Retention and Functional Effect of Adipose-Derived Stromal Cells Administered in Alginate Hydrogel in a Rat Model of Acute Myocardial Infarction

Annexin A1-Loaded Alginate Hydrogel Promotes Cardiac Repair via Modulation of Macrophage Phenotypes after Myocardial Infarction

Myocardial infarction (MI) is associated with inflammatory reaction, which is a pivotal component in MI pathogenesis. Moreover, excessive inflammation post-MI can lead to cardiac dysfunction and adverse remodeling, emphasizing the critical need for an effective inflammation-regulating treatment for cardiac repair. Macrophage polarization is crucial in the inflammation process, indicating its potential as an adjunct therapy for MI. In this study, we developed an injectable alginate hydrogel loaded with annexin A1 (AnxA1, an endogenous anti-inflammatory and pro-resolving mediator) for MI treatment. In vitro results showed that the composite hydrogel had good biocompatibility and consistently released AnxA1 for several days. Additionally, this hydrogel led to a reduced number of pro-inflammatory macrophages and an increased proportion of pro-healing macrophages via the adenosine monophosphate (AMP)-activated protein kinase (AMPK)-mammalian target of the rapamycin (mTOR) axis. Furthermore, the intramyocardial injection of this composite hydrogel into a mouse MI model effectively modulated macrophage transition to pro-healing phenotypes. This transition mitigated early inflammatory responses and cardiac fibrosis, promoted angiogenesis, and improved cardiac function. Therefore, our study findings suggest that combining biomaterials and endogenous proteins for MI treatment is a promising approach for limiting adverse cardiac remodeling, preventing cardiac damage, and preserving the function of infarcted hearts.

Injectable hydrogel-based combination therapy for myocardial infarction: a systematic review and Meta-analysis of preclinical trials

INTRODUCTION

This study evaluates the effectiveness of a combined regimen involving injectable hydrogels for the treatment of experimental myocardial infarction.

PATIENT CONCERNS

Myocardial infarction is an acute illness that negatively affects quality of life and increases mortality rates. Experimental models of myocardial infarction can aid in disease research by allowing for the development of therapies that effectively manage disease progression and promote tissue repair.

DIAGNOSIS

Experimental animal models of myocardial infarction were established using the ligation method on the anterior descending branch of the left coronary artery (LAD).

INTERVENTIONS

The efficacy of intracardiac injection of hydrogels, combined with cells, drugs, cytokines, extracellular vesicles, or nucleic acid therapies, was evaluated to assess the functional and morphological improvements in the post-infarction heart achieved through the combined hydrogel regimen.

OUTCOMES

A literature review was conducted using PubMed, Web of Science, Scopus, and Cochrane databases. A total of 83 papers, including studies on 1332 experimental animals (rats, mice, rabbits, sheep, and pigs), were included in the meta-analysis based on the inclusion and exclusion criteria. The overall effect size observed in the group receiving combined hydrogel therapy, compared to the group receiving hydrogel treatment alone, resulted in an ejection fraction (EF) improvement of 8.87% [95% confidence interval (CI): 7.53, 10.21] and a fractional shortening (FS) improvement of 6.31% [95% CI: 5.94, 6.67] in rat models, while in mice models, the improvements were 16.45% [95% CI: 11.29, 21.61] for EF and 5.68% [95% CI: 5.15, 6.22] for FS. The most significant improvements in EF (rats: MD = 9.63% [95% CI: 4.02, 15.23]; mice: MD = 23.93% [95% CI: 17.52, 30.84]) and FS (rats: MD = 8.55% [95% CI: 2.54, 14.56]; mice: MD = 5.68% [95% CI: 5.15, 6.22]) were observed when extracellular vesicle therapy was used. Although there have been significant results in large animal experiments, the number of studies conducted in this area is limited.

CONCLUSION

The present study demonstrates that combining hydrogel with other therapies effectively improves heart function and morphology. Further preclinical research using large animal models is necessary for additional study and validation.

Application of adipose-derived stem cells in ischemic heart disease: theory, potency, and advantage

Adipose-derived mesenchymal stem cells (ASCs) represent an innovative candidate to treat ischemic heart disease (IHD) due to their abundance, renewable sources, minor invasiveness to obtain, and no ethical limitations. Compared with other mesenchymal stem cells, ASCs have demonstrated great advantages, especially in the commercialization of stem cell-based therapy. Mechanistically, ASCs exert a cardioprotective effect not only through differentiation into functional cells but also via robust paracrine of various bioactive factors that promote angiogenesis and immunomodulation. Exosomes from ASCs also play an indispensable role in this process. However, due to the distinct biological functions of ASCs from different origins or donors with varing health statuses (such as aging, diabetes, or atherosclerosis), the heterogeneity of ASCs deserves more attention. This prompts scientists to select optimal donors for clinical applications. In addition, to overcome the primary obstacle of poor retention and low survival after transplantation, a variety of studies have been dedicated to the engineering of ASCs with biomaterials. Besides, clinical trials have confirmed the safety and efficacy of ASCs therapy in the context of heart failure or myocardial infarction. This article reviews the theory, efficacy, and advantages of ASCs-based therapy, the factors affecting ASCs function, heterogeneity, engineering strategies and clinical application of ASCs.

Application of Hydrogels in Cardiac Regeneration

Myocardial infarction (MI) is a leading cause of death globally. Due to limited cardiac regeneration, infarcted myocardial tissue is gradually replaced by cardiac fibrosis, causing cardiac dysfunction, arrhythmia, aneurysm, free wall rupture, and sudden cardiac death. Thus, the development of effective methods to promote cardiac regeneration is extremely important for MI treatment. In recent years, hydrogels have shown promise in various methods for cardiac regeneration. Hydrogels can be divided into natural and synthetic types. Different hydrogels have different features and can be cross-linked in various ways. Hydrogels are low in toxicity and highly stable. Since they have good biocompatibility, biodegradability, and transformability, moderate mechanical properties, and proper elasticity, hydrogels are promising biomaterials for promoting cardiac regeneration. They can be used not only as scaffolds for migration of stem cells, but also as ideal carriers for delivery of drugs, genetic materials, stem cells, growth factors, cytokines, and small molecules. In this review, the application of hydrogels in cardiac regeneration during or post-MI is discussed in detail. Hydrogels open a promising new area in cardiac regeneration for treating MI.

[68Ga]Ga-NODAGA-E[(cRGDyK)]2 and [64Cu]Cu-DOTATATE PET Predict Improvement in Ischemic Cardiomyopathy

An increasing number of patients are living with chronic ischemic cardiomyopathy (ICM) and/or heart failure. Treatment options and prognostic tools are lacking for many of these patients. Our aim was to investigate the prognostic value of imaging angiogenesis and macrophage activation via positron emission tomography (PET) in terms of functional improvement after cell therapy. Myocardial infarction was induced in rats. Animals were scanned with [¹⁸F]FDG PET and echocardiography after four weeks and randomized to allogeneic adipose tissue-derived stromal cells (ASCs, n = 18) or saline (n = 9). Angiogenesis and macrophage activation were assessed before and after treatment by [⁶⁸Ga]Ga-RGD and [⁶⁴Cu]Cu-DOTATATE. There was no overall effect of the treatment. Rats that improved left ventricular ejection fraction (LVEF) had higher uptake of both [⁶⁸Ga]Ga-RGD and [⁶⁴Cu]Cu-DOTATATE at follow-up (p = 0.006 and p = 0.008, respectively). The uptake of the two tracers correlated with each other (r = 0.683, p = 0.003 pre-treatment and r = 0.666, p = 0.004 post-treatment). SUVmax at follow-up could predict improvement in LVEF (p = 0.016 for [⁶⁸Ga]Ga-RGD and p = 0.045 for [⁶⁴Cu]Cu-DOTATATE). High uptake of [⁶⁸Ga]Ga-RGD and [⁶⁴Cu]Cu-DOTATATE PET after injection of ASCs or saline preceded improvement in LVEF. The use of these tracers could improve the monitoring of heart failure patients in treatment.

The Initial Cardiac Tissue Response to Cryopreserved Allogeneic Adipose Tissue-Derived Mesenchymal Stromal Cells in Rats with Chronic Ischemic Cardiomyopathy

Mesenchymal stromal cells have proven capable of improving cardiac pump function in patients with chronic heart failure, yet little is known about their mode of action. The aim of the study was to investigate the short-term effect of cryopreserved allogeneic rat adipose tissue-derived stromal cells (ASC) on cardiac composition, cellular subpopulations, and gene transcription in a rat model of chronic ischemic cardiomyopathy (ICM). Myocardial infarction (MI) was induced by permanent ligation of the left anterior descending coronary artery. After 6 weeks, the rats were treated with ASCs, saline, or no injection, using echo-guided trans-thoracic intramyocardial injections. The cardiac tissue was subsequently collected for analysis of cellular subpopulations and gene transcription 3 and 7 days after treatment. At day 3, an upregulation of genes associated with angiogenesis were present in the ASC group. On day 7, increases in CCR2+ and CD38+ macrophages (p = 0.047 and p = 0.021), as well as in the CD4/CD8 lymphocyte ratio (p = 0.021), were found in the ASC group compared to the saline group. This was supported by an upregulation of genes associated with monocytes/macrophages. In conclusion, ASC treatment initiated an immune response involving monocytes/macrophages and T-cells and induced a gene expression pattern associated with angiogenesis and monocyte/macrophage differentiation.

Injectable Hydrogels for Improving Cardiac Cell Therapy-In Vivo Evidence and Translational Challenges

Cell therapy has the potential to regenerate cardiac tissue and treat a variety of cardiac diseases which are currently without effective treatment. This novel approach to treatment has demonstrated clinical efficiency, despite low retention of the cell products in the heart. It has been shown that improving retention often leads to improved functional outcome. A feasible method of improving cell graft retention is administration of injectable hydrogels. Over the last decade, a variety of injectable hydrogels have been investigated preclinically for their potential to improve the effects of cardiac cell therapy. These hydrogels are created with different polymers, properties, and additional functional motifs and differ in their approaches for encapsulating different cell types. Only one combinational therapy has been tested in a clinical randomized controlled trial. In this review, the latest research on the potential of injectable hydrogels for delivery of cell therapy is discussed, together with potential roadblocks for clinical translation and recommendations for future explorations to facilitate future translation.

Adipose-Derived Stromal/Stem Cells from Large Animal Models: from Basic to Applied Science

Adipose-derived stem cells (ASCs) isolated from domestic animals fulfill the qualitative criteria of mesenchymal stem cells, including the capacity to differentiate along multiple lineage pathways and to self-renew, as well as immunomodulatory capacities. Recent findings on human diseases derived from studying large animal models, have provided evidence that administration of autologous or allogenic ASCs can improve the process of healing. In a narrow group of large animals used in bioresearch studies, pigs and horses have been shown to be the best suited models for study of the wound healing process, cardiovascular and musculoskeletal disorders. To this end, current literature demonstrates that ASC-based therapies bring considerable benefits to animal health in both spontaneously occurring and experimentally induced clinical cases. The purpose of this review is to provide an overview of the diversity, isolation, and characterization of ASCs from livestock. Particular attention has been paid to the functional characteristics of the cells that facilitate their therapeutic application in large animal models of human disease. In this regard, we describe outcomes of ASCs utilization in translational research with pig and horse models of disease. Furthermore, we evaluate the current status of ASC-based therapy in veterinary practice, particularly in the rapidly developing field of equine regenerative medicine. In conclusion, this review presents arguments that support the relevance of animal ASCs in the field of regenerative medicine and it provides insights into the future perspectives of ASC utilization in animal husbandry.

Alginate Formulations: Current Developments in the Race for Hydrogel-Based Cardiac Regeneration

Cardiovascular diseases, including myocardial infarction (MI), represent the main worldwide cause of mortality and morbidity. In this scenario, to contrast the irreversible damages following MI, cardiac regeneration has emerged as a novel and promising solution for in situ cellular regeneration, preserving cell behavior and tissue cytoarchitecture. Among the huge variety of natural, synthetic, and hybrid compounds used for tissue regeneration, alginate emerged as a good candidate for cellular preservation and delivery, becoming one of the first biomaterial tested in pre-clinical research and clinical trials concerning cardiovascular diseases. Although promising results have been obtained, recellularization and revascularization of the infarcted area present still major limitations. Therefore, the demand is rising for alginate functionalization and its combination with molecules, factors, and drugs capable to boost the regenerative potential of the cardiac tissue. The focus of this review is to elucidate the promising properties of alginate and to highlight its benefits in clinical trials in relation to cardiac regeneration. The definition of hydrogels, the alginate characteristics, and recent biomedical applications are herewith described. Afterward, the review examines in depth the ongoing developments to refine the material relevance in cardiac recovery and regeneration after MI and presents current clinical trials based on alginate.

Chemical Engineering of Cell Therapy for Heart Diseases

Cardiovascular disease (CVD) is a major health problem worldwide. Since adult cardiomyocytes irreversibly withdraw from the cell cycle soon after birth, it is hard for cardiac cells to proliferate and regenerate after myocardial injury, such as that caused myocardial infarction (MI). Live cell-based therapies, which we term as first generation of therapeutic strategies, have been widely used for the treatment of many diseases, including CVD. However, cellular approaches have the problems of poor retention of the transplanted cells and the significant entrapment of the cells in the lungs when delivered intravenously. Another big problem is the low storage/shipping stability of live cells, which limits the manufacturability of living cell products. The field of chemical engineering focuses on designing large-scale processes to convert chemicals, raw materials, living cells, microorganisms, and energy into useful forms and products. By definition, chemical engineers conceive and design processes to produce, transform, and transport materials. This matches the direction that cell therapies are heading toward: "produce", from live cells to synthetic artificial cells; "transform", from bare cells to cell/matrix/factor combinations; and "transport". from simple systemic injections to targeted delivery. Thus, we hereby introduce the "chemical engineering of cell therapies" as a concept. In this Account, we summarize our recent efforts to develop chemical engineering approaches to repair injured hearts. To address the limitations of poor cellular retention and integration, the first step was the artificial manipulation of stem cells before injections (we term this the second generation of therapeutic strategies). For example, we took advantage of the natural infarct-targeting ability of platelet membranes by fusing them onto the surface of cardiac stromal/stem cells (CSCs). By doing so, we improved the rate at which they were delivered through the vasculature to sites of MI. In addition to modifying natural CSCs, we described a bioengineering approach that involved the encapsulation of CSCs in a polymeric microneedle patch for myocardium regeneration. The painless microneedle patches were used as an in situ delivery device, which directly transported the loaded CSCs to the MI heart. In addition to low cell retention, there are some other barriers that need to be addressed before further clinical application is viable, including the storage/shipping stability of and the evident safety concerns about live cells. Therefore, we developed the third generation of therapeutic strategies, which utilize cell-free approaches for cardiac cell therapies. Numerous studies have indicated that paracrine mechanisms reasonably explain stem cell based heart repair. By imitating or adapting natural stem cells, as well as their secretions, and using them in conjunction with biocompatible materials, we can simulate the function of natural stem cells while avoiding the complications association with the first and second generation therapeutic options. Additionally, we can develop approaches to capture endogenous stem cells and directly transport them to the infarct site. Using these third generation therapeutic strategies, we can provide unprecedented opportunities for cardiac cell therapies. We hope that our designs will promote the use of chemical engineering approaches to transform, transport, and fabricate cell-free systems as novel cardiac cell therapeutic agents for clinical applications.