Chronic vagus nerve stimulation improves left ventricular function in a canine model of chronic mitral regurgitation.

BACKGROUND: Autonomic dysfunction, characterized by sympathetic activation and vagal withdrawal, contributes to the progression of heart failure (HF). We hypothesized that chronic vagus nerve stimulation (VNS) could prevent left ventricular (LV) remodeling and dysfunction in a canine HF model induced by chronic mitral regurgitation (MR). METHODS AND RESULTS: After the MR inducing procedure, 12 survived canines were randomly divided into the control (n = 6) and the VNS (n = 6) groups. At month 2, a VNS stimulator system was implanted in all canines. From month 3 to month 6, VNS therapy was applied in the VNS group but not in the control group. At month 6, compared with the control group, the canines in VNS group had significantly higher cardiac output (2.3 ± 0.3 versus 2.9 ± 0.4 L/min, P < 0.05, LV forward stroke volume (20.1 ± 3.7 versus 24.8 ± 3.9 ml, P < 0.05), and end-systolic stiffness constant (2.2 ± 0.3 versus 2.7 ± 0.3, P < 0.05). NT-proBNP and C-reactive protein were decreased significantly in the VNS group. However, no statistical difference was found in LV ejection fraction, LV end-diastolic dimension, LV end-diastolic volume, myocyte cross-sectional area, or collagen volume fraction between two groups. CONCLUSIONS: Chronic VNS therapy may ameliorate MR-induced LV contractile dysfunction and improve the expression of biomarkers, but has less effect in improving LV chamber remodeling.

Bioenergetic and functional consequences of bone marrow-derived multipotent progenitor cell transplantation in hearts with postinfarction left ventricular remodeling.

BACKGROUND: The present study examined whether transplantation of adherent bone marrow-derived stem cells, termed pMultistem, induces neovascularization and cardiomyocyte regeneration that stabilizes bioenergetic and contractile function in the infarct zone and border zone (BZ) after coronary artery occlusion. METHODS AND RESULTS: Permanent left anterior descending artery occlusion in swine caused left ventricular remodeling with a decrease of ejection fraction from 55+/-5.6% to 30+/-5.4% (magnetic resonance imaging). Four weeks after left anterior descending artery occlusion, BZ myocardium demonstrated profound bioenergetic abnormalities, with a marked decrease in subendocardial phosphocreatine/ATP (31P magnetic resonance spectroscopy; 1.06+/-0.30 in infarcted hearts [n=9] versus 1.90+/-0.15 in normal hearts [n=8; P<0.01]). This abnormality was significantly improved by transplantation of allogeneic pMultistem cells (subendocardial phosphocreatine/ATP to 1.34+/-0.29; n=7; P<0.05). The BZ protein expression of creatine kinase-mt and creatine kinase-m isoforms was significantly reduced in infarcted hearts but recovered significantly in response to cell transplantation. MRI demonstrated that the infarct zone systolic thickening fraction improved significantly from systolic "bulging" in untreated animals with myocardial infarction to active thickening (19.7+/-9.8%, P<0.01), whereas the left ventricular ejection fraction improved to 42.0+/-6.5% (P<0.05 versus myocardial infarction). Only 0.35+/-0.05% donor cells could be detected 4 weeks after left anterior descending artery ligation, independent of cell transplantation with or without immunosuppression with cyclosporine A (with cyclosporine A, n=6; no cyclosporine A, n=7). The fraction of grafted cells that acquired an endothelial or cardiomyocyte phenotype was 3% and approximately 2%, respectively. Patchy spared myocytes in the infarct zone were found only in pMultistem transplanted hearts. Vascular density was significantly higher in both BZ and infarct zone of cell-treated hearts than in untreated myocardial infarction hearts (P<0.05). CONCLUSIONS: Thus, allogeneic pMultistem improved BZ energetics, regional contractile performance, and global left ventricular ejection fraction. These improvements may have resulted from paracrine effects that include increased vascular density in the BZ and spared myocytes in the infarct zone.

Cytokine-induced differentiation of multipotent adult progenitor cells into functional smooth muscle cells.

Smooth muscle formation and function are critical in development and postnatal life. Hence, studies aimed at better understanding SMC differentiation are of great importance. Here, we report that multipotent adult progenitor cells (MAPCs) isolated from rat, murine, porcine, and human bone marrow demonstrate the potential to differentiate into cells with an SMC-like phenotype and function. TGF-beta1 alone or combined with PDGF-BB in serum-free medium induces a temporally correct expression of transcripts and proteins consistent with smooth muscle development. Furthermore, SMCs derived from MAPCs (MAPC-SMCs) demonstrated functional L-type calcium channels. MAPC-SMCs entrapped in fibrin vascular molds became circumferentially aligned and generated force in response to KCl, the L-type channel opener FPL64176, or the SMC agonists 5-HT and ET-1, and exhibited complete relaxation in response to the Rho-kinase inhibitor Y-27632. Cyclic distention (5% circumferential strain) for 3 weeks increased responses by 2- to 3-fold, consistent with what occurred in neonatal SMCs. These results provide evidence that MAPC-SMCs are phenotypically and functionally similar to neonatal SMCs and that the in vitro MAPC-SMC differentiation system may be an ideal model for the study of SMC development. Moreover, MAPC-SMCs may lend themselves to tissue engineering applications.

Multipotent adult progenitor cells from swine bone marrow.

We show that multipotent adult progenitor cells (MAPCs) can be derived from both postnatal and fetal swine bone marrow (BM). Although swine MAPC (swMAPC) cultures are initially mixed, cultures are phenotypically homogenous by 50 population doublings (PDs) and can be maintained as such for more than 100 PDs. swMAPCs are negative for CD44, CD45, and major histocompatibility complex (MHC) classes I and II; express octamer binding transcription factor 3a (Oct3a) mRNA and protein at levels close to those seen in human ESCs (hESCs); and have telomerase activity preventing telomere shortening even after 100 PDs. Using quantitative-reverse transcription-polymerase chain reaction (Q-RT-PCR), immunofluorescence, and functional assays, we demonstrate that swMAPCs differentiate into chondrocytes, adipocytes, osteoblasts, smooth muscle cells, endothelium, hepatocyte-like cells, and neuron-like cells. Consistent with what we have shown for human and rodent MAPCs, Q-RT-PCR demonstrated a significant upregulation of transcription factors and other lineage-specific transcripts in a time-dependent fashion similar to development. When swMAPCs were passaged for 3-6 passages at high density (2,000-8,000 cells per cm(2)), Oct3a mRNA levels were no longer detectable, cells acquired the phenotype of mesenchymal stem cells (CD44(+), MHC class I(+)), and could differentiate into typical mesenchymal lineages (adipocytes, osteoblasts, and chondroblasts), but not endothelium, hepatocyte-like cells, or neuron-like cells. Even if cultures were subsequently replated at low density (approximately 100-500 cells per cm(2)) for >20 PDs, Oct3a was not re-expressed, nor were cells capable of differentiating to cells other than mesenchymal-type cells. This suggests that the phenotype and functional characteristics of swMAPCs may not be an in vitro culture phenomenon.

Profound bioenergetic abnormalities in peri-infarct myocardial regions.

Regions of myocardial infarct (MI) are surrounded by a border zone (BZ) of normally perfused but dysfunctional myocardium. Although systolic dysfunction has been attributed to elevated wall stress in this region, there is evidence that intrinsic abnormalities of contractile performance exist in BZ myocardium. This study examined whether decreases of high-energy phosphates (HEP) and mitochondrial F(1)F(0)-ATPase (mtATPase) subunits typical of failing myocardium exist in BZ myocardium of compensated postinfarct remodeled hearts. Eight pigs were studied 6 wk after MI was produced by ligation of the left anterior descending coronary artery (LAD) distal to the second diagonal. Animals developed compensated LV remodeling with a decrease of ejection fraction from 54.6 +/- 5.4% to 31 +/- 2.1% (MRI) 5 wk after LAD occlusion. The remote zone (RZ) myocardium demonstrated modest decreases of ATP and mtATPase components. In contrast, BZ myocardium demonstrated profound abnormalities with ATP levels decreased to 42% of normal, and phosphocreatine-to-ATP ratio ((31)P-magnetic resonance spectroscopy) decreased from 2.06 +/- 0.19 in normal hearts to 1.07 +/- 0.10, with decreases in alpha-, beta-, OSCP, and IF(1) subunits of mtATPase, especially in the subendocardium. The reduction of myocardial creatine kinase isoform protein expression was also more severe in the BZ relative to the RZ myocardium. These abnormalities were independent of a change in mitochondrial content because the mitochondrial citrate synthase protein level was not different between the BZ and RZ. This regional heterogeneity of ATP content and expression of key enzymes in ATP production suggests that energetic insufficiency in the peri-infarct region may contribute to the transition from compensated LV remodeling to congestive heart failure.

Autologous stem cell transplantation for myocardial repair.

Current therapies for heart failure due to transmural left ventricular (LV) infarction are limited. We have developed a novel patch method for delivering autologous bone marrow stem cells to sites of myocardial infarction for the purpose of improving LV function and preventing LV aneurysm formation. The patch consisted of a fibrin matrix seeded with autologous porcine mesenchymal stem cells labeled with lacZ. We applied this patch to a swine model of postinfarction LV remodeling. Myocardial infarction was produced by using a 60-min occlusion of the left anterior descending coronary artery distal to the first diagonal branch followed by reperfusion. Results were compared between eight pigs with stem cell patch transplantation, six pigs with the patch but no stem cells (P), and six pigs with left anterior descending coronary artery ligation alone (L). Magnetic resonance imaging data collected 19 +/- 1 days after the myocardial infarction indicated a significant increase of LV systolic wall thickening fraction in the infarct zone of transplanted hearts compared with P or L hearts. Blue X-gal staining was observed in the infarcted area of transplanted hearts. PCR amplification of specimens from the X-gal-positive area revealed the Ad5 RSV-lacZ vector fragment DNA sequence. Light microscopy demonstrated that transplanted cells had differentiated into cells with myocyte-like characteristics and a robust increase of neovascularization as evidenced by von Willebrand factor-positive angioblasts and capillaries in transplanted hearts. Thus this patch-based autologous stem cell procedure may serve as a therapeutic modality for myocardial repair.