Intramyocardial transplantation of fibroblasts expressing vascular endothelial growth factor attenuates cardiac dysfunction

A deep dive into the darning effects of biomaterials in infarct myocardium: current advances and future perspectives

Myocardial infarction (MI) occurs due to the obstruction of coronary arteries, a major crux that restricts blood flow and thereby oxygen to the distal part of the myocardium, leading to loss of cardiomyocytes and eventually, if left untreated, leads to heart failure. MI, a potent cardiovascular disorder, requires intense therapeutic interventions and thereby presents towering challenges. Despite the concerted efforts, the treatment strategies for MI are still demanding, which has paved the way for the genesis of biomaterial applications. Biomaterials exhibit immense potentials for cardiac repair and regeneration, wherein they act as extracellular matrix replacing scaffolds or as delivery vehicles for stem cells, protein, plasmids, etc. This review concentrates on natural, synthetic, and hybrid biomaterials; their function; and interaction with the body, mechanisms of repair by which they are able to improve cardiac function in a MI milieu. We also provide focus on future perspectives that need attention. The cognizance provided by the research results certainly indicates that biomaterials could revolutionize the treatment paradigms for MI with a positive impact on clinical translation.

Preservation of cardiac function in left ventricle cardiac hypertrophy using an AAV vector which provides VEGF-A expression in response to p53

Here we present the application of our adeno-associated virus (AAV2) vector where transgene expression is driven by a synthetic, p53-responsive promoter, termed PG, used to supply human vascular endothelial growth factor-A165 (VEGF-A). Thus, p53 is harnessed to promote the beneficial expression of VEGF-A encoded by the AAVPG vector, bypassing the negative effect of p53 on HIF-1α which occurs during cardiac hypertrophy. Wistar rats were submitted to pressure overload induced by thoracic aorta coarctation (TAC) with or without concomitant gene therapy (intramuscular delivery in the left ventricle). After 12 weeks, rats receiving AAVPG-VEGF gene therapy were compared to those that did not, revealing significantly improved cardiac function under hemodynamic stress, lack of fibrosis and reversal of capillary rarefaction. With these functional assays, we have demonstrated that application of the AAVPG-VEGF vector under physiologic conditions known to stimulate p53 resulted in the preservation of cardiac performance.

VEGF transfer based on gene-modified fibroblasts using a hypoxia-induced vector to modulate neoangiogenesis in ischaemic regions of myocutaneous transplants

The effect of a hypoxia-inducible VEGF-expressing on wound healing in an ischaemic hind leg rat model was evaluated in this study. 180 Wistar rats were assigned randomly to three groups. After ligation of the femoral artery, group 1 received pRTP801-VEGF165, group 2 untransfected fibroblasts, group 3 saline; injection was into the subcutaneous tissue, proximal and distal to the artery ligation. Biopsy specimens were obtained on days 3, 5, 7, 14 after implementation. VEGF transgene expression, vessel architecture, the amount and total area of vessel formation were investigated. Results showed a significantly higher level of VEGF protein expression in group 1 compared to group 2 (P≤0.001) throughout the investigational period. Group 1 exhibited a significant growth of CD31-positive blood vessels in the subcutaneous tissue on day 14 compared to groups 2 and 3 (P≤0.001) (group 1, 62.20±1.92; group 2, 20.60±1.67; group 3, 12.40±1.14). Alpha-SMA-positive staining also showed significant vessel growth in group 1 on day 5 (group 1, 27.00±1.87; group 2, 7.20±1.48; group 3, 10.00±1.73). These results were confirmed in the distal muscle tissue. No significant results were obtained for the proximal muscle tissue. The subcutaneous application of pRTP801-VEGF165 showed a long-lasting effect, with an increased expression of VEGF over the entire observation period. It appears that the use of fibroblasts transfected with VEGF is a promising way to increase early angiogenesis in ischaemic tissue.

Early postnatal rat ventricle resection leads to long-term preserved cardiac function despite tissue hypoperfusion

One‐day‐old mice display a brief capacity for heart regeneration after apex resection. We sought to examine this response in a different model and to determine the impact of this early process on long‐term tissue perfusion and overall cardiac function in response to stress. Apical resection of postnatal rats at day 1 (P1) and 7 (P7) rendered 18 ± 1.0% and 16 ± 1.3% loss of cardiac area estimated by magnetic resonance imaging (MRI), respectively (P > 0.05). P1 was associated with evidence of cardiac neoformation as indicated by Troponin I and Connexin 43 expression at 21 days postresection, while in the P7 group mainly scar tissue replacement ensued. Interestingly, there was an apparent lack of uniform alignment of newly formed cells in P1, and we detected cardiac tissue hypoperfusion for both groups at 21 and 60 days postresection using SPECT scanning. Direct basal cardiac function at 60 days, when the early lesion is undetectable, was preserved in all groups, whereas under hemodynamic stress the degree of change on LVDEP, Stroke Volume and Stroke Work indicated diminished overall cardiac function in P7 (P < 0.05). Furthermore, the End‐Diastolic Pressure–Volume relationship and increased interstitial collagen deposition in P7 is consistent with increased chamber stiffness. Taken together, we provide evidence that early cardiac repair response to apex resection in rats also leads to cardiomyocyte neoformation and is associated to long‐term preservation of cardiac function despite tissue hypoperfusion.

We provide evidence that 1‐day‐old rats display early repair capacity after apex resection and this response is lost in 1‐week‐old animals similarly described for mice. The repair response is associated with long‐term preservation of overall cardiac function, despite the fact that repair is incomplete and there is tissue hypoperfusion at 21 and 60 day post injury.

Development of a closed-artery catheter-based myocardial infarction in pigs using sponge and lidocaine hydrochloride infusion to prevent irreversible ventricular fibrillation

The objectives of this study were to develop a robust, homogeneous, viable and inexpensive model of closed‐artery catheter‐based model of myocardial infarction (MI) in pigs without major cardiac dysfunction. Suitable animal models that mimic human cardiovascular conditions are of paramount importance to understand the effects of novel therapeutic strategies to improve tissue perfusion and prevent cardiac deterioration post‐MI. Pigs (N = 21, BW = 17 ± 1 kg) receiving continuous iv lidocaine hydrochloride were subjected to percutaneous intracoronary implant of foam sponge into the proximal left circumflex coronary artery. Intraprocedure mortality was 23.8%. ST segment elevation and increased serum Troponin T and CK‐MB were documented in all animals. Thirty days after occlusion, echocardiography (95% IC [9.3–12.4%]) and anatomopathological (95% CI [9.3–12.6%]) analyses confirmed a significant and reproducible MI. Taken together, we provide evidence for a suitable closed‐artery catheter‐based method to produce MI in pigs accompanied by tissue hypoperfusion and absence of overt heart failure.

We provide evidence that an inexpensive and easily available material can be used to produce a robust and homogenous percutaneous closed‐artery model of MI in pigs, when associated with lidocaine hydrochloride use. Thirty days after occlusion, anatomopathological (95% IC [9.3–12.6%]) analyses confirmed a significant and reproducible MI accompanied by hypoperfusion and absence of overt heart failure.

Short-term mechanical stretch fails to differentiate human adipose-derived stem cells into cardiovascular cell phenotypes

Background

We and others have previously demonstrated that adipose-derived stem cells (ASCs) transplantation improve cardiac dysfunction post-myocardium infarction (MI) under hemodynamic stress in rats. The beneficial effects appear to be associated with pleiotropic factors due to a complex interplay between the transplanted ASCs and the microenvironment in the absence of cell transdifferentiation. In the present work, we tested the hypothesis that mechanical stretch per se could change human ASCs (hASCs) into cardiovascular cell phenotypes that might influence post-MI outcomes.

Methods

Human ASCs were obtained from patients undergoing liposuction procedures. These cells were stretched 12%, 1Hz up to 96 hours by using Flexercell 4000 system. Protein and gene expression were evaluated to identify cardiovascular cell markers. Culture medium was analyzed to determine cell releasing factors, and contraction potential was also evaluated.

Results

Mechanical stretch, which is associated with extracellular signal-regulated kinase (ERK) phosphorylation, failed to induce the expression of cardiovascular cell markers in human ASCs, and mesenchymal cell surface markers (CD29; CD90) remained unchanged. hASCs and smooth muscle cells (SMCs) displayed comparable contraction ability. In addition, these cells demonstrated a profound ability to secrete an array of cytokines. These two properties of human ASCs were not influenced by mechanical stretch.

Conclusions

Altogether, our findings demonstrate that hASCs secrete an array of cytokines and display contraction ability even in the absence of induction of cardiovascular cell markers or the loss of mesenchymal surface markers when exposed to mechanical stretch. These properties may contribute to beneficial post-MI cardiovascular outcomes and deserve to be further explored under the controlled influence of other microenvironment components associated with myocardial infarction, such as tissue hypoxia.

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.

Scaffold-based transplantation of vascular endothelial growth factor-overexpressing stem cells leads to neovascularization in ischemic myocardium but did not show a functional regenerative effect

The transplantation of skeletal myoblasts (SkM) might improve cardiac function after myocardial infarction via paracrine action. We used scaffold-based cell transfer by using vascular endothelial growth factor (VEGF)-overexpressing myoblasts. Skeletal myoblasts were isolated and expanded from newborn Lewis rats. Cells were transfected with pCINeo-VEGF(121) and seeded on polyurethane (PU) scaffolds. The seeded scaffolds were epicardially implanted in rats 2 weeks after myocardial infarction (group: PU-VEGF-SkM). Before this intervention and 6 weeks later, pressure/volume loops were analyzed followed by histology. Additional study groups (n = 10 per group) were injected with VEGF-overexpressing myoblasts (Inj-VEGF-SkM) or unmodified myoblasts (Inj-SkM) or underwent a sham operation. Overexpression of VEGF was verified in vitro. The transplantation of growth factor producing myoblast-seeded scaffolds resulted in enhanced angiogenesis of ischemically damaged myocardium in vivo. However, the infarction size was not reduced. In group Inj-SkM, hemodynamics remained unchanged. Systolic function as measured by dP/dt(max) was not significantly altered in PU-VEGF-SkM (preinterventionally 2,156 ± 1,222 mmHg vs. postinterventionally 2,134 ± 850 mmHg). Other systolic function and diastolic function parameters as measured by dP/dt(min), tau, and pressure half-time were not restored in groups PU-VEGF-SkM and Inj-VEGF-SkM either. Transplantation of VEGF-overexpressing skeletal myoblasts leads to neovascularization in infarcted hearts. No functional myocardial recovery was observed. Scaffold-based transfer of genetically-modified cells remains a useful tool to study paracrine stem cell action.

Fibrin as a scaffold for cardiac tissue engineering

Fibrin is a natural biopolymer with many interesting properties, such as biocompatibility, bioresorbability, ease of processing, ability to be tailored to modify the conditions of polymerization, and potential for incorporation of both cells and cell mediators. Moreover, the fibrin network has a nanometric fibrous structure, mimicking extracellular matrix, and it can also be used in autologous applications. Therefore, fibrin has found many applications in tissue engineering, combined with cells, growth factors, or drugs. Because a major limitation of cardiac cell therapy is low cell engraftment, the use of biodegradable scaffolds for specific homing and in situ cell retention is desirable. Thus, fibrin-based injectable cardiac tissue engineering may enhance cell therapy efficacy. Fibrin-based biomaterials can also be used for engineering heart valves or cardiac patches. The aim of this review is to show cardiac bioengineering uses of fibrin, both as a cell delivery vehicle and as an implantable biomaterial.

Engineering human cells for in vivo secretion of antibody and non-antibody therapeutic proteins

Purified proteins such as antibodies are widely used as therapeutic agents in clinical medicine. However, clinical-grade proteins for therapeutic use require sophisticated technologies and are extremely expensive to produce. In vivo secretion of therapeutic proteins by genetically engineered human cells may advantageously replace injection of highly purified proteins. The use of gene transfer methods circumvents problems related to large-scale production and purification and offers additional benefits by achieving sustained concentrations of therapeutic protein with a syngenic glycosylation pattern that make the protein potentially less immunogenic. The feasibility of the in vivo production of therapeutic proteins by diverse cells/tissues has now been demonstrated using different techniques, such as ex vivo genetically modified cells and in vivo gene transfer mediated by viral vectors.

RevaTen platelet-rich plasma improves cardiac function after myocardial injury

OBJECTIVE

Cell therapy is an exciting area of investigation for repair of injured myocardial tissue. Platelet-rich plasma (PRP) is an autologous fractionation of whole blood containing high concentrations of growth factors including vascular endothelial growth factor and insulin-like growth factor, among many others. PRP has been shown to safely and effectively enhance healing of musculoskeletal tissue primarily by reparative cell signaling. Despite a growing body of evidence on PRP's safety and efficacy, limited studies have been performed using PRP in cardiovascular tissues. Utilizing a murine myocardial permanent ligation and ischemia/reperfusion model, this study sought to determine whether RevaTen PRP (Menlo Park, CA, USA), a proprietary formulation of PRP, improves cardiac function as measured by left ventricular ejection fraction (LVEF).

METHODS

Via thoracotomy, the left anterior descending arteries (LAD) of 28 mice were occluded by suture either permanently or for 45 min to induce ischemic injury and then reperfused. Mice undergoing permanent ligation had intramyocardial injections of either RevaTen PRP (n=5) or phosphate-buffered saline (PBS; n=4). Magnetic resonance (MR) imaging was performed to calculate LVEF at 7 days. Mice undergoing ischemia and reperfusion had intramyocardial injections of either PRP (n=10) or PBS (n=9) and underwent MR imaging to calculate LVEF at 21 days. Hearts were harvested for histologic examination following imaging.

RESULTS

Compared with PBS controls, RevaTen PRP-treated animals that underwent LAD ligation had a 38% higher LVEF 7 days after injury (PRP=36.1±6.1%; PBS=26.4±3.6%, P=.027). Compared with PBS controls, PRP-treated animals who underwent ischemia-reperfusion of the LAD had a 28% higher LVEF 21 days after injury (PRP=37.6±4.8%, control=29.3±9.7%, P=.038). Histologic analysis suggested the presence of more scar tissue in the control group compared to the PRP-treated animals.

CONCLUSION

MR imaging demonstrated a positive effect of RevaTen PRP on left ventricular function in both a ligation and ischemia-reperfusion murine model. Our results suggest RevaTen PRP should be investigated further as a potential point-of-care biologic treatment following myocardial injury.

Challenges in using stem cells for cardiac repair

Of the many diseases discussed in the context of stem cell therapy, those concerning the heart account for almost one-third of the publications in the field. However, the long-term clinical outcomes have been disappointing, in part because of preclinical studies failing to optimize the timing, number, type, and method of cell delivery and to account for shape changes that the heart undergoes during failure. In situations in which cardiomyocytes have been used in cell therapy, their alignment and integration with host tissue have not been realized. Here we review the present status of direct delivery of stem cells or their derivative cardiomyocytes to the heart and the particular challenges each cell type brings, and consider where we should go from here.