Viable Fibroblast Matrix Patch Induces Angiogenesis and Increases Myocardial Blood Flow in Heart Failure After Myocardial Infarction

Biologically derived epicardial patch induces macrophage mediated pathophysiologic repair in chronically infarcted swine hearts

There are nearly 65 million people with chronic heart failure (CHF) globally, with no treatment directed at the pathologic cause of the disease, the loss of functioning cardiomyocytes. We have an allogeneic cardiac patch comprised of cardiomyocytes and human fibroblasts on a bioresorbable matrix. This patch increases blood flow to the damaged heart and improves left ventricular (LV) function in an immune competent rat model of ischemic CHF. After 6 months of treatment in an immune competent Yucatan mini swine ischemic CHF model, this patch restores LV contractility without constrictive physiology, partially reversing maladaptive LV and right ventricular remodeling, increases exercise tolerance, without inducing any cardiac arrhythmias or a change in myocardial oxygen consumption. Digital spatial profiling in mice with patch placement 3 weeks after a myocardial infarction shows that the patch induces a CD45pos immune cell response that results in an infiltration of dendritic cells and macrophages with high expression of macrophages polarization to the anti-inflammatory reparative M2 phenotype. Leveraging the host native immune system allows for the potential use of immunomodulatory therapies for treatment of chronic inflammatory diseases not limited to ischemic CHF.

Coronary blood flow in heart failure: cause, consequence and bystander

Heart failure is a clinical syndrome where cardiac output is not sufficient to sustain adequate perfusion and normal bodily functions, initially during exercise and in more severe forms also at rest. The two most frequent forms are heart failure of ischemic origin and of non-ischemic origin. In heart failure of ischemic origin, reduced coronary blood flow is causal to cardiac contractile dysfunction, and this is true for stunned and hibernating myocardium, coronary microembolization, myocardial infarction and post-infarct remodeling, possibly also for the takotsubo syndrome. The most frequent form of non-ischemic heart failure is dilated cardiomyopathy, caused by genetic mutations, myocarditis, toxic agents or sustained tachyarrhythmias, where alterations in coronary blood flow result from and contribute to cardiac contractile dysfunction. Hypertrophic cardiomyopathy is caused by genetic mutations but can also result from increased pressure and volume overload (hypertension, valve disease). Heart failure with preserved ejection fraction is characterized by pronounced coronary microvascular dysfunction, the causal contribution of which is however not clear. The present review characterizes the alterations of coronary blood flow which are causes or consequences of heart failure in its different manifestations. Apart from any potentially accompanying coronary atherosclerosis, all heart failure entities share common features of impaired coronary blood flow, but to a different extent: enhanced extravascular compression, impaired nitric oxide-mediated, endothelium-dependent vasodilation and enhanced vasoconstriction to mediators of neurohumoral activation. Impaired coronary blood flow contributes to the progression of heart failure and is thus a valid target for established and novel treatment regimens.

Epicardially Placed Bioengineered Cardiomyocyte Xenograft in Immune-Competent Rat Model of Heart Failure

Background

Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) are under preclinical investigation as a cell-based therapy for heart failure post-myocardial infarction. In a previous study, tissue-engineered cardiac grafts were found to improve hosts' cardiac electrical and mechanical functions. However, the durability of effect, immune response, and in vitro properties of the tissue graft remained uncharacterized. This present study is aimed at confirming the graft therapeutic efficacy in an immune-competent chronic heart failure (CHF) model and providing evaluation of the in vitro properties of the tissue graft.

Methods

hiPSC-CMs and human dermal fibroblasts were cultured into a synthetic bioabsorbable scaffold. The engineered grafts underwent epicardial implantation in infarcted immune-competent male Sprague-Dawley rats. Plasma samples were collected throughout the study to quantify antibody titers. At the study endpoint, all cohorts underwent echocardiographic, hemodynamic, electrophysiologic, and histopathologic assessments.

Results

The epicardially placed tissue graft therapy improved (p < 0.05) in vivo and ex vivo cardiac function compared to the untreated CHF cohort. Total IgM and IgG increased for both the untreated and graft-treated CHF cohorts. An immune response to the grafts was detected after seven days in graft-treated CHF rats only. In vitro, engineered grafts exhibited responsiveness to beta-adrenergic receptor agonism/antagonism and SERCA inhibition and elicited complex molecular profiles.

Conclusions

This hiPSC-CM-derived cardiac graft improved systolic and diastolic cardiac function in immune-competent CHF rats. The improvements were detectable at seven weeks post-graft implantation despite an antibody response beginning at week one and peaking at week three. This suggests that non-integrating cell-based therapy delivered by a bioengineered tissue graft for ischemic cardiomyopathy is a viable treatment option.

Modulating the Infarcted Ventricle's Refractoriness with an Epicardial Biomaterial

Patients diagnosed with heart failure with reduced ejection fraction (HFrEF) are at increased risk of monomorphic ventricular tachycardia (VT) and ventricular fibrillation. The presence of myocardial fibrosis provides both anatomical and functional barriers that promote arrhythmias in these patients. Propagation of VT in a reentrant circuit depends on the presence of excitable myocardium and the refractoriness of the circuit. We hypothesize that myocardial refractoriness can be modulated surgically in a model of HFrEF, leading to decreased susceptibility to VT.Male Sprague-Dawley rats were infarcted via permanent left coronary artery ligation. At 3 weeks post-infarction, engineered grafts composed of human dermal fibroblasts cultured into a polyglactin-910 biomaterial were implanted onto the epicardium to cover the area of infarction. Three weeks post-graft treatment, all rats underwent a terminal electrophysiologic study to compare monophasic action potential electroanatomic maps and susceptibility to inducible monomorphic VT.HFrEF rats (n=29) demonstrated a longer (p=0.0191) ventricular effective refractory period (ERP) and a greater (p=0.0394) VT inducibility compared with sham (n=7). HFrEF rats treated with the graft (n=12) exhibited no change in capture threshold (p=0.3220), but had a longer ventricular ERP (p=0.0029) compared with HFrEF. No statistically significant change in VT incidence was found between HFrEF rats treated with the graft and untreated HFrEF rats (p=0.0834).Surgical deployment of a fibroblast-containing biomaterial in a rodent ischemic cardiomyopathy model prolonged ventricular ERP as measured by programmed electrical stimulation. This hypothesis-generating study warrants additional studies to further characterize the antiarrhythmic or proarrhythmic effects of this novel surgical therapy.

Surgical treatment for heart failure: cell-based therapy with engineered tissue

This review will outline cell-based therapy for heart failure focusing on tissue engineering to deliver cells to the damaged heart. We will present an overview of the central approaches focusing on pluripotent stem cell-derived cells, mechanisms of action, autologous vs. allogeneic cell approaches, immunologic modulation, and safety considerations. We will outline the progress that has been made to-date and define the areas that still need to be investigated in order to advance the field.

Human Induced Pluripotent Stem Cell-Derived Cardiomyocyte Patch in Rats With Heart Failure

BACKGROUND

To treat chronic heart failure (CHF), we developed a robust, easy to handle bioabsorbable tissue-engineered patch embedded with human neonatal fibroblasts and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). This patch was implanted on the epicardial surface of the heart covering the previously infarcted tissue.

METHODS

Sprague-Dawley rats (6-8 weeks old) underwent sham surgery (n = 12) or left coronary artery ligation (n = 45). CHF rats were randomized 3 weeks after ligation to CHF control with sham thoracotomy (n = 21), or a fibroblasts/hiPSC-CMs patch (n = 24) was implanted. All sham surgery rats also underwent a sham thoracotomy. At 3 weeks after randomization, hemodynamics, echocardiography, electrophysiologic, and cell survival studies were performed.

RESULTS

Patch-treated rats had decreased (P < .05) left ventricular-end diastolic pressure and the time constant of left ventricular relaxation (Tau), increased anterior wall thickness in diastole, and improved echocardiography-derived indices of diastolic function (E/e' [ratio of early peak flow velocity to early peak LV velocity] and e'/a' [ratio of early to late peak left ventricular velocity]). All rats remained in normal sinus rhythm, with no dysrhythmias. Rats treated with the patch showed improved electrical activity. Transplanted hiPSC-CMs were present at 7 days but not detected at 21 days after implantation. The patch increased (P < .05) gene expression of vascular endothelial growth factor, angiopoietin 1, gap junction α-1 protein (connexin 43), β-myosin heavy 7, and insulin growth factor-1 expression in the infarcted heart.

CONCLUSIONS

Epicardial implantation of a fibroblasts/hiPSC-CMs patch electrically enhanced conduction, lowered left ventricular end-diastolic pressure, and improved diastolic function in rats with CHF. These changes were associated with increases in cytokine expression.

Cellular Therapeutics for Heart Failure: Focus on Mesenchymal Stem Cells

Resulting from a various etiologies, the most notable remains ischemia; heart failure (HF) manifests as the common end pathway of many cardiovascular processes and remains among the top causes for hospitalization and a major cause of morbidity and mortality worldwide. Current pharmacologic treatment for HF utilizes pharmacologic agents to control symptoms and slow further deterioration; however, on a cellular level, in a patient with progressive disease, fibrosis and cardiac remodeling can continue leading to end-stage heart failure. Cellular therapeutics have risen as the new hope for an improvement in the treatment of HF. Mesenchymal stem cells (MSCs) have gained popularity given their propensity of promoting endogenous cellular repair of a myriad of disease processes via paracrine signaling through expression of various cytokines, chemokines, and adhesion molecules resulting in activation of signal transduction pathways. While the exact mechanism remains to be completely elucidated, this remains the primary mechanism identified to date. Recently, MSCs have been incorporated as the central focus in clinical trials investigating the role how MSCs can play in the treatment of HF. In this review, we focus on the characteristics of MSCs that give them a distinct edge as cellular therapeutics and present results of clinical trials investigating MSCs in the setting of ischemic HF.

Doppler Assessment of Diastolic Function Reflect the Severity of Injury in Rats With Chronic Heart Failure

OBJECTIVE

For chronic heart failure (CHF), more emphasis has been placed on evaluation of systolic as opposed to diastolic function. Within the study of diastology, measurements of left ventricular (LV) longitudinal myocardial relaxation have the most validation. Anterior wall radial myocardial tissue relaxation velocities along with mitral valve inflow (MVI) patterns are applicable diastolic parameters in the differentiation between moderate and severe disease in the ischemic rat model of CHF. Myocardial tissue relaxation velocities correlate with traditional measurements of diastolic function (ie, hemodynamics, Tau, and diastolic pressure-volume relationships).

METHODS AND RESULTS

Male Sprague-Dawley rats underwent left coronary artery ligation or sham operation. Echocardiography was performed at 3 and 6 weeks after coronary ligation to evaluate LV ejection fraction (EF) and LV diastolic function through MVI patterns (E, A, and E/A) and Doppler imaging of the anterior wall (e' and a'). The rats were categorized into moderate or severe CHF according to their LV EF at 3 weeks postligation. Invasive hemodynamic measurements with solid-state pressure catheters were obtained at the 6-week endpoint. Moderate (N = 20) and severe CHF (N = 22) rats had significantly (P < .05) different EFs, hemodynamics, and diastolic pressure-volume relationships. Early diastolic anterior wall radial relaxation velocities as well as E/e' ratios separated moderate from severe CHF and both diastolic parameters had strong correlations with invasive hemodynamic measurements of diastolic function.

CONCLUSION

Radial anterior wall e' and E/e' can be used for serial assessment of diastolic function in rats with moderate and severe CHF.

In vivo Electrophysiological Study of Induced Ventricular Tachycardia in Intact Rat Model of Chronic Ischemic Heart Failure

OBJECTIVE

The objective of this study was to define the clinical relevance of in vivo electrophysiologic (EP) studies in a rat model of chronic ischemic heart failure (CHF).

METHODS

Electrical activation sequences, voltage amplitudes, and monophasic action potentials (MAPs) were recorded from adult male Sprague-Dawley rats six weeks after left coronary artery ligation. Programmed electrical stimulation (PES) sequences were developed to induce sustained ventricular tachycardia (VT). The inducibility of sustained VT was defined by PES and the recorded tissue MAPs.

RESULTS

Rats in CHF were defined ( 0.05) by elevated left ventricular (LV) end-diastolic pressure (5 ± 1 versus 18 ± 2 mmHg), decreased LV + d P/dt (7496 ± 225 versus 5502 [Formula: see text] s), LV - dP/dt (7723 ± 208 versus 3819 [Formula: see text]), LV ejection fraction (79 ± 3 versus [Formula: see text]), peak developed pressure (176 ± 4 versus 145 ± 9 mmHg), and prolonged time constant of LV relaxation Tau (18 ± 1 versus 29 ± 2 ms). The EP data showed decreased ( 0.05) electrogram amplitude in border and infarct zones (Healthy zone (H): 8.7 ± 2.1 mV, Border zone (B): 5.3 ± 1.6 mV, and Infarct zone (I): 2.3 ± 1.2 mV), decreased MAP amplitude in the border zone (H: [Formula: see text] 1.0 mV, B: 9.7 ± 0.5 mV), and increased repolarization heterogeneity in the border zone (H: 8.1 ± 1.5 ms, B: 20.2 ± 3.1 ms). With PES we induced sustained VT (>15 consecutive PVCs) in rats with CHF (10/14) versus Sham (0/8).

CONCLUSIONS

These EP studies establish a clinically relevant protocol for studying genesis of VT in CHF.

SIGNIFICANCE

The in vivo rat model of CHF combined with EP analysis could be used to determine the arrhythmogenic potential of new treatments for CHF.

Quantitative phase microscopy: automated background leveling techniques and smart temporal phase unwrapping

In order for time-dynamic quantitative phase microscopy to yield meaningful data to scientists, raw phase measurements must be converted to sequential time series that are consistently phase unwrapped with minimal residual background shape. Beyond the initial phase unwrapping, additional steps must be taken to convert the phase to time-meaningful data sequences. This consists of two major operations both outlined in this paper and shown to operate robustly on biological datasets. An automated background leveling procedure is introduced that consistently removes background shape and minimizes mean background phase value fluctuations. By creating a background phase value that is stable over time, the phase values of features of interest can be examined as a function of time to draw biologically meaningful conclusions. Residual differences between sequential frames of data can be present due to inconsistent phase unwrapping, causing localized regions to have phase values at similar object locations inconsistently changed by large values between frames, not corresponding to physical changes in the sample being observed. This is overcome by introducing a new method, referred to as smart temporal unwrapping that temporally unwraps and filters the phase data such that small motion between frames is accounted for and phase data are unwrapped consistently between frames. The combination of these methods results in the creation of phase data that is stable over time by minimizing errors introduced within the processing of the raw data.

Bone marrow-derived multipotent stromal cells promote myocardial fibrosis and reverse remodeling of the left ventricle

Cell therapy is increasingly recognized as a beneficial practice in various cardiac conditions, but its fundamentals remain largely unclear. The fates of transplanted multipotent stromal cells in postinfarction cardiac microenvironments are particularly understudied. To address this issue, labeled multipotent stromal cells were infused into rat myocardium at day 30 after myocardial infarction, against the background of postinfarction cardiosclerosis. Therapeutic effects of the transplantation were assessed by an exercise tolerance test. Histological examination at 14 or 30 days after the transplantation was conducted by means of immunostaining and quantitative image analysis. An improvement in the functional status of the cardiovascular system was observed after both the autologous and the allogeneic transplantations. Location of the label-positive cells within the heart was restricted to the affected part of myocardium. The transplanted cells could give rise to fibroblasts or myofibroblasts but not to cardiac myocytes or blood vessel cells. Both types of transplantation positively influenced scarring processes, and no expansion of fibrosis to border myocardium was observed. Left ventricular wall thickening associated with reduced dilatation index was promoted by transplantation of the autologous cells. According to the results, multipotent stromal cell transplantation prevents adverse remodeling and stimulates left ventricular reverse remodeling.

Clenbuterol plus granulocyte colony-stimulating factor regulates stem/progenitor cell mobilization and exerts beneficial effect by increasing neovascularization in rats with heart failure

BACKGROUND

Treatment of beta2-adrenergic receptor agonists with myeloid cytokines, such as granulocyte colony-stimulating factor (G-CSF) has been reported to enhance stem/progenitor cell mobilization and proliferation in ischemic myocardium. However, whether the combination therapy of G-CSF and clenbuterol (Clen) contributes to improved left ventricular (LV) function remains uncertain. We investigated whether this combination therapy induced bone marrow-derived stem/progenitor cell mobilization, neovascularization, and altered LV function after acute myocardial infarction (MI).

METHODS AND RESULTS

Following MI, rats were treated with single Clen, high-dose Clen, and G-CSF + Clen. We evaluated LV function and remodeling with the use of echocardiography in addition to hemodynamics 3 weeks after MI. Treatment with G-CSF + Clen increased (P < .05), compared with no treatment, LV ejection fraction 46 ± 3% vs 34 ± 2%, LV dP/dt 5,789 ± 394 mm Hg vs 4,503 ± 283 mm Hg, and the percentage of circulating CD34+ cells, appearing to correlate with improvements in LV function.

CONCLUSIONS

Combination therapy improved LV function 3 weeks after MI, suggesting that G-CSF + Clen might augment stem/progenitor cell migration, contributing to tissue healing. These data raise the possibility that enhancing endogenous bone marrow-derived stem/progenitor cell mobilization may be a new treatment for ischemic heart failure after MI.

An electrically coupled tissue-engineered cardiomyocyte scaffold improves cardiac function in rats with chronic heart failure

BACKGROUND

Varying strategies are currently being evaluated to develop tissue-engineered constructs for the treatment of ischemic heart disease. This study examines an angiogenic and biodegradable cardiac construct seeded with neonatal cardiomyocytes for the treatment of chronic heart failure (CHF).

METHODS

We evaluated a neonatal cardiomyocyte (NCM)-seeded 3-dimensional fibroblast construct (3DFC) in vitro for the presence of functional gap junctions and the potential of the NCM-3DFC to restore left ventricular (LV) function in an in vivo rat model of CHF at 3 weeks after permanent left coronary artery ligation.

RESULTS

The NCM-3DFC demonstrated extensive cell-to-cell connectivity after dye injection. At 5 days in culture, the patch contracted spontaneously in a rhythmic and directional fashion at 43 ± 3 beats/min, with a mean displacement of 1.3 ± 0.3 mm and contraction velocity of 0.8 ± 0.2 mm/sec. The seeded patch could be electrically paced at nearly physiologic rates (270 ± 30 beats/min) while maintaining coordinated, directional contractions. Three weeks after implantation, the NCM-3DFC improved LV function by increasing (p < 0.05) ejection fraction 26%, cardiac index 33%, dP/dt(+) 25%, dP/dt(-) 23%, and peak developed pressure 30%, while decreasing (p < 0.05) LV end diastolic pressure 38% and the time constant of relaxation (Tau) 16%. At 18 weeks after implantation, the NCM-3DFC improved LV function by increasing (p < 0.05) ejection fraction 54%, mean arterial pressure 20%, dP/dt(+) 16%, dP/dt(-) 34%, and peak developed pressure 39%.

CONCLUSIONS

This study demonstrates that a multicellular, electromechanically organized cardiomyocyte scaffold, constructed in vitro by seeding NCM onto 3DFC, can improve LV function long-term when implanted in rats with CHF.

Methodology of fibroblast and mesenchymal stem cell coating of surgical meshes: a pilot analysis

Coating of various synthetic, absorbable, and biologic meshes with mesenchymal stem cells (MSCs) and fibroblasts was analyzed qualitatively and quantitatively. Five hernia meshes-light weight monofilament polypropylene (Soft Mesh), polyester (Parietex-TET), polylactide composite (TIGR), heavy weight monofilament polypropylene (Marlex), and porcine dermal collagen (Strattice)-were coated with three cell lines: human dermal fibroblasts (HFs), rat kidney fibroblasts (NRKs), and rat MSCs. Cell densities were determined at different time points. Samples also underwent histology and transmission electron microscopic (TEM) analyses. It required HFs 3 weeks to cover the entire mesh, while only 2 weeks for NRKs and MSCs to do so. MSCs had no preference for any of the meshes and produced the highest cell densities on Parietex and TIGR. Substrate-preference accounted for the significantly lower fibroblast densities on TIGR than Parietex. Fibroblasts failed to coat Marlex. Strattice, which had the least surface area, generated comparable cell densities to Parietex. Both histology and TEM confirmed cell coating of mesh surface. Various prosthetics can be coated by certain cell strains. Both mesh composition and cell preference dramatically influence the coating process. This methodology provides foundation for novel avenues of modulation of host response to various modern synthetic and biologic meshes.

The effect of polymer degradation time on functional outcomes of temporary elastic patch support in ischemic cardiomyopathy

Biodegradable polyurethane patches have been applied as temporary mechanical supports to positively alter the remodeling and functional loss following myocardial infarction. How long such materials need to remain in place is unclear. Our objective was to compare the efficacy of porous onlay support patches made from one of three types of biodegradable polyurethane with relatively fast (poly(ester urethane)urea; PEUU), moderate (poly(ester carbonate urethane)urea; PECUU), and slow (poly(carbonate urethane)urea; PCUU) degradation rates in a rat model of ischemic cardiomyopathy. Microporous PEUU, PECUU or PCUU (n = 10 each) patches were implanted over left ventricular lesions 2 wk following myocardial infarction in rat hearts. Infarcted rats without patching and age-matched healthy rats (n = 10 each) were controls. Echocardiography was performed every 4 wk up to 16 wk, at which time hemodynamic and histological assessments were performed. The end-diastolic area for the PEUU group at 12 and 16 wk was significantly larger than for the PECUU or PCUU groups. Histological analysis demonstrated greater vascular density in the infarct region for the PECUU or PCUU versus PEUU group at 16 wk. Improved left ventricular contractility and diastolic performance in the PECUU group was observed at 16 wk compared to infarction controls. The results indicate that the degradation rate of an applied elastic patch influences the functional benefits associated patch placement, with a moderately slow degrading PECUU patch providing improved outcomes.

Calcium-alginate hydrogel-encapsulated fibroblasts provide sustained release of vascular endothelial growth factor

Vascularization of engineered or damaged tissues is essential to maintain cell viability and proper tissue function. Revascularization of the left ventricle (LV) of the heart after myocardial infarction is particularly important, since hypoxia can give rise to chronic heart failure due to inappropriate remodeling of the LV after death of cardiomyocytes (CMs). Fibroblasts can express vascular endothelial growth factor (VEGF), which plays a major role in angiogenesis and also acts as a chemoattractant and survival factor for CMs and cardiac progenitors. In this in vitro model study, mouse NIH 3T3 fibroblasts encapsulated in 2% w/v Ca-alginate were shown to remain viable for 150 days. Semiquantitative reverse transcription-polymerase chain reaction and immunohistochemistry demonstrated that over 21 days of encapsulation, fibroblasts continued to express VEGF, while enzyme-linked immunosorbent assay showed that there was sustained release of VEGF from the Ca-alginate during this period. The scaffold degraded gradually over the 21 days, without reduction in volume. Cells released from the Ca-alginate at 7 and 21 days as a result of scaffold degradation were shown to retain viability, to adhere to fibronectin in a normal manner, and continue to express VEGF, demonstrating their potential to further contribute to maintenance of cardiac function after scaffold degradation. This model in vitro study therefore demonstrates that fibroblasts encapsulated in Ca-alginate provide sustained release of VEGF.

Biodegradable elastic patch plasty ameliorates left ventricular adverse remodeling after ischemia-reperfusion injury: a preclinical study of a porous polyurethane material in a porcine model

OBJECTIVE

Myocardial infarction (MI) can lead to irreversible adverse left ventricular remodeling resulting in subsequent severe dysfunction. The objective of this study was to investigate the potential for biodegradable, elastomeric patch implantation to positively alter the remodeling process after MI in a porcine model.

METHODS

Yorkshire pigs underwent a 60-minute catheter balloon occlusion of the left circumflex artery. Two weeks after MI animals underwent epicardial placement of a biodegradable, porous polyurethane (poly(ester urethane)urea; PEUU) patch (MI+PEUU, n = 7) or sham surgery (MI+sham, n = 8). Echocardiography before surgery and at 4 and 8 weeks after surgery measured the end-diastolic area (EDA) and fractional area change (%FAC). All animals were humanely killed 8 weeks after surgery and hearts were histologically assessed.

RESULTS

At 8 weeks, echocardiography revealed greater EDA values in the MI+sham group (23.6 ± 6.6 cm(2), mean ± standard deviaation) than in the MI+PEUU group (15.9 ± 2.5 cm(2)) (P < .05) and a lower %FAC in the MI+sham group (24.8 ± 7.6) than in the MI+PEUU group (35.9 ± 7.8) (P < .05). The infarcted ventricular wall was thicker in the MI+PEUU group (1.56 ± 0.5 cm) than in the MI+sham group (0.91 ± 0.24 cm) (P < .01).

CONCLUSIONS

Biodegradable elastomeric PEUU patch implantation onto the porcine heart 2 weeks post-MI attenuated left ventricular adverse remodeling and functional deterioration and was accompanied by increased neovascularization. These findings, although limited to a 2-month follow-up, may suggest an attractive clinical option to moderate post-MI cardiac failure.

Electrospun biocomposite nanofibrous patch for cardiac tissue engineering

A bioengineered construct that matches the chemical, mechanical, biological properties and extracellular matrix morphology of native tissue could be suitable as a cardiac patch for supporting the heart after myocardial infarction. The potential of utilizing a composite nanofibrous scaffold of poly(dl-lactide-co-glycolide)/gelatin (PLGA/Gel) as a biomimetic cardiac patch is studied by culturing a population of cardiomyocyte containing cells on the electrospun scaffolds. The chemical characterization and mechanical properties of the electrospun PLGA and PLGA/Gel nanofibers were studied by Fourier transform infrared spectroscopy, scanning electron microscopy and tensile measurements. The biocompatibility of the scaffolds was also studied and the cardiomyocytes seeded on PLGA/Gel nanofibers were found to express the typical functional cardiac proteins such as alpha-actinin and troponin I, showing the easy integration of cardiomyocytes on PLGA/Gel scaffolds. Our studies strengthen the application of electrospun PLGA/Gel nanofibers as a bio-mechanical support for injured myocardium and as a potential substrate for induction of endogenous cardiomyocyte proliferation, ultimately reducing the cardiac dysfunction and improving cardiac remodeling.