Angiogenic therapy for cardiac repair based on protein delivery systems

Angiogenesis induction as a key step in cardiac tissue Regeneration: From angiogenic agents to biomaterials

Cardiovascular diseases are the leading cause of death worldwide. After myocardial infarction, the vascular supply of the heart is damaged or blocked, leading to the formation of scar tissue, followed by several cardiac dysfunctions or even death. In this regard, induction of angiogenesis is considered as a vital process for supplying nutrients and oxygen to the cells in cardiac tissue engineering. The current review aims to summarize different approaches of angiogenesis induction for effective cardiac tissue repair. Accordingly, a comprehensive classification of induction of pro-angiogenic signaling pathways through using engineered biomaterials, drugs, angiogenic factors, as well as combinatorial approaches is introduced as a potential platform for cardiac regeneration application. The angiogenic induction for cardiac repair can enhance patient treatment outcomes and generate economic prospects for the biomedical industry. The development and commercialization of angiogenesis methods often involves collaboration between academic institutions, research organizations, and biomedical companies.

Control of the post-infarct immune microenvironment through biotherapeutic and biomaterial-based approaches

Ischemic heart failure (IHF) is a leading cause of morbidity and mortality worldwide, for which heart transplantation remains the only definitive treatment. IHF manifests from myocardial infarction (MI) that initiates tissue remodeling processes, mediated by mechanical changes in the tissue (loss of contractility, softening of the myocardium) that are interdependent with cellular mechanisms (cardiomyocyte death, inflammatory response). The early remodeling phase is characterized by robust inflammation that is necessary for tissue debridement and the initiation of repair processes. While later transition toward an immunoregenerative function is desirable, functional reorientation from an inflammatory to reparatory environment is often lacking, trapping the heart in a chronically inflamed state that perpetuates cardiomyocyte death, ventricular dilatation, excess fibrosis, and progressive IHF. Therapies can redirect the immune microenvironment, including biotherapeutic and biomaterial-based approaches. In this review, we outline these existing approaches, with a particular focus on the immunomodulatory effects of therapeutics (small molecule drugs, biomolecules, and cell or cell-derived products). Cardioprotective strategies, often focusing on immunosuppression, have shown promise in pre-clinical and clinical trials. However, immunoregenerative therapies are emerging that often benefit from exacerbating early inflammation. Biomaterials can be used to enhance these therapies as a result of their intrinsic immunomodulatory properties, parallel mechanisms of action (e.g., mechanical restraint), or by enabling cell or tissue-targeted delivery. We further discuss translatability and the continued progress of technologies and procedures that contribute to the bench-to-bedside development of these critically needed treatments.

Alleviation of cardiac fibrosis using acellular peritoneal matrix-loaded pirfenidone nanodroplets after myocardial infarction in rats

Myocardial fibrosis (MF) in the remote myocardium is a feature at the micoscopic level of pathological remodeling after myocardial infarction (MI). Although pirfenidone (PFD), an antifibrotic agent, is commonly used to inhibit fibrosis in multiple organs, its clinical use is limited because of the high doses required for favorable therapeutic outcomes and various side effects. Nanodrug technology has allowed for delayed quantitative drug release and reduced the amount of medication required, improving the treatment strategy for MF. In this study, we investigated the possible therapeutic effect of peritoneal matrix-loaded pirfenidone nanodroplets (NDs) on MI fibrosis. The results showed that the Perfluoropentane-Pirfenidone@Nanodroplets-Polyethylene glycol 2000 (PFP-PFD@NDs-PEG) described in this study was successfully synthesized and demonstrated a high potential for the targeted treatment of MI. The total duration of pirfenidone release from PFP-PFD@NDs-PEG was increased by loading it into an acellular peritoneal matrix (APM). Additionally, pirfenidone inhibited the transformation of cardiac fibroblasts into cardiac myofibroblasts in vitro and reduced the synthesis and secretion of collagen I and collagen III by cardiac myofibroblasts. The combination of the APM with pirfenidone nanodroplets achieved a slow drug release and showed excellent therapeutic effects on fibrosis in MI rats. Our study confirmed the feasibility and synergistic effectiveness of the APM combined with pirfenidone nanodroplets in the treatment of fibrosis in MI rats. Moreover, our technique offers a great potential for applying nanomedicine in other biomedical fields.

Microfluidic 3D Platform to Evaluate Endothelial Progenitor Cell Recruitment by Bioactive Materials

Most of the conventional in vitro models to test biomaterial-driven vascularization are too simplistic to recapitulate the complex interactions taking place in the actual cell microenvironment, which results in a poor prediction of the in vivo performance of the material. However, during the last decade, cell culture models based on microfluidic technology have allowed attaining unprecedented levels of tissue biomimicry. In this work, we propose a microfluidic-based 3D model to evaluate the effect of bioactive biomaterials capable of releasing signalling cues (such as ions or proteins) in the recruitment of endogenous endothelial progenitor cells, a key step in the vascularization process. The usability of the platform is demonstrated using experimentally-validated finite element models and migration and proliferation studies with rat endothelial progenitor cells (rEPCs) and bone marrow-derived rat mesenchymal stromal cells (BM-rMSCs). As a proof of concept of biomaterial evaluation, the response of rEPCs to an electrospun composite made of polylactic acid with calcium phosphates nanoparticles (PLA+CaP) was compared in a co-culture microenvironment with BM-rMSC to a regular PLA control. Our results show a significantly higher rEPCs migration and the upregulation of several pro-inflammatory and proangiogenic proteins in the case of the PLA+CaP. The effects of osteopontin (OPN) on the rEPCs migratory response were also studied using this platform, suggesting its important role in mediating their recruitment to a calcium-rich microenvironment. This new tool could be applied to screen the capacity of a variety of bioactive scaffolds to induce vascularization and accelerate the preclinical testing of biomaterials. STATEMENT OF SIGNIFICANCE: : For many years researchers have used neovascularization models to evaluate bioactive biomaterials both in vitro, with low predictive results due to their poor biomimicry and minimal control over cell cues such as spatiotemporal biomolecule signaling, and in vivo models, presenting drawbacks such as being highly costly, time-consuming, poor human extrapolation, and ethically controversial. We describe a compact microphysiological platform designed for the evaluation of proangiogenesis in biomaterials through the quantification of the level of sprouting in a mimicked endothelium able to react to gradients of biomaterial-released signals in a fibrin-based extracellular matrix. This model is a useful tool to perform preclinical trustworthy studies in tissue regeneration and to better understand the different elements involved in the complex process of vascularization.

Regenerative strategies for the consequences of myocardial infarction: Chronological indication and upcoming visions

Heart muscle injury and an elevated troponin level signify myocardial infarction (MI), which may result in defective and uncoordinated segments, reduced cardiac output, and ultimately, death. Physicians apply thrombolytic therapy, coronary artery bypass graft (CABG) surgery, or percutaneous coronary intervention (PCI) to recanalize and restore blood flow to the coronary arteries, albeit they were not convincingly able to solve the heart problems. Thus, researchers aim to introduce novel substitutional therapies for regenerating and functionalizing damaged cardiac tissue based on engineering concepts. Cell-based engineering approaches, utilizing biomaterials, gene, drug, growth factor delivery systems, and tissue engineering are the most leading studies in the field of heart regeneration. Also, understanding the primary cause of MI and thus selecting the most efficient treatment method can be enhanced by preparing microdevices so-called heart-on-a-chip. In this regard, microfluidic approaches can be used as diagnostic platforms or drug screening in cardiac disease treatment. Additionally, bioprinting technique with whole organ 3D printing of human heart with major vessels, cardiomyocytes and endothelial cells can be an ideal goal for cardiac tissue engineering and remarkable achievement in near future. Consequently, this review discusses the different aspects, advancements, and challenges of the mentioned methods with presenting the advantages and disadvantages, chronological indications, and application prospects of various novel therapeutic approaches.

Myocardial protection by heparin-based coacervate of FGF10

Heart disease is still the leading killer all around the world, and its incidence is expected to increase over the next decade. Previous reports have already shown the role of fibroblast growth factor10 (FGF10) in alleviating heart diseases. However, FGF10 has not been used to treat heart diseases because the free protein has short half-life and low bioactivity. Here, an injectable coacervate was designed to protect growth factor from degradation during delivery and the effects of the FGF10 coacervate were studied using a mice acute myocardial infarction (MI) model. As shown in our echocardiographic results, a single injection of FGF10 coacervate effectively inhibited preserved cardiac contractibility and ventricular dilation when compared with free FGF10 and the saline treatment 6 weeks after MI. It is revealed in histological results that the MI induced myocardial inflammation and fibrosis was reduced after FGF10 coacervate treatment. Furthermore, FGF10 coacervate treatment could improve arterioles and capillaries stabilization through increasing the proliferation of endothelial and mural cells. However, with the same dosage, no statistically significant difference was shown between free FGF10, heparin+FGF10 and saline treatment, especially in long term. On another hand, FGF10 coacervate also increased the expression of cardiac-associated the mRNA (cTnT, Cx43 and α-SMA), angiogenic factors (Ang-1 and VEGFA) and decreased the level of inflammatory factor (tumor necrosis factor-α). The downstream signaling of the FGF10 was also investigated, with the western blot results showing that FGF10 coacervate activated the p-FGFR, PI3K/Akt and ERK1/2 pathways to a more proper level than free FGF10 or heparin+FGF10. In general, it is revealed in this research that one-time injection of FGF10 coacervate sufficiently attenuated MI induced injury when compared with an equal dose of free FGF10 or heparin+FGF10 injection.

The Roles of Noncardiomyocytes in Cardiac Remodeling

Cardiac remodeling is a common characteristic of almost all forms of heart disease, including cardiac infarction, valvular diseases, hypertension, arrhythmia, dilated cardiomyopathy and other conditions. It is not merely a simple outcome induced by an increase in the workload of cardiomyocytes (CMs). The remodeling process is accompanied by abnormalities of cardiac structure as well as disturbance of cardiac function, and emerging evidence suggests that a wide range of cells in the heart participate in the initiation and development of cardiac remodeling. Other than CMs, there are numerous noncardiomyocytes (non-CMs) that regulate the process of cardiac remodeling, such as cardiac fibroblasts and immune cells (including macrophages, lymphocytes, neutrophils, and mast cells). In this review, we summarize recent knowledge regarding the definition and significant effects of various non-CMs in the pathogenesis of cardiac remodeling, with a particular emphasis on the involved signaling mechanisms. In addition, we discuss the properties of non-CMs, which serve as targets of many cardiovascular drugs that reduce adverse cardiac remodeling.

Mending a broken heart: current strategies and limitations of cell-based therapy

The versatility of pluripotent stem cells, attributable to their unlimited self-renewal capacity and plasticity, has sparked a considerable interest for potential application in regenerative medicine. Over the past decade, the concept of replenishing the lost cardiomyocytes, the crux of the matter in ischemic heart disease, with pluripotent stem cell-derived cardiomyocytes (PSC-CM) has been validated with promising pre-clinical results. Nevertheless, clinical translation was hemmed in by limitations such as immature cardiac properties, long-term engraftment, graft-associated arrhythmias, immunogenicity, and risk of tumorigenicity. The continuous progress of stem cell-based cardiac therapy, incorporated with tissue engineering strategies and delivery of cardio-protective exosomes, provides an optimistic outlook on the development of curative treatment for heart failure. This review provides an overview and current status of stem cell-based therapy for heart regeneration, with particular focus on the use of PSC-CM. In addition, we also highlight the associated challenges in clinical application and discuss the potential strategies in developing successful cardiac-regenerative therapy.

Development and in vitro characterization of polymeric nanoparticles containing recombinant adrenomedullin-2 intended for therapeutic angiogenesis

Cardiovascular diseases (CVD) are the leading cause of death worldwide. Growth factor therapy has emerged as novel therapeutic strategy under investigation for CVD. In this sense, adrenomedullin-2 (ADM-2) has been recently identified as a new angiogenic factor able to regulate the regional blood flow and cardiovascular function. However, the therapeutic value of ADM-2 is limited by its short biological half-life and low plasma stability. Poly (lactic-co-glycolic acid) (PLGA) micro- and nanoparticles have been investigated as growth factor delivery systems for cardiac repair. In this study, we aimed to develop PLGA nanoparticles containing ADM-2 intended for therapeutic angiogenesis. PLGA nanoparticles containing ADM-2 were prepared by a double emulsion modified method, resulting in 300 nm-sized stable particles with zeta potential around - 30 mV. Electron microscopy analysis by SEM and TEM revealed spherical particles with a smooth surface. High encapsulation efficiency was reached (ca.70%), as quantified by ELISA. ADM-2 associated to polymer nanoparticles was also determined by EDS elemental composition analysis, SDS-PAGE and LC-MS/MS for peptide identification. In vitro release assays showed the sustained release of ADM-2 from polymer nanoparticles for 21 days. Cell viability experiments were performed in J774 macrophages and H9c2 cardiomyocyte cells, about which PLGA nanoparticles loaded with ADM-2 did not cause toxicity in the range 0.01-1 mg/ml. Of note, encapsulated ADM-2 significantly induced cell proliferation in EA.hy926 endothelial cells, indicating the ADM-2 bioactivity was preserved after the encapsulation process. Collectively, these results demonstrate the feasibility of using PLGA nanoparticles as delivery systems for the angiogenic peptide ADM-2, which could represent a novel approach for therapeutic angiogenesis in CVD using growth factor therapy.

Cardiac progenitors and paracrine mediators in cardiogenesis and heart regeneration

The mammalian hearts have the least regenerative capabilities among tissues and organs. As such, heart regeneration has been and continues to be the ultimate goal in the treatment against acquired and congenital heart diseases. Uncovering such a long-awaited therapy is still extremely challenging in the current settings. On the other hand, this desperate need for effective heart regeneration has developed various forms of modern biotechnologies in recent years. These involve the transplantation of pluripotent stem cell-derived cardiac progenitors or cardiomyocytes generated in vitro and novel biochemical molecules along with tissue engineering platforms. Such newly generated technologies and approaches have been shown to effectively proliferate cardiomyocytes and promote heart repair in the diseased settings, albeit mainly preclinically. These novel tools and medicines give somehow credence to breaking down the barriers associated with re-building heart muscle. However, in order to maximize efficacy and achieve better clinical outcomes through these cell-based and/or cell-free therapies, it is crucial to understand more deeply the developmental cellular hierarchies/paths and molecular mechanisms in normal or pathological cardiogenesis. Indeed, the morphogenetic process of mammalian cardiac development is highly complex and spatiotemporally regulated by various types of cardiac progenitors and their paracrine mediators. Here we discuss the most recent knowledge and findings in cardiac progenitor cell biology and the major cardiogenic paracrine mediators in the settings of cardiogenesis, congenital heart disease, and heart regeneration.

Spatiotemporal delivery of basic fibroblast growth factor to directly and simultaneously attenuate cardiac fibrosis and promote cardiac tissue vascularization following myocardial infarction

Following myocardial infarction (MI), the destruction of vasculature in the infarcted heart muscle and progression of cardiac fibrosis lead to cardiac function deterioration. Vascularization of the damaged tissue and prevention of cardiac fibrosis represent promising strategies to improve cardiac function. Herein we have developed a bFGF release system with suitable release kinetics to simultaneously achieve the two goals. The release system was based on an injectable, thermosensitive, and fast gelation hydrogel and bFGF. The hydrogel had gelation time <7 s. It can quickly solidify upon injection into tissue so as to increase drug retention in the tissue. Hydrogel complex modulus can be tuned by hydrogel solution concentration. The complex modulus of 176.6 Pa and lower allowed cardiac fibroblast to maintain its phenotype. Bioactive bFGF was able to gradually release from the hydrogel for 4 weeks. The released bFGF promoted cardiac fibroblast survival under ischemic conditions mimicking those of the infarcted hearts. It also attenuated cardiac fibroblasts from differentiating into myofibroblasts in the presence of TGFβ when tested in 3D collagen model mimicking the scenario when the bFGF release system was injected into hearts. Furthermore, the released bFGF stimulated human umbilical endothelial cells to form endothelial lumen. After 4 weeks of implantation into infarcted hearts, the bFGF release system significantly increased blood vessel density, decreased myofibroblast density and collagen content, augmented cardiac cell survival/proliferation, and reduced macrophage density. In addition, the bFGF release system significantly increased cardiac function. These results demonstrate that delivery of bFGF with appropriate release kinetics alone may represent an efficient approach to control cardiac remodeling after MI.

mRNA-Based Protein Replacement Therapy for the Heart

Myocardial infarction (MI) and heart failure (HF) are the leading causes of death in the United States and in most other industrialized nations. MI leads to a massive loss of cardiomyocytes (CMs), which are replaced with non-CM cells, leading to scarring and, in most cases, HF. The adult mammalian heart has a low intrinsic regenerative capacity, mainly because of cell-cycle arrest in CMs. No effective treatment promoting heart regeneration is currently available. Recent efforts to use DNA-based or viral gene therapy approaches to induce cardiac regeneration post-MI or in HF conditions have encountered major challenges, mostly because of the poor and uncontrolled delivery of the introduced genes. Modified mRNA (modRNA) is a safe, non-immunogenic, efficient, transient, local, and controlled nucleic acid delivery system that can overcome the obstacles to DNA-based or viral approaches for cardiac gene delivery. We here review the use of modRNA in cardiac therapy, to induce cardioprotection and vascular or cardiac regeneration after MI. We discuss the current challenges in modRNA-based cardiac treatment, which will need to be overcome for the application of such treatment to ischemic heart disease.

PEG hydrogel containing calcium-releasing particles and mesenchymal stromal cells promote vessel maturation

The use of human mesenchymal stromal cells (hMSC) for treating diseased tissues with poor vascularization has received significant attention, but low cell survival has hampered its translation to the clinic. Bioglasses and glass-ceramics have also been suggested as therapeutic agents for stimulating angiogenesis in soft tissues, but these effects need further evaluation in vivo. In this study, calcium-releasing particles and hMSC were combined within a hydrogel to examine their vasculogenic potential in vitro and in vivo. The particles provided sustained calcium release and showed proangiogenic stimulation in a chorioallantoic membrane (CAM) assay. The number of hMSC encapsulated in a degradable RGD-functionalized PEG hydrogel containing particles remained constant over time and IGF-1 release was increased. When implanted in the epidydimal fat pad of immunocompromised mice, this composite material improved cell survival and stimulated vessel formation and maturation. Thus, the combination of hMSC and calcium-releasing glass-ceramics represents a new strategy to achieve vessel stabilization, a key factor in the revascularization of ischemic tissues.

STATEMENT OF SIGNIFICANCE

Increasing blood vessel formation in diseased tissues with poor vascularization is a current clinical challenge. Cell therapy using human mesenchymal stem cells has received considerable interest, but low cell survival has hampered its translation to the clinic. Bioglasses and glass-ceramics have been explored as therapeutic agents for stimulating angiogenesis in soft tissues, but these effects need further evaluation in vivo. By incorporating both human mesenchymal stem cells and glass-ceramic particles in an implantable hydrogel, this study provides insights into the vasculogenic potential in soft tissues of the combined strategies. Enhancement of vessel formation and maturation supports further investigation of this strategy.

Alignment of inducible vascular progenitor cells on a micro-bundle scaffold improves cardiac repair following myocardial infarction

Ischemic heart disease is still the leading cause of death even with the advancement of pharmaceutical therapies and surgical procedures. Early vascularization in the ischemic heart is critical for a better outcome. Although stem cell therapy has great potential for cardiovascular regeneration, the ideal cell type and delivery method of cells have not been resolved. We tested a new approach of stem cell therapy by delivery of induced vascular progenitor cells (iVPCs) grown on polymer micro-bundle scaffolds in a rat model of myocardial infarction. iVPCs partially reprogrammed from vascular endothelial cells (ECs) had potent angiogenic potential and were able to simultaneously differentiate into vascular smooth muscle cells (SMCs) and ECs in 2D culture. Under hypoxic conditions, iVPCs also secreted angiogenic cytokines such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) as measured by enzyme-linked immunosorbent assay (ELISA). A longitudinal micro-scaffold made from poly(lactic-co-glycolic acid) was sufficient for the growth and delivery of iVPCs. Co-cultured ECs and SMCs aligned well on the micro-bundle scaffold similarly as in the vessels. 3D cell/polymer micro-bundles formed by iVPCs and micro-scaffolds were transplanted into the ischemic myocardium in a rat model of myocardial infarction (MI) with ligation of the left anterior descending artery. Our in vivo data showed that iVPCs on the micro-bundle scaffold had higher survival, and better retention and engraftment in the myocardium than free iVPCs. iVPCs on the micro-bundles promoted better cardiomyocyte survival than free iVPCs. Moreover, iVPCs and iVPC/polymer micro-bundles treatment improved cardiac function (ejection fraction and fractional shortening, endocardial systolic volume) measured by echocardiography, increased vessel density, and decreased infarction size [endocardial and epicardial infarct (scar) length] better than untreated controls at 8 weeks after MI. We conclude that iVPCs grown on a polymer micro-bundle scaffold are new promising approach for cell-based therapy designed for cardiovascular regeneration in ischemic heart disease.

Fibroblast Growth Factor-1 Released from a Heparin Coacervate Improves Cardiac Function in a Mouse Myocardial Infarction Model

Emerging evidence supports the beneficial effect of fibroblast growth factor-1 (FGF1) on heart diseases, but its application has been hindered by the short half-life and limited bioactivity of the free protein. We designed an injectable coacervate to facilitate robust growth factor delivery, which would both protect and increase the bioactivity of growth factors. In this study, a model for acute myocardial infarction was established in mice, and the cardioprotective effect of the FGF1 coacervate was investigated. Echocardiographic results showed that the FGF1 coacervate inhibited ventricular dilation and preserved cardiac contractibility more than the free FGF1 and the saline control within the 6-week duration of the experiments. Histological examination revealed that the FGF1 coacervate reduced inflammation and fibrosis post-MI, significantly increased the proliferation of endothelial and mural cells, and resulted in stable arterioles and capillaries. Furthermore, the FGF1 coacervate improved the proliferation of cardiac stem cells 6 weeks post-MI. However, free FGF1, dosed identically, did not show significant difference from saline treatment. Thus, one injection of FGF1 coacervate was sufficient to attenuate the injury caused by MI, and the results were significantly better than those obtained from an equal dose of free FGF1.

Delivery of growth factor-based therapeutics in vascular diseases: Challenges and strategies

Either cardiovascular or peripheral vascular diseases have become the major cause of morbidity and mortality worldwide. Recently, growth factors therapeutics, whatever administrated in form of exogenous growth factors or their relevant genes have been discovered to be an effective strategy for the prevention and therapy of vascular diseases, because of their promoting angiogenesis. Besides, as an alternative, stem cell-based therapy has been also developed in view of their paracrine-mediated effect or ability of differentiation toward angiogenesis-related cells under assistance of growth factors. Despite of being specific and potent, no matter growth factors or stem cells-based therapy, their full clinical transformation is limited from bench to bedside. In this review, the potential choices of therapeutic modes based on types of different growth factors or stem cells were firstly summarized for vascular diseases. The confronted various challenges such as lack of non-invasive delivery method, the physiochemical challenge, the short half-life time, and poor cell survival, were carefully analyzed for these therapeutic modes. Various strategies to overcome these limitations are put forward from the perspective of drug delivery. The expertised design of a suitable delivery form will undoubtedly provide valuable insight into their clinical application in the regenerative medicine.

Cardiac Regeneration using Growth Factors: Advances and Challenges

Myocardial infarction is the most significant manifestation of ischemic heart disease and is associated with high morbidity and mortality. Novel strategies targeting at regenerating the injured myocardium have been investigated, including gene therapy, cell therapy, and the use of growth factors. Growth factor therapy has aroused interest in cardiovascular medicine because of the regeneration mechanisms induced by these biomolecules, including angiogenesis, extracellular matrix remodeling, cardiomyocyte proliferation, stem-cell recruitment, and others. Together, these mechanisms promote myocardial repair and improvement of the cardiac function. This review aims to address the strategic role of growth factor therapy in cardiac regeneration, considering its innovative and multifactorial character in myocardial repair after ischemic injury. Different issues will be discussed, with emphasis on the regeneration mechanisms as a potential therapeutic resource mediated by growth factors, and the challenges to make these proteins therapeutically viable in the field of cardiology and regenerative medicine. Resumo O infarto do miocárdio representa a manifestação mais significativa da cardiopatia isquêmica e está associado a elevada morbimortalidade. Novas estratégias vêm sendo investigadas com o intuito de regenerar o miocárdio lesionado, incluindo a terapia gênica, a terapia celular e a utilização de fatores de crescimento. A terapia com fatores de crescimento despertou interesse em medicina cardiovascular, devido aos mecanismos de regeneração induzidos por essas biomoléculas, incluindo angiogênese, remodelamento da matriz extracelular, proliferação de cardiomiócitos e recrutamento de células-tronco, dentre outros. Em conjunto, tais mecanismos promovem a reparação do miocárdio e a melhora da função cardíaca. Esta revisão pretende abordar o papel estratégico da terapia, com fatores de crescimento, para a regeneração cardíaca, considerando seu caráter inovador e multifatorial sobre o reparo do miocárdio após dano isquêmico. Diferentes questões serão discutidas, destacando-se os mecanismos de regeneração como recurso terapêutico potencial mediado por fatores de crescimento e os desafios para tornar essas proteínas terapeuticamente viáveis no âmbito da cardiologia e da medicina regenerativa.

Antagomir-92a impregnated gelatin hydrogel microsphere sheet enhances cardiac regeneration after myocardial infarction in rats

Introduction

We investigated whether attachment of gelatin hydrogel microsphere (GHM) sheet impregnated with antagomir-92a on the infarcted heart promotes angiogenesis and cardiomyogenesis, and improves cardiac function after myocardial infarction (MI) in rats.

Methods

GHM sheet impregnated with antagomir-92a, its scramble sequence antagomir-control sheet or the sheet alone was attached on the area at risk of MI after the left anterior descending coronary artery ligation. Bromodeoxyuridine (BrdU) was included in the sheet to trace proliferating cells.

Results

The antagomir-92a sheet significantly increased capillary density in the infarct border zone 14 days after MI compared to the antagomir-control sheet or the sheet alone, associated with an increase in endothelial cells incorporated with BrdU. The antagomir-92a sheet significantly increased cardiac stem cells incorporated with BrdU 3 days after MI in the infarct border zone. This was associated with an increase in cardiomyocytes incorporated with BrdU 14 days after MI. Scar area was significantly reduced by the antagomir-92a sheet compared to the antagomir-control sheet or the sheet alone (12.8 ± 1.3 vs 25.2 ± 2.2, 24.0 ± 1.7% LV area, respectively) 14 days after MI. LV dilatation was inhibited, and LV wall motion was improved 14 days after MI in rats with the antagomir-92a sheet compared to the antagomir-control sheet or the sheet alone.

Conclusions

These results suggest that attachment of the GHM sheet impregnated with antagomir-92a on the area at risk of MI enhances angiogenesis, promotes cardiomyogenesis, and ameliorates LV function.

Factorial Design of Experiments to Optimize Multiple Protein Delivery for Cardiac Repair

Myocardial infarction (MI) is a major cardiovascular disease responsible for millions of deaths annually. Protein therapies can potentially repair and regenerate the infarcted myocardium. However, because of the short half-lives of proteins in vivo, their low retention at the target tissue, and the lack of spatiotemporal cues upon injection, the efficacy of protein therapy can be limited. This efficacy can be improved by utilizing controlled release systems to overcome shortcomings associated with a direct bolus injection. Equally important is the determination of an optimal combination of different proteins having distinct roles in cardiac function and repairs to prevent or reverse the multiple pathologies that develop after infarction. In this work, we used a rat MI model to test a combination of potentially complementary proteins: tissue inhibitor of metalloproteinases 3 (TIMP-3), interleukin-10 (IL-10), basic fibroblast growth factor (FGF-2), and stromal cell-derived factor 1 alpha (SDF-1α). To achieve controlled and timed release of the proteins per their physiologic cues during proper tissue repair, we used a fibrin gel-coacervate composite. TIMP-3 and IL-10 were encapsulated in fibrin gel to offer early release, while FGF-2 and SDF-1α were encapsulated in heparin-based coacervates and distributed in the same fibrin gel to offer sustained release. We utilized a powerful statistical tool, factorial design of experiments (DOE), to refine this protein combination based on its improvement of ejection fraction 4 weeks after MI. We found that TIMP-3, FGF-2, and SDF-1α demonstrated significant contributions toward improving the ejection fraction, while the IL-10's effect was insignificant. The results also suggested that the higher doses tested for TIMP-3, FGF-2, and SDF-1α had greater benefit on function than lower doses and that there existed slight antagonism between TIMP-3 and FGF-2. Taken together, we conclude that factorial DOE can guide the evolution of multiple protein therapies in a small number of runs, saving time, money, and resources for finding the optimal dose and composition.

Nanoparticle drug delivery systems and their use in cardiac tissue therapy

Cardiovascular diseases make up one of the main causes of death today, with myocardial infarction and ischemic heart disease contributing a large share of the deaths reported. With mainstream clinical therapy focusing on palliative medicine following myocardial infarction, the structural changes that occur in the diseased heart will eventually lead to end-stage heart failure. Heart transplantation remains the only gold standard of cure but a shortage in donor organs pose a major problem that led to clinicians and researchers looking into alternative strategies for cardiac repair. This review will examine some alternative methods of treatment using chemokines and drugs carried by nanoparticles as drug delivering agents for the purposes of treating myocardial infarction through the promotion of revascularization. We will also provide an overview of existing studies involving such nanoparticulate drug delivery systems, their reported efficacy and the challenges facing their translation into ubiquitous clinical use.

Towards comprehensive cardiac repair and regeneration after myocardial infarction: Aspects to consider and proteins to deliver

Ischemic heart disease is a leading cause of death worldwide. After the onset of myocardial infarction, many pathological changes take place and progress the disease towards heart failure. Pathologies such as ischemia, inflammation, cardiomyocyte death, ventricular remodeling and dilation, and interstitial fibrosis, develop and involve the signaling of many proteins. Proteins can play important roles in limiting or countering pathological changes after infarction. However, they typically have short half-lives in vivo in their free form and can benefit from the advantages offered by controlled release systems to overcome their challenges. The controlled delivery of an optimal combination of proteins per their physiologic spatiotemporal cues to the infarcted myocardium holds great potential to repair and regenerate the heart. The effectiveness of therapeutic interventions depends on the elucidation of the molecular mechanisms of the cargo proteins and the spatiotemporal control of their release. It is likely that multiple proteins will provide a more comprehensive and functional recovery of the heart in a controlled release strategy.

Platelet-Derived Growth Factor in Heart Failure

Defective vascular and cardiomyocyte function are implicated in the development and progression of both heart failure with reduced and preserved ejection fraction. Any treatment option that augments these myocardial processes may therefore be of significant value. The platelet-derived growth factor (PDGF) family is involved in a wide range of growth processes and plays a key role in both regulating angiogenesis and mesenchymal cell development. Thus, PDGF may serve as a potent therapy for heart failure. While numerous animal studies have demonstrated beneficial cardiovascular effects of growth factor therapy, promising laboratory data has not yet translated to effective therapies. In this review, we outline the biological role of PDGF and summarize previous studies that have focused on the cardiovascular effects of normal PDGF signaling, administration of PDGF, and the effects of PDGF on stem cell therapy.

Sequential delivery of angiogenic growth factors improves revascularization and heart function after myocardial infarction

Treatment of ischemia through therapeutic angiogenesis faces significant challenges. Growth factor (GF)-based therapies can be more effective when concerns such as GF spatiotemporal presentation, bioactivity, bioavailability, and localization are addressed. During angiogenesis, vascular endothelial GF (VEGF) is required early to initiate neovessel formation while platelet-derived GF (PDGF-BB) is needed later to stabilize the neovessels. The spatiotemporal delivery of multiple bioactive GFs involved in angiogenesis, in a close mimic to physiological cues, holds great potential to treat ischemic diseases. To achieve sequential release of VEGF and PDGF, we embed VEGF in fibrin gel and PDGF in a heparin-based coacervate that is distributed in the same fibrin gel. In vitro, we show the benefits of this controlled delivery approach on cell proliferation, chemotaxis, and capillary formation. A rat myocardial infarction (MI) model demonstrated the effectiveness of this delivery system in improving cardiac function, ventricular wall thickness, angiogenesis, cardiac muscle survival, and reducing fibrosis and inflammation in the infarct zone compared to saline, empty vehicle, and free GFs. Collectively, our results show that this delivery approach mitigated the injury caused by MI and may serve as a new therapy to treat ischemic hearts pending further examination.

Infiltration of plasma rich in growth factors enhances in vivo angiogenesis and improves reperfusion and tissue remodeling after severe hind limb ischemia

PRGF is a platelet concentrate within a plasma suspension that forms an in situ-generated fibrin-matrix delivery system, releasing multiple growth factors and other bioactive molecules that play key roles in tissue regeneration. This study was aimed at exploring the angiogenic and myogenic effects of PRGF on in vitro endothelial cells (HUVEC) and skeletal myoblasts (hSkMb) as well as on in vivo mouse subcutaneously implanted matrigel and on limb muscles after a severe ischemia. Human PRGF was prepared and characterized. Both proliferative and anti-apoptotic responses to PRGF were assessed in vitro in HUVEC and hSkMb. In vivo murine matrigel plug assay was conducted to determine the angiogenic capacity of PRGF, whereas in vivo ischemic hind limb model was carried out to demonstrate PRGF-driven vascular and myogenic regeneration. Primary HUVEC and hSkMb incubated with PRGF showed a dose dependent proliferative and anti-apoptotic effect and the PRGF matrigel plugs triggered an early and significant sustained angiogenesis compared with the control group. Moreover, mice treated with PRGF intramuscular infiltrations displayed a substantial reperfusion enhancement at day 28 associated with a fibrotic tissue reduction. These findings suggest that PRGF-induced angiogenesis is functionally effective at expanding the perfusion capacity of the new vasculature and attenuating the endogenous tissue fibrosis after a severe-induced skeletal muscle ischemia.

Controlled delivery of fibroblast growth factor-1 and neuregulin-1 from biodegradable microparticles promotes cardiac repair in a rat myocardial infarction model through activation of endogenous regeneration

Acidic fibroblast growth factor (FGF1) and neuregulin-1 (NRG1) are growth factors involved in cardiac development and regeneration. Microparticles (MPs) mediate cytokine sustained release, and can be utilized to overcome issues related to the limited therapeutic protein stability during systemic administration. We sought to examine whether the administration of microparticles (MPs) containing FGF1 and NRG1 could promote cardiac regeneration in a myocardial infarction (MI) rat model. We investigated the possible underlying mechanisms contributing to the beneficial effects of this therapy, especially those linked to endogenous regeneration. FGF1- and NRG1-loaded MPs were prepared using a multiple emulsion solvent evaporation technique. Seventy-three female Sprague-Dawley rats underwent permanent left anterior descending coronary artery occlusion, and MPs were intramyocardially injected in the peri-infarcted zone four days later. Cardiac function, heart tissue remodeling, revascularization, apoptosis, cardiomyocyte proliferation, and stem cell homing were evaluated one week and three months after treatment. MPs were shown to efficiently encapsulate FGF1 and NRG1, releasing the bioactive proteins in a sustained manner. Three months after treatment, a statistically significant improvement in cardiac function was detected in rats treated with growth factor-loaded MPs (FGF1, NRG1, or FGF1/NRG1). The therapy led to inhibition of cardiac remodeling with smaller infarct size, a lower fibrosis degree and induction of tissue revascularization. Cardiomyocyte proliferation and progenitor cell recruitment were detected. Our data support the therapeutic benefit of NRG1 and FGF1 when combined with protein delivery systems for cardiac regeneration. This approach could be scaled up for use in pre-clinical and clinical studies.

Therapeutics targeting angiogenesis: genetics and epigenetics, extracellular miRNAs and signaling networks (Review)

Angiogenesis is a process of neovascular formation from pre-existing blood vessels, which consists of sequential steps for vascular destabilization, angiogenic sprouting, lumen formation and vascular stabilization. Vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), angiopoietin, Notch, transforming growth factor-β (TGF-β), Hedgehog and WNT signaling cascades orchestrate angiogenesis through the direct or indirect regulation of quiescence, migration and the proliferation of endothelial cells. Small-molecule compounds and human/humanized monoclonal antibodies interrupting VEGF signaling have been developed as anti-angiogenic therapeutics for cancer and neovascular age-related macular degeneration (AMD). Gene or protein therapy delivering VEGF, FGF2 or FGF4, as well as cell therapy using endothelial progenitor cells (EPCs), mesenchymal stem cells (MSCs) or induced pluripotent stem cells (iPSCs) have been developed as pro-angiogenic therapeutics for ischemic heart disease and peripheral vascular disease. Anti-angiogenic therapy for cancer and neovascular AMD is more successful than pro-angiogenic therapy for cardiovascular diseases, as VEGF-signal interruption is technically feasible compared with vascular re-construction. Common and rare genetic variants are detected using array-based technology and personal genome sequencing, respectively. Drug and dosage should be determined based on personal genotypes of VEGF and other genes involved in angiogenesis. As epigenetic alterations give rise to human diseases, polymer-based hydrogel film may be utilized for the delivery of drugs targeting epigenetic processes and angiogenesis as treatment modalities for cardiovascular diseases. Circulating microRNAs (miRNAs) in exosomes and microvesicles are applied as functional biomarkers for diagnostics and prognostics, while synthetic miRNAs in polymer-based nanoparticles are applicable for therapeutics. A more profound understanding of the spatio-temporal interactions of regulatory signaling cascades and advances in personal genotyping and miRNA profiling are required for the optimization of targeted therapy.

Functional benefits of PLGA particulates carrying VEGF and CoQ10 in an animal of myocardial ischemia

Myocardial ischemia (MI) remains one of the leading causes of death worldwide. Angiogenic therapy with the vascular endothelial growth factor (VEGF) is a promising strategy to overcome hypoxia and its consequences. However, from the clinical data it is clear that fulfillment of the potential of VEGF warrants a better delivery strategy. On the other hand, the compelling evidences of the role of oxidative stress in diseases like MI encourage the use of antioxidant agents. Coenzyme Q10 (CoQ10) due to its role in the electron transport chain in the mitochondria seems to be a good candidate to manage MI but is associated with poor biopharmaceutical properties seeking better delivery approaches. The female Sprague Dawley rats were induced MI and were followed up with VEGF microparticles intramyocardially and CoQ10 nanoparticles orally or their combination with appropriate controls. Cardiac function was assessed by measuring ejection fraction before and after three months of therapy. Results demonstrate significant improvement in the ejection fraction after three months with both treatment forms individually; however the combination therapy failed to offer any synergism. In conclusion, VEGF microparticles and CoQ10 nanoparticles can be considered as promising strategies for managing MI.