Cardiac tissue engineering: current state-of-the-art materials, cells and tissue formation / Engenharia de tecidos cardíacos: atual estado da arte a respeito de materiais, células e formação tecidual

ABSTRACT Cardiovascular diseases are the major cause of death worldwide. The heart has limited capacity of regeneration, therefore, transplantation is the only solution in some cases despite presenting many disadvantages. Tissue engineering has been considered the ideal strategy for regenerative medicine in cardiology. It is an interdisciplinary field combining many techniques that aim to maintain, regenerate or replace a tissue or organ. The main approach of cardiac tissue engineering is to create cardiac grafts, either whole heart substitutes or tissues that can be efficiently implanted in the organism, regenerating the tissue and giving rise to a fully functional heart, without causing side effects, such as immunogenicity. In this review, we systematically present and compare the techniques that have drawn the most attention in this field and that generally have focused on four important issues: the scaffold material selection, the scaffold material production, cellular selection and in vitro cell culture. Many studies used several techniques that are herein presented, including biopolymers, decellularization and bioreactors, and made significant advances, either seeking a graft or an entire bioartificial heart. However, much work remains to better understand and improve existing techniques, to develop robust, efficient and efficacious methods.

RESUMO Doenças cardiovasculares são responsáveis pelo maior número de mortes no mundo. O coração possui capacidade de regeneração limitada, e o transplante, por consequência, representa a única solução em alguns casos, apresentando várias desvantagens. A engenharia de tecidos tem sido considerada a estratégia ideal para a medicina cardíaca regenerativa. Trata-se de uma área interdisciplinar, que combina muitas técnicas as quais buscam manter, regenerar ou substituir um tecido ou órgão. A abordagem principal da engenharia de tecidos cardíacos é criar enxertos cardíacos, sejam substitutos do coração inteiro ou de tecidos que podem ser implantados de forma eficiente no organismo, regenerando o tecido e dando origem a um coração completamente funcional, sem desencadear efeitos colaterais, como imunogenicidade. Nesta revisão, apresentase e compara-se sistematicamente as técnicas que ganharam mais atenção nesta área e que geralmente focam em quatro assuntos importantes: seleção do material a ser utilizado como enxerto, produção do material, seleção das células e cultura de células in vitro. Muitos estudos, fazendo uso de várias das técnicas aqui apresentadas, incluindo biopolímeros, descelularização e biorreatores, têm apresentado avanços significativos, seja para obter um enxerto ou um coração bioartifical inteiro. No entanto, ainda resta um grande esforço para entender e melhorar as técnicas existentes, para desenvolver métodos robustos, eficientes e eficazes.

Myocardial protective effect of dexmedetomidine in pediatric patients undergoing total correction of tetralogy of Fallot / 中华麻醉学杂志

Objective To evaluate the myocardial protective effect of dexmedetomidine in the pediatric patients undergoing total correction of tetralogy of Fallot.Methods Forty ASA physical status Ⅱ] or Ⅲ pediatric patients of both sexes,aged 9 months-5 yr,weighing 7-21 kg,scheduled for elective total correction of tetralogy of Fallot under cardiopulmonary bypass,were randomly divided into 2 groups (n =20 each):control group (C group) and dexmedetomidine group (D group).Anesthesia was induced with iv injection of midazolam,sufentanil,etomidate and rocuronium.The patients were endotracheally intubated and mechanically ventilated.After intubation,dexmedetomidine was infused intravenously at 0.6 μg· kg-1 · h-1 until the end of operation in group D,while the equal volume normal saline was given instead of dexmedetomidine in group C.Venous blood samples were obtained before operation,at the end of operation and at 24 h after operation for determination of plasma TNF-α and IL-6 concentrations.The occurence of anoxic spells was recorded.Results The concentrations of plasma TNF-α and IL-6 were significantly lower at the end of operation and 24 h after operation in group D than in group C(P ＜0.05).The incidence of anoxic spells was 0 in group D,however it was 20％ in group C.Conclusion For the pediatric patients undergoing total correction of tetralogy of Fallot under cardiopulmonary bypass,dexmedetomidine infused at 0.6 μg· kg-1 · h-1 during operation can exert myocardial protective effect with clinical significance.

Autotrasplante cardiaco en el tratamiento quirúrgico de tumores cardiacos primarios: Caso clínico / Heart autotrasplantation for the treatment of a rhabdomyosarcoma of the left ventricle: Report of one case

Background: Heart autotrasplantation is an exceptional surgical technique used in the treatment of uncontrolled cardiac arrhythmias and primary unresectable cardiac tumors. We report a 28-year-old male with a rhabdomyosarcoma of the left ventricle, localized in the lateral and posterior wall, which involved the mitral valve and circumflex artery. After a complete study ruling out dissemination of the tumor, the patient was operated. Surgical exploration determined the unresectabilility of the tumor with the heart in situ. Therefore, the heart was explanted, preserving the right atrium and coronary sinus for re-implantation. Fifty percent of the mitral valve and the circumflex artery from its origin, were resected due to tumor infiltration. The heart was reconstructed with bovine pericardium and a mechanical valve was implanted in the mitral position. Afterward, the heart was implanted again following the same sequence as in bicaval transplantation, followed by a double bypass grafting to the distal circumflex territory. The patient had no significant complications and after nine months of follow up, there was no evidence of local recurrence. In the fourth postoperative month, a subcutaneous mass in the left thigh that was considered a metastasis without histological confirmation appeared. The lesion disappeared with radio and chemotherapy.

Há proliferação de cardiomiócitos no infarto? / There is proliferation of cardiomyocytes in infarction

Pesquisa de proliferação de cardiomiócitos no infarto. Método: foram colhidas amostras de tecido miocárdico de cadáveres do Serviço de Verificação de òbito, de 19 homens e 03 mulheres. Essas amostras foram coradas com o marcador Ki 67. Realizada também a análise morfométrica dos cardiomiócitos, com objetivo de 10X, em áreas de infarto e em área normal, comparando-se o perímetro e a área dos mesmo. Resultados: mos 22 casos selecionados não foi observado nenhum núcleo de cardiomiócito marcado com Ki-67, evidenciando uma provável ausência de mitose. Em relação à análise morfométrica, o aumento do perímetro e área dos cardiomiócitos em área infartada, em relação á área normal, foi, estatisticamente, significante. Conclusão: Acreditamos que a metodologia empregada, coloração com hematoxilina e eosina e marcação com Ki-67, não é suficientemente precisa para a detecção da prolferação de cardiomiócitos, requerendo-se futuros trabalhos com maiores recursos metodológicos.

Asistencia y regeneración del miocardio combinando terapia celular e ingeniería de tejidos. Resultados del estudio clínico MAGNUM / Myocardial regeneration and asistance combined cardiac tissue engineering and stem cell therapy. Outcome of trial MAGNUM

Objetivos. El trasplante celular para la regeneración del miocardio está limitado por la escasa viabilidad del injerto y la baja retención celular. En la miocardiopatía isquémica la matriz extracelular está profundamente alterada, por consiguiente, sería importante asociar un procedimiento para regenerar las células miocárdicas y restaurar la función de la matriz extracelular. En este estudio clínico, fue evaluada la terapia celular intrainfarto asociada a una matriz de colágeno sembrada con células e implantada sobre ventrículos infartados.Métodos. En 15 pacientes (54,2±3,8 años de edad) que presentaban cicatrices miocárdicas postisquémicas en el ventrículo izquierdo (VI) y con indicación de cirugía de revascularización miocárdica, se implantaron, durante la operación, células de la médula ósea mononucleares autólogas (CMO) en la cicatriz. Se agregó sobre esa zona infartada una matriz de colágeno tipo I con el mismo número de CMO

Resultados. No hubo mortalidad ni eventos adversos relacionados (seguimiento 15±4,2 meses). La clase funcional según la New York Heart Association (NYHA) mejoró de 2,3±0,5 a 1,4±0,3 (p=0,005). El volumen de fin de diástole del VI evolucionó de 142±24 a 117±21 mL (p=0,03), el tiempo de desaceleración del llenado del VI mejoró aumentando de 162±7 mseg a 196±8 mseg (p=0,01). El espesor del área cicatrizada progresó de 6±1,4 a 9±1,5 mm (p=0,005). La fracción de eyección (FE) mejoró de 25±7 a 33±5% (p=0,04).Conclusiones. La inyección intramiocárdica de células de médula ósea y la fijación simultánea de una matriz sembrada con progenitores celulares (stem cells) sobre el epicardio fue simple y sin complicaciones. La matriz de colágeno aumento el espesor de la zona del infarto con nuevos tejidos viables, limitando la dilatación ventricular y mejorando la función diastólica. Estos resultados positivos no pueden ser absolutamente relacionados a las células y la matriz, pues se asociaron puentes de revascularización coronaria. En conclusión, la ingeniería de tejidos puede extender las indicaciones y beneficios de la terapia con células madre en cardiología, convirtiéndose en un camino prometedor para la creación de un “miocardio bioartificial”

Objectives. Stem cell therapy for myocardial regeneration is limited by poor graft viability and low cell retention. In ischemic cardiomyopathy the extracellular matrix is pathologically modified, therefore it could be important to associate a procedure aiming at regenerating both, myocardial cells and the extracellular matrix. We evaluated intrainfarct cell therapy associated with a cell-seeded collagen scaffold grafted onto infarcted hearts.Methods. In 15 patients (aged 54.2±3.8 years) presenting LV postischemic myocardial scars and with indication for a single off-pump-CABG, autologous mononuclear bone marrow cells (BMC) were implanted during surgery in the scar. A 3D collagen type I matrix seeded with the same number of BMC was grafted onto the infarction zone.Results. There was no mortality and any related adverse events (follow-up 15±4.2 months). NYHA FC improved from 2.3±0.5 to 1.4±0.3 (p=0.005). LV end-diastolic volume evolved from 142±24 to 117±21 mL (p=0.03), LV filling deceleration time improved from 162±7 ms to 196±8 ms (p=0.01). Scar area thickness progress from 6±1.4 to 9±1.5mm (p=0.005). EF improved from 25±7 to 33±5% (p=0.04).Conclusions. Simultaneous intramyocardial injection of mononuclear bone marrow cells and fixation of a BMC-seeded matrix onto the epicardium is feasible and safe. The cell seeded collagen matrix seems to increase the thickness of the infarct scar with viable tissues and help to normalize cardiac wall stress in injured regions, thus limiting ventricular remodelling and improving diastolic function. Patients’ improvements can not be conclusively related to the cells and matrix due to the association of CABG. Cardiac tissue engineering should extend the indications and benefits of stem cell therapy in cardiology, becoming a promising way for the creation of a “bioartificial myocardium”

Stem cells and their potential as cardiac therapeutics.

Stem cells are the foundation cells for every organ and tissue in the body. They are undifferentiated cells that under proper conditions begin to develop into specialized tissues and organs. Most of the body’s specialized cells cannot be replaced by natural processes if they are seriously damaged or diseased, such as in Myocardial Infarction. Recent interest has focused on stem cells, which can proliferate, and differentiate into cardiomyocytes.This paper aim to provide overview of stem cell transplantation in myocardial infarction, milestones and setbacks in the study of cellular cardiomyoplasty.

Perspectivas de las células tallo en infartos del miocardio / Stem cell perspectives in myocardial infarctions

Myocardial infarction is the leading cause of congestive heart failure and death in industrializated countries. The cellular cardiomyoplasty has emerged as an alternative treatment in the regeneration of infarted myocardial tissue. In animals' models, differents cellular lines such as cardiomyocites, sheletal myoblast, embryonic stem cells and adult mesenchymal stem cells has been used, resulting in an improvement in ventricular function and decrease in amount of infarted tissue. The first three cells line have disvantages as they are allogenics and are difficult to obtain. The adult mesenchymal stem cells are autologous and can be obtained throught the aspiration of bone marrow or from peripherical circulation, prior to stimulating with cytokines (G-CSF). The implantation in humans with recent and old myocardial infarction have shown improvements similar to those shown in animal models. These findings encourage the continued investigation in the mechanism of cellular differentiation and implantation metods in infarted myocardial tissue.

El infarto del miocardio es la principal causa de falla cardiaca y muerte en países industrializados. A la fecha, la cardiomioplastia celular ha emergido como una alternativa en la regeneración de infartos miocárdicos. En modelos animales se han utilizado diferentes líneas celulares como cardiomiocitos fetales, mioblastos de músculo esquelético, células tallo embrionarias y células tallo mesenquimales del adulto, con mejoría en la función ventricular y disminución del área de tejido infartado. Las tres primeras líneas celulares tienen desventajas porque son alogénicas y difíciles de obtener. Las células tallo mesenquimales del adulto son autólogas y se pueden obtener de aspirados de médula ósea o de la circulación periférica previa estimulación con citocinas (G-CSF). La implantación de estas células en seres humanos con infartos del miocardio recientes y antiguos han mostrado mejorías similares a los reportes con modelos animales. Estos hallazgos alientan a continuar la investigación clínica y básica en busca de los mecanismos de diferenciación celular y selección de vías de implantación, en tejido miocárdico infartado.

Study on the Short-Term Hemodynamic Effects of Experimental Cardiomyoplasty in Heart Failure Model / 대한흉부외과학회지

BACKGROUND: To evaluate the short-term effect of dynamic cardiomyoplasty on circulatory function and detect the related factors that can affect it, experimental cardiomyoplasties were performed under the state of normal cardiac function and heart failure. MATERIAL AND METHOD: A total of 10 mongrel dogs weighing 20 to 30kg were divided arbitrarily into two groups. Five dogs of group A underwent cardiomyoplasty with latissimus dorsi(LD) muscle mobilization followed by a 2-week vascular delay and 6-week muscle training. Then, hemodynamic studies were conducted. In group B, doxorubicin was given to 5 dogs in an IV dose of 1 mg/kg once a week for 8 weeks to induce chronic heart failure, and simultaneous muscle training was given for preconditioning during this period. Then, cardiomyoplasties were performed and hemodynamic studies were conducted immediately after these cardiomyoplasties in group B. RESULT: In group A, under the state of normal cardiac function, only mean right atrial pressure significantly increased with the pacer-on(p0.05), the larger augmentation effect seen in group B is presumed to be mainly attributed to the viability and contractility of the LD muscle. CONCLUSION: These results indicate that the positive circulatory augmentation effect of cardiomyoplasty is apparent only under the state of heart failure and the preservation of muscle contractility is important to maximize this effect.

First Successful Dynamic Cardiomyoplasty in Korea / 대한흉부외과학회지

A 25-year-old man with viral cardiomyopathy and chronic active hepatitis successfully underwent dynamic cardiomyoplasty for the first time in Korea on July 30, 1996. The patient had been intermittently dyspneic for 5 years and was admitted to our center twice because of heart failure. For the past 2 years, he was NYHA functional class III status with a left ventricular ejection fraction (LVEF) of around 30%. The patient was born with scoliosis and showed a short stature. The liver function showed elevated liver enzymes, and hepatitis B antigen was positive. The liver biopsy revealed chronic active hepatitis. The preoperative echocardiogram showed decreased left ventricular function with grade II mitral and grade II tricuspid regurgitation with dilated left and right atrium. Recently his symptoms worsened and we decided to perform a dynamic cardiomyoplasty. The left latissmus dorsi muscle (LDM) was mobilized and tested with lead placement on his right lateral decubitus position. The patient was positioned into supine and, after median sternotomy, the heart was wrapped with the mobilized muscle. The Russian made cardiomyostimulator (EKS-445) and leads (Myocardial PEMB for heart and PEMP-1 for LDM) were used. The total operation time was 8 hours and there were no perioperative episodes. Postoperatively the LDM had been trained for a 10 week period and currently the stimulation ratio is maintained at 1:4. The postoperative LVEF did not increase with the value of 30-35%. However, the patient feels better postoperatively with slightly increased activity.

Anesthetic Experience of Dynamic Cardiomyoplasty: A case report / 대한마취과학회지

Dynamic cardiomyoplasty is a recently introduced surgical method to improve myocardial performance. It consists of a placement of a skeletal muscle flap around the heart and stimulation of the flap in synchrony with ventricular contraction. We experienced a case of cardiomyoplasty in a 25 year old male patient with congestive heart failure. Anesthesia was induced and maintained with fentanyl, midazolam and isoflurane. The operation was performed for 8hrs without cardiopulmonary bypass and the patient was transferred to the intensive care unit. He was mechanically ventilated electively overnight and extubation was done 18hrs postoperatively. The patient was discharged home on the 40days after operation and improved in exercise tolerance. We report the anesthetic management and hemodynamic changes in a patient who underwent dynamic cardiomyoplasty.

Fast and slow gating types of SR ryanodine receptor/channel purified from canine latissimus dorsi muscle

The ryanodine receptor/channel (RyR) mediates the release of calcium from the sarcoplasmic reticulum (SR) in both skeletal and cardiac muscle cells. There are three isoforms of the RyR: RyR1, RyR2, and RyR3. RyR1 is specifically expressed in skeletal muscles and RyR2 in cardiac muscles. RyR3 is yet another isoform found in non-muscle cells such as neuronal cells. Single channel recordings of RyR1 and RyR2 reconstituted in artificial lipid bilayer show that the characteristics of two isoforms are very distinct. RyR1 has a shorter mean open time and is activated at a higher concentration of Ca2+ than RyR2. In this study, we isolated the heavy SR membranes from canine latissimus dorsi muscles and investigated the single channel activities from the heavy SR membrane fraction using Cs+ as a charge carrier. Two different types of activities were observed. The fast-gating type (FG) with the mean open time of 0.9 ms was more frequently recorded (n = 12) than the slow-gating type (SG) with the mean open time of 269.2 ms. From the I-V relation, the slope conductance of the FG was calculated to be 514.7 pS and the SG, to 625.6 pS. The activity of the fast gating type increased by raising the concentration of Ca2+ in the cis-solution up to 100 microM. The appearance of the SG in the canine heavy SR membrane fraction suggests a possibility that two types of RyR isoform are co-expressed in mammalian skeletal muscle as well as in avian, amphibian and piscine fast twitch muscles.

Avaliação das alterações morfológicas crônicas do músculo grande dorsal, após cardiomioplastia, através da ressonância magnética / Evaluation of chronic morphologic changes In latissimus dorsi after cardiomyoplasty by magnetic ressonance

PURPOSE--Long term clinical and hemodynamic benefits of dynamic cardiomyoplasty (DC) have been reported. However, no information is available about long-term morphological changes in the wrapped latissimus dorsi (LD) muscle in humans. METHODS--The latissimus dorsi muscle flap was evaluated by magnetic resonance imaging (MRI) in 5 patients submitted to DC for treatment of severe dilated cardiomyopathy. All patients were studied from 24 to 52 months after the surgical procedure at the time of the cardiomyostimulator replacement. In the interim, LD was stimulated with burst of 6 pulses (burst duration 185 msec, burst freq 30Hz) synchronized to every cardiac contraction with a maximum of 100 LD contractions/min. Images were acquired on a GE Sigma 1.5 T system (TE = 25ms, TR = R- Rx2, slice thickness 8mm). RESULTS--The thickness of was 7.6 +/- 0.8mm. In addition, the signal intensity of the LD was compared with that of thoracic skeletal muscle and was found to be increased (2.19 +/- 0.42). The signal intensity was similar to that of subcutaneous fat in those images. CONCLUSION--Morphologic changes in the wrapped LD muscle consistent with fatty degeneration occur after DC and can be detected by MRI. Further studies will be necessary to demonstrate the clinical significance of such LD muscle flap changes.

Objetivo - Os benefícios clínicos e hemodinâmicos da cardiomioplastia (CD) a longo prazo têm sido relatados. Contudo existem poucos estudos sobre mudanças morfológicas crônicas no músculo grande dorsal (GD) em pacientes submetidos à cirurgia. Métodos - Avaliação através da ressonância magnética (RM) do músculo GD de 5 pacientes no período entre 24 e 52 meses após procedimento cirúrgico, no momento de substituição do cardiomioestimulador. Nesse interim, o GD foi estimulado com seqüência de 6 pulsos (duração de 185ms e freqüência de 30Hz) sincronizado com todas as contrações cardíacas, com um máximo de 100 contrações do GD por minuto. As imagens foram adquiridas pelo aparelho 1,5 Tesla da GE (tempo-echo, 25ms; tempo de repetição, R-R x 2 e espessura do corte, 8mm). Resultados - A espessura média do GD foi de 7,6±0,8mm; a intensidade do sinal do GD foi comparada com a do músculo esquelético do tórax, apresentando-se aumentada (2,19±0,42 proximal e 2,01±0,49 distal). A intensidade do sinal do GD foi similar a da gordura subcutânea da parede do tórax (2,01±0,49 vs 2,67±0,6, P=NS). Conclusão - Mudanças morfalógicas no músculo GD ocorrem após CD, e podem ser detectadas pela RM. Estudos adicionais serão necessários para demonstrar o significado clínico de tais mudanças do músculo GD