RESUMEN
BACKGROUND: Left ventricular hypertrophy and heart failure with preserved ejection fraction (HFpEF) are primary manifestations of the cardiorenal syndrome in patients with chronic kidney disease (CKD). Therapies that improve morbidity and mortality in HFpEF are lacking. Cell-based therapies promote cardiac repair in ischemic and non-ischemic cardiomyopathies. We hypothesized that cell-based therapy ameliorates CKD-induced HFpEF. METHODS AND RESULTS: Yorkshire pigs (n = 26) underwent 5/6 embolization-mediated nephrectomy. CKD was confirmed by increased creatinine and decreased glomerular filtration rate (GFR). Mean arterial pressure (MAP) was not different between groups from baseline to 4 weeks. HFpEF was evident at 4 weeks by increased LV mass, relative wall thickening, end-diastolic pressure, and end-diastolic pressure-volume relationship, with no change in ejection fraction (EF). Four weeks post-embolization, allogeneic (allo) bone marrow-derived mesenchymal stem cells (MSC; 1 × 107 cells), allo-kidney-derived stem cells (KSC; 1 × 107 cells), allo-cell combination therapy (ACCT; MSC + KSC; 1:1 ratio; total = 1 × 107 cells), or placebo (Plasma-Lyte) was delivered via intra-renal artery. Eight weeks post-treatment, there was a significant increase in MAP in the placebo group (21.89 ± 6.05 mmHg) compared to the ACCT group. GFR significantly improved in the ACCT group. EF, relative wall thickness, and LV mass did not differ between groups at 12 weeks. EDPVR improved in the ACCT group, indicating decreased ventricular stiffness. CONCLUSIONS: Intra-renal artery allogeneic cell therapy was safe in a CKD swine model manifesting the characteristics of HFpEF. The beneficial effect on renal function and ventricular compliance in the ACCT group supports further research of cell therapy for cardiorenal syndrome.
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Síndrome Cardiorrenal , Insuficiencia Cardíaca , Fallo Renal Crónico , Insuficiencia Renal Crónica , Células Alogénicas , Animales , Síndrome Cardiorrenal/terapia , Enfermedad Crónica , Insuficiencia Cardíaca/terapia , Humanos , Insuficiencia Renal Crónica/complicaciones , Insuficiencia Renal Crónica/terapia , Volumen Sistólico , PorcinosRESUMEN
AIMS: Sex differences impact the occurrence, presentation, prognosis, and response to therapy in heart disease. Particularly, the phenotypic presentation of patients with non-ischaemic dilated cardiomyopathy (NIDCM) differs between men and women. However, whether the response to mesenchymal stem cell (MSC) therapy is influenced by sex remains unknown. We hypothesize that males and females with NIDCM respond similarly to MSC therapy. METHODS AND RESULTS: Male (n = 24) and female (n = 10) patients from the POSEIDON-DCM trial who received MSCs via transendocardial injections were evaluated over 12 months. Endothelial function was measured at baseline and 3 months post-transendocardial stem cell injection (TESI). At baseline, ejection fraction (EF) was lower (P = 0.004) and end-diastolic volume (EDV; P = 0.0002) and end-systolic volume (ESV; P = 0.0002) were higher in males vs. females. In contrast, baseline demographic characteristics, Minnesota Living with Heart Failure Questionnaire (MLHFQ), and 6-min walk test (6MWT) were similar between groups. EF improved in males by 6.2 units (P = 0.04) and in females by 8.6 units (P = 0.04; males vs. females, P = 0.57). EDV and ESV were unchanged over time. The MLHFQ score, New York Heart Association (NYHA) class, endothelial progenitor cell-colony forming units, and serum tumour necrosis factor alpha improved similarly in both groups. CONCLUSION: Despite major differences in phenotypic presentation of NIDCM in males and females, this study is the first of its kind to demonstrate that MSC therapy improves a variety of parameters in NIDCM irrespective of patient sex. These findings have important clinical and pathophysiologic implications regarding the impact of sex on responses to cell-based therapy for NIDCM.
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Cardiomiopatía Dilatada/cirugía , Trasplante de Células Madre Mesenquimatosas , Adulto , Anciano , Biomarcadores/sangre , Cardiomiopatía Dilatada/sangre , Cardiomiopatía Dilatada/patología , Cardiomiopatía Dilatada/fisiopatología , Células Progenitoras Endoteliales/metabolismo , Células Progenitoras Endoteliales/patología , Tolerancia al Ejercicio , Femenino , Florida , Estado Funcional , Disparidades en el Estado de Salud , Humanos , Masculino , Trasplante de Células Madre Mesenquimatosas/efectos adversos , Persona de Mediana Edad , Calidad de Vida , Recuperación de la Función , Factores Sexuales , Volumen Sistólico , Factores de Tiempo , Resultado del Tratamiento , Factor de Necrosis Tumoral alfa/sangre , Función Ventricular Izquierda , Remodelación VentricularRESUMEN
BACKGROUND: Left ventricular assist device (LVAD) implantation is a lifesaving intervention in advanced heart failure. However, LVAD is not without complication. In this case, an inadvertent intraperitoneal driveline caused small bowel obstruction, subsequently requiring pexy of the driveline to the abdominal wall to avoid future complications. CASE PRESENTATION: A 37-year-old male with worsening, nonischemic, dilated cardiomyopathy underwent LVAD implantation. Postoperative day (POD) 15 he developed small bowel obstruction, and abdominal exploration showed transition point at an inadvertently placed intraperitoneal LVAD driveline. The patient was LVAD-dependent precluding removal, so the driveline was secured to the anterior abdominal wall. He subsequently improved and was discharged. CONCLUSIONS: While LVAD is increasingly common for heart failure patients, the tunneled driveline may inadvertently enter the peritoneal cavity where it can cause significant morbidity. In this case, we propose securing the driveline to the abdominal wall to prevent complications when LVAD removal is not an option.
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Remoción de Dispositivos/métodos , Ventrículos Cardíacos , Corazón Auxiliar/efectos adversos , Obstrucción Intestinal/etiología , Intestino Delgado , Complicaciones Posoperatorias/etiología , Implantación de Prótesis/efectos adversos , Adulto , Cardiomiopatías/cirugía , Humanos , Masculino , Cavidad Peritoneal , Implantación de Prótesis/métodosRESUMEN
BACKGROUND: Ischemic cardiomyopathy (ICM) and dilated cardiomyopathy (DCM) differ in histopathology and prognosis. Although transendocardial delivery of mesenchymal stem cells is safe and provides cardiovascular benefits in both, a comparison of mesenchymal stem cell efficacy in ICM versus DCM has not been done. METHODS AND RESULTS: We conducted a subanalysis of 3 single-center, randomized, and blinded clinical trials: (1) TAC-HFT (Transendocardial Autologous Mesenchymal Stem Cells and Mononuclear Bone Marrow Cells in Ischemic Heart Failure Trial); (2) POSEIDON (A Phase I/II, Randomized Pilot Study of the Comparative Safety and Efficacy of Transendocardial Injection of Autologous Mesenchymal Stem Cells Versus Allogeneic Mesenchymal Stem Cells in Patients With Chronic Ischemic Left Ventricular Dysfunction Secondary to Myocardial Infarction); and (3) POSEIDON-DCM (Percutaneous Stem Cell Injection Delivery Effects on Neomyogenesis in Dilated Cardiomyopathy). Baseline and 1-year cardiac structure and function and quality-of-life data were compared in a post hoc pooled analysis including ICM (n=46) and DCM (n=33) patients who received autologous or allogeneic mesenchymal stem cells. Ejection fraction improved in DCM by 7% (within-group, P=0.002) compared to ICM (1.5%; within-group, P=0.14; between-group, P=0.003). Similarly, stroke volume increased in DCM by 10.59 mL (P=0.046) versus ICM (-0.2 mL; P=0.73; between-group, P=0.02). End-diastolic volume improved only in ICM (10.6 mL; P=0.04) and end-systolic volume improved only in DCM (17.8 mL; P=0.049). The sphericity index decreased only in ICM (-0.04; P=0.0002). End-diastolic mass increased in ICM (23.1 g; P<0.0001) versus DCM (-4.1 g; P=0.34; between-group, P=0.007). The 6-minute walk test improved in DCM (31.1 m; P=0.009) and ICM (36.3 m; P=0.006) with no between-group difference (P=0.79). The New York Heart Association class improved in DCM (P=0.005) and ICM (P=0.02; between-group P=0.20). The Minnesota Living with Heart Failure Questionnaire improved in DCM (-19.5; P=0.002) and ICM (-6.4; P=0.03; δ between-group difference P=0.042) patients. CONCLUSIONS: Mesenchymal stem cell therapy is beneficial in DCM and ICM patients, despite variable effects on cardiac phenotypic outcomes. Whereas cardiac function improved preferentially in DCM patients, ICM patients experienced reverse remodeling. Mesenchymal stem cell therapy enhanced quality of life and functional capacity in both etiologies. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifiers: TAC-HFT: NCT00768066, POSEIDON: NCT01087996, POSEIDON-DCM: NCT01392625.
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Cardiomiopatía Dilatada/terapia , Insuficiencia Cardíaca/terapia , Trasplante de Células Madre Mesenquimatosas , Disfunción Ventricular Izquierda/terapia , Adulto , Anciano , Cardiomiopatías/etiología , Cardiomiopatías/fisiopatología , Cardiomiopatías/terapia , Cardiomiopatía Dilatada/fisiopatología , Femenino , Insuficiencia Cardíaca/etiología , Insuficiencia Cardíaca/fisiopatología , Humanos , Masculino , Persona de Mediana Edad , Infarto del Miocardio/complicaciones , Isquemia Miocárdica/complicaciones , Calidad de Vida , Ensayos Clínicos Controlados Aleatorios como Asunto , Volumen Sistólico , Disfunción Ventricular Izquierda/etiología , Disfunción Ventricular Izquierda/fisiopatología , Remodelación VentricularRESUMEN
Given the rising prevalence of cardiovascular disease worldwide and the limited therapeutic options for severe heart failure, novel technologies that harness the regenerative capacity of the heart are sorely needed. The therapeutic use of stem cells has the potential to reverse myocardial injury and improve cardiac function, in contrast to most current medical therapies that only mitigate heart failure symptoms. Nearly 2 decades and >200 trials for cardiovascular disease have revealed that most cell types are safe; however, their efficacy remains controversial, limiting the transition of this therapy from investigation to practice. Lessons learned from these initial studies are driving the design of new clinical trials; higher fidelity of cell isolation techniques, standardization of conditions, more consistent use of state of the art measurement techniques, and assessment of multiple end points to garner insights into the efficacy of stem cells. Translation to clinical trials has almost outpaced our mechanistic understanding, and individual patient factors likely play a large role in stem cell efficacy. Therefore, careful analysis of dosing, delivery methods, and the ideal patient populations is necessary to translate cell therapy from research to practice. We are at a pivotal stage in the field in which information from many relatively small clinical trials must guide carefully executed efficacy trials. Larger efficacy trials are being launched to answer questions about older, first-generation stem cell therapeutics, while novel, second-generation products are being introduced into the clinical realm. This review critically examines the current state of clinical research on cell-based therapies for cardiovascular disease, highlighting the controversies in the field, improvements in clinical trial design, and the application of exciting new cell products.
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Enfermedades Cardiovasculares/terapia , Ensayos Clínicos como Asunto , Medicina Regenerativa/métodos , Trasplante de Células Madre/métodos , Humanos , Medicina Regenerativa/tendencias , Trasplante de Células Madre/efectos adversos , Trasplante de Células Madre/tendenciasRESUMEN
BACKGROUND: The combination of autologous mesenchymal stem cells (MSCs) and cardiac stem cells (CSCs) synergistically reduces scar size and improves cardiac function in ischemic cardiomyopathy. Whereas allogeneic (allo-)MSCs are immunoevasive, the capacity of CSCs to similarly elude the immune system remains controversial, potentially limiting the success of allogeneic cell combination therapy (ACCT). OBJECTIVES: This study sought to test the hypothesis that ACCT synergistically promotes cardiac regeneration without provoking immunologic reactions. METHODS: Göttingen swine with experimental ischemic cardiomyopathy were randomized to receive transendocardial injections of allo-MSCs + allo-CSCs (ACCT: 200 million MSCs/1 million CSCs, n = 7), 200 million allo-MSCs (n = 8), 1 million allo-CSCs (n = 4), or placebo (Plasma-Lyte A, n = 6). Swine were assessed by cardiac magnetic resonance imaging and pressure volume catheterization. Immune response was tested by histologic analyses. RESULTS: Both ACCT and allo-MSCs reduced scar size by -11.1 ± 4.8% (p = 0.012) and -9.5 ± 4.8% (p = 0.047), respectively. Only ACCT, but not MSCs or CSCs, prevented ongoing negative remodeling by offsetting increases in chamber volumes. Importantly, ACCT exerted the greatest effect on systolic function, improving the end-systolic pressure-volume relation (+0.98 ± 0.41 mm Hg/ml; p = 0.016). The ACCT group had more phospho-histone H3+ (a marker of mitosis) cardiomyocytes (p = 0.04), and noncardiomyocytes (p = 0.0002) than did the placebo group in some regions of the heart. Inflammatory sites in ACCT and MSC-treated swine contained immunotolerant CD3+/CD25+/FoxP3+ regulatory T cells (p < 0.0001). Histologic analysis showed absent to low-grade inflammatory infiltrates without cardiomyocyte necrosis. CONCLUSIONS: ACCT demonstrates synergistic effects to enhance cardiac regeneration and left ventricular functional recovery in a swine model of chronic ischemic cardiomyopathy without adverse immunologic reaction. Clinical translation to humans is warranted.
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Ventrículos Cardíacos/fisiopatología , Trasplante de Células Madre Mesenquimatosas/métodos , Células Madre Mesenquimatosas/citología , Isquemia Miocárdica/terapia , Remodelación Ventricular , Animales , Modelos Animales de Enfermedad , Femenino , Ventrículos Cardíacos/diagnóstico por imagen , Inyecciones , Imagen por Resonancia Cinemagnética , Isquemia Miocárdica/diagnóstico , Isquemia Miocárdica/fisiopatología , Miocardio , Porcinos , Trasplante HomólogoRESUMEN
RATIONALE: Cell dose and concentration play crucial roles in phenotypic responses to cell-based therapy for heart failure. OBJECTIVE: To compare the safety and efficacy of 2 doses of allogeneic bone marrow-derived human mesenchymal stem cells identically delivered in patients with ischemic cardiomyopathy. METHODS AND RESULTS: Thirty patients with ischemic cardiomyopathy received in a blinded manner either 20 million (n=15) or 100 million (n=15) allogeneic human mesenchymal stem cells via transendocardial injection (0.5 cc per injection × 10 injections per patient). Patients were followed for 12 months for safety and efficacy end points. There were no treatment-emergent serious adverse events at 30 days or treatment-related serious adverse events at 12 months. The Major Adverse Cardiac Event rate was 20.0% (95% confidence interval [CI], 6.9% to 50.0%) in 20 million and 13.3% (95% CI, 3.5% to 43.6%) in 100 million (P=0.58). Worsening heart failure rehospitalization was 20.0% (95% CI, 6.9% to 50.0%) in 20 million and 7.1% (95% CI, 1.0% to 40.9%) in 100 million (P=0.27). Whereas scar size reduced to a similar degree in both groups: 20 million by -6.4 g (interquartile range, -13.5 to -3.4 g; P=0.001) and 100 million by -6.1 g (interquartile range, -8.1 to -4.6 g; P=0.0002), the ejection fraction improved only with 100 million by 3.7 U (interquartile range, 1.1 to 6.1; P=0.04). New York Heart Association class improved at 12 months in 35.7% (95% CI, 12.7% to 64.9%) in 20 million and 42.9% (95% CI, 17.7% to 71.1%) in 100 million. Importantly, proBNP (pro-brain natriuretic peptide) increased at 12 months in 20 million by 0.32 log pg/mL (95% CI, 0.02 to 0.62; P=0.039), but not in 100 million (-0.07 log pg/mL; 95% CI, -0.36 to 0.23; P=0.65; between group P=0.07). CONCLUSIONS: Although both cell doses reduced scar size, only the 100 million dose increased ejection fraction. This study highlights the crucial role of cell dose in the responses to cell therapy. Determining optimal dose and delivery is essential to advance the field, decipher mechanism(s) of action and enhance planning of pivotal Phase III trials. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifier: NCT02013674.
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Cardiomiopatías/cirugía , Trasplante de Células Madre Mesenquimatosas/métodos , Infarto del Miocardio/complicaciones , Disfunción Ventricular Izquierda/cirugía , Adulto , Anciano , Anciano de 80 o más Años , Biomarcadores/sangre , Cardiomiopatías/etiología , Cardiomiopatías/patología , Cardiomiopatías/fisiopatología , Femenino , Florida , Estado de Salud , Humanos , Masculino , Trasplante de Células Madre Mesenquimatosas/efectos adversos , Persona de Mediana Edad , Infarto del Miocardio/patología , Infarto del Miocardio/fisiopatología , Miocardio/metabolismo , Miocardio/patología , Péptido Natriurético Encefálico/sangre , Fragmentos de Péptidos/sangre , Calidad de Vida , Recuperación de la Función , Volumen Sistólico , Factores de Tiempo , Trasplante Homólogo , Resultado del Tratamiento , Disfunción Ventricular Izquierda/etiología , Disfunción Ventricular Izquierda/patología , Disfunción Ventricular Izquierda/fisiopatología , Función Ventricular Izquierda , Adulto JovenRESUMEN
BACKGROUND: Analogous to organ injury scales developed for trauma, a scoring system is needed for acute care surgery. The purpose of this study was to develop a disease severity score (DSS) for acute appendicitis, the most common surgical emergency. METHODS: A panel of acute care surgery experts reviewed the literature and developed a DSS for acute appendicitis as follows: grade 1, inflamed; Grade 2, gangrenous; Grade 3, perforated with localized free fluid; Grade 4, perforated with a regional abscess; and Grade 5, perforated with diffuse peritonitis. We applied the DSS to 1,000 consecutive patients undergoing appendectomy from 1999 to 2009 and examined its association with outcomes (mortality, length of hospital stay, incidence of in-hospital, and postdischarge complications). Of the 1,000 patients, 82 were excluded owing to negative or interval appendectomy or advanced end-stage renal disease. RESULTS: Among 918 eligible patients, the DSS distribution was Grade 1 at 62.4%, Grade 2 at 13.0%, Grade 3 at 18.7%, Grade 4 at 4.4%, and Grade 5 at 1.5%. Statistical analyses indicated a stepwise risk increase in adverse outcomes with higher DSS grades (c statistics ≥ 0.75 for all outcomes). Covariates (age, sex, and type of surgical access) did not add to the predictive power of DSS. CONCLUSION: Based on this single-institution study, the proposed appendicitis DSS seems to be a useful tool. This DSS can inform future, national efforts, which can build on the knowledge provided by the present investigation. This DSS may be useful for comparing therapeutic modalities, planning resource use, improving programs, and adjusting reimbursement LEVEL OF EVIDENCE: Epidemiologic study, level III.
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Apendicitis/clasificación , Índice de Severidad de la Enfermedad , Adulto , Apendicectomía/efectos adversos , Apendicitis/patología , Apendicitis/cirugía , Conversión a Cirugía Abierta , Femenino , Humanos , Laparoscopía , Tiempo de Internación , MasculinoRESUMEN
OBJECTIVES: Despite ample evidence of variation in timing of menopause, little is known about the extent or underlying causes of individual variation in ovarian reserve and age-related follicular decline. Anti-Müllerian hormone (AMH), a hormonal marker of ovarian reserve, may be a useful tool to clarify these questions. We describe AMH in a cohort of Filipino young adult women, and evaluate whether ovarian reserve in early adulthood relates to measures of life history scheduling (menarcheal age) and reproductive effort (parity). METHODS: Data and samples are obtained from 294 nonpregnant participants (21.5 years ± 0.3) in the Cebu Longitudinal Health and Nutrition Survey. Plasma AMH was assayed using an enzyme immunoassay and relationships between AMH, menarcheal age, and parity were examined. RESULTS: Mean AMH was 4.3 ng/mL. In multiple regression models, women who experienced menarche earlier had significantly higher AMH as young adults (P < 0.05). Women with two (P < 0.05) and three or more (P < 0.01) children had significantly lower AMH than those with no children. These associations were independent of age, smoking, and body mass index. CONCLUSIONS: These findings suggest that individual variation in life history scheduling and reproductive history could contribute to variation in ovarian reserve. Moreover, they demonstrate the utility of AMH as a tool for human reproductive ecology, and highlight the need for further research clarifying the extent of human population variation in ovarian reserve and the behavioral and ecological influences underlying this variation.
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Hormona Antimülleriana/sangre , Menarquia , Ovario/fisiología , Paridad , Adolescente , Factores de Edad , Biomarcadores/sangre , Niño , Estudios de Cohortes , Ensayo de Inmunoadsorción Enzimática , Femenino , Humanos , Filipinas , Estudios Prospectivos , Adulto JovenRESUMEN
BACKGROUND: We previously demonstrated that vascular smooth muscle cells (VSMC) proliferation and development of neointimal hyperplasia as well as the ability of nitric oxide (NO) to inhibit these processes is dependent on sex and hormone status. The aim of this study was to evaluate the role of estrogen receptor (ER) in mediating proliferation in male and female VSMC. MATERIALS AND METHODS: Proliferation was assessed in primary rat aortic male and female VSMC using (3)H-thymidine incorporation in the presence or absence of ER alpha (α) inhibitor methyl-piperidino-pyrazole, the ER beta (ß) inhibitor (R,R)-5,11-Diethyl-5,6,11,12-tetrahydro-2,8-chrysenediol, the combined ERαß inhibitor ICI 182,780, and/or the NO donor DETA/NO. Proliferation was also assessed in primary aortic mouse VSMC harvested from wildtype (WT), ERα knockout (ERα KO), and ERß knockout (ERß KO) mice in the presence or absence of DETA/NO and the ERα, ERß, and ERαß inhibitors. Protein levels were assessed using Western blot analysis. RESULTS: Protein expression of ERα and ERß was present and equal in male and female VSMC, and did not change after exposure to NO. Inhibition of either ERα or ERß had no effect on VSMC proliferation in the presence or absence of NO in either sex. However, inhibition of ERαß in rat VSMC mitigated NO-mediated inhibition in female but not male VSMC (P < 0.05). Evaluation of proliferation in the knockout mice revealed distinct patterns. Male ERαKO and ERßKO VSMC proliferated faster than male WT VSMC (P < 0.05). Female ERßKO proliferated faster than female WT VSMC (P < 0.05), but female ERαKO VSMC proliferated slower than female WT VSMC (P < 0.05). Last, we evaluated the effect of combined inhibition of ERα and ERß in these knockout strains. Combined ERαß inhibition abrogated NO-mediated inhibition of VSMC proliferation in female WT and knockout VSMC (P < 0.05), but not in male VSMC. CONCLUSIONS: These data clearly demonstrate a role for the ER in mediating VSMC proliferation in both sexes. However, these data suggest that the antiproliferative effects of NO may be regulated by the ER in females but not males.
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Proliferación Celular , Receptor alfa de Estrógeno/fisiología , Receptor beta de Estrógeno/fisiología , Músculo Liso Vascular/citología , Caracteres Sexuales , Animales , Proliferación Celular/efectos de los fármacos , Estradiol/análogos & derivados , Estradiol/farmacología , Antagonistas de Estrógenos/farmacología , Receptor alfa de Estrógeno/antagonistas & inhibidores , Receptor alfa de Estrógeno/genética , Receptor beta de Estrógeno/antagonistas & inhibidores , Receptor beta de Estrógeno/genética , Femenino , Fulvestrant , Hiperplasia/inducido químicamente , Hiperplasia/patología , Masculino , Ratones , Ratones Noqueados , Modelos Animales , Músculo Liso Vascular/efectos de los fármacos , Músculo Liso Vascular/fisiología , Neointima/inducido químicamente , Neointima/patología , Óxido Nítrico/efectos adversos , Óxido Nítrico/farmacología , Ratas , Ratas Sprague-Dawley , Transducción de SeñalRESUMEN
Nitric oxide (NO)-based therapies decrease neointimal hyperplasia; however, studies have been performed only in male animal models. Thus, we sought to evaluate the effect of NO on vascular smooth muscle cells (VSMC) in vitro and neointimal hyperplasia in vivo based on sex and hormone status. In hormone-replete medium, male VSMC proliferated at greater rates than female VSMC. In hormone-depleted medium, female VSMC proliferated at greater rates than male VSMC. However, in both hormone environments, NO inhibited proliferation and migration to a greater extent in male compared to female VSMC. These findings correlated with greater G0/G1 cell cycle arrest and changes in cell cycle protein expression in male compared to female VSMC after exposure to NO. Next, the rat carotid artery injury model was used to assess the effect of NO on neointimal hyperplasia in vivo. Consistent with the in vitro data, NO was significantly more effective at inhibiting neointimal hyperplasia in hormonally intact males compared to females using weight-based dosing. An increased weight-based dose of NO in females was able to achieve efficacy equal to that in males. Surprisingly, NO was less effective at inhibiting neointimal hyperplasia in castrated animals of both sexes. In conclusion, these data suggest that NO inhibits neointimal hyperplasia more effectively in males compared to females and in hormonally intact compared to castrated rats, indicating that the effects of NO in the vasculature may be sex- and hormone-dependent.