Cardiac-Adaptive Conductive Hydrogel Patch Enabling Construction of Mechanical-Electrical Anisotropic Microenvironment for Heart Repair

Engineering functional electroconductive hydrogels for targeted therapy in myocardial infarction repair

Myocardial infarction (MI) is characterized by a paucity of cardiomyocyte regeneration, leading to significant morbidity and mortality. Contemporary therapeutic modalities, while mitigating ischemic effects, fail to reconstitute the impaired electromechanical coupling within the infracted myocardium. Emerging evidence supports the utility of electroconductive hydrogels (ECHs) in facilitating post-MI cardiac function recovery by restoring the conductive microenvironment of the infarcted tissue. This comprehensive review delineates the taxonomy of ECHs predicated on their constituent conductive materials. It also encapsulates prevailing research trends in ECH-mediated MI repair, encompassing innovative design paradigms and microenvironment-sensitive strategies. The review also provides a critical appraisal of various implantation techniques, underscored by a thorough examination of the attendant considerations. It elucidates the mechanistic underpinnings by which hydrogels exert salutary effects on myocardial repair, namely by augmenting mechanical and electrical integrity, exerting anti-inflammatory actions, fostering angiogenesis, and curtailing adverse remodeling processes. Furthermore, the review engages with the pressing challenge of optimizing ECH functionality to achieve superior reparative outcomes post-MI. The discourse concludes with an anticipatory perspective on the evolution of ECH scaffolds, advocating for a tailored approach that integrates multifaceted physicochemical properties to cater to the nuances of personalized medicine.

Fish Swim Bladder-Derived ECM Hydrogels Effectively Treat Myocardial Ischemic Injury through Immunomodulation and Angiogenesis

Injectable hydrogel implants represent a promising therapeutic approach for ischemic heart failure; but their efficacy is often limited by low bioactivity, poor durability, and inadequate injection techniques. Herein, a unique hydrogel incorporating extracellular matrix from fish swim bladder (FSB-ECM), which has distinct advantages over mammalian derived ECM, such as low antigenicity, bioactivity, and source safety, is developed. It consists of collagen, glycoproteins, and proteoglycans, including 13 proteins common in the myocardial matrix and three specific proteins: HSPG, Col12a1, and vWF. This hydrogel enhances cardiac cell adhesion and stretching while promoting angiogenesis and M2 macrophage polarization. In addition, its storage modulus (G') increases over time, reaching about 1000 Pa after 5 min, which facilitates transcatheter delivery and in situ gelling. Furthermore, this hydrogel provides sustained support for cardiac contractions, exhibiting superior longevity. In a rat model of ischemic heart failure, the ejection fraction significantly improves with FSB-ECM treatment, accompanied by increased angiogenesis, reduced inflammation, and decreased infarct size. Finally, RNA sequencing combined with in vitro assays identifies ANGPTL4 as a key protein involved in mediating the effects of FSB-ECM treatment. Overall, this new injectable hydrogel based on FSB-ECM is suitable for transcatheter delivery and possesses remarkable reparative capabilities for treating heart failure.

Engineered Strategies to Interfere with Macrophage Fate in Myocardial Infarction

Myocardial infarction (MI), a severe cardiovascular condition, is typically triggered by coronary artery disease, resulting in ischemic damage and the subsequent necrosis of the myocardium. Macrophages, known for their remarkable plasticity, are capable of exhibiting a range of phenotypes and functions as they react to diverse stimuli within their local microenvironment. In recent years, there has been an increasing number of studies on the regulation of macrophage behavior based on tissue engineering strategies, and its regulatory mechanisms deserve further investigation. This review first summarizes the effects of key regulatory factors of engineered biomaterials (including bioactive molecules, conductivity, and some microenvironmental factors) on macrophage behavior, then explores specific methods for inducing macrophage behavior through tissue engineering materials to promote myocardial repair, and summarizes the role of macrophage-host cell crosstalk in regulating inflammation, vascularization, and tissue remodeling. Finally, we propose some future challenges in regulating macrophage-material interactions and tailoring personalized biomaterials to guide macrophage phenotypes.

Anisotropic conductive scaffolds for post-infarction cardiac repair

Myocardial infarction (MI) remains one of the most common and lethal cardiovascular diseases (CVDs), leading to the deterioration of cardiac function due to myocardial cell necrosis and fibrous scar tissue formation. Myocardial infarction (MI) remains one of the most common and lethal cardiovascular diseases (CVDs), leading to the deterioration of cardiac function due to myocardial cell necrosis and fibrous scar tissue formation. After MI, the anisotropic structural properties of myocardial tissue are destroyed, and its mechanical and electrical microenvironment also undergoes a series of pathological changes, such as ventricular wall stiffness, abnormal contraction, conduction network disruption, and irregular electrical signal propagation, which may further induce myocardial remodeling and even lead to heart failure. Therefore, bionic reconstruction of the anisotropic structural-mechanical-electrical microenvironment of the infarct area is key to repairing damaged myocardium. This article first summarizes the pathological changes in muscle fibre structure and conductive microenvironment after cardiac injury, and focuses on the classification and preparation methods of anisotropic conductive materials. In addition, the effects of these anisotropic conductive materials on the behavior of cardiac resident cells after myocardial infarction, such as directional growth, maturation, proliferation and migration, and the differentiation fate of stem cells and the possible molecular mechanisms involved are summarized. The design strategies for anisotropic conductive scaffolds for myocardial repair in future clinical research are also discussed, with the aim of providing new insights for researchers in related fields.

Biomimetic Versatile Anisotropic, Electroactive Cellulose Hydrogel Scaffolds Tailored from Fern Stem Serving as Nerve Conduit and Cardiac Patch

Peripheral nerve injury (PNI) and myocardial infarction (MI) are the two most clinically common soft excitable tissue injuries. Both nerve and cardiac tissues exhibit structural anisotropy and electrophysiological activity, providing a wide range of biophysical cues for cell and tissue repair. However, balancing microstructural anisotropy, electroactivity, and biocompatibility is challenging. To address this issue, Dicranopteris linearis (D. linearis) is proposed as a low-perceived value fern plant. Moreover, to enhance its usefulness, it can be designed into a tubular structure and a lamellar structure to bridge the damaged tissue. Therefore, a robust yet simple top-down approach is proposed to designing and fabricating the desired biomimetic versatile hydrogels orienting from the D. linearis to customize for different soft excitable tissue repair applications. These anisotropic electroactive hydrogels performed well as nerve guidance conduits (NGC) and engineered cardiac patches (ECP) in the repair of PNI and MI, respectively. Two birds, one stone. Accordingly, the biomimetic strategy of D. linearis to NGC and D. linearis to ECP is first proposed, opening a new horizon for constructing tissue engineering using natural sources.

Monascus pigment-protected bone marrow-derived stem cells for heart failure treatment

Mesenchymal stem cells (MSCs) have demonstrated significant therapeutic potential in heart failure (HF) treatment. However, their clinical application is impeded by low retention rate and low cellular activity of MSCs caused by high inflammatory and reactive oxygen species (ROS) microenvironment. In this study, monascus pigment (MP) nanoparticle (PPM) was proposed for improving adverse microenvironment and assisting in transplantation of bone marrow-derived MSCs (BMSCs). Meanwhile, in order to load PPM and reduce the mechanical damage of BMSCs, injectable hydrogels based on Schiff base cross-linking were prepared. The PPM displays ROS-scavenging and macrophage phenotype-regulating capabilities, significantly enhancing BMSCs survival and activity in HF microenvironment. This hydrogel demonstrates superior biocompatibility, injectability, and tissue adhesion. With the synergistic effects of injectable, adhesive hydrogel and the microenvironment-modulating properties of MP, cardiac function was effectively improved in the pericardial sac of rats. Our results offer insights into advancing BMSCs-based HF therapies and their clinical applications.

A Heart Rate Matched Patch for Mechano-Chemical Treatment of Myocardial Infarction: Optimal Design and Transspecies Application

After myocardial infarction (MI), ventricular dilation and the microscopic passive stretching of the infarcted border zone is the meaning contributor to the continuous expansion of myocardial fibrosis. Epicardial hydrogel patches have been demonstrated to alleviate this sequela of MI in small-animal models. However, these have not been successfully translated to humans or even large animals, in part because of challenges in attaining both the greater stiffness and slower viscoelastic relaxation that mathematical models predict to be optimal for application to larger, slower-beating hearts. Here, using borate-based dynamic covalent chemistry, we develop an injectable "heart rate matched" viscoelastic gelatin (VGtn) hydrogel with a gel point tunable across the stiffnesses and frequencies that are predicted to transspecies and cross-scale cardiac repair after MI. Small-animal experiments demonstrated that, compared to heart rate mismatched patches, the heart rate matched VGtn patches inhibited ventricular bulging and attenuated stress concentrations in the myocardium after MI. In particular, the viscoelastic patch can coordinate the microscopic strain at the infarction boundary. VGtn loaded with anti-fibrotic agents further reduced myocardial damage and promoted angiogenesis in the myocardium. The tuned heart rate matched patches demonstrated similar benefits in a larger-scale and lower heart rate porcine MI model. Results suggest that heart rate matched VGtn patches may hold potential for clinical translation.

A Biomimetic Optical Cardiac Fibrosis-on-a-Chip for High-Throughput Anti-Fibrotic Drug Screening

Cardiac fibrosis has emerged as the primary cause of morbidity, disability, and even mortality in numerous nations. In light of the advancements in precision medicine strategies, substantial attention has been directed toward the development of a practical and precise drug screening platform customized for individual patients. In this study, we introduce a biomimetic cardiac fibrosis-on-a-chip incorporating structural color hydrogels (SCHs) to enable optical high-throughput drug screening. By cocultivating a substantial proportion of cardiac fibroblasts (CFBs) with cardiomyocytes on the SCH, this biomimetic fibrotic microtissue successfully replicates the structural components and biomechanical properties associated with cardiac fibrosis. More importantly, the structural color shift observed in the SCH can be indicative of cardiac contraction and relaxation, making it a valuable tool for evaluating fibrosis progression. By incorporating such fibrotic microtissue into a microfluidic gradient chip, we develop a biomimetic optical cardiac fibrosis-on-a-chip platform that accurately and efficiently screens potential anti-fibrotic drugs. These characteristics suggest that this microphysiological platform possesses the capability to establish a preclinical framework for screening cardiac drugs, and may even contribute to the advancement of precision medicine.

Cardiac tissue engineering: an emerging approach to the treatment of heart failure

Heart failure is a major health problem in which the heart is unable to pump enough blood to meet the body's needs. It is a progressive disease that becomes more severe over time and can be caused by a variety of factors, including heart attack, cardiomyopathy and heart valve disease. There are various methods to cure this disease, which has many complications and risks. The advancement of knowledge and technology has proposed new methods for many diseases. One of the promising new treatments for heart failure is tissue engineering. Tissue engineering is a field of research that aims to create living tissues and organs to replace damaged or diseased tissue. The goal of tissue engineering in heart failure is to improve cardiac function and reduce the need for heart transplantation. This can be done using the three important principles of cells, biomaterials and signals to improve function or replace heart tissue. The techniques for using cells and biomaterials such as electrospinning, hydrogel synthesis, decellularization, etc. are diverse. Treating heart failure through tissue engineering is still under development and research, but it is hoped that there will be no transplants or invasive surgeries in the near future. In this study, based on the most important research in recent years, we will examine the power of tissue engineering in the treatment of heart failure.

Chemically Programmed Hydrogels for Spatiotemporal Modulation of the Cardiac Pathological Microenvironment

After myocardial infarction (MI), sustained ischemic events induce pathological microenvironments characterized by ischemia-hypoxia, oxidative stress, inflammatory responses, matrix remodeling, and fibrous scarring. Conventional clinical therapies lack spatially targeted and temporally responsive modulation of the infarct microenvironment, leading to limited myocardial repair. Engineered hydrogels have a chemically programmed toolbox for minimally invasive localization of the pathological microenvironment and personalized responsive modulation over different pathological periods. Chemically programmed strategies for crosslinking interactions, interfacial binding, and topological microstructures in hydrogels enable minimally invasive implantation and in situ integration tailored to the myocardium. This enhances substance exchange and signal interactions within the infarcted microenvironment. Programmed responsive polymer networks, intelligent micro/nanoplatforms, and biological therapeutic cues contribute to the formation of microenvironment-modulated hydrogels with precise targeting, spatiotemporal control, and on-demand feedback. Therefore, this review summarizes the features of the MI microenvironment and chemically programmed schemes for hydrogels to conform, integrate, and modulate the cardiac pathological microenvironment. Chemically programmed strategies for oxygen-generating, antioxidant, anti-inflammatory, provascular, and electrointegrated hydrogels to stimulate iterative and translational cardiac tissue engineering are discussed.

PEDOT-Integrated Fish Swim Bladders as Conductive Nerve Conduits

Advanced artificial nerve conduits offer a promising alternative for nerve injury repair. Current research focuses on improving the therapeutic effectiveness of nerve conduits by optimizing scaffold materials and functional components. In this study, a novel poly(3,4-ethylenedioxythiophene) (PEDOT)-integrated fish swim bladder (FSB) is presented as a conductive nerve conduit with ordered topology and electrical stimulation to promote nerve regeneration. PEDOT nanomaterials and adhesive peptides (IKVAV) are successfully incorporated onto the decellularized FSB substrate through pre-coating with polydopamine. The obtained PEDOT/IKVAV-integrated FSB substrate exhibits outstanding mechanical properties, high electrical conductivity, stability, as well as excellent biocompatibility and bioadhesive properties. In vitro studies confirm that the PEDOT/IKVAV-integrated FSB can effectively facilitate the growth and directional extension of pheochromocytoma 12 cells and dorsal root ganglion neurites. In addition, in vivo experiments demonstrate that the proposed PEDOT/IKVAV-integrated FSB conduit can accelerate defective nerve repair and functional restoration. The findings indicate that the FSB-derived conductive nerve conduits with multiple regenerative inducing signals integration provide a conducive milieu for nerve regeneration, exhibiting great potential for repairing long-segment neural defects.

Nanoparticle-Patch System for Localized, Effective, and Sustained miRNA Administration into Infarcted Myocardium to Alleviate Myocardial Ischemia-Reperfusion Injury

Timely blood reperfusion after myocardial infarction (MI) paradoxically triggers ischemia-reperfusion injury (I/RI), which currently has not been conquered by clinical treatments. Among innovative repair strategies for myocardial I/RI, microRNAs (miRNAs) are expected as genetic tools to rescue damaged myocardium. Our previous study identified that miR-30d can provide protection against myocardial apoptosis and fibrosis to alleviate myocardial injury. Although common methods such as liposomes and viral vectors have been used for miRNA transfection, their therapeutic efficiencies have struggled with inefficient in vivo delivery, susceptible inactivation, and immunogenicity. Here, we establish a nanoparticle-patch system for miR-30d delivery in a murine myocardial I/RI model, which contains ZIF-8 nanoparticles and a conductive microneedle patch. Loaded with miR-30d, ZIF-8 nanoparticles leveraging the proton sponge effect enable miR-30d to escape the endocytic pathway, thus avoiding premature degradation in lysosomes. Meanwhile, the conductive microneedle patch offers a distinct advantage by intramyocardial administration for localized, effective, and sustained miR-30d delivery, and it simultaneously releases Au nanoparticles to reconstruct electrical impulses within the infarcted myocardium. Consequently, the nanoparticle-patch system supports the consistent and robust expression of miR-30d in cardiomyocytes. Results from echocardiography and electrocardiogram (ECG) revealed improved heart functions and standard ECG wave patterns in myocardial I/RI mice after implantation of a nanoparticle-patch system for 3 and 6 weeks. In summary, our work incorporated conductive microneedle patch and miR-30d nanodelivery systems to synergistically transcend the limitations of common RNA transfection methods, thus mitigating myocardial I/RI.

A cigarette filter-derived biomimetic cardiac niche for myocardial infarction repair

Cell implantation offers an appealing avenue for heart repair after myocardial infarction (MI). Nevertheless, the implanted cells are subjected to the aberrant myocardial niche, which inhibits cell survival and maturation, posing significant challenges to the ultimate therapeutic outcome. The functional cardiac patches (CPs) have been proved to construct an elastic conductive, antioxidative, and angiogenic microenvironment for rectifying the aberrant microenvironment of the infarcted myocardium. More importantly, inducing implanted cardiomyocytes (CMs) adapted to the anisotropic arrangement of myocardial tissue by bioengineered structural cues within CPs are more conducive to MI repair. Herein, a functional Cig/(TA-Cu) CP served as biomimetic cardiac niche was fabricated based on structural anisotropic cigarette filter by modifying with tannic acid (TA)-chelated Cu2+ (TA-Cu complex) via a green method. This CP possessed microstructural anisotropy, electrical conductivity and mechanical properties similar to natural myocardium, which could promote elongation, orientation, maturation, and functionalization of CMs. Besides, the Cig/(TA-Cu) CP could efficiently scavenge reactive oxygen species, reduce CM apoptosis, ultimately facilitating myocardial electrical integration, promoting vascular regeneration and improving cardiac function. Together, our study introduces a functional CP that integrates multimodal cues to create a biomimetic cardiac niche and provides an effective strategy for cardiac repair.