Publications by authors named "Robert J Tomanek"

34 Publications

Developmental Progression of the Coronary Vasculature in Human Embryos and Fetuses.

Authors:
Robert J Tomanek

Anat Rec (Hoboken) 2016 Jan 28;299(1):25-41. Epub 2015 Nov 28.

Department of Anatomy and Cell Biology, and Cardiovascular Center, University of Iowa, Iowa City, Iowa.

Although considerable advances in our understanding of mammalian and avian embryonic coronary development have occurred during the last decade, our current knowledge of this topic in humans is limited. Accordingly, the aim of this study was to determine if the development of the human coronary vasculature in humans is like that of other mammals and avians. The data document a progression of events involving mesenchymal cell-containing villi from the proepicardium, establishment of blood islands and a capillary network. The major finding of the study is direct evidence that the capillary plexus associated with spindle cells and erythroblasts invades the base of the aorta to form coronary ostia. A role for the dorsal mesocardium is also indicated by the finding that cells from this region are continuous with the aorta and pulmonary artery. The development of the tunica media of the coronary arteries follows the same base-apex progression as in other species, with the development of branches occurring late in the embryonic period. The fetal period is characterized by 1) growth and a numerical increase in the smallest arterial branches, veins, and venules, 2) innervation of arteries, and 3) inclusion of elastic fibers in the tunica media of the coronary arteries and development of the tunica adventitia. In conclusion, the data demonstrate that the development of the coronary system in humans is similar to that of other mammalian and avian species, and for the first time documents that the formation of the ostia and coronary stems in humans occurs by ingrowth of a vascular plexus and associated cells from the epicardium.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ar.23283DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4715710PMC
January 2016

Effect of Chronic Heart Rate Reduction by I(f) Current Inhibitor Ivabradine on Left Ventricular Remodeling and Systolic Performance in Middle-Aged Rats With Postmyocardial Infarction Heart Failure.

J Cardiovasc Pharmacol Ther 2015 May 5;20(3):299-312. Epub 2014 Oct 5.

Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, IA, USA Cardiovascular Center, University of Iowa Carver College of Medicine, Iowa City, IA, USA.

Background: A large myocardial infarction (MI) initiates progressive cardiac remodeling that leads to systolic heart failure (HF). Long-term heart rate reduction (HRR) induced by the I f current inhibitor ivabradine (IVA) ameliorates left ventricular (LV) remodeling and improves systolic performance in young post-MI rats. However, the beneficial effects of chronic IVA treatment in middle-aged rats remain to be determined.

Methods: A large MI was induced in 12-month-old rats by left coronary artery ligation. Rats were treated with IVA via osmotic pumps intraperitoneal in a dose of 10.5 mg/kg/d (MI + IVA) and compared with MI and sham-operated animals 12 weeks after MI.

Results: Heart rate in MI + IVA rats was on average 29% lower than that of rats in the MI group. Left ventricular remodeling was comparable between post-MI groups, although MI + IVA rats did not show the compensatory thickening of the noninfarcted myocardium. Chronic HRR had no effect on transverse cardiac myocyte size and capillary growth, but it reduced the collagen content in noninfarcted myocardium. Left ventricular systolic performance remained similarly impaired in MI and MI + IVA rats. Moreover, abrupt IVA withdrawal led to worsening HF and reduction of coronary reserve.

Conclusion: Our data reveal that chronic IVA-induced HRR does not provide sustainable benefits for LV systolic performance in middle-aged rats with post-MI HF.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1177/1074248414553231DOI Listing
May 2015

Coronary anomalies in mice with congenital heart defects.

Anat Rec (Hoboken) 2015 Feb 13;298(2):408-17. Epub 2014 Oct 13.

Department of Anatomy and Cell Biology, Carver College of Medicine, The University of Iowa, Iowa City, Iowa.

Background: Coronary anomalies are frequently associated with congenital cardiac defects. Accordingly, we tested the hypothesis that the development of the tunica media of coronary arteries/arterioles is compromised in mice with cardiac defects of the outflow tract (persistent truncus arteriosus, double outlet right ventricle and transposition of the great arteries) by studying hearts of G7-9 generation mice bred from mutagenized mice caused by N-ethyl-N-nitrosourea. Mice were studied at embryonic days E16.5, E17.5, and postnatal days 1 and 11. Data were based on immunohistochemistry of serial sections.

Results: In 21 of 24 mice with outflow tract defects, the development of smooth muscle in arteries and arterioles was retarded; most commonly arterioles had an incomplete layer of smooth muscle or in a few instances, lacked a tunica media. In this model, an absence of a coronary ostium occurred in only 2 mice, indicating that the mechanisms underlying the formation of coronary ostia and the recruitment and differentiation of vascular smooth muscle differ. Coronary fistulas were present in 20% and dilated vessels in 30% of the hearts with cardiac defects.

Conclusions: The data suggest that vascular smooth muscle recruitment and differentiation are not necessarily linked to other coronary anomalies, such as absence of a main coronary artery or branching patterns.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ar.23056DOI Listing
February 2015

Coronary vessels and cardiac myocytes of middle-aged rats demonstrate regional sex-specific adaptation in response to postmyocardial infarction remodeling.

Biol Sex Differ 2014 Jan 3;5(1). Epub 2014 Jan 3.

Department of Biomedical Sciences, New York Institute of Technology College of Osteopathic Medicine, Rockefeller Building, Room 215E, Northern Boulevard, Old Westbury, NY 11568-8000, USA.

Background: An increasing body of evidence indicates that left ventricular (LV) remodeling, especially the degree of reactive myocardial hypertrophy after myocardial infarction (MI), differs in males and females. Surprisingly, to date, the sex-specific post-MI alterations of the coronary vasculature remain undetermined. Therefore, we tested the hypothesis that adaptive coronary arteriolar and capillary modifications occurring in response to reactive myocyte hypertrophy differ between middle-aged male and female post-MI rats.

Methods: A large MI was induced in 12-month-old male (M-MI) and female (F-MI) Sprague-Dawley rats by ligation of the left coronary artery. Four weeks after surgery, rats with transmural infarctions, greater than 50% of the LV free wall (FW), were evaluated. Sham-operated male (M-Sham) and female (F-Sham) rats served as an age-matched controls.

Results: F-MI and M-MI rats had similar sized infarcts (61.3% ± 3.9% vs. 61.5% ± 1.2%) and scale of LV remodeling, as indicated analogous remodeling indices (1.41 ± 0.11 vs. 1.39 ± 0.09). The degree of reactive post-MI myocardial hypertrophy was adequate to normalize LV weight-to-body weight ratio in both sexes; however, the F-MI rats, in contrast to males, showed no myocyte enlargement in the LVFW epimyocardium. At the same time, a greater than 50% expansion of myocyte area in the male epimyocardium and in the female endomyocardium was accompanied by a 23% (P < 0.05) increase in capillary-to-myocyte ratio, indicative of adaptive angiogenesis. Based on arteriolar length density in post-MI hearts, the resistance vessels grew in the male LVFW as well as the septum by 24% and 29%, respectively. In contrast, in females, a significant (30%) expansion of arteriolar bed was limited only to the LVFW. Moreover, in F-MI rats, the enlargement of the arteriolar bed occurred predominantly in the vessels with diameters <30 μm, whereas in M-MI rats, a substantial (two- to threefold) increase in the density of larger arterioles (30 to 50 μm in diameter) was also documented.

Conclusion: Our data reveal that while both sexes have a relatively similar pattern of global LV remodeling and adaptive angiogenesis in response to a large MI, male and female middle-aged rats differ markedly in the regional scale of reactive cardiac myocyte hypertrophy and adaptive arteriogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/2042-6410-5-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3892039PMC
January 2014

Structural composition of myocardial infarction scar in middle-aged male and female rats: does sex matter?

J Histochem Cytochem 2013 Nov 18;61(11):833-48. Epub 2013 Jul 18.

Department of Biomedical Sciences, New York Institute of Technology College of Osteopathic Medicine, Old Westbury, New York (YB,EID).

The present study was designed to determine whether the structural composition of the scar in middle-aged post-myocardial infraction (MI) rats is affected by the biological sex of the animals. A large MI was induced in 12-month-old male (M-MI) and female (F-MI) Sprague-Dawley rats by ligation of the left coronary artery. Four weeks after the MI, rats with transmural infarctions, greater than 50% of the left ventricular (LV) free wall, were evaluated. The extent of LV remodeling and fractional volumes of fibrillar collagen (FC), myofibroblasts, vascular smooth muscle (SM) cells, and surviving cardiac myocytes (CM) in the scars were compared between the two sexes. The left ventricle of post-MI male and female rats underwent a similar degree of remodeling as evidenced by the analogous scar thinning ratio (0.46 ± 0.02 vs. 0.42 ± 0.05) and infarct expansion index (1.06 ± 0.07 vs. 1.12 ± 0.08), respectively. Most important, the contents of major structural components of the scar revealed no evident difference between M-MI and F-MI rats (interstitial FC, 80.74 ± 2.08 vs. 82.57 ± 4.53; myofibroblasts, 9.59 ± 1.68 vs.9.56 ± 1.15; vascular SM cells, 2.27 ± 0.51 vs. 3.38 ± 0.47; and surviving CM, 3.26 ± 0.39 vs. 3.05 ± 0.38, respectively). Our data are the first to demonstrate that biological sex does not influence the structural composition of a mature scar in middle-aged post-MI rats.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1369/0022155413499794DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3808574PMC
November 2013

Embryonic coronary vasculogenesis and angiogenesis are regulated by interactions between multiple FGFs and VEGF and are influenced by mesenchymal stem cells.

Dev Dyn 2010 Dec;239(12):3182-91

Department of Anatomy and Cell Biology, The University of Iowa Carver College of Medicine and The Cardiovascular Center, University of Iowa, Iowa City, Iowa 52242, USA.

In embryonic hearts explanted on collagen gels, epicardial cells delaminate and form vascular tubes, thus providing a model for coronary tubulogenesis. Using this model, we show that fibroblast growth factors (FGFs) 1, 2, 4, 8, 9, and 18 contribute to tubulogenesis and that the availability of multiple FGFs provides the optimal tubulogenic response. Moreover, the FGF effects are vascular endothelial growth factor (VEGF) -dependent, while VEGF-induced tubulogenesis requires FGF signaling. The number of endothelial cells (ECs) is increased by all of the FGFs, while EC migration is significantly enhanced only by FGF-2 and FGF-18. Finally, addition of embryonic mesenchymal stem cells (EMSC) to the explants markedly enhances EC numbers and a 23-fold increase in stromal derived factor-1α (SDF-1α), which is FGF dependent. Both explants and EMSCs produce SDF-1α. In conclusion, coronary tubulogenesis of embryonic epicardium: (1) is responsive to many FGF family members, (2) requires both FGF and VEGFA signaling, and (3) is responsive to EMSCs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/dvdy.22460DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2991485PMC
December 2010

Lin- cells mediate tissue repair by regulating MCP-1/CCL-2.

Am J Pathol 2010 Oct 2;177(4):2002-10. Epub 2010 Sep 2.

Departments of Integrative Physiology, The University of Iowa, Iowa City, Iowa 52242, USA.

Exogenous bone marrow-derived cells (BMDCs) are promising therapeutic agents for the treatment of tissue ischemia and traumatic injury. However, until we identify the molecular mechanisms that underlie their actions, there can be no rational basis for the design of therapeutic strategies using BMDCs. The pro-healing effects of BMDCs are apparent very shortly after treatment, which suggests that they may exert their effects by the modulation of acute inflammation. We investigated this hypothesis by taking advantage of the fact that BMDCs from healthy, young, but not obese, diabetic mice stimulate vascular growth. By comparing both in vitro secretion and in vivo local induction of acute phase inflammatory cytokines by these cells, we identified monocyte chemoattractant factor 1 and tumor necrosis factor α as potential mediators of BMDC-induced tissue repair. In vivo analysis of BMDC-treated ischemic limbs and cutaneous wounds revealed that the production of monocyte chemoattractant factor 1 by exogenous and endogenous BMDCs is essential for BMDC-mediated vascular growth and tissue healing, while the inability of BMDCs to produce tumor necrosis factor α appears to play a lesser but still meaningful role. Thus, measurements of the secretion of cytokines by BMDCs may allow us to identify a priori individuals who would or would not be good candidates for BMDC-based therapies.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.2353/ajpath.2010.091232DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2947294PMC
October 2010

Chronic heart rate reduction facilitates cardiomyocyte survival after myocardial infarction.

Anat Rec (Hoboken) 2010 May;293(5):839-48

Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa, USA.

Chronic heart rate reduction (HRR) therapy following myocardial infarction, using either the pure HRR agent ivabradine or the beta-blocker atenolol, has been shown to preserve maximal coronary perfusion, via reduction of perivascular collagen and a decrease in renin-angiotensin system activation. In addition ivabradine, but not atenolol, treatment attenuated the decline in ejection fraction and decreased left ventricular wall stress. In this study, we tested the hypothesis that cell survival within the infarct region was enhanced by these two pharmacological agents. Four weeks after ligating the left anterior descending coronary artery, the percentage of the LV that contained the infarct was similar in the untreated (MI) rats and those chronically treated with ivabradine (MI + IVA) or atenolol (MI + ATEN). However, the mean thickness (mm) of the ventricular wall containing the scar was significantly greater in the MI + IVA, 1.54 (P < or = 0.01) and the MI + ATEN 1.32, compared to 1.1 in the MI group, due to a 2-fold greater area of surviving cardiomyocytes (P < or = 0.01) in the treated rats compared to the untreated group. Regions of cell survival were usually in the subepicardium, with cardiomyocytes surrounding veins or venules. However, some hearts displayed surviving cells along the endocardium. These data suggest that HRR by either ivabradine or atenolol facilitates a more favorable O2 microenvironment via improved venous flow and decreased O2 demand. We conclude that chronic HRR by these agents may serve to limit infarct expansion and wall thinning and may serve to reduce the potential for ventricular rupture.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ar.21081DOI Listing
May 2010

Postmyocardial infarction remodeling and coronary reserve: effects of ivabradine and beta blockade therapy.

Am J Physiol Heart Circ Physiol 2009 Jul 1;297(1):H322-30. Epub 2009 May 1.

Department of Anatomy and Cell Biology, Department of Internal Medicine, and Cardiovascular Center, University of Iowa, Iowa City, IA 52242, USA.

We compared the effects of heart rate reduction (HRR) by the hyperpolarization-activated pacemaker current (I(f)) channel inhibitor ivabradine (MI+Iva) and the beta(1)-blocker atenolol (MI+Aten) on ventricular remodeling and perfusion after myocardial infarction (MI) in middle-aged (12 mo) Sprague-Dawley rats. Mean HRR was virtually identical in the two treated groups (19%). Four weeks after coronary artery ligation, maximal myocardial perfusion fell in the MI group but was preserved in infarcted rats treated with either Iva or Aten. However, coronary reserve in the remodeled hearts was preserved only with Iva, since Aten treatment elevated baseline perfusion in response to a higher wall stress. The higher maximal perfusion noted in the two treated groups was not due to arteriogenesis or angiogenesis. Plasma levels of angiotensin (ANG) II and myocardial ANG type 1 (AT(1)) receptor and transforming growth factor (TGF)-beta1 were reduced during the first week of treatment by both Iva and Aten. Moreover, treatment also reduced arteriolar perivascular collagen density. Despite these similar effects of Iva and Aten on vascularity and ANG II, Iva, but not Aten, attenuated the decline in ejection fraction and lowered left ventricular (LV) end-diastolic volume (LVEDV)-to-LV mass ratio, determined by echocardiography. In conclusion, 1) Iva has advantages over Aten in postinfarction therapy that are not due to differential effects of the drugs on heart rate, and 2) age limits growth factor upregulation, angiogenesis, and arteriogenesis in the postinfarcted heart.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/ajpheart.01337.2008DOI Listing
July 2009

Hypoxia increases placenta growth factor expression in human myocardium and cultured neonatal rat cardiomyocytes.

J Heart Lung Transplant 2009 Feb;28(2):183-90

College of Pharmacy and Health Sciences, Drake University, Des Moines, Iowa 50311-4505, USA.

Background: Placenta growth factor (PlGF) plays an important role in pathologic angiogenesis and is believed to be an independent biomarker in patients with coronary artery disease. However, little is known regarding the regulation of PlGF expression in heart tissue.

Methods: We determined expression changes in PlGF and its receptor, VEGFR1, in normal and abnormal biopsies from human cardiac allografts and in cardiomyocytes cultured under hypoxia or cyclical stretch conditions.

Results: Human donor myocardium and biopsies from allografts without fibrin deposits expressed PlGF and VEGFR1 mRNA. Biopsies (n = 7) with myocardial fibrin, elevated serum cardiac troponin I titers (p < 0.03) and cellular infiltrates (p < 0.05) expressed 1.6-fold more PlGF mRNA than biopsies from allografts without fibrin (n = 11; p < 0.05). PlGF protein was localized in cardiomyocytes, extracellular matrix and some microvessels in areas with fibrin deposition. VEGFR1 mRNA expression was not different between groups. Cultured neonatal rat cardiomyocytes constitutively expressed PlGF/VEGFR1 under normoxia. PlGF expression was increased 3.88 +/- 0.62-fold after 12 hours (n = 6; p
Conclusions: Cardiomyocyte PIGF expression is upregulated by hypoxia in vitro and its expression increases significantly in allografts with myocardial damage. Collectively, these results provide important temporal and spatial evidence that endogenous PlGF may facilitate cardiac healing after myocardial hypoxia/ischemia.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.healun.2008.11.917DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2885281PMC
February 2009

Differential effects of cyclic and static stretch on coronary microvascular endothelial cell receptors and vasculogenic/angiogenic responses.

Am J Physiol Heart Circ Physiol 2008 Aug 27;295(2):H794-800. Epub 2008 Jun 27.

Dept. of Anatomy and Cell Biology, Univ. of Iowa, 1-402, Bowen Science Bldg., Iowa City, IA 52242, USA.

Mechanical stretch, an important growth stimulus, results not only from pulsatile blood flow and diastolic stretch of the ventricles [cyclic stretch (CS)] but also from tissue expansion during growth [constant static stretch (SS)]. We compared growth factor receptor expression and vasculogenic/angiogenic responses of rat coronary microvascular endothelial cells (ECs) by exposing cells to CS (10% elongation at 30 cycles/min) and SS (constant 10% elongation). Both CS and SS increased VEGF receptor (VEGF-R)2 protein levels and the extent of tube formation and branching. Moreover, both CS and SS enhanced VEGF-induced cell proliferation and tube formation, indicating that both types of stretch increase the sensitivity of ECs to VEGF. Blockade of VEGF-R2 prevented the increases in EC proliferation and aggregate tube length. However, CS but not SS enhanced EC Tie-2 protein and migration. CS affected a greater increase in tube length and branch formation than did SS. A unique finding was that SS but not CS increased VEGFR-1 in ECs. Our study is the first to distinguish between the effects of CS and SS on growth factor receptor expression and rat coronary microvascular EC proliferation, migration, and tube formation. In conclusion, EC angiogenic responses to these two types of stretch display both differences and similarities, but both CS and SS are dependent on VEGF-R2 signaling for their vasculogenic/angiogenic effects.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/ajpheart.00343.2008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2519222PMC
August 2008

Temporally expressed PDGF and FGF-2 regulate embryonic coronary artery formation and growth.

Arterioscler Thromb Vasc Biol 2008 Jul 17;28(7):1237-43. Epub 2008 Apr 17.

Department of Anatomy & Cell Biology, The University of Iowa, 1-402 Bowen Science Building, Iowa City, Iowa 52242, USA.

Objective: PDGF and FGF-2 are important regulators of vascular wall assembly. We tested the hypothesis that their embryonic temporal expression facilitates 2 specific events: (1) the endothelial invasion of the aortic root to form the coronary artery stems and (2) the subsequent growth and development of the arterial tree.

Methods And Results: Addition of FGF-2 and PDGF-BB proteins to embryonic quail heart explants stimulated a 3- and 7-fold increase, respectively, in tubulogenesis, whereas neutralizing antibodies to these growth factors attenuated tubulogenesis by 40%. Anti-FGF-2 and anti-PDGF neutralizing antibodies were then introduced in ovo via the vitelline vein at various embryonic (E) days. When injections occurred before coronary ostial formation, the embryos usually developed only 1 coronary artery or lacked coronary arteries. When 1 or both major coronary arteries formed: (1) their branches had a thinner tunica media, and (2) smooth muscle investment did not progress as far distally as in shams. Other anomalies included smaller diameter coronary artery stems in some hearts. Inhibition of VEGF via injections of aflibercept (VEGF-Trap, a VEGFR-1 and -2 chimera), previously shown to be essential for coronary stem formation, limited development of the coronary arteries even though introduced after formation of coronary ostia (at E9 or EI0).

Conclusions: Our data (1) document a role for FGF-2 and PDGF in the temporal regulation of coronary artery stem formation and growth of the coronary arterial tree and (2) reveal that VEGF expression is required for normal artery/arterial formation, even after coronary artery stem formation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/ATVBAHA.108.166454DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2748328PMC
July 2008

Synectin/syndecan-4 regulate coronary arteriolar growth during development.

Dev Dyn 2007 Jul;236(7):2004-10

Department of Anatomy and Cell Biology, Carver College of Medicine, The University of Iowa, Iowa City, Iowa 52242, USA.

Syndecan-4 and its cytoplasmic binding partner, synectin, are known to play a role in FGF-2 signaling and vascular growth. To determine their roles in coronary artery/arteriolar formation and growth, we compared syndecan-4 and synectin null mice with their wild-type counterparts. Image analysis of arterioles visualized by smooth muscle alpha-actin immunostaining revealed that synectin (-/-) mice had lower arteriolar length and volume densities than wild-type mice. As shown by electron microscopic analysis, arterioles from the two did not differ in morphology, including their endothelial cell junctions, and the organization and distribution of smooth muscle. Using micro-computer tomography, we found that the size and branching patterns of coronary arteries (diameters > 50 microm) were similar for the two groups, a finding that indicates that the growth of arteries is not influenced by a loss of synectin. Syndecan-4 null male mice also had lower arteriolar length densities than their gender wild-type controls. However, female syndecan-4 null mice were characterized by higher arteriolar length and volume densities than their gender-matched wild-type controls. Thus, we conclude that both synectin and syndecan-4 play a role in arteriolar development, a finding that is consistent with previous evidence that FGF-2 plays a role in coronary arterial growth. Moreover, our data reveal that gender influences the arteriolar growth response to syndecan-4 but not to synectin.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/dvdy.21201DOI Listing
July 2007

Preservation of coronary reserve by ivabradine-induced reduction in heart rate in infarcted rats is associated with decrease in perivascular collagen.

Am J Physiol Heart Circ Physiol 2007 Jul 23;293(1):H590-8. Epub 2007 Mar 23.

Department of Biomedical Sciences, New York College of Osteopathic Medicine/NYIT, Old Westbury, NY 11568, USA.

We tested the hypothesis that chronically reducing the heart rate in infarcted middle-aged rats using ivabradine (IVA) would induce arteriolar growth and attenuate perivascular collagen and, thereby, improve maximal perfusion and coronary reserve in the surviving myocardium. Myocardial infarction (MI) was induced in 12-mo-old male Sprague-Dawley rats, which were then treated with either IVA (10.5 mg.kg(-1).day(-1); MI + IVA) or placebo (MI) via intraperitoneal osmotic pumps for 4 wk. Four weeks of IVA treatment limited the increase in left ventricular end-diastolic pressure and the decrease in ejection fraction but did not affect the size of the infarct, the magnitude of myocyte hypertrophy, or the degree of arteriolar and capillary growth. However, treatment reduced interstitial and periarteriolar collagen in the surviving myocardium of MI + IVA rats. The reduced periarteriolar collagen content was associated with improvement in maximal myocardial perfusion and coronary reserve. Although the rates of proliferation of periarteriolar fibroblasts were similar in the MI and MI + IVA groups, the expression levels of the AT(1) receptor and transforming growth factor (TGF)-beta(1) in the myocardium, as well as the plasma level of the ANG II peptide, were lower in treated rats 14 days after MI. Therefore, our data reveal that improved maximal myocardial perfusion and coronary reserve in MI + IVA rats are most likely the result of reduced periarteriolar collagen rather than enhanced arteriolar growth.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/ajpheart.00047.2007DOI Listing
July 2007

Vascular patterning of the quail coronary system during development.

Anat Rec A Discov Mol Cell Evol Biol 2006 Sep;288(9):989-99

Department of Anatomy and Cell Biology and Cardiovascular Center, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA.

Recent studies have provided insights into specific events that contribute to vasculogenesis and angiogenesis in the developing coronary vasculature. This study focused on the developmental progression of coronary vascularization beginning with tube formation and ending with the establishment of a coronary arterial tree. We used electron microscopy, histology of serial sections, and immunohistochemistry in order to provide a comprehensive view of coronary vessel formation during the embryonic and fetal periods of the quail heart, a species that has been used in a number of studies addressing myocardial vascularization. Our data reveal features of progenitor cells and blood islands, tubular formation, and the anatomical relationship of a transformed periarterial tubular network and sympathetic ganglia to the emergence and branching of the right and left coronary arteries. We have traced the pattern of coronary artery branching and documented its innervation. Finally, our data include the relationship of fibronectin, laminin, and apoptosis to coronary artery growth. Our findings bring together morphological events that occur over the embryonic and fetal periods and provide a baseline for studies into the mechanisms that regulate the various events that occur during these time periods.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/ar.a.20365DOI Listing
September 2006

The coronary microcirculation in cyanotic congenital heart disease.

Circulation 2006 Jul 10;114(3):196-200. Epub 2006 Jul 10.

Department of Anatomy and Cell Biology and Cardiovascular Center, University of Iowa Carver College of Medicine, Iowa City, USA.

Background: Despite an appreciable increase in basal coronary blood flow in cyanotic congenital heart disease, flow reserve remains normal. We hypothesized that preservation of flow reserve resides in remodeling of the coronary microcirculation. Microcirculatory morphometric analyses were performed to test this hypothesis.

Methods And Results: Necropsy specimens from 4 sources were studied: (1) hearts from patients with Eisenmenger's syndrome (A; n=5), (2) structurally abnormal hearts with ventricular hypertrophy (B; n=8), (3) structurally normal hearts with ventricular hypertrophy (C; n=6), and (4) normal hearts (D; n=5). To compare responses of the microcirculation to hypoxia versus hypertrophy, sections were taken from the left ventricular free wall, which in group A, was hypoxemic but not hypertrophied; in groups B and C, was hypertrophied but not hypoxemic; and in group D, was neither hypertrophied nor hypoxemic. Coronary arterioles were immunolabeled for smooth muscle alpha-actin. Measured morphometric parameters included long and short axes, area, and perimeter. Arteriolar length, volume and surface densities were calculated. There was a significant intergroup difference for arteriolar length density (P=0.03) and diameter (P=0.03). Total length density in group A hearts was markedly lower, but mean arteriolar diameter was significantly greater (34%) compared with group B (P=0.03). Arteriolar volume density was similar to that in the other groups.

Conclusions: Remodeling of the coronary microcirculation is the key mechanism for preservation of flow reserve in cyanotic congenital heart disease. The increase in short axis (diameter) compensated for lower arteriolar length density and was the principal anatomic basis for maintenance of normal flow reserve.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/CIRCULATIONAHA.105.602771DOI Listing
July 2006

Compensatory growth of coronary arterioles in postinfarcted heart: regional differences in DNA synthesis and growth factor/receptor expression patterns.

Am J Physiol Heart Circ Physiol 2006 Oct 19;291(4):H1686-93. Epub 2006 May 19.

Dept. of Anatomy and Cell Biology, 1-402 Bowen Science Bldg., The Univ. of Iowa, Iowa City, IA 52242, USA.

Previous studies have not addressed regional differences in adaptive arteriolar growth in the surviving left ventricular (LV) myocardium after infarction in appropriately aged animals, namely middle-aged or older. Accordingly, we examined the adaptive postinfarction growth of arterioles in two distinct regions, i.e., the LV free wall (LVFW) and septum, of middle-aged rats. We induced a myocardial infarction (MI) in 12-mo-old rats to analyze 1) protein expression in VEGF/Flt-1/Flk-1 and angiopoietin (Ang)-1/Ang-2/Tie-2 systems, 2) the arteriolar DNA synthesis, 3) the extent of the arteriolar bed, and 4) the alteration in minimal coronary vascular resistance. In both regions, arteriolar DNA synthesis was activated between days 4 and 7 after MI. Whereas in the LVFW the degree of DNA synthesis declined between days 11 and 14 post-MI, it continued to rise in the septum, and at day 14, the percentage of the arterioles undergoing DNA synthesis was comparable in the LVFW and the septum (9.7 +/- 1.6 and 7 +/- 2.1%, respectively). Arteriolar DNA synthesis was mainly associated with upregulation of Ang-2 and Tie-2 in both LV regions. Although 4 wk after MI the arteriolar beds in the LVFW and the septum expanded to the size of sham-operated rats, this growth did not compensate for the greater minimal coronary vascular resistance in the former. Thus our findings suggest that 1) the dynamics in adaptive arteriolar growth were similar between the two regions, despite a delay in the septum; and 2) the perfusion deficit in post-MI rats cannot be accounted for by inadequate adaptive growth of arterioles.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/ajpheart.00307.2006DOI Listing
October 2006

VEGF family members regulate myocardial tubulogenesis and coronary artery formation in the embryo.

Circ Res 2006 Apr 9;98(7):947-53. Epub 2006 Mar 9.

Department of Anatomy & Cell Biology, Cardiovascular Center, Carver College of Medicine, The University of Iowa, Iowa City, IA, USA.

This study tested the hypothesis that coronary tubulogenesis and coronary artery formation require VEGF family members. Quail embryos were injected with soluble vascular endothelial growth factor (VEGF) receptors R1 (Flt-1), R2 (Flk-1), R3 (Flt-4), VEGF-Trap (a chimera of R1 and R2), or neutralizing antibodies to VEGF-A, VEGF-B, or fibroblast growth factor (FGF)-2. Our data document that tubulogenesis is temporally dependent on multiple VEGF family members, because the early stage of tubulogenesis was markedly inhibited by VEGF-Trap and to a lesser extent by soluble VEGFR-1. Some inhibition of tubulogenesis was documented when anti-FGF-2, but not anti-VEGF-A, antibodies were injected at embryonic day 6 (E6). Most importantly, we found that VEGF-Trap injected at either E6 or E7 prevented the formation of coronary arteries. Soluble VEGFR-1 and soluble VEGFR-2 modified the formation of coronary arteries, whereas soluble VEGFR-3 was without effect. Antibodies to VEGF-B, but not VEGF-A, had a strong inhibitory effect on coronary artery development. The absence of coronary artery stems, and thus a functional coronary circulation, in the embryos injected with VEGF-Trap caused an accumulation of erythrocytes in the subepicardium and muscular interventricular septum. Using retroviral cell tagging, we showed that some of the erythrocytes in blood islands and small vascular tubes were progeny of the proepicardium. Thus, another salient finding of this study is the first definitive documentation of proepicardially derived hemangioblasts, which can differentiate into erythrocytes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/01.RES.0000216974.75994.daDOI Listing
April 2006

Differential healing activities of CD34+ and CD14+ endothelial cell progenitors.

Arterioscler Thromb Vasc Biol 2006 Apr 12;26(4):758-64. Epub 2006 Jan 12.

Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA 52242, USA.

Objective: Peripheral blood contains primitive (stem cell-like) and monocytic-like endothelial cell progenitors. Diabetes apparently converts these primitive progenitors, from a pro-angiogenic to anti-angiogenic phenotype. Monocytic progenitors seem to be less affected by diabetes, but potential pro-angiogenic activities of freshly isolated monocytic progenitors remain unexplored. We compared the ability of primitive and monocytic endothelial cell progenitors to stimulate vascular growth and healing in diabetes and investigated potential molecular mechanisms through which the cells mediate their in vivo effects.

Methods And Results: Human CD34+ primitive progenitors and CD14+ monocytic progenitors were injected locally into the ischemic limbs of diabetic mice. CD14+ cell therapy improved healing and vessel growth, although not as rapidly or effectively as CD34+ cell treatment. Western blot analysis revealed that cell therapy modulated expression of molecules in the VEGF, MCP-1, and angiopoietin pathways.

Conclusions: Injection of freshly isolated circulating CD14+ cells improves healing and vascular growth indicating their potential for use in acute clinical settings. Importantly, CD14+ cells could provide a therapeutic option for people with diabetes, the function of whose CD34+ cells may be compromised. At least some progenitor-induced healing probably is mediated through increased sensitivity to VEGF and increases in MCP-1, and possibly modulation of angiopoietins.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/01.ATV.0000203513.29227.6fDOI Listing
April 2006

Formation of the coronary vasculature during development.

Authors:
Robert J Tomanek

Angiogenesis 2005 25;8(3):273-84. Epub 2005 Nov 25.

Department of Anatomy and Cell Biology, The University of Iowa, 1-402 BSB Carver College of Medicine, Iowa City, Iowa, USA.

The formation of the coronary vasculature involves a series of carefully regulated temporal events that include vasculogenesis, angiogenesis, arteriogenesis and remodeling. This review explores these events, which begin with the migration of proepicardial cells to form the epicardium and end with postnatal growth and remodeling. Coronary endothelial, smooth muscle and fibroblast cells differentiate via epithelial-mesenchymal transformation; these cells delaminate from the epicardium. Following the formation of a tubular network by endothelial cells, an aortic ring of endothelial cells penetrates the aorta at the left and right aortic cusps to form the two ostia. Smooth muscle cell recruitment occurs rapidly and the coronary artery network begins forming as blood flow is established. Recent studies have identified a number of regulatory molecules that play key roles in epicardial formation and the transformation of its component cells into mesenchyme. Moreover, we are finally gaining some understanding regarding the interplay of angiogenic growth factors in the complex process of establishing the coronary vascular tree. Understanding coronary embryogenesis is important for interventions regarding adult cardiovascular diseases as well as those necessary to correct congenital defects.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s10456-005-9014-9DOI Listing
October 2006

Myocardial vascular and metabolic adaptations in chronically anemic fetal sheep.

Am J Physiol Regul Integr Comp Physiol 2005 Dec 25;289(6):R1736-45. Epub 2005 Aug 25.

Dept. of Surgery, Univ. of Iowa Carver College of Medicine, Iowa City, IA 52242, USA.

Little is known about the vascular and metabolic adaptations that take place in the fetal heart to maintain cardiac function in response to increased load. Chronic fetal anemia has previously been shown to result in increased ventricular mass, increased myocardial vascularization, and increased myocardial expression of hypoxia-inducible factor-1 (HIF-1) and vascular endothelial growth factor (VEGF). We therefore sought to determine whether chronic fetal anemia induces expression of HIF-1-regulated angiogenic factors and glycolytic enzymes in the fetal myocardium. Anemia was produced in chronically instrumented fetal sheep by daily isovolemic hemorrhage (80-100 ml) for either 3 (n = 4) or 7 days (n = 11) beginning at 134 days of gestation (term 145 days). Catheterized, nonbled twins served as controls. Isovolemic hemorrhage over 7 days resulted in decreased fetal hematocrit (37 +/- 1 to 20 +/- 1%) and arterial oxygen content (6.5 +/- 0.4 to 2.8 +/- 0.2 ml O2/dl). Myocardial blood flow and vascularization were significantly increased after 7 days of anemia. Myocardial HIF-1 protein expression and VEGF (left ventricular), VEGF receptor-1 (right ventricular), and VEGF receptor-2 (right ventricular, left ventricular) mRNA levels were elevated (P < 0.05) in 7-day anemic compared with control animals. Myocardial expressions of the glycolytic enzymes aldolase, lactate dehydrogenase A, phosphofructokinase (liver), and phosphoglycerol kinase were also significantly elevated after 7 days of anemia. Despite the absence of a significant increase in myocardial HIF-1alpha protein in 3-day anemic fetuses, expressions of VEGF, VEGF receptor-1, and the glycolytic enzymes were greater in 3-day compared with 7-day anemic animals. These data suggest that HIF-1 likely participates in the fetal myocardial response to anemia by coordinating an increase in gene expressions that promote capillary growth and anaerobic metabolism. However, factors other than HIF-1 also appear important in the regulation of these genes. We speculate that the return of mRNA levels of angiogenic and glycolytic enzymes toward control levels in the 7-day anemic fetus is explained by a significantly increased resting myocardial blood flow, resulting from coronary vascular growth and increased coronary conductance, and a return to a state of adequate oxygen and nutrient delivery, obviating the need for enhanced transcription of genes encoding angiogenic and glycolytic enzymes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/ajpregu.00278.2005DOI Listing
December 2005

Bradycardia stimulates vascular growth during gradual coronary occlusion.

Arterioscler Thromb Vasc Biol 2005 Oct 28;25(10):2122-7. Epub 2005 Jul 28.

Department of Internal Medicine, University of Iowa, Roy J. and Lucille A. Carver College of Medicine, Iowa City, IA, USA.

Objective: In cultured endothelium, stretch induces release of growth factors that contribute to angiogenesis. We tested the hypothesis that bradycardia, which prolongs ventricular diastolic filling time and volume, promotes collateral vessel growth.

Methods And Results: An ameroid occluder was placed on coronary arteries of dogs with normal heart rates (AM) or bradycardia (55 bpm; AM+BC). A third group had normal heart rates and no ameroid (control [CON]). Four weeks after occluder placement, myocardial blood flow at rest and maximal vasodilation (adenosine) at equivalent heart rates and vascular morphometry of hearts were measured. In AM dogs, conductance (myocardial flow/diastolic pressure) of collateral-dependent myocardium was similar to collateral-independent myocardium during rest but increased to only one third of CON during maximal vasodilation. In contrast, in AM+BC dogs, conductance was similar in collateral-dependent and -independent regions during maximal vasodilation. Arteriolar length density in collateral-dependent myocardium was 80% greater in AM+BC than AM dogs. Capillary length density in collateral-dependent region of AM dogs was lower than CON but normal in AM+BC dogs. The angiopoietin receptor Tie-2 increased in collateral-dependent regions of AM and AM+BC groups, whereas vascular endothelial growth factor increased in collateral-dependent and -independent regions only in AM+BC dogs.

Conclusions: Chronic bradycardia during gradual coronary artery occlusion facilitates angiogenesis/arteriogenesis in collateral-dependent myocardium and preserves maximal perfusion.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/01.ATV.0000179598.57819.77DOI Listing
October 2005

Reduction of heart rate by chronic beta1-adrenoceptor blockade promotes growth of arterioles and preserves coronary perfusion reserve in postinfarcted heart.

Am J Physiol Heart Circ Physiol 2005 Jun 28;288(6):H2684-93. Epub 2005 Jan 28.

Dept. of Anatomy and Cell Biology, Carver College of Medicine, 1-402 Bowen Science Bldg., Univ. of Iowa, Iowa City, IA 52242, USA.

Adequate growth of coronary vasculature in the remaining left ventricular (LV) myocardium after myocardial infarction (post-MI) is a crucial factor for myocyte survival and performance. We previously demonstrated that post-MI coronary angiogenesis can be stimulated by bradycardia induced with the ATP-sensitive K(+) channel antagonist alinidine. In this study, we tested the hypothesis that heart rate reduction with beta-blockade may also induce coronary growth in the post-MI heart. Transmural MI was induced in 12-mo-old male Sprague-Dawley rats by occlusion of the left anterior descending coronary artery. Bradycardia was induced by administration of the beta-adrenoceptor blocker atenolol (AT) via drinking water (30 mg/day). Three groups of rats were compared: 1) control/sham (C/SH), 2) MI, and 3) MI + AT. In the MI + AT rats, heart rate was consistently reduced by 25-28% compared with C/SH rats. At 4 wk after left anterior descending coronary ligation, infarct size was similar in MI and MI + AT rats (67.1 and 61.5%, respectively), whereas a greater ventricular hypertrophy occurred in bradycardic rats, as indicated by a higher ventricular weight-to-body weight ratio (3.4 +/- 0.1 vs. 2.8 +/- 0.1 mg/g in MI rats). Analysis of LV function revealed a smaller drop in ejection fraction in the MI + AT than in the MI group ( approximately 24 vs. approximately 35%). Furthermore, in MI + AT rats, maximal coronary conductance and coronary perfusion reserve were significantly improved compared with the MI group. The better myocardial perfusion indexes in MI + AT rats were associated with a greater increase in arteriolar length density than in the MI group. Thus chronic reduction of heart rate induced with beta-selective blockade promotes growth of coronary arterioles and, thereby, facilitates regional myocardial perfusion in post-MI hearts.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/ajpheart.01047.2004DOI Listing
June 2005

Stretch induces upregulation of key tyrosine kinase receptors in microvascular endothelial cells.

Am J Physiol Heart Circ Physiol 2004 Dec;287(6):H2739-45

Dept. of Anatomy and Cell Biology, 1-402, Bowen Science Bldg., Univ. of Iowa, Iowa City, IA 52242, USA.

We previously demonstrated that cyclic stretch of cardiac myocytes activates paracrine signaling via vascular endothelial growth factor (VEGF) leading to angiogenesis. The present study tested the hypothesis that cyclic stretch upregulates tyrosine kinase receptors in rat coronary microvascular endothelial cells (RCMEC) and human umbilical vein endothelial cells (HUVEC). VEGF receptor-2 (Flk-1) protein levels increased in HUVEC and RCMEC in a time-dependent manner, but the increase occurred much earlier in RCMEC than in HUVEC. The enhancement of Flk-1 protein level was not inhibited by addition of VEGF neutralizing antibodies, indicating that VEGF is not involved in stretch-induced Flk-1 expression. VEGF receptor-1 (Flt-1) protein and mRNA were not changed by stretch. However, Tie-2 and Tie-1 protein levels increased in RCMEC. Angiopoietin-1 and -2, the ligands for Tie-2, increased in cardiac myocytes subjected to cyclic stretch but were not affected by stretch in endothelial cells (EC). Stretch or incubation of RCMEC with VEGF increased cell proliferation moderately, whereas stretch + VEGF had an additive effect on proliferation. Mechanical stretch induces upregulation of the key tyrosine kinase receptors Flk-1, Tie-2, and Tie-1 in vascular EC, which underlies the increase in sensitivity of EC to growth factors and, therefore, facilitates angiogenesis. These in vitro findings support the concept that stretch of cardiac myocytes and EC plays a key role in coronary angiogenesis.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/ajpheart.00410.2004DOI Listing
December 2004

Growth factor activation in myocardial vascularization: therapeutic implications.

Mol Cell Biochem 2004 Sep;264(1-2):3-11

Department of Anatomy and Cell Biology, University of Iowa, Iowa City, IA 52242, USA.

A rapid growth of the coronary vasculature occurs during prenatal and early postnatal periods as precursor cells from the epi- and sub-epicardium differentiate, migrate and form vascular structures (vasculogenesis) which then fuse, branch and in some cases recruit cells to form three tunics (angiogenesis). These processes are tightly controlled by temporally and spatially expressed growth factors which are stimulated by metabolic and mechanical factors. The process of angiogenesis in the myocardium is not limited to developmental periods of life, but may occur when the heart is challenged by enhanced loading conditions or during hypoxia or ischemia. This review focuses on the activation of growth factors by metabolic and mechanical stimuli in the developing heart and in the adult heart undergoing adaptive responses. Experimental studies support the hypotheses that both metabolic (hypoxia) and mechanical (stretch) factors serve as powerful stimuli for the up-regulation of growth factors which facilitate angiogenesis and arteriogenesis. Both hypoxia and stretch are powerful inducers of VEGF and its receptors, and provide for paracrine and autocrine signaling. In addition to the VEGF family, bFGF and angiopoietins play major roles in myocardial vascularization. Sufficient evidence supports the hypothesis that mechanical (e.g., bradycardia) and metabolic (e.g., thyroxine analogs) may provide effective non-invasive angiogenic therapies for the ischemic and post-infarcted heart.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1023/b:mcbi.0000044369.88528.a3DOI Listing
September 2004

TGF-beta1, -beta2 and -beta3 cooperate to facilitate tubulogenesis in the explanted quail heart.

J Vasc Res 2004 Nov-Dec;41(6):491-8. Epub 2004 Oct 28.

Department of Anatomy and Cell Biology and Cardiovascular Center, University of Iowa, Iowa City, IA 52242, USA.

Background: Transforming growth factor-beta (TGF-beta) isoforms have been implicated as both pro- and anti-angiogenic modulators. In this study we addressed the roles of TGF-beta isoforms on coronary tubulogenesis.

Methods: Embryonic (E6) quail ventricular specimens were explanted onto collagen gels allowing endothelial cells to migrate and form vascular tubes. Growth factors and/or neutralizing growth factor antibodies were added to the cultures. Endothelial cells were identified using a quail endothelial cell marker, QH1. Image analysis was used to quantify aggregate tube length.

Results: Addition of any isoform (TGF-beta(1), TGF-beta(2) or TGF-beta(3)) virtually prevented tubulogenesis (>95% inhibition), while stimulation of tubulogenesis occurred by adding neutralizing antibodies to TGF-beta(3), but not to TGF-beta(1) or -beta(2). When all three isoforms were added, tubulogenesis was enhanced, indicating the key role of TGF-beta(3). Documentation of the inhibitory effect of TGF-beta isoforms on tubulogenesis is further supported by our experiments in which the marked enhancement of tube formation by bFGF and VEGF was negated when exogenous TGF-beta(1), -beta(2), or -beta(3) were added to the cultures.

Conclusions: (1) TGF-beta(1), -beta(2) and -beta(3) each inhibits angiogenesis; (2) cooperation between the three TGF-beta isoforms and other angiogenic factors is essential for the regulation of normal tubulogenesis and (3) the stimulatory effect of VEGF or bFGF on tubulogenesis is negated by exogenous TGB-betas.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1159/000081805DOI Listing
January 2005

Bradycardia induces angiogenesis, increases coronary reserve, and preserves function of the postinfarcted heart.

Circulation 2004 Aug 9;110(7):796-802. Epub 2004 Aug 9.

Department of Anatomy and Cell Biology, University of Iowa Carver College of Medicine, Iowa City, IA 52242, USA.

Background: We tested the hypothesis that induction of chronic bradycardia would trigger an upregulation of key growth factors and receptors, which would then lead to angiogenesis and improve coronary reserve in the left ventricle after myocardial infarction.

Methods And Results: Bradycardia was induced in rats by administering alinidine via osmotic pumps beginning 1 day after coronary artery ligation. Echocardiographic analysis was conducted before and after treatment. Morphometric analysis was used in perfusion-fixed hearts to document arteriolar and capillary growth. Western blots were used to evaluate growth factor and receptor changes. During the first week of treatment, vascular endothelial growth factor (VEGF), VEGF receptor 1 (Flt-1), and basic fibroblast growth factor proteins were higher in the treated group, whereas VEGF receptor 2 (Flk-1), angiopoietin-1, and angiopoietin-2 were not affected by treatment. After 3 weeks, VEGF protein remained elevated, and bradycardia was associated with a higher capillary length density in the border (40%) and remote (14%) regions and a higher arteriolar length density in the septum (62%), despite a greater increase in left ventricular mass. Although arteriolar length density increased in all size classes, the greatest increase occurred in the smallest (terminal) arterioles. This vascular growth was associated with a 23% greater coronary reserve. Echocardiography revealed a smaller increase in ventricular volume and a greater preservation of ejection fraction in rats treated with bradycardia.

Conclusions: Pharmacologic induction of bradycardia enhances vascularity and coronary reserve, preserves function of surviving myocardium, and therefore, is a noninvasive, therapeutic avenue that provides an alternative to gene therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1161/01.CIR.0000138933.85923.36DOI Listing
August 2004

DITPA stimulates arteriolar growth and modifies myocardial postinfarction remodeling.

Am J Physiol Heart Circ Physiol 2004 May;286(5):H1994-2000

Department of Anatomy and Cell Biology, University of Iowa, Iowa City, Iowa 52242, USA.

Myocardial infarction (MI) is characterized by ventricular remodeling, hypertrophy of the surviving myocardium, and an insufficient angiogenic response. Thyroxine is a powerful stimulus for myocardial angiogenesis. Male rats that underwent coronary artery ligation and subsequent MI were given 3,5-diiodothyropropionic acid (DITPA; MI+DITPA group) during a 3-wk period. We evaluated ventricular remodeling using echocardiography and histology and myocardial vessel growth using image analysis. Protein expression was assessed using Western blotting and immunohistochemistry. This study tested the hypothesis that the thyroxine analog DITPA facilitates angiogenesis and influences postinfarction remodeling in the surviving hypertrophic myocardium. The increase in the region of akinesis (infarct expansion) was blunted in the MI+DITPA rats compared with the MI group (3 vs. 21%); the treated rats had smaller percent increases in the left ventricular (LV) volume (64 +/- 14 vs. 95 +/- 12) and the LV volume-to-mass ratio (47 +/- 13 vs. 84 +/- 10) as well as a blunted decrease in ejection fraction (-9 +/- 8 vs. -30 +/- 7%). Arteriolar length density was higher after treatment in the largest (>50% of the free wall) infarcts (64 +/- 3 vs. 43 +/- 7). Angiogenic growth factors [vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF)] and the angiopoietin receptor tyrosine kinase with immunoglobulin and epidermal growth factor homology domains (Tie-2) values were elevated during the first week after infarction. DITPA did not cause additional increases in VEGF or Tie-2 values but did induce an increase in bFGF value after 3 days of treatment. This study provides the first evidence for an anatomical basis, i.e., attenuated ventricular remodeling and arteriolar growth, for improved function attributed to DITPA therapy of the infarcted heart. The favorable influences of DITPA on LV remodeling after large infarction are principally due to border zone preservation.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/ajpheart.00991.2003DOI Listing
May 2004

Mechanical, cellular, and molecular factors interact to modulate circulating endothelial cell progenitors.

Am J Physiol Heart Circ Physiol 2004 May 8;286(5):H1985-93. Epub 2004 Jan 8.

Department of Exercise Science, University of Iowa, Iowa City, Iowa 52242, USA.

It appears that there are two classes of human circulating endothelial cell (EC) progenitors, CD34+ and CD34-CD14+ cells. Attention has focused on CD34+ cells, yet CD34-CD14+ monocytic cells are far more abundant and may represent the most common class of circulating EC progenitor. Little is known about molecular or physiological factors that regulate putative CD34-CD14+ EC progenitor function, although factors secreted by other blood and cardiovascular cells to which they are exposed probably affect their behavior. Hypoxia and stretch are two important physiological stimuli known to trigger growth factors in cardiovascular cells and accordingly may modulate EC progenitors. To investigate the impact of these environmental parameters on EC progenitors, EC production in CD34-CD14+ cultures was evaluated. Our data indicate that neither stretch nor hypoxia alters EC production by EC progenitors directly but do so indirectly through their effects on cardiovascular cells. Conditioned media (CM) from coronary artery smooth muscle cells inhibit EC production in culture, and this inhibition is stronger if the coronary smooth muscle cells have been subjected to cyclic stretch. In contrast, cardiomyocyte CM increases EC cell number, an effect that is potentiated if the myocytes have been subjected to hypoxia. Significantly, EC progenitor responses to CM are altered by the presence of CD34-CD14- peripheral blood mononuclear cells (PBMCs). Moreover, CD34-CD14- PBMCs attenuate EC progenitor responsiveness to the angiogenic factors basic fibroblast growth factor (FGF-2), vascular endothelial cell growth factor-A165, and erythropoietin while inducing EC progenitor death in the presence of transforming growth factor-beta1 in vitro
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1152/ajpheart.00431.2003DOI Listing
May 2004

Hypoxic induction of myocardial vascularization during development.

Adv Exp Med Biol 2003 ;543:139-49

Department of Anatomy and Cell Biology, University of Iowa, Iowa City 52242, USA.

The development of the heart is closely linked to its temporally and spatially regulated vascularization. Hypoxia has been shown to stimulate myocardial capillary growth and improve myocardial perfusion during reperfusion in postnatal animals exposed to chronic or intermittent exposure to hypobaria. Vascular endothelial growth factor (VEGF) is up-regulated by hypoxia via HIF-1alpha, and these two molecules are colocalized with presumptive regions of hypoxia. VEGF up-regulation in embryonic and fetal hearts correlates with vascular tube formation which progresses from an epicardial to endocardial direction prior to the establishment of a functional coronary circulation. Our studies on explanted embryonic quail hearts indicate that vascular tube formation is enhanced by hypoxia (5-10% O2) and inhibited by hyperoxia. Three splice variants of VEGF (122, 126, 190) were found to increase and decrease with hypoxia and hyperoxia, respectively. While VEGF synthesis is stimulated by hypoxia, there are differences in the vascular patterning between exogenous VEGF-induced vascularization and that induced by hypoxia. Thus, other, yet to be identified, molecules are recruited by hypoxia. Acute hypoxia selectively enhances at least three splice variants of VEGF-A, and also selectively up-regulates VEGFR-1 (flt-1). However, we suggest that VEGF-B, a ligand for VEGFR-1 may contribute to embryonic myocardial vascularization, since we have shown that it plays a key role in this process under normoxic conditions. A second mechanism by which hypoxia may play a role in vascularization of the heart is via its vasodilatory effects, once the coronary circulation is functional. Increased blood flow serves as a mechanical (stretch) trigger for activation of VEGF and its receptors. In sum, there is evidence that a relative hypoxia provides both metabolic and mechanical stimuli for vascular growth in the developing heart.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/978-1-4419-8997-0_10DOI Listing
February 2004