Intramyocardial injection of hydrogel with high interstitial spread does not impact action potential propagation

Biomaterials for direct cardiac repair-A rapid scoping review 2012-2022

A plethora of biomaterials for heart repair are being tested worldwide for potential clinical application. These therapeutics aim to enhance the quality of life of patients with heart disease using various methods to improve cardiac function. Despite the myriad of therapeutics tested, only a minority of these studied biomaterials have entered clinical trials. This rapid scoping review aims to analyze literature available from 2012 to 2022 with a focus on clinical trials using biomaterials for direct cardiac repair, i.e., where the intended function of the biomaterial is to enhance the repair of the endocardium, myocardium, epicardium or pericardium. This review included neither biomaterials related to stents and valve repair nor biomaterials serving as vehicles for the delivery of drugs. Surprisingly, the literature search revealed that only 8 different biomaterials mentioned in 23 different studies out of 7038 documents (journal articles, conference abstracts or clinical trial entries) have been tested in clinical trials since 2012. All of these, intended to treat various forms of ischaemic heart disease (heart failure, myocardial infarction), were of natural origin and most used direct injections as their delivery method. This review thus reveals notable gaps between groups of biomaterials tested pre-clinically and clinically. STATEMENT OF SIGNIFICANCE: Rapid scoping review of clinical application of biomaterials for cardiac repair. 7038 documents screened; 23 studies mention 8 different biomaterials only. Biomaterials for repair of endocardium, myocardium, epicardium or pericardium. Only 8 different biomaterials entered clinical trials in the past 10 years. All of the clinically translated biomaterials were of natural origin.

Myocardial Matrix Hydrogels Mitigate Negative Remodeling and Improve Function in Right Heart Failure Model

This study evaluates the effectiveness of myocardial matrix (MM) hydrogels in mitigating negative right ventricular (RV) remodeling in a rat model of RV heart failure. The goal was to assess whether a hydrogel derived from either the right or left ventricle could promote cardiac repair. Injured rat right ventricles were injected with either RV-or left ventricular-derived MM hydrogels. Both hydrogels improved RV function and morphology and reduced negative remodeling. This study supports the potential of injectable biomaterial therapies for treating RV heart failure.

Advances in biomaterial-based cardiac organoids

Cardiovascular disease (CVD) is one of the important causes of death worldwide. The incidence and mortality rates are increasing annually with the intensification of social aging. The efficacy of drug therapy is limited in individuals suffering from severe heart failure due to the inability of myocardial cells to undergo regeneration and the challenging nature of cardiac tissue repair following injury. Consequently, surgical transplantation stands as the most efficient approach for treatment. Nevertheless, the shortage of donors and the considerable number of heart failure patients worldwide, estimated at 26 million, results in an alarming treatment deficit, with only around 5000 heart transplants feasible annually. The existing major alternatives, such as mechanical or xenogeneic hearts, have significant flaws, such as high cost and rejection, and are challenging to implement for large-scale, long-term use. An organoid is a three-dimensional (3D) cell tissue that mimics the characteristics of an organ. The critical application has been rated in annual biotechnology by authoritative journals, such as Science and Cell. Related industries have achieved rapid growth in recent years. Based on this technology, cardiac organoids are expected to pave the way for viable heart repair and treatment and play an essential role in pathological research, drug screening, and other areas. This review centers on the examination of biomaterials employed in cardiac repair, strategies employed for the reconstruction of cardiac structure and function, clinical investigations pertaining to cardiac repair, and the prospective applications of cardiac organoids. From basic research to clinical practice, the current status, latest progress, challenges, and prospects of biomaterial-based cardiac repair are summarized and discussed, providing a reference for future exploration and development of cardiac regeneration strategies.

Progress in Bioengineering Strategies for Heart Regenerative Medicine

The human heart has the least regenerative capabilities among tissues and organs, and heart disease continues to be a leading cause of mortality in the industrialized world with insufficient therapeutic options and poor prognosis. Therefore, developing new therapeutic strategies for heart regeneration is a major goal in modern cardiac biology and medicine. Recent advances in stem cell biology and biotechnologies such as human pluripotent stem cells (hPSCs) and cardiac tissue engineering hold great promise for opening novel paths to heart regeneration and repair for heart disease, although these areas are still in their infancy. In this review, we summarize and discuss the recent progress in cardiac tissue engineering strategies, highlighting stem cell engineering and cardiomyocyte maturation, development of novel functional biomaterials and biofabrication tools, and their therapeutic applications involving drug discovery, disease modeling, and regenerative medicine for heart disease.

Therapeutic Acellular Scaffolds for Limiting Left Ventricular Remodelling-Current Status and Future Directions

Myocardial infarction (MI) is one of the leading causes of heart-related deaths worldwide. Following MI, the hypoxic microenvironment triggers apoptosis, disrupts the extracellular matrix and forms a non-functional scar that leads towards adverse left ventricular (LV) remodelling. If left untreated this eventually leads to heart failure. Besides extensive advancement in medical therapy, complete functional recovery is never accomplished, as the heart possesses limited regenerative ability. In recent decades, the focus has shifted towards tissue engineering and regenerative strategies that provide an attractive option to improve cardiac regeneration, limit adverse LV remodelling and restore function in an infarcted heart. Acellular scaffolds possess attractive features that have made them a promising therapeutic candidate. Their application in infarcted areas has been shown to improve LV remodelling and enhance functional recovery in post-MI hearts. This review will summarise the updates on acellular scaffolds developed and tested in pre-clinical and clinical scenarios in the past five years with a focus on their ability to overcome damage caused by MI. It will also describe how acellular scaffolds alone or in combination with biomolecules have been employed for MI treatment. A better understanding of acellular scaffolds potentialities may guide the development of customised and optimised therapeutic strategies for MI treatment.

A novel intramural TGF β 1 hydrogel delivery method to decrease murine abdominal aortic aneurysm and rat aortic pseudoaneurysm formation and progression

OBJECTIVES

Aneurysms are generally the result of dilation of all 3 layers of the vessel wall, and pseudoaneurysms are the result of localized extravasation of blood that is contained by surrounding tissue. Since there is still no recommended protocol to decrease aneurysm formation and progression, we hypothesised that intramural delivery of TGF β1 hydrogel can decrease aneurysm and pseudoaneurysm formation and progression.

MATERIALS

Male C57BL/6 J mice (12-14 wk), SD rats (200 g) and pig abdominal aortas were used, and hydrogels were fabricated by the interaction of sodium alginate (SA), hyaluronic acid (HA) and CaCO3.

METHODS

A CaCl2 adventitial incubation model in mice and a decellularized human great saphenous vein patch angioplasty model in rats were used. TGF β1 hydrogel was intramurally delivered after CaCl2 incubation in mice; at day 7, the abdomen in some mice was reopened, and TGF β1 hydrogel was injected intramurally into the aorta. In rats, TGF β1 hydrogel was delivered intramurally after patch angioplasty completion. Tissues were harvested at day 14 and analysed by histology and immunohistochemistry staining. The pig aorta was also intramurally injected with hydrogel.

RESULTS

In mice, rhodamine hydrogel was still found between the medium and adventitia at day 14. In the mouse aneurysm model, there was a thicker wall and smaller amount of elastin breaks in the TGF β1 hydrogel-delivered groups both at day 0 and day 7 after CaCl2 incubation, and there were larger numbers of p-smad2- and TAK1-positive cells in the TGF β1 hydrogel-injected groups. In the rat decellularized human saphenous vein patch pseudoaneurysm model, there was a higher incidence of pseudoaneurysm formation when the patch was decellularized using 3% SDS, and delivery of TGF β1 hydrogel could effectively decrease the formation of pseudoaneurysm formation and increase p-smad2 and TAK1 expression. In pig aortas, hydrogels can be delivered between the medium and adventitia easily and successfully.

CONCLUSIONS

Intramural delivery of TGF β1 hydrogel can effectively decease aneurysm and pseudoaneurysm formation and progression in both mice and rats, and pig aortas can also be successfully intramurally injected with hydrogel. This technique may be a promising drug delivery method and therapeutic choice to decrease aneurysm and pseudoaneurysm formation and progression in the clinic.

Immunomodulatory biomaterials and their application in therapies for chronic inflammation-related diseases

The degree of tissue injuries such as the level of scarring or organ dysfunction, and the immune response against them primarily determine the outcome and speed of healing process. The successful regeneration of functional tissues requires proper modulation of inflammation-producing immune cells and bioactive factors existing in the damaged microenvironment. In the tissue repair and regeneration processes, different types of biomaterials are implanted either alone or by combined with other bioactive factors, which will interact with the immune systems including immune cells, cytokines and chemokines etc. to achieve different results highly depending on this interplay. In this review article, the influences of different types of biomaterials such as nanoparticles, hydrogels and scaffolds on the immune cells and the modification of immune-responsive factors such as reactive oxygen species (ROS), cytokines, chemokines, enzymes, and metalloproteinases in tissue microenvironment are summarized. In addition, the recent advances of immune-responsive biomaterials in therapy of inflammation-associated diseases such as myocardial infarction, spinal cord injury, osteoarthritis, inflammatory bowel disease and diabetic ulcer are discussed.

In-silico study of the cardiac arrhythmogenic potential of biomaterial injection therapy

Biomaterial injection is a novel therapy to treat ischemic heart failure (HF) that has shown to reduce remodeling and restore cardiac function in recent preclinical studies. While the effect of biomaterial injection in reducing mechanical wall stress has been recently demonstrated, the influence of biomaterials on the electrical behavior of treated hearts has not been elucidated. In this work, we developed computational models of swine hearts to study the electrophysiological vulnerability associated with biomaterial injection therapy. The propagation of action potentials on realistic biventricular geometries was simulated by numerically solving the monodomain electrophysiology equations on anatomically-detailed models of normal, HF untreated, and HF treated hearts. Heart geometries were constructed from high-resolution magnetic resonance images (MRI) where the healthy, peri-infarcted, infarcted and gel regions were identified, and the orientation of cardiac fibers was informed from diffusion-tensor MRI. Regional restitution properties in each case were evaluated by constructing a probability density function of the action potential duration (APD) at different cycle lengths. A comparative analysis of the ventricular fibrillation (VF) dynamics for every heart was carried out by measuring the number of filaments formed after wave braking. Our results suggest that biomaterial injection therapy does not affect the regional dispersion of repolarization when comparing untreated and treated failing hearts. Further, we found that the treated failing heart is more prone to sustain VF than the normal heart, and is at least as susceptible to sustained VF as the untreated failing heart. Moreover, we show that the main features of VF dynamics in a treated failing heart are not affected by the level of electrical conductivity of the biogel injectates. This work represents a novel proof-of-concept study demonstrating the feasibility of computer simulations of the heart in understanding the arrhythmic behavior in novel therapies for HF.

Delivering More of an Injectable Human Recombinant Collagen III Hydrogel Does Not Improve Its Therapeutic Efficacy for Treating Myocardial Infarction

Injectable hydrogels are a promising method to enhance repair in the heart after myocardial infarction (MI). However, few studies have compared different strategies for the application of biomaterial treatments. In this study, we use a clinically relevant mouse MI model to assess the therapeutic efficacy of different treatment protocols for intramyocardial injection of a recombinant human collagen III (rHCIII) thermoresponsive hydrogel. Comparing a single hydrogel injection at an early time point (3 h) versus injections at multiple time points (3 h, 1 week, and 2 weeks) post-MI revealed that the single injection group led to superior cardiac function, reduced scar size and inflammation, and increased vascularization. Omitting the 3 h time point and delivering the hydrogel at 1 and 2 weeks post-MI led to poorer cardiac function. The positive effects of the single time point injection (3 h) on scar size and vascular density were lost when the hydrogel's collagen concentration was increased from 1% to 2%, and it did not confer any additional functional improvement. This study shows that early treatment with a rHCIII hydrogel can improve cardiac function post-MI but that injecting more rHCIII (by increased concentration or more over time) can reduce its efficacy, thus highlighting the importance of investigating optimal treatment strategies of biomaterial therapy for MI.

Dose optimization of decellularized skeletal muscle extracellular matrix hydrogels for improving perfusion and subsequent validation in an aged hindlimb ischemia model

Peripheral artery disease (PAD) affects more than 27 million individuals in North America and Europe, and current treatment strategies mainly aim to restore blood perfusion. However, many patients are ineligible for existing procedures, and these therapies are often ineffective. Previous studies have demonstrated success of an injectable decellularized skeletal muscle extracellular matrix (ECM) hydrogel in a young rat hindlimb ischemia model of PAD, but further pre-clinical studies are necessary prior to clinical translation. In this study, varying concentrations of a skeletal muscle ECM hydrogel were investigated for material properties and in vivo effects on restoring blood perfusion. Rheological measurements indicated an increase in viscosity and mechanical strength with the higher concentrations of the ECM hydrogels. When injecting dye-labelled ECM hydrogels into a healthy rat, differences were also observed for the spreading and degradation rate of the various concentrations. The three concentrations for the ECM hydrogel were then further examined in a young rat hindlimb ischemia model. The efficacy of the optimal ECM hydrogel concentration was then further confirmed in an aged mouse hindlimb ischemia model. These results further validate the use of decellularized skeletal muscle ECM hydrogels for improving blood perfusion in small animal models of PAD.

An in Vivo miRNA Delivery System for Restoring Infarcted Myocardium

A major challenge in myocardial infarction (MI)-related heart failure treatment using microRNA is the efficient and sustainable delivery of miRNAs into myocardium to achieve functional improvement through stimulation of intrinsic myocardial restoration. In this study, we established an in vivo delivery system using polymeric nanoparticles to carry miRNA (miNPs) for localized delivery within a shear-thinning injectable hydrogel. The miNPs triggered proliferation of human embryonic stem cell-derived cardiomyocytes and endothelial cells (hESC-CMs and hESC-ECs) and promoted angiogenesis in hypoxic conditions, showing significantly lower cytotoxicity than Lipofectamine. Furthermore, one injected dose of hydrogel/miNP in MI rats demonstrated significantly improved cardiac functions: increased ejection fraction from 45% to 64%, reduced scar size from 20% to 10%, and doubled capillary density in the border zone compared to the control group at 4 weeks. As such, our results indicate that this injectable hydrogel/miNP composite can deliver miRNA to restore injured myocardium efficiently and safely.

A comparison of two quasi-static computational models for assessment of intra-myocardial injection as a therapeutic strategy for heart failure

Myocardial infarction, or heart attack, is the leading cause of mortality globally. Although the treatment of myocardial infarct has improved significantly, scar tissue that persists can often lead to increased stress and adverse remodeling of surrounding tissue and ultimately to heart failure. Intra-myocardial injection of biomaterials represents a potential treatment to attenuate remodeling, mitigate degeneration, and reverse the disease process in the tissue. In vivo experiments on animal models have shown functional benefits of this therapeutic strategy. However, a poor understanding of the optimal injection pattern, volume, and material properties has acted as a barrier to its widespread clinical adoption. In this study, we developed two quasistatic finite element simulations of the left ventricle to investigate the mechanical effect of intra-myocardial injection. The first model employed an idealized left ventricular geometry with rule-based cardiomyocyte orientation. The second model employed a subject-specific left ventricular geometry with cardiomyocyte orientation from diffusion tensor magnetic resonance imaging. Both models predicted cardiac parameters including ejection fraction, systolic wall thickening, and ventricular twist that matched experimentally reported values. All injection simulations showed cardiomyocyte stress attenuation, offering an explanation for the mechanical reinforcement benefit associated with injection. The study also enabled a comparison of injection location and the corresponding effect on cardiac performance at different stages of the cardiac cycle. While the idealized model has lower fidelity, it predicts cardiac function and differentiates the effects of injection location. Both models represent versatile in silico tools to guide optimal strategy in terms of injection number, volume, site, and material properties.

Toward Regeneration of the Heart: Bioengineering Strategies for Immunomodulation

Myocardial Infarction (MI) is the most common cardiovascular disease. An average-sized MI causes the loss of up to 1 billion cardiomyocytes and the adult heart lacks the capacity to replace them. Although post-MI treatment has dramatically improved survival rates over the last few decades, more than 20% of patients affected by MI will subsequently develop heart failure (HF), an incurable condition where the contracting myocardium is transformed into an akinetic, fibrotic scar, unable to meet the body's need for blood supply. Excessive inflammation and persistent immune auto-reactivity have been suggested to contribute to post-MI tissue damage and exacerbate HF development. Two newly emerging fields of biomedical research, immunomodulatory therapies and cardiac bioengineering, provide potential options to target the causative mechanisms underlying HF development. Combining these two fields to develop biomaterials for delivery of immunomodulatory bioactive molecules holds great promise for HF therapy. Specifically, minimally invasive delivery of injectable hydrogels, loaded with bioactive factors with angiogenic, proliferative, anti-apoptotic and immunomodulatory functions, is a promising route for influencing the cascade of immune events post-MI, preventing adverse left ventricular remodeling, and offering protection from early inflammation to fibrosis. Here we provide an updated overview on the main injectable hydrogel systems and bioactive factors that have been tested in animal models with promising results and discuss the challenges to be addressed for accelerating the development of these novel therapeutic strategies.

Decellularized Extracellular Matrix Materials for Cardiac Repair and Regeneration

Decellularized extracellular matrix (dECM) is a promising biomaterial for repairing cardiovascular tissue, as dECM most effectively captures the complex array of proteins, glycosaminoglycans, proteoglycans, and many other matrix components that are found in native tissue, providing ideal cues for regeneration and repair of damaged myocardium. dECM can be used in a variety of forms, such as solid scaffolds that maintain native matrix structure, or as soluble materials that can form injectable hydrogels for tissue repair. dECM has found recent success in many regeneration and repair therapies, such as for musculoskeletal, neural, and liver tissues. This review focuses on dECM in the context of cardiovascular applications, with variations in tissue and species sourcing, and specifically discusses advances in solid and soluble dECM development, in vitro studies, in vivo implementation, and clinical translation.

Thermosensitive, fast gelling, photoluminescent, highly flexible, and degradable hydrogels for stem cell delivery

Stem cell therapy is a promising approach to regenerate ischemic cardiovascular tissues yet experiences low efficacy. One of the major causes is inferior cell retention in tissues. Injectable cell carriers that can quickly solidify upon injection into tissues so as to immediately increase viscosity have potential to largely improve cell retention. A family of injectable, fast gelling, and thermosensitive hydrogels were developed for delivering stem cells into heart and skeletal muscle tissues. The hydrogels were also photoluminescent with low photobleaching, allowing for non-invasively tracking hydrogel biodistribution and retention by fluorescent imaging. The hydrogels were polymerized by N-isopropylacrylamide (NIPAAm), 2-hydroxyethyl methacrylate (HEMA), 1-vinyl-2-pyrrolidinone (VP), and acrylate-oligolactide (AOLA), followed by conjugation with hypericin (HYP). The hydrogel solutions had thermal transition temperatures around room temperature, and were readily injectable at 4 °C. The solutions were able to quickly solidify within 7 s at 37 °C. The formed gels were highly flexible possessing similar moduli as the heart and skeletal muscle tissues. In vitro, hydrogel fluorescence intensity decreased proportionally to weight loss. After being injected into thigh muscles, the hydrogel can be detected by an in vivo imaging system for 4 weeks. The hydrogels showed excellent biocompatibility in vitro and in vivo, and can stimulate mesenchymal stem cell (MSC) proliferation and paracrine effects. The fast gelling hydrogel remarkably increased MSC retention in thigh muscles compared to slow gelling collagen, and non-gelling PBS. These hydrogels have potential to efficiently deliver stem cells into tissues. Hydrogel degradation can be non-invasively and real-time tracked. STATEMENT OF SIGNIFICANCE: Low cell retention in tissues represents one of the major causes for limited therapeutic efficacy in stem cell therapy. A family of injectable, fast gelling, and thermosensitive hydrogels that can quickly solidify upon injection into tissues were developed to improve cell retention. The hydrogels were also photoluminescent, allowing for non-invasively and real-time tracking hydrogel biodistribution and retention by fluorescent imaging.

Medium-term Electrophysiologic Effects of a Cellularized Scaffold Implanted in Rats After Myocardial Infarction

Background Cardiac repair strategies are being evaluated for myocardial infarctions, but the safety issues regarding their arrhythmogenic potential remain unresolved. By utilizing the in-vivo rat model, we have examined the medium-term electrophysiologic effects of a biomaterial scaffold that has been cellularized with spheroids of human adipose tissue, derived from mesenchymal stem cells and umbilical vein endothelial cells. Methods Mesenchymal stem cells, which exhibit adequate differentiation capacity, were co-cultured with umbilical vein endothelial cells and were seeded on an alginate based scaffold. After in-vitro characterization, the cellularized scaffold was implanted in (n=15) adult Wistar rats 15 min post ligation of the left coronary artery, with an equal number of animals serving as controls. Two weeks thereafter, monophasic action potentials were recorded and activation-mapping was performed with a multi-electrode array. An arrhythmia score for inducible ventricular tachyarrhythmias was calculated after programmed electrical stimulation. Results The arrhythmia score was comparable between the treated animals and controls. No differences were detected in the local conduction at the infarct border and in the voltage rise in monophasic action potential recordings. Treatment did not affect the duration of local repolarization, but tended to enhance its dispersion. Conclusions The fabricated bi-culture cellularized scaffold displayed favorable properties after in-vitro characterization. Medium-term electrophysiologic assessment after implantation in the infarcted rat myocardium revealed low arrhythmogenic potential, but the long-term effects on repolarization dispersion will require further investigation.

Whole Cardiac Tissue Bioscaffolds

Bioscaffolds serve as structures for cells in building complex tissues and full organs including heart. Decellularizing cardiac tissue results in cell-free extracellular matrix (ECM) that can be used as a cardiac tissue bioscaffold. The field of whole-heart tissue engineering has been revolutionized since the 2008 publication of the first perfusion-decellularized whole heart, and since then, studies have shown how decellularized cardiac tissue retains its native architecture and biochemistry following recellularization. Chemical, enzymatic, and physical decellularization methods preserve the ECM to varying degrees with the widely accepted standard of less than 50 ng/mg of double-stranded DNA present in decellularized ECM. Following decellularization, replacement of cells occurs via recellularization: seeding cells into the decellularized ECM structure either via perfusion of cells into the vascular conduits, injection into parenchyma, or a combination of perfusion and injection. Endothelial cells are often perfused through existing vessel conduits to provide an endothelial lining of the vasculature, with cardiomyocytes and other parenchymal cells injected into the myocardium of decellularized ECM bioscaffolds. Uniform cell density and cell retention throughout the bioscaffold still needs to be addressed in larger animal models of the whole heart. Generating the necessary cell numbers and types remains a challenge. Still, recellularized cardiac tissue bioscaffolds offer therapeutic solutions to heart failure, heart valve replacement, and acute myocardial infarction. New technologies allow for decellularized ECM to be bioprinted into cardiac bioscaffolds or formed into a cardiac hydrogel patch. This chapter reviews the advances made in decellularization and recellularization of cardiac ECM bioscaffolds with a discussion of the potential clinical applications of ECM bioscaffolds.

Ventricular wall biomaterial injection therapy after myocardial infarction: Advances in material design, mechanistic insight and early clinical experiences

Intramyocardial biomaterial injection therapy for myocardial infarction has made significant progress since concept initiation more than 10 years ago. The interim successes and progress in the first 5 years have been extensively reviewed. During the last 5 years, two phase II clinical trials have reported their long term follow up results and many additional biomaterial candidates have reached preclinical and clinical testing. Also in recent years deeper investigations into the mechanisms behind the beneficial effects associated with biomaterial injection therapy have been pursued, and a variety of process and material parameters have been evaluated for their impact on therapeutic outcomes. This review explores the advances made in this biomaterial-centered approach to ischemic cardiomyopathy and discusses potential future research directions as this therapy seeks to positively impact patients suffering from one of the world's most common sources of mortality.

Designing Acellular Injectable Biomaterial Therapeutics for Treating Myocardial Infarction and Peripheral Artery Disease

As the number of global deaths attributed to cardiovascular disease continues to rise, viable treatments for cardiovascular events such as myocardial infarction (MI) or conditions like peripheral artery disease (PAD) are critical. Recent studies investigating injectable biomaterials have shown promise in promoting tissue regeneration and functional improvement, and in some cases, incorporating other therapeutics further augments the beneficial effects of these biomaterials. In this review, we aim to emphasize the advantages of acellular injectable biomaterial-based therapies, specifically material-alone approaches or delivery of acellular biologics, in regards to manufacturability and the capacity of these biomaterials to regenerate or repair diseased tissue. We will focus on design parameters and mechanisms that maximize therapeutic efficacy, particularly, improved functional perfusion and neovascularization regarding PAD and improved cardiac function and reduced negative left ventricular (LV) remodeling post-MI. We will then discuss the rationale and challenges of designing new injectable biomaterial-based therapies for the clinic.