Cardiac Rehabilitation for Patients With Stable Ischemic Heart Disease Without Revascularization　- Rationale and Design of a Single-Arm Pilot Study.

Background: Clinical practice guidelines strongly recommend optimal medical therapy (OMT), including lifestyle modification, pharmacotherapy, and exercise-based cardiac rehabilitation (CR), in patients with stable ischemic heart disease (SIHD). However, the efficacy and safety of CR in patients with SIHD without revascularization remain unclear. Methods and Results: The Prospective Registry of STable Angina RehabiliTation (Pre-START) study is a multicenter, prospective, single-arm, open-label pilot study to evaluate the efficacy and safety of CR on health-related quality of life (HRQL), exercise capacity, and clinical outcomes in Japanese patients with SIHD without revascularization. In this study, all patients will undergo guideline-based OMT and are encouraged to have 36 outpatient CR sessions within 5 months after enrollment. The primary endpoint is the change in the Seattle Angina Questionnaire-7 summary score between baseline and the 6-month visit; an improvement of ≥5 points will be defined as a clinically important change. Secondary endpoints include changes in other HRQL scores and exercise capacity between baseline and the 6-month visit, as well as clinical outcomes between enrollment and the 6-month visit. Conclusions: The Pre-START study will provide valuable evidence to elucidate the efficacy and safety of CR in patients with SIHD and indispensable information for a subsequent randomized controlled trial. The study was registered with the University Hospital Medical Information Network (UMIN) Clinical Trials Registry (ID: UMIN000045415) on April 1, 2022.

Controlled delivery of basic fibroblast growth factor promotes human cardiosphere-derived cell engraftment to enhance cardiac repair for chronic myocardial infarction.

OBJECTIVES: This study was designed to determine whether controlled release of basic fibroblast growth factor (bFGF) might improve human cardiosphere-derived cell (hCDC) therapy in a pig model of chronic myocardial infarction. BACKGROUND: Current cell therapies for cardiac repair are limited by loss of the transplanted cells and poor differentiation. METHODS: We conducted 2 randomized, placebo-controlled studies in immunosuppressed pigs with anterior myocardial infarctions. Four weeks after coronary reperfusion, 14 pigs were randomly assigned to receive an intramyocardial injection of placebo medium with or without bFGF-incorporating hydrogel implantation. As a second study, 26 pigs were randomized to receive controlled release of bFGF combined with or without hCDCs or bone marrow-derived mesenchymal stem cell transplantation 4 weeks after reperfusion. RESULTS: Controlled release of bFGF in ischemic myocardium significantly augmented the formation of microvascular networks to enhance myocardial perfusion and contractile function. When combined with cell transplantation, the additive effects of bFGF were confined to hCDC-injected animals, but were not observed in animals receiving human bone marrow-derived mesenchymal stem cell transplantation. This was shown by increased donor-cell engraftment and enhanced cardiomyocyte differentiation in the transplanted hearts, resulting in synergistically improved ventricular function and regional wall motion and reduced infarct size. CONCLUSIONS: Controlled delivery of bFGF modulates the post-ischemic microenvironment to enhance hCDC engraftment and differentiation. This novel strategy demonstrates significant functional improvements after myocardial infarction and may potentially represent a therapeutic approach to be studied in a clinical trial in human heart failure.

Stemming heart failure with cardiac- or reprogrammed-stem cells.

Despite extensive efforts to control myocyte growth by genetic targeting of the cell cycle machinery and small molecules for cardiac repair, adult myocytes themselves appeared to divide a limited number of times in response to a variety of cardiac muscle stresses. Rare tissue-resident stem cells are thought to exist in many adult organs that are capable of self-renewal and differentiation and possess a range of actions that are potentially therapeutic. Recent studies suggest that a population of cardiac stem cells (CSCs) is maintained after cardiac development in the adult heart in mammals including human beings; however, homeostatic cardiomyocyte replacement might be stem cell-dependent, and functional myocardial regeneration after cardiac muscle damage is not yet considered as sufficient to fully maintain or reconstitute the cardiovascular system and function. Although it is clear that adult CSCs have limitations in their capabilities to proliferate extensively and differentiate in response to injury in vivo for replenishing mature car-diomyocytes and potentially function as resident stem cells. Transplantation of CSCs expanded ex vivo seems to require an integrated strategy of cell growth-enhancing factor(s) and tissue engineering technologies to support the donor cell survival and subsequent proliferation and differentiation in the host microenvironment. There has been substantial interest regarding the evidence that mammalian fibroblasts can be genetically reprogrammed to induced pluripotent stem (iPS) cells, which closely resemble embryonic stem (ES) cell properties capable of differentiating into functional cardiomyocytes, and these cells may provide an alternative cell source for generating patient-specific CSCs for therapeutic applications.

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.

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.

Clonally amplified cardiac stem cells are regulated by Sca-1 signaling for efficient cardiovascular regeneration.

Recent studies have shown that cardiac stem cells (CSCs) from the adult mammalian heart can give rise to functional cardiomyocytes; however, the definite surface markers to identify a definitive single entity of CSCs and the molecular mechanisms regulating their growth are so far unknown. Here, we demonstrate a single-cell deposition analysis to isolate individually selected CSCs from adult murine hearts and investigate the signals required for their proliferation and survival. Clonally proliferated CSCs express stem cell antigen-1 (Sca-1) with embryonic stem (ES) cell-like and mesenchymal cell-like characteristics and are associated with telomerase reverse transcriptase (TERT). Using a transgene that expresses a GFP reporter under the control of the TERT promoter, we demonstrated that TERT(GFP)-positive fractions from the heart were enriched for cells expressing Sca-1. Knockdown of Sca-1 transcripts in CSCs led to retarded ex vivo expansion and apoptosis through Akt inactivation. We also show that ongoing CSC proliferation and survival after direct cell-grafting into ischemic myocardium require Sca-1 to upregulate the secreted paracrine effectors that augment neoangiogenesis and limit cardiac apoptosis. Thus, Sca-1 might be an essential component to promote CSC proliferation and survival to directly facilitate early engraftment, and might indirectly exert the effects on late cardiovascular differentiation after CSC transplantation.

Therapeutic potential of stem/progenitor cells in human skeletal muscle for cardiovascular regeneration.

Although myoblast transplantation in patients with ischemic heart failure results in a significant improvement of cardiac function, subsequent studies have consistently shown the myotubes formation in the absence of electromechanical coupling with the neighboring host myocardium, accompanied with the short-term release of paracrine effectors from implanted cells. One major pitfall of using myoblasts is that transplanted cells do not differentiate into cardiomyocytes, which may cause the inherent proarrhythmogenic events. Therefore, whether a discrete subpopulation in heterogeneous muscle-cell cultures is responsible for substantial cardiovascular regeneration has yet to be investigated. We describe here the isolation of progenitor cells from human skeletal muscle. These cells proliferated as non-adherent myospheres in suspension and displayed early embryonic factors and mesenchymal cell-like characteristics. Flow cytometric analyses demonstrated that CD56/N-CAM/Leu-19, a neural cell adhesion molecule abundantly present in myoblasts, was absent in myospheres but was expressed in an adherent cell population containing myogenic precursors. Myosphere-derived progenitor cells (MDPCs) differentiated in culture to produce cardiac, smooth muscle, and endothelial cells. Transplantation of MDPCs into ischemic hearts in NOD/scid mice promoted angiogenesis with substantial cardiovascular regeneration. Our results provide a foundation to further study the cell and biological function of human MDPCs which may have potential therapeutic implications.

Skeletal myosphere-derived progenitor cell transplantation promotes neovascularization in delta-sarcoglycan knockdown cardiomyopathy.

Bone marrow cells have been shown to contribute to neovascularization in ischemic hearts, whereas their impaired maturation to restore the delta-sarcoglycan (delta-SG) expression responsible for focal myocardial degeneration limits their utility to treat the pathogenesis of cardiomyopathy. Here, we report the isolation of multipotent progenitor cells from adult skeletal muscle, based on their ability to generate floating-myospheres. Myosphere-derived progenitor cells (MDPCs) are distinguishable from myogenic C2C12 cells and differentiate into vascular smooth muscle cells and mesenchymal progeny. The mutation in the delta-SG has been shown to develop vascular spasm to affect sarcolemma structure causing cardiomyopathy. We originally generated delta-SD knockdown (KD) mice and transplanted MDPCs into the hearts. MDPCs enhanced neoangiogenesis and restored delta-SG expression in impaired vasculatures through trans-differentiation, leading to improvement of cardiac function associated with paracrine effectors secretion. We propose that MDPCs may be the promising progenitor cells in skeletal muscle to treat delta-sarcoglycan complex mutant cardiomyopathy.

Human cardiac stem cells exhibit mesenchymal features and are maintained through Akt/GSK-3beta signaling.

Recent evidence suggested that human cardiac stem cells (hCSCs) may have the clinical application for cardiac repair; however, their characteristics and the regulatory mechanisms of their growth have not been fully investigated. Here, we show the novel property of hCSCs with respect to their origin and tissue distribution in human heart, and demonstrate the signaling pathway that regulates their growth and survival. Telomerase-active hCSCs were predominantly present in the right atrium and outflow tract of the heart (infant > adult) and had a mesenchymal cell-like phenotype. These hCSCs expressed the embryonic stem cell markers and differentiated into cardiomyocytes to support cardiac function when transplanted them into ischemic myocardium. Inhibition of Akt pathway impaired the hCSC proliferation and induced apoptosis, whereas inhibition of glycogen synthase kinase-3 (GSK-3) enhanced their growth and survival. We conclude that hCSCs exhibit mesenchymal features and that Akt/GSK-3beta may be crucial modulators for hCSC maintenance in human heart.

Myocardium-targeted delivery of endothelial progenitor cells by ultrasound-mediated microbubble destruction improves cardiac function via an angiogenic response.

Application of ultrasound-mediated destruction of microbubbles (US + Bubble) to skeletal muscle creates capillary ruptures leading to leakage of the cell components. We studied whether US + Bubble combined with bone-marrow-derived mononuclear cells (BM-MNCs) infusion enables the targeted delivery of endothelial-lineage cells into the myocardium and improves cardiac function of the cardiomyopathy model due to the paucity of neocapillary formation. Pulsed US was applied to the anterior chest of BIOTO2 cardiomyopathy hamsters for 90 s after the intravenous injection of microbubble (Optison) followed by infusion of BM-MNCs. Cardiac samples from US + microbubble + BM-MNCs (US + Bubble + BM), US + Bubble, US + BM without Bubble, and saline infusion control groups were analyzed 12 weeks after treatment. Labeled BM-MNCs transplanted by US + Bubble were found to be mainly localized in the microvessels, but not by US stimulation without microbubble (121.2 +/- 24.5 vs. 2.80 +/- 1.30 cells/mm2, P < 0.001). Capillary densities in US + Bubble + BM group were increased 1.7-fold (P < 0.05) over the control, and neither US + Bubble nor US + BM enhanced neocapillary formation. 99mTc-Tetrofosmin scintigraphy revealed that blood perfusion area in the US + Bubble + BM group was 48% greater than the control (P < 0.01). US + Bubble stimulation induces the expression of adhesion molecules (VCAM-1 and ICAM-1) in capillaries, and the US + Bubble-mediated supply of BM-MNCs increased the myocardial content of VEGF and bFGF. The left ventricular wt/body wt, area of cardiac fibrosis, and apoptotic cell numbers in the US + Bubble + BM group significantly (P < 0.05) decreased by 82%, 73%, and 64% relative to the control, respectively. The cardiac function in myopathic hamsters (assessed by fractional shortening) was markedly improved 36% (P < 0.05) by US + Bubble + BM treatment. Targeted delivery of BM-MNCs by US + Bubble to the myocardium of the cardiomyopathic hamster increased the capillary densities and regional blood flow and inhibited cardiac remodeling, resulting in the prevention of heart failure. This non-invasive cell delivery system may be useful as a novel efficient approach for angiogenic cell therapy to the myocardium.

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.

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.

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.