(Hypertension. 2007;50:531.)
© 2007 American Heart Association, Inc.
Original Articles |
From the Divisions of Genetic Therapeutics (T.I., R.U., M.U., H.M., A.K., K.O.), Cardiovascular Medicine (T.I., H.M., K.S.), and Cell and Molecular Medicine (J.M.,Y.S.), Jichi Medical University, Tochigi, Japan; the Department of Molecular Therapy (T.O.), National Institute of Neuroscience, National Center of Neurology and Psychiatry, Tokyo, Japan; and the Department of Organ Regeneration (M.T., U.I.), Shinshu University Graduate School of Medicine, Matsumoto, Japan.
Correspondence to Takayuki Ito or Keiya Ozawa, Division of Genetic Therapeutics, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan. E-mail titou{at}jichi.ac.jp or kozawa@jichi.ac.jp
| Abstract |
|---|
|
|
|---|
increased in a vector dose-dependent manner. At this time point, the PGIS transduction (1x1010 genome copies per body) significantly decreased mean pulmonary arterial pressure (33.9±2.4 versus 46.1±3.0 mm Hg; P<0.05), pulmonary vascular resistance (0.26±0.03 versus 0.41±0.03 mm Hg · mL–1 · min–1· kg–1; P<0.05), and medial thickness of the peripheral pulmonary artery (14.6±1.5% versus 23.5±0.5%; P<0.01) as compared with the controls. Furthermore, the PGIS-transduced rats demonstrated significantly improved survival rates as compared with the controls (100% versus 50%; P<0.05) at 8 weeks postmonocrotaline administration. An intramuscular injection of AAV-PGIS prevents monocrotaline-pulmonary arterial hypertension in rats and provides a new therapeutic alternative for preventing pulmonary arterial hypertension in humans.
Key Words: hypertension pulmonary gene therapy remodeling prostacyclin synthase
| Introduction |
|---|
|
|
|---|
In this study, we used an adenoassociated virus (AAV) vector together with an intramuscular approach to obtain more efficient PGI2 expression. AAV vectors permit efficient and sustained gene expression in nondividing skeletal muscle cells with minimal inflammatory and immune responses. We reported previously that a stable serum concentration of a secretory protein was achieved over a 1-year period by using a single intramuscular injection of several AAV vector (AAV2 and AAV5) serotypes in mice.7 Currently, AAV1 is one of the most efficient serotypes for muscle transduction.8,9 Single subcutaneous injection of a pyrrolizidine alkaloid, namely, monocrotaline (MCT), produces severe PAH and PA remodeling in rats. We examined the effects of sustained PGIS expression in preventing PAH development and progression by means of this widely used model and an AAV1 vector.
| Methods |
|---|
|
|
|---|
AAV-PGIS Production and PGI2 Expression
We developed a recombinant AAV1-based vector containing the human PGIS or eGFP gene controlled by a modified chicken ß-actin promoter with a cytomegalovirus immediate-early enhancer (AAV-PGIS or AAV-eGFP) to obtain efficient transgene expression in skeletal muscle cells. The AAV vectors were prepared according to the previously described 3-plasmid transfection adenovirus-free protocol with minor modifications for enabling the use of an active gassing system.10,11 In brief, 60% confluent HEK293 cells that were incubated in a large culture vessel with active air circulation were cotransfected with phPGIS, AAV-1 chimeric helper plasmid (p1RepCap), and adenoviral helper plasmid pAdeno (Avigen Inc). The crude viral lysate was purified with 2 rounds of cesium chloride 2-tier centrifugation.12 The titer of the viral stock was determined against plasmid standards by real-time PCR with primers 5'-CCCGCGAGGTTGTGGTGGAC-3' and 5'-ATGGGCGGATGCGGTAGC-3'; subsequently, the stock was dissolved in a buffer (50 mmol/L of HEPES [pH 7.4] and 0.15 mol/L of NaCl [HN buffer]) before infection. The HEK293 cells cultured in 6-well plates containing DMEM and nutrient mixture F12 with 5% FCS were infected with AAV-PGIS at 1x104 genome copies per cell to evaluate PGI2 expression in vitro, and the supernatant was harvested after 72 hours. Concentrations of 6-keto-prostaglandin F1
(6-keto-PGF1
) in plasma or culture media were determined by enzyme immunoassay (R&D Systems) according to the manufacturers instructions. The minimum detectable dose of the assay was <1.4 pg/mL. Interassay and intra-assay precision of the kit was <10%.
Animal Models
All of the animal experiments were approved by the Jichi Medical University ethics committee and were performed in accordance with the National Institutes of Health Guide for the Care and Use of Laboratory Animals. To evaluate the efficiency of gene expression in vivo, AAV-eGFP (200 µL; 1x1011 gene copies per body) or AAV-PGIS (200 µL; 1x1010 to 1x1011 gene copies per body) was injected into the bilateral anterior tibial muscles (n=3 each) of 3-week–old male Wistar rats (Clea Japan Inc) weighing 45 to 55 g. For hemodynamics and histological analyses, the rats were divided into 4 groups: sham rats that were administered the HN buffer (group 1, negative control [NC] group; n=4); MCT-PAH rats administered the HN buffer (group 2, MCT group; n=6); MCT rats administered AAV-eGFP (group 3, MCT+eGFP group; n=6); and MCT rats administered AAV-PGIS (group 4, MCT+PGIS group; n=10). After the anesthesia with spontaneous inhalation of 1% isoflurane, the rats in groups 3 and 4 were intramuscularly injected with AAV-eGFP or AAV-PGIS (1x1010 gene copies per body), whereas those in groups 1 and 2 were injected with the HN buffer (200 µL). MCT (Wako Pure Chemicals) was dissolved in 0.1 N HCl, and the pH was adjusted to 7.4 with 1.0 N NaOH. After the anesthesia with spontaneous inhalation of 1% isoflurane, all of the rats except for those in the NC group were injected subcutaneously with MCT (40 mg/kg) 4 weeks after the injecting the vector. Blood samples were collected from the tail vein on ethylenediamine tetraacetic acid tubes, and the concentrations of the leukocytes, platelets, hematocrit, alanine aminotransferase, and creatinine were determined by standard procedures.
Hemodynamics Analysis
Four weeks after the MCT injection, the rats were anesthetized with spontaneous inhalation of 1% isoflurane, and a tracheotomy was performed. Then, they were mechanically ventilated with 1% isoflurane (tidal volume, 10 mL/kg; respiratory rate, 30 breaths per minute) through a tracheostomy. After the thoracic cavity was opened using a midsternal approach, 2F high-fidelity manometer-tipped catheters (SPC-320; Millar Instruments Inc) were inserted directly into the right or left ventricle, and an ultrasonic flow probe (flow probe 2.5S176; Transonic Systems Inc) was placed on the ascending root of the aorta. The heart rate, mean pulmonary arterial pressure (mPAP), aortic systolic arterial pressure, left ventricular end-diastolic pressure (LVEDP), and mean aortic flow indicating the cardiac output (CO) were measured. Cardiac indices (CI) and pulmonary vascular resistance (PVR) were calculated using the following formula: CI (mL · min–1 · kg–1)=CO/body weight, PVR (mm Hg · mL–1 · min–1 · kg–1)=(mPAP–LVEDP)/CI.
Ventricular Weight Measurement and Morphometric Analysis of the PA
After the hemodynamic analysis, the rats were killed with an overdose (5%) of isoflurane through a tracheostomy. Their lungs were perfused with 5 mL of saline followed by 10 mL of cold 4% paraformaldehyde. Each ventricle and the lungs were then excised, dissected free, and weighed. The weight ratio of the right ventricle to the left ventricle plus septum [RV/(LV+S)] was calculated as an index of right ventricular hypertrophy (RVH). The lung tissues were fixed overnight at 4°C in 4% paraformaldehyde and frozen in Tissue-Tek OCT compound (Sakura Finetechnical Co) at –20°C. Hematoxylin and eosin staining was performed on 7-µm–thick sections that were subsequently examined using light microscopy. A morphometric analysis was performed on a PA having an external diameter of 25 to 50 µm or 51 to 100 µm. The medial wall thickness was calculated using the following formula: medial thickness (%)=medial wall thickness/external diameterx100.13 For the quantitative analysis, 30 vessels of each rat were measured and averaged randomly by the 2 external observers.
Survival Analysis
The 3-week–old Wistar rats were divided into 3 groups (MCT, MCT+eGFP, and MCT+PGIS; n=8 each). After the anesthesia with spontaneous inhalation of 1% isoflurane, the rats in the MCT+eGFP or MCT+PGIS group were intramuscularly injected with AAV-eGFP or AAV-PGIS at 1x1010 genome copies per body, respectively. Under the same anesthetic condition, all of the rats were injected subcutaneously with MCT (40 mg/kg) at 4 weeks after injecting the vector. The survival rate was estimated from the date of the MCT administration until death or after 8 weeks of the injection. Survival curves were analyzed using the Kaplan-Meier method and compared by log-rank tests.
Statistical Analysis
The statistical analysis and correlations were performed using StatView (Abacus Concepts, Inc). Data are presented as mean±SEM. Differences in parameters were evaluated using ANOVA combined with Fishers test. A value of P<0.05 was considered statistically significant.
| Results |
|---|
|
|
|---|
, a stable metabolite of PGI2, in culture supernatants as compared with that without vector infection (Figure 1B).
|
AAV Vector-Mediated Systemic PGI2 Expression in the Rats
Four weeks after the injection of AAV vectors (1x1010 genome copies per body), the PGIS-transduced rats began exhibiting significant increases in the plasma 6-keto-PGF1
levels as compared with the control rats (Figure 2A). Eight weeks after the injection, the 6-keto-PGF1
levels increased further in a vector dose-dependent manner in the treated rats (Figure 2B) as compared with the untreated controls (6.68±1.33 versus 1.62±0.30 ng/mL, 1x1011 versus 1x1010 genome copies per body, respectively; P<0.05; n=3 each). The vectors at 1x1010 genome copies per body were used for all of the subsequent experiments. In contrast, injection of 1x1011 genome copies per body of AAV-eGFP produced no significant change in the 6-keto-PGF1
levels.
|
Effects of PGI2 Expression on Hemodynamics and RVH
Four weeks after the MCT administration, the mPAP levels were significantly elevated in the treated rats as compared with the untreated controls (Figure 3A). Treatment with AAV-PGIS but not AAV-eGFP significantly inhibited this increase (Figure 3A). In addition, the expression of PGI2 significantly mitigated an increase in PVR and a decrease in CI that were induced by MCT (Figure 3B and 3C, respectively); however, it produced no significant changes in the heart rate and aortic systolic arterial pressure (Table). PGI2 expression also had a beneficial effect on RVH. Treatment with AAV-PGIS but not AAV-eGFP significantly inhibited the MCT-induced increase in RV/(LV+S) (Figure 3D).
|
|
Effects on Medial Hypertrophy of the PA
Medial hypertrophy is a hallmark of pathological vascular remodeling in PAH. Four weeks after the MCT injection, the medial thickness of the PA was greater in the MCT-administered rats than in the untreated controls (Figure 4A). Treatment with AAV-PGIS but not AAV-eGFP prevented the MCT-induced increase in the percentage of medial thickness significantly (Figure 4B, 25 to 50 µm; Figure 4C, 51 to 100 µm in external diameter).
|
Effects on the Survival of the MCT-PAH Rats and Their Organ Dysfunctions
The PGIS-transduced rats exhibited significantly improved survival rates as compared with the eGFP-transduced rats (Figure 5). The MCT administration produced a slight but not significant decrease in the body weight of the rats, and PGIS gene transfer prevented this decrease. Although the MCT group showed only a slight but not significant increase in the leukocyte count and serum alanine aminotransferase levels as compared with the NC group, the AAV-PGIS treatment caused no additional change in these parameters (Table).
|
| Discussion |
|---|
|
|
|---|
The expression of PGI2 and PGIS decreased in the remodeled PAs of the idiopathic PAH patients.14,15 Impaired PGI2 synthesis resulting from a decrease in PGIS expression may be implicated in the pathogenesis of PAH. In fact, continuous intravenous infusion of exogenous PGI2 markedly lowers PVR and improves survival in PAH patients. However, this system requires lifelong infusion with a central venous catheter because of the short biological half-life of PGI2. Furthermore, because this system is associated with life-threatening complications (eg, shock and sepsis) that may result in poor survival and quality of life of patients, stable production of endogenous PGI2 would be more desirable. Consistent with previous gene therapy studies, our strategy presented high levels of endogenous PGI2 expression. In addition, this strategy caused no systemic hypotension and hyperdynamic heart failure, which are the major adverse effects arising from uncontrolled blood levels during intravenous delivery of exogenous PGI2.3,4,6
In this study, we used an AAV serotype 1 vector because it is effective not only in efficient muscle transduction but also in long-term secretion of therapeutic proteins into the systemic circulation. The cDNA for human PGIS shares a high identity with its rat counterpart.16 In fact, the administration of a plasmid or hemagglutinating virus of the Japan-liposome vector encoding human PGIS successfully ameliorated MCT-PAH. However, the use of these vectors requires repeated administration for achieving sustained gene expression.3–5 In contrast, the AAV vector used in this study achieved PGIS expression with a single intramuscular injection, and this expression was sustained for 1 year.7
Furthermore, gene transfer was believed to be safer when performed via an intramuscular approach as opposed to the intratracheal or intrahepatic approaches.6 Currently, researchers are using adenoviral gene transfer in most clinical trials because of its high efficiency for gene expression. However, the potential toxic effects of adenoviruses, such as strong immunogenicity, are well known. In contrast, the intramuscular administration of AAV vectors is a promising strategy for delivering therapeutic proteins safely and efficiently, and their use has been examined in clinical trials for hemophilia.17
Although PGI2 is known to be a short-acting vasodilator, recent studies have shown its antiremodeling effects when used in high doses. The administration of PGI2 analogues cicaprost and iloprost in high concentrations (>10–7 mol/L) inhibits mitogen-induced proliferation of rat primary PA smooth muscle cells in a cAMP-dependent manner.18 Interestingly, another PGI2 analogue, treprostinil, also inhibits the proliferation of human and mouse primary lung fibroblasts through the activation of a peroxisome proliferator-activated receptor-ß/
when used in equivalent doses.19 These observations suggest that high levels of PGI2 may attenuate PA remodeling in vivo through antiproliferative effects. Consistent with previous studies, we demonstrated that high levels of endogenous PGI2 successfully attenuated medial hypertrophy of the PA.3,4,6 To discover new drug targets, the roles of peroxisome proliferator-activated receptors and high-level PGI2 in PAH therapy should be determined, because peroxisome proliferator-activated receptors are associated with many inflammatory and proliferative disorders, including PAH.2,20
Finally, we will discuss the clinical implications and limitations of this study. Consistent with previous studies, maximum gene expression was noted 6 to 8 weeks after the intramuscular injection of AAV vectors. AAV-PGIS was injected 4 weeks before MCT administration for the transgene expression to reach plateau levels when MCT-PAH was fully developed (3 to 4 weeks after the injection). Our results are completely based on a preventive protocol, which may be rare in a clinical setting. However, PGI2 is an established therapeutic molecule, and the advantage of early initiation of PGI2 therapy for improving survival in patients with idiopathic PAH has been demonstrated in a large clinical trial.21 These observations convinced us to propose the possible preemptive use of AAV-PGIS as a strategy to maintain basal levels of PGI2 in patients with mild symptoms of PAH or in those identified as high-risk subjects who have not experienced PAH. As an alternative, the combined use of AAV-PGIS and an initial infusion of intravenous PGI2 might be promising; the intravenous infusion should be tapered when sufficient levels of PGI2 are attained. To evaluate the efficacy of AAV-PGIS in a therapeutic protocol (ie, vector injection after the development of PAH), use of a chronic hypoxic PAH model or newly developed self-complementary AAV vectors that can express transgenes earlier than the conventional vectors should be considered.22
Perspectives
The present study has demonstrated that the single intramuscular injection of AAV-PGIS achieved a sustained expression of PGI2. This expression retarded the progression of MCT-PAH in rats without causing significant adverse effects. Thus, this strategy provides a new therapeutic alternative for PAH patients. However, the system in this study lacks the ability to regulate excessive transgene expression. Therefore, regulatory mechanisms to ensure adequate gene expression should be established to facilitate successful translation of this strategy in a clinical setting.
| Acknowledgments |
|---|
Sources of Funding
This work was supported in part by grants from the Ministry of Health, Labor and Welfare of Japan; Grants-in-Aid for Scientific Research; grant for the 21st Century Centes of Excellence Program; "High-Tech Research Center" Project for Private Universities, matching fund subsidy, from the Ministry of Education, Culture, Sports, Science and Technology of Japan; and the Research Award to Jichi Medical School Graduate Student.
Disclosures
None.
Received March 25, 2007; first decision April 13, 2007; accepted June 22, 2007.
| References |
|---|
|
|
|---|
2. Ito T, Ozawa K, Shimada K. Current drug targets and future therapy of pulmonary arterial hypertension. Curr Med Chem. 2007; 14: 719–733.[CrossRef][Medline] [Order article via Infotrieve]
3. Nagaya N, Yokoyama C, Kyotani S, Shimonishi M, Morishita R, Uematsu M, Nishikimi T, Nakanishi N, Ogihara T, Yamagishi M, Miyatake K, Kaneda Y, Tanabe T. Gene transfer of human prostacyclin synthase ameliorates monocrotaline-induced pulmonary hypertension in rats. Circulation. 2000; 102: 2005–2010.
4. Suhara H, Sawa Y, Fukushima N, Kagisaki K, Yokoyama C, Tanabe T, Ohtake S, Matsuda H. Gene transfer of human prostacyclin synthase into the liver is effective for the treatment of pulmonary hypertension in rats. J Thorac Cardiovasc Surg. 2002; 123: 855–861.
5. Ono M, Sawa Y, Mizuno S, Fukushima N, Ichikawa H, Bessho K, Nakamura T, Matsuda H. Hepatocyte growth factor suppresses vascular medial hyperplasia and matrix accumulation in advanced pulmonary hypertension of rats. Circulation. 2004; 110: 2896–2902.
6. Tahara N, Kai H, Niiyama H, Mori T, Sugi Y, Takayama N, Yasukawa H, Numaguchi Y, Matsui H, Okumura K, Imaizumi T. Repeated gene transfer of naked prostacyclin synthase plasmid into skeletal muscles attenuates monocrotaline-induced pulmonary hypertension and prolongs survival in rats. Hum Gene Ther. 2004; 15: 1270–1278.[CrossRef][Medline] [Order article via Infotrieve]
7. Yoshioka T, Okada T, Maeda Y, Ikeda U, Shimpo M, Nomoto T, Takeuchi K, Nonaka-Sarukawa M, Ito T, Takahashi M, Matsushita T, Mizukami H, Hanazono Y, Kume A, Ookawara S, Kawano M, Ishibashi S, Shimada K, Ozawa K. Adeno-associated virus vector-mediated interleukin-10 gene transfer inhibits atherosclerosis in apolipoprotein E-deficient mice. Gene Ther. 2004; 11: 1772–1779.[CrossRef][Medline] [Order article via Infotrieve]
8. Chen S, Kapturczak MH, Wasserfall C, Glushakova OY, Campbell-Thompson M, Deshane JS, Joseph R, Cruz PE, Hauswirth WW, Madsen KM, Croker BP, Berns KI, Atkinson MA, Flotte TR, Tisher CC, Agarwal A. Interleukin 10 attenuates neointimal proliferation and inflammation in aortic allografts by a heme oxygenase-dependent pathway. Proc Natl Acad Sci U S A. 2005; 102: 7251–7256.
9. Mu W, Ouyang X, Agarwal A, Zhang L, Long DA, Cruz PE, Roncal CA, Glushakova OY, Chiodo VA, Atkinson MA, Hauswirth WW, Flotte TR, Rodriguez-Iturbe B, Johnson RJ. IL-10 suppresses chemokines, inflammation, and fibrosis in a model of chronic renal disease. J Am Soc Nephrol. 2005; 16: 3651–3660.
10. Matsushita T, Elliger S, Elliger C, Podsakoff G, Villarreal L, Kurtzman GJ, Iwaki Y, Colosi P. Adeno-associated virus vectors can be efficiently produced without helper virus. Gene Ther. 1998; 5: 938–945.[CrossRef][Medline] [Order article via Infotrieve]
11. Okada T, Nomoto T, Yoshioka T, Nonaka-Sarukawa M, Ito T, Ogura T, Iwata-Okada M, Uchibori R, Shimazaki K, Mizukami H, Kume A, Ozawa K. Large-scale production of recombinant viruses by use of a large culture vessel with active gassing. Hum Gene Ther. 2005; 16: 1212–1218.[CrossRef][Medline] [Order article via Infotrieve]
12. Okada T, Nomoto T, Shimazaki K, Lijun W, Lu Y, Matsushita T, Mizukami H, Urabe M, Hanazono Y, Kume A, Muramatsu S, Nakano I, Ozawa K. Adeno-associated virus vectors for gene transfer to the brain. Methods. 2002; 28: 237–247.[CrossRef][Medline] [Order article via Infotrieve]
13. Kay JM, Keane PM, Suyama KL, Gauthier D. Angiotensin converting enzyme activity and evolution of pulmonary vascular disease in rats with monocrotaline pulmonary hypertension. Thorax. 1982; 37: 88–96.
14. Christman BW, McPherson CD, Newman JH, King GA, Bernard GR, Groves BM, Loyd JE. An imbalance between the excretion of thromboxane and prostacyclin metabolites in pulmonary hypertension. N Engl J Med. 1992; 327: 70–75.[Abstract]
15. Tuder RM, Cool CD, Geraci MW, Wang J, Abman SH, Wright L, Badesch D, Voelkel NF. Prostacyclin synthase expression is decreased in lungs from patients with severe pulmonary hypertension. Am J Respir Crit Care Med. 1999; 159: 1925–1932.
16. Miyata A, Hara S, Yokoyama C, Inoue H, Ullrich V, Tanabe T. Molecular cloning and expression of human prostacyclin synthase. Biochem Biophys Res Commun. 1994; 200: 1728–1734.[CrossRef][Medline] [Order article via Infotrieve]
17. High K. AAV-mediated gene transfer for hemophilia. Genet Med. 2002; 4: 56S–61S.[Medline] [Order article via Infotrieve]
18. Phillips PG, Long L, Wilkins MR, Morrell NW. cAMP phosphodiesterase inhibitors potentiate effects of prostacyclin analogs in hypoxic pulmonary vascular remodeling. Am J Physiol Lung Cell Mol Physiol. 2005; 288: L103–L115.
19. Ali FY, Egan K, FitzGerald GA, Desvergne B, Wahli W, Bishop-Bailey D, Warner TD, Mitchell JA. Role of prostacyclin versus peroxisome proliferator-activated receptor beta receptors in prostacyclin sensing by lung fibroblasts. Am J Respir Cell Mol Biol. 2006; 34: 242–246.
20. Ameshima S, Golpon H, Cool CD, Chan D, Vandivier RW, Gardai SJ, Wick M, Nemenoff RA, Geraci MW, Voelkel NF. Peroxisome proliferator-activated receptor gamma (PPARgamma) expression is decreased in pulmonary hypertension and affects endothelial cell growth. Circ Res. 2003; 92: 1162–1169.
21. Sitbon O, Humbert M, Nunes H, Parent F, Garcia G, Herve P, Rainisio M, Simonneau G. Long-term intravenous epoprostenol infusion in primary pulmonary hypertension: prognostic factors and survival. J Am Coll Cardiol. 2002; 40: 780–788.
22. Nathwani AC, Gray JT, McIntosh J, Ng CY, Zhou J, Spence Y, Cochrane M, Gray E, Tuddenham EG, Davidoff AM. Safe and efficient transduction of the liver after peripheral vein infusion of self-complementary AAV vector results in stable therapeutic expression of human FIX in nonhuman primates. Blood. 2007; 109: 1414–1421.
This article has been cited by other articles:
![]() |
K. R. Stenmark, B. Meyrick, N. Galie, W. J. Mooi, and I. F. McMurtry Animal models of pulmonary arterial hypertension: the hope for etiological discovery and pharmacological cure Am J Physiol Lung Cell Mol Physiol, December 1, 2009; 297(6): L1013 - L1032. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. Strassheim, S. R. Riddle, D. L. Burke, M. W. Geraci, and K. R. Stenmark Prostacyclin Inhibits IFN-{gamma}-Stimulated Cytokine Expression by Reduced Recruitment of CBP/p300 to STAT1 in a SOCS-1-Independent Manner J. Immunol., December 1, 2009; 183(11): 6981 - 6988. [Abstract] [Full Text] [PDF] |
||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Hypertension Home | Subscriptions | Archives | Feedback | Authors | Help | AHA Journals Home | Search Copyright © 2007 American Heart Association, Inc. All rights reserved. Unauthorized use prohibited. |