pharmacological activation of canonical Wnt signaling by [2'Z, 3'E]-6-bromoindirubin-3'-oxime (BIO) restored Brachyury expression in NFAT5DN-expressing cells. Inhibition of NFAT5 markedly attenuated Wnt3 and Wnt3a induction. Expression of Dkk1 and Cerberus1, which are secreted Wnt antagonists, was also inhibited by NFAT5 inhibition. Thus, endogenous NFAT5 regulates the coordinated expression of Wnt ligands and antagonists, which are essential for cardiomyogenesis through the canonical Wnt pathway. These results demonstrated a novel role of NFAT5 in cardiac differentiation of stem cells.

PARM-1 promotes cardiomyogenic differentiation through regulating the BMP/Smad signaling pathway.

PARM-1, prostatic androgen repressed message-1, is an endoplasmic reticulum (ER) molecule that is involved in ER stress-induced apoptosis in cardiomyocytes. In this study, we assessed whether PARM-1 plays a role in the differentiation of stem cells into cardiomyocytes. While PARM-1 was not expressed in undifferentiated P19CL6 embryonic carcinoma cells, PARM-1 expression was induced during cardiomyogenic differentiation. This expression followed expression of mesodermal markers, and preceded expression of cardiac transcription factors. PARM-1 overexpression did not alter the expression of undifferentiated markers and the proliferative property in undifferentiated P19CL6 cells. Expression of cardiac transcription factors during cardiomyogenesis was markedly enhanced by overexpression of PARM-1, while expression of mesodermal markers was not altered, suggesting that PARM-1 is involved in the differentiation from the mesodermal lineage to cardiomyocytes. Furthermore, overexpression of PARM-1 induced BMP2 mRNA expression in undifferentiated P19CL6 cells and enhanced both BMP2 and BMP4 mRNA expression in the early phase of cardiomyogenesis. PARM-1 overexpression also enhanced phosphorylation of Smads1/5/8. Thus, PARM-1 plays an important role in the cardiomyogenic differentiation of P19CL6 cells through regulating BMP/Smad signaling pathways, demonstrating a novel role of PARM-1 in the cardiomyogenic differentiation of stem cells.

Endothelial FGF receptor signaling accelerates atherosclerosis.

Members of the fibroblast growth factor (FGF) family have been clinically applied to the treatment of ischemic diseases because of their strong angiogenic actions. Although tissue ischemia is predominantly caused by atherosclerosis, the roles of endothelial FGF receptors (FGF-Rs) in atherosclerosis remain obscure. We generated endothelial cell (EC)-targeted constitutively active FGF-R2-overexpressing mice, using the Tie2 promoter (Tie2-FGF-R2-Tg), and crossed them with apolipoprotein E (ApoE)-deficient mice (ApoE-KO) to generate Tie2-FGF-R2-Tg/ApoE-deficient mice (Tie2-FGF-R2-Tg/ApoE-KO). After being fed a Western diet for 8 wk, the Tie2-FGF-R2-Tg/ApoE-KO demonstrated 2.0-fold greater atherosclerotic lesion area on the luminal surfaces of the aortas than the ApoE-KO (P < 0.01). The level of p21(Cip1) protein, a cell cycle inhibitor, in the FGF-R2-overexpressing EC was 2.5-fold greater than that in the wild-type (WT) EC at the baseline (P < 0.01). FGF-R2 overexpression in the EC resulted in increased expression of VCAM-1 and ICAM-1, acceleration of apoptosis, and decreased proliferative activity, all of which were normalized by small interfering RNA (siRNA)-mediated knockdown of p21(Cip1) (75% reduction in protein level, P < 0.01). Furthermore, the expression of PDGF-B and Egr-1, a PDGF/p21(Cip1)-inducible transcription factor, in the aortic endothelium of Tie2-FGF-R2-Tg/ApoE-KO was significantly greater than that in ApoE-KO. The proliferation of vascular smooth muscle cells in the aortic media of Tie2-FGF-R2-Tg/ApoE-KO was 2.0-fold higher than that in ApoE-KO (P < 0.01). Thus our study reveals that endothelial FGF-R2 signaling aggravates atherosclerosis by promoting p21(Cip1)-mediated EC dysfunction and cautions against the use of FGF for therapeutic angiogenesis in the setting of atherosclerosis.

Paracrine osteogenic signals via bone morphogenetic protein-2 accelerate the atherosclerotic intimal calcification in vivo.

OBJECTIVE: Vascular calcification is an important risk factor for cardiovascular diseases. Here, we investigated a role of dedifferentiated vascular smooth muscle cells (VSMCs) in the atherosclerotic intimal calcification. METHODS AND RESULTS: We prepared human cultured VSMCs in either redifferentiatiated or dedifferentiated state and analyzed the gene expressions of bone-calcification regulatory factors. Expression of bone morphogenetic protein-2 (BMP-2), a potent initiator for osteoblast differentiation, was significantly enhanced in dedifferentiated VSMCs. Furthermore, endogenous BMP-2 antagonists, such as noggin, chordin, and matrix gamma-carboxyglutamic acid protein, were all downregulated in the dedifferentiated VSMCs. Conditioned medium from dedifferentiated VSMCs, but not from redifferentiated VSMCs, stimulated the osteoblastic differentiation of the mesenchymal progenitor C2C12 cells, which was abolished by BMP-2 knockdown. In atherosclerotic intima from apolipoprotein (apo)E-deficient mice, αSM-actin-positive cells, presumably dedifferentiated VSMCs, expressed BMP-2. We generated BMP-2-transgenic mice using αSM-actin promoter and crossed them with apoE-deficient mice (BMP-2-transgenic/apoE-knockout). Significantly accelerated atherosclerotic intimal calcification was detected in BMP-2-transgenic/apoE-knockout mice, although serum lipid concentration and atherosclerotic plaque size were not different from those in apoE-knockout mice. Enhanced calcification appeared to be associated with the frequent emergence of osteoblast-like cells in atherosclerotic intima in BMP-2-transgenic/apoE-knockout mice. CONCLUSIONS: Our findings collectively demonstrate an important role of dedifferentiated VSMCs in the pathophysiology of atherosclerotic calcification through activating paracrine BMP-2 osteogenic signals.

Bone marrow AT1 augments neointima formation by promoting mobilization of smooth muscle progenitors via platelet-derived SDF-1{alpha}.

OBJECTIVE: Bone marrow (BM)-derived endothelial progenitor cells (EPCs) and vascular smooth muscle progenitor cells (VPCs) contribute to neointima formation, whereas the angiotensin II (Ang II) type 1 receptor (AT(1))-mediated action on BM-derived progenitors remains undefined. METHODS AND RESULTS: A wire-induced vascular injury was performed in the femoral artery of BM-chimeric mice whose BM was repopulated with AT(1)-deficient (BM-Agtr1(-/-)) or wild-type (BM-Agtr1(+/+)) cells. Neointima formation was profoundly reduced by 38% in BM-Agtr1(-/-) mice. Although the number of circulating EPCs (Sca-1(+)Flk-1(+)) and extent of reendothelialization did not differ between the 2 groups, the numbers of both circulating VPCs (c-Kit(-)Sca-1(+)Lin(-)) and tissue VPCs (Sca-1(+)CD31(-)) incorporated into neointima were markedly decreased in BM-Agtr1(-/-) mice. The accumulation of aggregated platelets and their content of stromal cell-derived factor-1alpha (SDF-1alpha) were significantly reduced in BM-Agtr1(-/-) mice, accompanied by a decrease in the serum level of SDF-1alpha. Thrombin-induced platelets aggregation was dose-dependently inhibited (45% at 0.1 IU/mL, P<0.05) in Agtr1(-/-) platelets compared with Agtr1(+/+) platelets, accompanied by the reduced expression and release of SDF-1alpha. CONCLUSIONS: The BM-AT(1) receptor promotes neointima formation by regulating the mobilization and homing of BM-derived VPCs in a platelet-derived SDF-1alpha-dependent manner without affecting EPC-mediated reendothelialization.

Bone marrow angiotensin AT1 receptor regulates differentiation of monocyte lineage progenitors from hematopoietic stem cells.

BACKGROUND: The angiotensin II (Ang II) type 1 (AT(1)) receptor is expressed in bone marrow (BM) cells, whereas it remains poorly defined how Ang II regulates differentiation/proliferation of monocyte-lineage cells to exert proatherogenic actions. METHODS AND RESULTS: We generated BM chimeric apoE(-/-) mice repopulated with AT(1)-deficient (Agtr1(-/-)) or wild-type (Agtr1(+/+)) BM cells. The atherosclerotic development was significantly reduced in apoE(-/-)/BM-Agtr1(-/-) mice compared with apoE(-/-)/BM-Agtr1(+/+) mice, accompanied by decreased numbers of BM granulocyte/macrophage progenitors (GMP:c-Kit(+)Sca-1(-)Lin(-)CD34(+)CD16/32(+)) and peripheral blood monocytes. Macrophage-colony-stimulating factor (M-CSF)-induced differentiation from hematopoietic stem cells (HSCs:c-Kit(+)Sca-1(+)Lin(-)) to promonocytes (CD11b(high)Ly-6G(low)) was markedly reduced in HSCs from Agtr1(-/-) mice. The expression of M-CSF receptor c-Fms was decreased in HSCs/promonocytes from Agtr1(-/-) mice, accompanied by a marked inhibition in M-CSF-induced phosphorylation of PKC-delta and JAK2. c-Fms expression in HSCs/promonocytes was mainly regulated by TNF-alpha derived from BM CD45(-)CD34(-) stromal cells, and Ang II specifically regulated the TNF-alpha synthesis and release from BM stromal cells. CONCLUSIONS: Ang II regulates the expression of c-Fms in HSCs and monocyte-lineage cells through BM stromal cell-derived TNF-alpha to promote M-CSF-induced differentiation/proliferation of monocyte-lineage cells and contributes to the proatherogenic action.

Replicative senescence of vascular smooth muscle cells enhances the calcification through initiating the osteoblastic transition.

Medial artery calcification, which does not accompany lipid or cholesterol deposit, preferentially occurs in elderly population, but its underlying mechanisms remain unclear. In the present study, we investigated the potential role of senescent vascular smooth muscle cells (VSMCs) in the formation of senescence-associated medial calcification. Replicative senescence was induced by the extended passages (until passages 11-13) in human primary VSMCs, and cells in early passage (passage 6) were used as control young cells. VSMC calcification was markedly enhanced in the senescent cells compared with that in the control young cells. We identified that genes highly expressed in osteoblasts, such as alkaline phosphatase (ALP) and type I collagen, were significantly upregulated in the senescent VSMCs, suggesting their osteoblastic transition during the senescence. Knockdown of either ALP or type I collagen significantly reduced the calcification in the senescent VSMCs. Of note, runt-related transcription factor-2 (RUNX-2), a core transcriptional factor that initiates the osteoblastic differentiation, was also upregulated in the senescent VSMCs. Knockdown of RUNX-2 significantly reduced the ALP expression and calcification in the senescent VSMCs, suggesting that RUNX-2 is involved in the senescence-mediated osteoblastic transition. Furthermore, immunohistochemistry of aorta from the klotho(-/-) aging mouse model demonstrated in vivo emergence of osteoblast-like cells expressing RUNX-2 exclusively in the calcified media. We also found that statin and Rho-kinase inhibitor effectively reduced the VSMC calcification by inhibiting P(i)-induced apoptosis and potentially enhancing matrix Gla protein expression in the senescent VSMCs. These findings strongly suggest an important role of senescent VSMCs in the pathophysiology of senescence-associated medial calcification, and the inhibition of osteoblastic transition could be a new therapeutic approach for the prevention of senescence-associated medial calcification.

Prorenin induces ERK activation in endothelial cells to enhance neovascularization independently of the renin-angiotensin system.

Prorenin is an enzymatically inactive precursor of renin, and its biological function in endothelial cells (ECs) is unknown despite its relevance with the incidence of diabetic microvascular complications. Recently, (pro)renin receptor was identified, and the receptor-associated prorenin system has been discovered, whereas its expression as well as function in ECs remain unclear. In the present study, we found that ECs express the (pro)renin receptor, and that prorenin provoked ERK activation through (pro)renin receptor independently of the renin-angiotensin system (RAS). Prorenin stimulated the proliferation, migration and tube-formation of ECs, while it inhibited endothelial apoptosis induced by serum and growth factor depletion. MEK inhibitor abrogated these proangiogenic effects of prorenin, while AT1 receptor antagonist or angiotensin-converting enzyme inhibitor failed to block them. In vivo neovascularization in the Matrigel-plugs implanted into mouse flanks was significantly enhanced by prorenin, in which significant ERK activation was detected in ECs. Furthermore, tumor xenografts stably transfected with prorenin demonstrated the significantly accelerated growth rate concomitantly with enhanced intratumoral neovascularization. Our data demonstrated that the RAS-independent (pro)renin receptor-mediated signal transduction plays a pivotal role in the regulation of ECs function as well as in the neovascularization, and thus prorenin is potentially involved in the pathophysiology of diabetic microvascular complications as well as cancers.

Stage-specific role of endogenous Smad2 activation in cardiomyogenesis of embryonic stem cells.

The role of Smads and their specific ligands during cardiomyogenesis in ES cells was examined. Smad2 was activated bimodally in the early and late phases of cardiac differentiation, whereas Smad1 was activated after the middle phase. Nodal and Cripto were expressed in the early stage and then downregulated, whereas transforming growth factor-beta and activin were expressed only in the late phase. Suppression of early Smad2 activation by SB-431542 produced complete inhibition of endodermal and mesodermal induction but augmented neuroectodermal differentiation, followed by poor cardiomyogenesis, whereas inhibition during the late phase alone promoted cardiomyogenesis. Inhibitory effect of Smad2 on cardiomyogenesis in the late phase was mainly mediated by transforming growth factor-beta, and inhibition of transforming growth factor-beta-mediated Smad2 activation resulted in a greater replicative potential in differentiated cardiac myocytes and enhanced differentiation of nonmyocytes into cardiac myocytes. Thus, endogenous Smad2 activation is indispensable for endodermal and mesodermal induction in the early phase. In the late phase, endogenous transforming growth factor-beta negatively regulates cardiomyogenesis through Smad2 activation by modulating proliferation and differentiation of cardiac myocytes.

Altered expression of Na+ transporters at the mRNA level in rat normal and hypertrophic myocardium.

Intracellular Na(+) ([Na(+)](i)) regulation plays a crucial role in the structural, mechanical, and electrical properties of myocardium. It is assumed that the [Na(+)](i) handling system may differ not only between normal and diseased hearts but also regionally within a heart. To gain new insight concerning disease- and region-dependent differences in the [Na(+)](i)-regulatory system, we investigated mRNA expression of Na+ transporters, the principal determinants of [Na(+)](i). Nonischemic pressure-overloaded hypertrophy was created by suprarenal abdominal aortic constriction of 50% for 7 weeks. mRNA abundances of Na(+)-Ca(2+) exchanger (NCX1), Na(+)-H(+) exchanger (NHE1), Na(+)-K(+)-2Cl(-) exchanger (NKCC1) and Na(+), K(+)-ATPase multigene family(alpha(1), alpha(2), alpha(3), and beta(1) isoforms) were measured by the real-time quantitative polymerase chain reaction method. mRNA abundance of all transporters mediating Na(+) influx (NCX1, NHE1, and NKCC1) was significantly upregulated as compared to normal. In contrast, Na(+)-efflux-mediating transporter (Na(+), K(+)-ATPase) mRNA expression was unaltered between normal and hypertrophic hearts. Losartan, an angiotensin II AT1 receptor antagonist, significantly attenuated upregulation of Na(+)-influx-mediating transporters induced by aortic constriction. The onset of Na(+)-influx-mediating transporter upregulation occurred within 5 days following constriction. In normal and hypertrophied hearts, mRNA of all Na(+)-influx-mediating transporters was expressed in order of abundance as: apex > septum approximately free wall of left ventricles. A transmural gradient in expression was also evident in normal hearts (midcardium > endo- and epicardium), which was attenuated under hypertrophic development. Myocardial hypertrophy is associated with significant changes in the spatial distribution and expression levels of Na(+) transporters. The upregulation of Na influx transporters during hypertrophy may contribute to the remodeling process, modulate contractility and promote arrhythmias.

Central role of calcium-dependent tyrosine kinase PYK2 in endothelial nitric oxide synthase-mediated angiogenic response and vascular function.

BACKGROUND: The involvement of Ca2+-dependent tyrosine kinase PYK2 in the Akt/endothelial NO synthase pathway remains to be determined. METHODS AND RESULTS: Blood flow recovery and neovessel formation after hind-limb ischemia were impaired in PYK2-/- mice with reduced mobilization of endothelial progenitors. Vascular endothelial growth factor (VEGF)-mediated cytoplasmic Ca2+ mobilization and Ca2+-independent Akt activation were markedly decreased in the PYK2-deficient aortic endothelial cells, whereas the Ca2+-independent AMP-activated protein kinase/protein kinase-A pathway that phosphorylates endothelial NO synthase was not impaired. Acetylcholine-mediated aortic vasorelaxation and cGMP production were significantly decreased. Vascular endothelial growth factor-dependent migration, tube formation, and actin cytoskeletal reorganization associated with Rac1 activation were inhibited in PYK2-deficient endothelial cells. PI3-kinase is associated with vascular endothelial growth factor-induced PYK2/Src complex, and inhibition of Src blocked Akt activation. The vascular endothelial growth factor-mediated Src association with PLCgamma1 and phosphorylation of 783Tyr-PLCgamma1 also were abolished by PYK2 deficiency. CONCLUSION: These findings demonstrate that PYK2 is closely involved in receptor- or ischemia-activated signaling events via Src/PLCgamma1 and Src/PI3-kinase/Akt pathways, leading to endothelial NO synthase phosphorylation, and thus modulates endothelial NO synthase-mediated vasoactive function and angiogenic response.

Skeletal muscle-derived progenitors capable of differentiating into cardiomyocytes proliferate through myostatin-independent TGF-beta family signaling.

The existence of skeletal muscle-derived stem cells (MDSCs) has been suggested in mammals; however, the signaling pathways controlling MDSC proliferation remain largely unknown. Here we report the isolation of myosphere-derived progenitor cells (MDPCs) that can give rise to beating cardiomyocytes from adult skeletal muscle. We identified that follistatin, an antagonist of TGF-beta family members, was predominantly expressed in MDPCs, whereas myostatin was mainly expressed in myogenic cells and mature skeletal muscle. Although follistatin enhanced the replicative growth of MDPCs through Smad2/3 inactivation and cell cycle progression, disruption of myostatin did not increase the MDPC proliferation. By contrast, inhibition of activin A (ActA) or growth differentiation factor 11 (GDF11) signaling dramatically increased MDPC proliferation via down-regulation of p21 and increases in the levels of cdk2/4 and cyclin D1. Thus, follistatin may be an effective progenitor-enhancing agent neutralizing ActA and GDF11 signaling to regulate the growth of MDPCs in skeletal muscle.

Erythropoietin-mobilized endothelial progenitors enhance reendothelialization via Akt-endothelial nitric oxide synthase activation and prevent neointimal hyperplasia.

We investigated whether the mobilization of endothelial progenitor cells (EPCs) by exogenous erythropoietin (Epo) promotes the repair of injured endothelium. Recombinant human Epo was injected (1000 IU/kg for the initial 3 days) after wire injury of the femoral artery of mice. Neointimal formation was inhibited by Epo to 48% of the control (P<0.05) in an NO-dependent manner. Epo induced a 1.4-fold increase in reendothelialized area of day 14 denuded vessels, 55% of which was derived from bone marrow (BM) cells. Epo increased the circulating Sca-1(+)/Flk-1(+) EPCs (2.0-fold, P<0.05) with endothelial properties NO dependently. BM replacement by GFP- or beta-galactosidase-overexpressing cells showed that Epo stimulated both differentiation of BM-derived EPCs and proliferation of resident ECs. BM-derived ECs increased 2.2- to 2.7-fold (P<0.05) in the Epo-induced neoendothelium, where the expression of Epo receptor was upregulated. Epo induced Akt/eNOS phosphorylation and NO synthesis on EPCs and exerted an antiapoptotic action on wire-injured arteries. In conclusion, Epo treatment inhibits the neointimal hyperplasia after arterial injury in an NO-dependent manner by acting on the injured vessels and mobilizing EPCs to the neo-endothelium.

Lamin A/C deficiency causes defective nuclear mechanics and mechanotransduction.

Mutations in the lamin A/C gene (LMNA) cause a variety of human diseases including Emery-Dreifuss muscular dystrophy, dilated cardiomyopathy, and Hutchinson-Gilford progeria syndrome. The tissue-specific effects of lamin mutations are unclear, in part because the function of lamin A/C is incompletely defined, but the many muscle-specific phenotypes suggest that defective lamin A/C could increase cellular mechanical sensitivity. To investigate the role of lamin A/C in mechanotransduction, we subjected lamin A/C-deficient mouse embryo fibroblasts to mechanical strain and measured nuclear mechanical properties and strain-induced signaling. We found that Lmna-/- cells have increased nuclear deformation, defective mechanotransduction, and impaired viability under mechanical strain. NF-kappaB-regulated transcription in response to mechanical or cytokine stimulation was attenuated in Lmna-/- cells despite increased transcription factor binding. Lamin A/C deficiency is thus associated with both defective nuclear mechanics and impaired mechanically activated gene transcription. These findings suggest that the tissue-specific effects of lamin A/C mutations observed in the laminopathies may arise from varying degrees of impaired nuclear mechanics and transcriptional activation.

Spironolactone modulates expressions of cardiac mineralocorticoid receptor and 11beta-hydroxysteroid dehydrogenase 2 and prevents ventricular remodeling in post-infarct rat hearts.

Aldosterone antagonists have been reported to prevent ventricular remodeling after myocardial infarction (MI) via their action to extracellular matrix (ECM). However, it remains largely unknown whether aldosterone antagonists attenuate myocyte loss in the remodeling process. The present study examined whether spironolactone prevents myocyte apoptosis and improves post-infarct ventricular remodeling in rats. MI was achieved by permanent occlusion of the left coronary artery. Administration of spironolactone (100 mg/kg/day) was started immediately after MI. Sprague-Dawley rats were divided into four groups: 1) sham, 2) spironolactone-treated sham, 3) untreated MI, 4) spironolactone-treated MI. Echocardiographic parameters (left ventricular [LV] diastolic dimension [LVDd], fractional shortening [%FS]), hemodynamic parameters (LV systolic pressure [LVSP], LV end-diastolic pressure [LVEDP], dP/dt(max) and dP/dt(min)) and collagen accumulation quantitated by Masson's Trichrome staining were significantly improved in the spironolactone-treated MI group on the 14th day, compared with the untreated MI group. Moreover, the percentage of apoptotic myocytes evaluated by terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) assay was significantly lower in the spironolactone-treated MI group on the 2nd (3.54% vs. 5.79% in untreated MI group), 7th (0.65% vs. 1.37% in untreated MI group) and 14th days (0.11% vs. 0.16% in untreated MI group). Real time reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that the expression of mineralocorticoid receptor (MR) mRNA and that of 11beta-hydroxysteroid dehydrogenase 2 (11beta-HSD2) mRNA, which is known to confer aldosterone selectivity on MR, were upregulated in the untreated MI group, and that spironolactone significantly suppressed the expression of these genes. Moreover, spironolactone significantly inhibited aldosterone-induced apoptosis in cultured rat cardiac myocytes in a dose-dependent fashion. Our study demonstrates that, in addition to their effect on ECM, aldosterone antagonists inhibit myocyte apoptosis and prevent post-infarct ventricular remodeling by modulating the expression levels of MR and 11beta-HSD2, which are enhanced in the remodeling heart.

Granulocyte colony-stimulating factor-mobilized circulating c-Kit+/Flk-1+ progenitor cells regenerate endothelium and inhibit neointimal hyperplasia after vascular injury.

BACKGROUND: Granulocyte colony-stimulating factor (G-CSF) treatment was shown to inhibit neointimal formation of balloon-injured vessels, whereas neither the identification of progenitor cells involved in G-CSF-mediated endothelial regeneration with a bone marrow (BM) transplant experiment nor the functional properties of regenerated endothelium have been studied. METHODS AND RESULTS: Recombinant human G-CSF (100 microg/kg per day) was injected daily for 14 days starting 3 days before balloon injury in the rat carotid artery. Neointimal formation of denuded vessels on day 14 was markedly attenuated by G-CSF (39% versus the control; P<0.05). Endothelial cell-specific immunostaining revealed an enhancement of re-endothelialization (1.8-fold increase versus the control; P<0.05) and inhibition of extravasation of Evans Blue dye (47%; P=0.02). The regenerated endothelium exhibited acetylcholine-mediated vasodilatation in NO-dependent manner. G-CSF increased the circulating c-Kit+/Flk-1+ cells (9.1-fold; P<0.02), which showed endothelial properties in vitro (acetylated low-density lipoprotein uptake and lectin binding) and incorporated into the regenerated endothelium in vivo. A BM replacement experiment with green fluorescent protein (GFP)-overexpressing cells showed that BM-derived GFP+/CD31+ endothelial cells occupied 39% of the total luminal length in the G-CSF-mediated neo-endothelium (2% in the control). CONCLUSIONS: The G-CSF-induced mobilization of BM-derived c-Kit+/Flk-1+ cells contributes to endothelial regeneration, and this cytokine therapy may be a feasible strategy for the promotion of re-endothelialization after angioplasty.

Injectable self-assembling peptide nanofibers create intramyocardial microenvironments for endothelial cells.

BACKGROUND: Promoting survival of transplanted cells or endogenous precursors is an important goal. We hypothesized that a novel approach to promote vascularization would be to create injectable microenvironments within the myocardium that recruit endothelial cells and promote their survival and organization. METHODS AND RESULTS: In this study we demonstrate that self-assembling peptides can be injected and that the resulting nanofiber microenvironments are readily detectable within the myocardium. Furthermore, the self-assembling peptide nanofiber microenvironments recruit progenitor cells that express endothelial markers, as determined by staining with isolectin and for the endothelial-specific protein platelet-endothelial cell adhesion molecule-1. Vascular smooth muscle cells are recruited to the microenvironment and appear to form functional vascular structures. After the endothelial cell population, cells that express alpha-sarcomeric actin and the transcription factor Nkx2.5 infiltrate the peptide microenvironment. When exogenous donor green fluorescent protein-positive neonatal cardiomyocytes were injected with the self-assembling peptides, transplanted cardiomyocytes in the peptide microenvironment survived and also augmented endogenous cell recruitment. CONCLUSIONS: These experiments demonstrate that self-assembling peptides can create nanofiber microenvironments in the myocardium and that these microenvironments promote vascular cell recruitment. Because these peptide nanofibers may be modified in a variety of ways, this approach may enable injectable tissue regeneration strategies.

Carbon dioxide-rich water bathing enhances collateral blood flow in ischemic hindlimb via mobilization of endothelial progenitor cells and activation of NO-cGMP system.

BACKGROUND: Carbon dioxide-rich water bathing has the effect of vasodilatation, whereas it remains undetermined whether this therapy exerts an angiogenic action associated with new vessel formation. METHODS AND RESULTS: Unilateral hindlimb ischemia was induced by resecting the femoral arteries of C57BL/J mice. Lower limbs were immersed in CO2-enriched water (CO2 concentration, 1000 to 1200 mg/L) or freshwater (control) at 37 degrees C for 10 minutes once a day. Laser Doppler imaging revealed increased blood perfusion in ischemic limbs of CO2 bathing (38% increase at day 28, P<0.001), whereas N(G)-nitro-L-arginine methyl ester treatment abolished this effect. Angiography or immunohistochemistry revealed that collateral vessel formation and capillary densities were increased (4.1-fold and 3.7-fold, P<0.001, respectively). Plasma vascular endothelial growth factor (VEGF) levels were elevated at day 14 (18%, P<0.05). VEGF mRNA levels, phosphorylation of NO synthase, and cGMP accumulation in the CO2-bathed hindlimb muscles were increased (2.7-fold, 2.4-fold, and 3.4-fold, respectively) but not in forelimb muscles. The number of circulating Lin-/Flk-1+/CD34- endothelial-lineage progenitor cells was markedly increased by CO2 bathing (24-fold at day 14, P<0.001). The Lin-/Flk-1+/CD34- cells express other endothelial antigens (endoglin and VE-cadherin) and incorporated acetylated LDL. CONCLUSIONS: Our present study demonstrates that CO2 bathing of ischemic hindlimb causes the induction of local VEGF synthesis, resulting in an NO-dependent neocapillary formation associated with mobilization of endothelial progenitor cells.

Trichostatin A, an inhibitor of histone deacetylase, inhibits smooth muscle cell proliferation via induction of p21(WAF1).

The proliferation of vascular smooth muscle cells (VSMCs) can contribute to a variety of pathological states, including atherosclerosis and post-angioplasty restenosis. The p21(WAF1) cyclin-dependent kinase inhibitor regulates cell-cycle progression, senescence, and differentiation in injured blood vessels. Histone deacetylase (HDAC) inhibitors have shown utility in controlling proliferation in a wide range of tumor cell lines, possibly by inducing the expression of p21(WAF1). Our goal was to investigate the effect of trichostatin A (TSA), a specific and potent HDAC inhibitor, on the proliferation of vascular smooth muscle cells (VSMCs) isolated from rat thoracic aorta. TSA suppressed the HDAC activity of VSMCs in a dose-dependent manner and inhibited VSMC proliferation as demonstrated by cell number counting and the degree of [3H] thymidine incorporation. Further, TSA reduced the phosphorylation of Rb protein, a regulator of cell-cycle progression. TSA treatment also induced the expression of p21(WAF1) but not of p16(INK4), p27(KIP1) or p53. Finally, TSA inhibited HDAC activity of VSMCs from p21(WAF1) knock-out mice but had no effect on VSMC proliferation in these animals. In conclusion, TSA inhibits VSMC proliferation via the induction of p21(WAF1) expression and subsequent cell-cycle arrest with reduction of the phosphorylation of Rb protein at the G1-S phase.