Masamichi Koyanagi

MicroRNA-92a Controls Angiogenesis and Functional Recovery of Ischemic Tissues in Mice

Of Life, Limb, and a Small RNA Gene expression in mammals is controlled not only by proteins but by small noncoding RNAs called microRNAs. The involvement of these RNAs provides powerful clues about the molecular origins of human diseases and how they might be treated. Ischemic diseases arise from an inadequate blood supply. Bonauer et al. (p. 1710, published online 21 May) find that a specific microRNA that is expressed in the cells lining blood vessels (called miR-92a) functions to repress the growth of new blood vessels. MiR-92a probably acts through effects on expression of integrins, proteins involved in cell adhesion and migration. In mouse models in which an inadequate blood supply had caused damage either to heart or limb muscle, therapeutic inhibition of miR-92a led to an increase in blood vessel density in the damaged tissues and enhanced functional recovery. Inhibition of a microRNA that represses blood vessel growth enhances the recovery of tissue damaged by an inadequate blood supply. MicroRNAs (miRs) are small noncoding RNAs that regulate gene expression by binding to target messenger RNAs (mRNAs), leading to translational repression or degradation. Here, we show that the miR-17~92 cluster is highly expressed in human endothelial cells and that miR-92a, a component of this cluster, controls the growth of new blood vessels (angiogenesis). Forced overexpression of miR-92a in endothelial cells blocked angiogenesis in vitro and in vivo. In mouse models of limb ischemia and myocardial infarction, systemic administration of an antagomir designed to inhibit miR-92a led to enhanced blood vessel growth and functional recovery of damaged tissue. MiR-92a appears to target mRNAs corresponding to several proangiogenic proteins, including the integrin subunit alpha5. Thus, miR-92a may serve as a valuable therapeutic target in the setting of ischemic disease.

Angina pectoris caused by coronary microvascular spasm

BACKGROUND Microvascular angina can occur during exercise and at rest. Reduced vasodilator capacity of the coronary microvessels is implicated as a cause of angina during exercise, but the mechanism of angina at rest is not known. Our aim was to test the hypothesis that primary hyperconstriction (spasm) of coronary microvessels causes myocardial ischaemia at rest. METHODS Acetylcholine induces coronary artery spasm in patients with variant angina. We tested the effects of intracoronary acetylcholine at graded doses in 117 consecutive patients with chest pain (at rest, during exertion, or both) and no flow-limiting (>50%) organic stenosis in the large epicardial coronary arteries. We also assessed the metabolism of myocardial lactate during acetylcholine administration in 36 of the patients by measurement of lactate in paired blood samples from the coronary artery and coronary sinus vein. FINDINGS Of the 117 patients, 63 (54%) had large-artery spasm, 29 (25%) had microvascular spasm, and 25 (21%) had atypical chest pain. The 29 patients with microvascular spasm developed angina-like chest pain, ischaemic electrocardiogram (ECG) changes, or both spontaneously (two patients) or after administration of acetylcholine (27 patients) without spasm of the large epicardial coronary arteries. Testing of paired samples of arterial and coronary sinus venous blood showed that lactate was produced during angina attack in nine of 11 patients with microvascular spasm. There was more women (p<0.01) and fewer coronary risk factors (p<0.01) in patients with microvascular spasm than in those with large-artery spasm. INTERPRETATION Coronary microvascular spasm and resultant myocardial ischaemia may be the cause of chest pain in a subgroup of patients with microvascular angina.

New Anti–Monocyte Chemoattractant Protein-1 Gene Therapy Attenuates Atherosclerosis in Apolipoprotein E–Knockout Mice

BackgroundMonocyte recruitment into the arterial wall and its activation may be the central event in atherogenesis. Monocyte chemoattractant protein-1 (MCP-1) is an important chemokine for monocyte recruitment, and its receptor (CCR2) may mediate such in vivo response. Although the importance of the MCP-1/CCR2 pathway in atherogenesis has been clarified, it remains unanswered whether postnatal blockade of the MCP-1 signals could be a unique site-specific gene therapy. Methods and ResultsWe devised a new strategy for anti-MCP-1 gene therapy to treat atherosclerosis by transfecting an N-terminal deletion mutant of the human MCP-1 gene into a remote organ (skeletal muscle) in apolipoprotein E-knockout mice. This strategy effectively blocked MCP-1 activity and inhibited the formation of atherosclerotic lesions but had no effect on serum lipid concentrations. Furthermore, this strategy increased the lesional extracellular matrix content. ConclusionsWe conclude that this anti-MCP-1 gene therapy may serve not only to reduce atherogenesis but also to stabilize vulnerable atheromatous plaques. This strategy may be a useful and feasible form of gene therapy against atherosclerosis in humans.

Ex vivo pretreatment of bone marrow mononuclear cells with endothelial NO synthase enhancer AVE9488 enhances their functional activity for cell therapy.

Bone marrow mononuclear cells (BMC) from patients with ischemic cardiomyopathy (ICMP) show a reduced neovascularization capacity in vivo. NO plays an important role in neovascularization, and NO bioavailability is typically reduced in patients with ICMP. We investigated whether the impaired neovascularization capacity of ICMP patient-derived progenitor cells can be restored by pretreatment with the novel endothelial NO synthase (eNOS) transcription enhancer AVE9488 (AVE). Ex vivo pretreatment of BMC from patients with ICMP with AVE significantly increased eNOS mRNA expression by 2.1-fold (P < 0.05) and eNOS activity as assessed by ESR by >3-fold (P < 0.05). The increased eNOS expression was associated with an enhanced migratory capacity in vitro (P < 0.01) and improved neovascularization capacity of the infused BMC in an ischemic hind limb model in vivo (P < 0.001). The improvement in ischemic limb perfusion after infusion of AVE-pretreated BMC resulted in an increase in swimming time (P < 0.05). The enhancement of limb perfusion by AVE-treated BMC was abrogated by ex vivo pretreatment with the eNOS inhibitor NG-nitro-l-arginine methyl ester. Consistently, AVE showed no effect on the impaired migratory capacity of BMC derived from eNOS-deficient mice, documenting the specific involvement of NO. The reduced neovascularization capacity of BMC from patients with ICMP may limit their therapeutic potential in cell therapy studies. Here, we show that pharmacological enhancement of eNOS expression with AVE at least partially reverses the impaired functional activity of BMC from ICMP patients, highlighting the critical role of NO for progenitor cell function.

Cell-to-cell Connection of Endothelial Progenitor Cells With Cardiac Myocytes by Nanotubes: A Novel Mechanism for Cell Fate Changes?

The regeneration of new myocardium by stem or progenitor cells is an important therapeutic option. Cellular or nuclear fusion is considered as an alternative to cell reprogramming by transdifferentiation. However, the generation of hybrid cells may also be a consequence of a transient transmembrane exchange of proteins and organelles between cells. Therefore, we investigated the formation of intercellular connections, which may allow the transport of macromolecular structures between labeled adult human endothelial progenitor cells (EPC) and GFP-expressing neonatal rat cardiomyocytes (CM) in a coculture system. FACS analysis revealed that, 6 days after initiation of coculture, 2.1±0.4% of the cells stained positive for GFP and Dil-ac-LDL. 6 hours after initiation of the coculture, ultrafine intercellular structures between Dil-ac-LDL-labeled EPC and GFP-expressing CM were observed. The number of EPC, which established nanotubular connections with CM increased from 0.5±0.2% after 6 hours to 2.6±0.3% after 24 hours of coculture. The intercellular connections had a diameter from 50 to 800 nm, a length of 5 to 120 &mgr;m, and were only transiently established. To determine whether the nanotubular structures allowed the transport of organelles, we labeled CM with a mitochondrial live tracker (MitoTracker). Using time-lapse video microscopy, we observed the transport of stained complexes between CM and EPC resulting in up-take of MitoTracker-positive structures in EPC. Thus, the present study shows a novel type of cell-to-cell communication between progenitor cells and CM in vitro, which may contribute to the acquisition of a cardiomyogenic phenotype independent of permanent cellular or nuclear fusion.

Early Induction of Transforming Growth Factor-β via Angiotensin II Type 1 Receptors Contributes to Cardiac Fibrosis Induced by Long-term Blockade of Nitric Oxide Synthesis in Rats

We previously reported that the chronic inhibition of nitric oxide (NO) synthesis increases cardiac tissue angiotensin-converting enzyme expression and causes cardiac fibrosis in rats. However, the mechanisms are not known. Transforming growth factor-beta (TGF-beta) is a key molecule that is responsible for tissue fibrosis. The present study investigated the role of TGF-beta in the pathogenesis of cardiac fibrosis. The development of cardiac fibrosis by oral administration of the NO synthesis inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) to normal rats was preceded by increases in mRNA levels of cardiac TGF-beta1 and extracellular matrix (ECM) proteins. TGF-beta immunoreactivity was increased in the areas of fibrosis. Treatment with a specific angiotensin II type 1 receptor antagonist, but not with hydralazine, completely prevented the L-NAME-induced increases in the gene expression of TGF-beta1 and ECM proteins and also prevented cardiac fibrosis. Intraperitoneal injection of neutralizing antibody against TGF-beta did not affect the L-NAME-induced increase in TGF-beta1 mRNA levels but prevented an increase in the mRNA levels of ECM protein. These results suggest that the early induction of TGF-beta1 via the angiotensin II type 1 receptor plays a major role in the development of cardiac fibrosis in this model.

Important Role of Local Angiotensin II Activity Mediated via Type 1 Receptor in the Pathogenesis of Cardiovascular Inflammatory Changes Induced by Chronic Blockade of Nitric Oxide Synthesis in Rats

BACKGROUND The chronic inhibition of NO synthesis by N(omega)-nitro-L-arginine methyl ester (L-NAME) upregulates the cardiovascular tissue angiotensin II (Ang II)-generating system and induces cardiovascular inflammatory changes in rats. METHODS AND RESULTS We used a rat model to investigate the role of local Ang II activity in the pathogenesis of such inflammatory changes. Marked increases in monocyte infiltration into coronary vessels and myocardial interstitial areas, monocyte chemoattractant protein-1 (MCP-1) expression, and nuclear factor-kappaB (NF-kappaB, an important redox-sensitive transcriptional factor that induces MCP-1) activity were observed on day 3 of L-NAME administration. Along with these changes, vascular superoxide anion production was also increased. Treatment with an Ang II type 1 receptor antagonist or with a thiol-containing antioxidant, N-acetylcysteine, prevented all of these changes. CONCLUSIONS Increased Ang II activity mediated via the type 1 receptor may thus be important in the pathogenesis of early cardiovascular inflammatory changes in this model. Endothelium-derived NO may decrease MCP-1 production and oxidative stress-sensitive signals by suppressing localized activity of Ang II.

Enhancing the Outcome of Cell Therapy for Cardiac Repair Progress From Bench to Bedside and Back

Cell therapy has emerged as a promising option to treat myocardial infarction or heart failure; more than 1500 patients with cardiovascular diseases are treated with adult progenitor cells worldwide. The treatment of acute and chronic myocardial infarction with adult bone marrow-derived cells provided a modest benefit in most but not all studies. A number of plausible reasons have been discussed to explain the modest effects, sending researchers back to the bench to elucidate strategies to overcome the limitations of cell therapy and to develop more efficient approaches. Such strategies include the use of other sources to isolate adult progenitor cells (eg, adipose or cardiac tissue) or the generation of pluripotent cells by the reprogramming of somatic cell types. Successful cardiac cell therapy in clinical practice also depends on the efficient delivery and the appropriate integration and alignment of injected or infused cells. The pretreatment of cells with activators to augment cell homing and survival or the improvement of cell delivery tools may provide an opportunity to increase the number of active cells in ischemic or diseased tissues, thereby increasing their therapeutic potential. Finally, the identification of molecules guiding cardiac differentiation provides novel tools to enforce the formation of new functionally active cardiomyocytes to augment cardiac regeneration in its pure sense. This section provides a short overview of the different cell types that have been or are currently being tested for the treatment of patients with acute myocardial infarction or chronic heart failure (Figure 1). Most of the clinical studies performed so far have used bone marrow-derived mononuclear cells (BMCs) for treating patients with acute or chronic infarcts (for review, see elsewhere1). Overall, a modest but significant benefit was seen in meta-analyses of all published studies.2,3 Particularly in the acute setting, the infusion of BMCs via balloon catheters into …

Non-canonical Wnt Signaling Enhances Differentiation of Human Circulating Progenitor Cells to Cardiomyogenic Cells

Human endothelial circulating progenitor cells (CPCs) can differentiate to cardiomyogenic cells during co-culture with neonatal rat cardiomyocytes. Wnt proteins induce myogenic specification and cardiac myogenesis. Here, we elucidated the effect of Wnts on differentiation of CPCs to cardiomyogenic cells. CPCs from peripheral blood mononuclear cells were isolated from healthy volunteers and co-cultured with neonatal rat cardiomyocytes. 6–10 days after co-culture, cardiac differentiation was determined by α-sarcomeric actinin staining of human lymphocyte antigen-positive cells (fluorescence-activated cell-sorting analysis) and mRNA expression of human myosin heavy chain and atrial natriuretic peptide. Supplementation of co-cultures with Wnt11-conditioned medium significantly enhanced the differentiation of CPCs to cardiomyocytes (1.7 ± 0.3-fold), whereas Wnt3A-conditioned medium showed no effect. Cell fusion was not affected by Wnt11-conditioned medium. Because Wnts inhibit glycogen synthase kinase-3β, we further determined whether the glycogen synthase kinase-3β inhibitor LiCl also enhanced cardiac differentiation of CPCs. However, LiCl (10 mm) did not affect CPC differentiation. In contrast, Wnt11-conditioned medium time-dependently activated protein kinase C (PKC). Moreover, the PKC inhibitors bisindolylmaleimide I and III significantly blocked differentiation of CPCs to cardiomyocytes. PKC activation by phorbol 12-myristate 13-acetate significantly increased CPC differentiation to a similar extent as compared with Wnt11-conditioned medium. Our data demonstrate that Wnt11, but not Wnt3A, augments cardiomyogenic differentiation of human CPCs. Wnt11 promotes cardiac differentiation via the non-canonical PKC-dependent signaling pathway.

Interleukin-10 From Transplanted Bone Marrow Mononuclear Cells Contributes to Cardiac Protection After Myocardial Infarction

Bone marrow mononuclear cells (BM-MNCs) have successfully been used as a therapy for the improvement of left ventricular (LV) function after myocardial infarction (MI). It has been suggested that paracrine factors from BM-MNCs may be a key mechanism mediating cardiac protection. We previously performed microarray analysis and found that the pleiotropic cytokine interleukin (IL)-10 was highly upregulated in human progenitor cells in comparison with adult endothelial cells and CD14+ cells. Moreover, BM-MNCs secrete significant amounts of IL-10, and IL-10 could be detected from progenitor cells transplanted in infarcted mouse hearts. Specifically, intramyocardial injection of wild-type BM-MNCs led to a significant decrease in LV end-diastolic pressure (LVEDP) and LV end-systolic volume (LVESV) compared to hearts injected with either diluent or IL-10 knock-out BM-MNCs. Furthermore, intramyocardial injection of wild-type BM-MNCs led to a significant increase in stroke volume (SV) and rate of the development of pressure over time (+dP/dt) compared to hearts injected with either diluent or IL-10 knock-out BM-MNCs. The IL-10–dependent improvement provided by transplanted cells was not caused by reduced infarct size, neutrophil infiltration, or capillary density, but rather was associated with decreased T lymphocyte accumulation, reactive hypertrophy, and myocardial collagen deposition. These results suggest that BM-MNCs mediate cardiac protection after myocardial infarction and this is, at least in part, dependent on IL-10.