A Regenerative Cardiac Patch Formed by Spray Painting of Biomaterials onto the Heart

An infusible biologically active adhesive for chemotherapy-related heart failure in elderly rats

Chemotherapy-induced cardiotoxicity with subsequent heart failure (HF) is a major cause of morbidity and mortality in cancer survivors worldwide. Chemotherapy-induced HF is exceptionally challenging as it generally manifests in patients who are typically not eligible for left ventricular device implantation or heart transplantation. To explore alternative treatment strategies for cancer survivors suffering from chemotherapy-induced HF, we developed a minimally invasive infusible cardiac stromal cell secretomes adhesive (MISA) that could be delivered locally through an endoscope-guided intrapericardial injection. To mimic the typical clinical presentation of chemotherapy-induced HF in elder patients, we established an aged rat model in which restrictive cardiomyopathy with sequential HF was induced via consecutive doxorubicin injections. In vitro, we prove that MISA not only enhanced cardiomyocytes proliferation potency and viability, but also inhibited their apoptosis. In vivo, we prove that MISA improved the ventricular contractility indexes and led to beneficial effects on histological and structural features of restrictive cardiomyopathy via promoting cardiomyocyte proliferation, angiogenesis, and mitochondrial respiration. Additionally, we also evaluated the safety and feasibility of MISA intrapericardial delivery in a healthy porcine model with an intact immune system. In general, our data indicates that MISA has a strong potential for translation into large animal models and ultimately clinical applications for chemotherapy-induced HF prior to the final option of heart transplantation.

Mesenchymal stem cell-secretome laden photopolymerizable hydrogels for wound healing

Mesenchymal stem cell-derived secretome represents an emerging acellular therapeutic which possess significant opportunity for clinical applications due to its anti-inflammatory, immunomodulatory, and wound healing properties. However, maintaining therapeutic efficacy and ensuring stability of cell-based products is challenging, requiring a robust delivery method. Therefore, we designed a hydrogel-based scaffold loaded with CK Cell Technologies' proprietary Mesenchymal stem cell-secretome for controlled release treatment of acute and chronic wounds. We incorporated both conditioned media (CM) and extracellular vesicles (EVs) into gelatin methacryloyl (GelMA) hydrogels and demonstrated how we can tune the diffusive release of the EVs from them. To demonstrate viability of the approach, we developed a wound healing scratch assay where we see in situ release of CM and EVs promote enhanced migration of human dermal fibroblasts (hDFs). We see the colocalization of these EVs in the fibroblasts using fluorescent microscopy. Finally, as a surrogate for in vivo neovascularization, we conducted an in vitro tube formation assay for the MSC-secretome using matrigel-embedded human microvascular endothelial cells. By adding CM and EVs, we observe an increase in tubulogenesis. Collectively, our data demonstrates by tuning the GelMA properties, we can influence the controlled release of the MSC-secretome for a wound dressing and bandage application for chronic and acute wounds.

A paintable and adhesive hydrogel cardiac patch with sustained release of ANGPTL4 for infarcted heart repair

The infarcted heart undergoes irreversible pathological remodeling after reperfusion involving left ventricle dilation and excessive inflammatory reactions in the infarcted heart, frequently leading to fatal functional damage. Extensive attempts have been made to attenuate pathological remodeling in infarcted hearts using cardiac patches and anti-inflammatory drug delivery. In this study, we developed a paintable and adhesive hydrogel patch using dextran-aldehyde (dex-ald) and gelatin, incorporating the anti-inflammatory protein, ANGPTL4, into the hydrogel for sustained release directly to the infarcted heart to alleviate inflammation. We optimized the material composition, including polymer concentration and molecular weight, to achieve a paintable, adhesive hydrogel using 10% gelatin and 5% dex-ald, which displayed in-situ gel formation within 135 s, cardiac tissue-like modulus (40.5 kPa), suitable tissue adhesiveness (4.3 kPa), and excellent mechanical stability. ANGPTL4 was continuously released from the gelatin/dex-ald hydrogel without substantial burst release. The gelatin/dex-ald hydrogel could be conveniently painted onto the beating heart and degraded in vivo. Moreover, in vivo studies using animal models of acute myocardial infarction revealed that our hydrogel cardiac patch containing ANGPTL4 significantly improved heart tissue repair, evaluated by echocardiography and histological evaluation. The heart tissues treated with ANGPTL4-loaded hydrogel patches exhibited increased vascularization, reduced inflammatory macrophages, and structural maturation of cardiac cells. Our novel hydrogel system, which allows for facile paintability, appropriate tissue adhesiveness, and sustained release of anti-inflammatory drugs, will serve as an effective platform for the repair of various tissues, including heart, muscle, and cartilage.

The recent advances in cell delivery approaches, biochemical and engineering procedures of cell therapy applied to coronary heart disease

Cell therapy is an important topic in the field of regeneration medicine that is gaining attention within the scientific community. However, its potential for treatment in coronary heart disease (CHD) has yet to be established. Several various strategies, types of cells, routes of distribution, and supporting procedures have been tried and refined to trigger heart rejuvenation in CHD. However, only a few of them result in a real considerable promise for clinical usage. In this review, we give an update on techniques and clinical studies of cell treatment as used to cure CHD that are now ongoing or have been completed in the previous five years. We also highlight the emerging efficacy of stem cell treatment for CHD. We specifically examine and comment on current breakthroughs in cell treatment applied to CHD, including the most effective types of cells, transport modalities, engineering, and biochemical approaches used in this context. We believe the current review will be helpful for the researcher to distill this information and design future studies to overcome the challenges faced by this revolutionary approach for CHD.

Hydrogels for Cardiac Restorative Support: Relevance of Gelation Mechanisms for Prospective Clinical Use

PURPOSE OF REVIEW

Cardiac tissue regenerative strategies have gained much traction over the years, in particular those utilizing hydrogels. With our review, and with special focus on supporting post-myocardial infarcted tissue, we aim to provide insights in determining crucial design considerations of a hydrogel and the implications these could have for future clinical use.

RECENT FINDINGS

To date, two hydrogel delivery strategies are being explored, cardiac injection or patch, to treat myocardial infarction. Recent advances have demonstrated that the mechanism by which a hydrogel is gelated (i.e., physically or chemically cross-linked) not only impacts the biocompatibility, mechanical properties, and chemical structure, but also the route of delivery of the hydrogel and thus its effect on cardiac repair. With regard to cardiac regeneration, various hydrogels have been developed with the ability to function as a delivery system for therapeutic strategies (e.g., drug and stem cells treatments), as well as a scaffold to guide cardiac tissue regeneration following myocardial infarction. However, these developments remain within the experimental and pre-clinical realm and have yet to transition towards the clinical setting.

Axitinib targets cardiac fibrosis in pressure overload-induced heart failure through VEGFA-KDR pathway

Background

There are no specific clinical medications that target cardiac fibrosis in heart failure (HF). Recent studies have shown that tyrosine kinase inhibitors (TKIs) may benefit fibrosis in various organs. However, there is limited research on their application in cardiac fibrosis. Axitinib, an FDA-approved tyrosine kinase inhibitor, was used to evaluate its effects on cardiac fibrosis and function in pressure overload-induced heart failure.

Methods

To build a pharmacological network, the pharmacological targets of axitinib were first retrieved from databases and coupled with key heart failure gene molecules for analysis and prediction. To validate the results outlined above, 8-week-old male C57BL/6 J mice were orally administrated of axitinib (30 mg/kg) daily for 8 weeks after Transverse Aortic Constriction (TAC) surgery. Mouse cardiomyocytes and cardiac fibroblasts were used as cell lines to test the function and mechanism of axitinib.

Results

We found that the pharmacological targets of axitinib could form a pharmacological network with key genes involved in heart failure. The VEGFA-KDR pathway was found to be closely related to the differential gene expression of human heart-derived primary cardiomyocyte cell lines treated with axitinib, based on analysis of the publicly available dataset. The outcomes of animal experiments demonstrated that axitinib therapy greatly reduced cardiac fibrosis and improved TAC-induced cardiac dysfunction. Further research has shown that the expression of transforming growth factor-β(TGF-β) and other fibrosis genes was significantly reduced in vivo and in vitro.

Conclusion

Our study provides evidence for the repurposing of axitinib to combat cardiac fibrosis, and offers new insights into the treatment of patients with HF.

Advances in the design, generation, and application of tissue-engineered myocardial equivalents

Due to the limited regenerative ability of cardiomyocytes, the disabling irreversible condition of myocardial failure can only be treated with conservative and temporary therapeutic approaches, not able to repair the damage directly, or with organ transplantation. Among the regenerative strategies, intramyocardial cell injection or intravascular cell infusion should attenuate damage to the myocardium and reduce the risk of heart failure. However, these cell delivery-based therapies suffer from significant drawbacks and have a low success rate. Indeed, cardiac tissue engineering efforts are directed to repair, replace, and regenerate native myocardial tissue function. In a regenerative strategy, biomaterials and biomimetic stimuli play a key role in promoting cell adhesion, proliferation, differentiation, and neo-tissue formation. Thus, appropriate biochemical and biophysical cues should be combined with scaffolds emulating extracellular matrix in order to support cell growth and prompt favorable cardiac microenvironment and tissue regeneration. In this review, we provide an overview of recent developments that occurred in the biomimetic design and fabrication of cardiac scaffolds and patches. Furthermore, we sift in vitro and in situ strategies in several preclinical and clinical applications. Finally, we evaluate the possible use of bioengineered cardiac tissue equivalents as in vitro models for disease studies and drug tests.

Application of locally responsive design of biomaterials based on microenvironmental changes in myocardial infarction

Morbidity and mortality caused by acute myocardial infarction (AMI) are on the rise, posing a grave threat to the health of the general population. Up to now, interventional, surgical, and pharmaceutical therapies have been the main treatment methods for AMI. Effective and timely reperfusion therapy decreases mortality, but it cannot stimulate myocardial cell regeneration or reverse ventricular remodeling. Cell therapy, gene therapy, immunotherapy, anti-inflammatory therapy, and several other techniques are utilized by researchers to improve patients' prognosis. In recent years, biomaterials for AMI therapy have become a hot spot in medical care. Biomaterials furnish a microenvironment conducive to cell growth and deliver therapeutic factors that stimulate cell regeneration and differentiation. Biomaterials adapt to the complex microenvironment and respond to changes in local physical and biochemical conditions. Therefore, environmental factors and material properties must be taken into account when designing biomaterials for the treatment of AMI. This article will review the factors that need to be fully considered in the design of biological materials.

Conductive Hydrogel Patches with High Elasticity and Fatigue Resistance for Cardiac Microenvironment Remodeling

Remodeling the conductive zone to assist normal myocardial contraction and relaxation during myocardial fibrosis has become the primary concern of myocardial infarction (MI) regeneration. Herein, we report an unbreakable and self-recoverable hyaluronic acid conductive cardiac patch for MI treatment, which can maintain structural integrity under mechanical load and integrate mechanical and electrical conduction and biological cues to restore cardiac electrical conduction and diastolic contraction function. Using the free carboxyl groups and aldehyde groups in the hydrogel system, excellent adhesion properties are achieved in the interface between the myocardial patch and the tissue, which can be closely integrated with the rabbit myocardial tissue, reducing the need for suture. Interestingly, the hydrogel patch exhibits sensitive conductivity (ΔR/R0 ≈ 2.5) for 100 cycles and mechanical stability for 500 continuous loading cycles without collapse, which allows the patch to withstand mechanical damage caused by sustained contraction and relaxation of the myocardial tissue. Moreover, considering the oxidative stress state caused by excessive ROS in the MI area, we incorporated Rg1 into the hydrogel to improve the abnormal myocardial microenvironment, which achieved more than 80% free radicalscavenging efficiency in the local infarcted region and promoted myocardial reconstruction. Overall, these Rg1-loaded conductive hydrogels with highly elastic fatigue resistance have great potential in restoring the abnormal electrical conduction pathway and promoting the myocardial microenvironment, thereby repairing the heart and improving the cardiac function.

Nanomaterial-Based Electrically Conductive Hydrogels for Cardiac Tissue Repair

Cardiovascular disease is one of major causes of deaths, and its incidence has gradually increased worldwide. For cardiovascular diseases, several therapeutic approaches, such as drugs, cell-based therapy, and heart transplantation, are currently employed; however, their therapeutic efficacy and/or practical availability are still limited. Recently, biomaterial-based tissue engineering approaches have been recognized as promising for regenerating cardiac function in patients with cardiovascular diseases, including myocardial infarction (MI). In particular, materials mimicking the characteristics of native cardiac tissues can potentially prevent pathological progression and promote cardiac repair of the heart tissues post-MI. The mechanical (softness) and electrical (conductivity) properties of biomaterials as non-biochemical cues can improve the cardiac functions of infarcted hearts by mitigating myocardial cell death and subsequent fibrosis, which often leads to cardiac tissue stiffening and high electrical resistance. Consequently, electrically conductive hydrogels that can provide mechanical strength and augment the electrical activity of the infarcted heart tissue are considered new functional materials capable of mitigating the pathological progression to heart failure and stimulating cardiac regeneration. In this review, we highlight nanomaterial-incorporated hydrogels that can induce cardiac repair after MI. Nanomaterials, including carbon-based nanomaterials and recently discovered two-dimensional nanomaterials, offer great opportunities for developing functional conductive hydrogels owing to their excellent electrical conductivity, large surface area, and ease of modification. We describe recent results using nanomaterial-incorporated conductive hydrogels as cardiac patches and injectable hydrogels for cardiac repair. While further evaluations are required to confirm the therapeutic efficacy and toxicity of these materials, they could potentially be used for the regeneration of other electrically active tissues, such as nerves and muscles.

Detachable Microneedle Patches Deliver Mesenchymal Stromal Cell Factor-Loaded Nanoparticles for Cardiac Repair

Intramyocardial injection is a direct and efficient approach to deliver therapeutics to the heart. However, the injected volume must be very limited, and there is injury to the injection site and leakage issues during heart beating. Herein, we developed a detachable therapeutic microneedle (MN) patch, which is comprised of mesenchymal stromal cell-secreted factors (MSCF)-loaded poly(lactic-co-glycolic acid) nanoparticles (NP) in MN tips made of elastin-like polypeptide gel, with a resolvable non-cross-linked hyaluronic acid (HA) gel as the MN base. The tips can be firmly inserted into the infarcted myocardium after base removal, and no suture is needed. In isolated neonatal rat cardiac cells, we found that the cellular uptake of MSCF-NP in the cardiomyocytes was higher than in cardiac fibroblasts. MSCF-NP promoted the proliferation of injured cardiomyocytes. In a rat model of myocardial infarction, MN-MSCF-NP treatment reduced cardiomyocyte apoptosis, restored myocardium volume, and reduced fibrosis during the cardiac remodeling process. Our work demonstrated the therapeutic potential of MN to deliver MSCF directly into the myocardium and provides a promising treatment approach for cardiac diseases.

Myocardial infarction from a tissue engineering and regenerative medicine point of view: A comprehensive review on models and treatments

In the modern world, myocardial infarction is one of the most common cardiovascular diseases, which are responsible for around 18 million deaths every year or almost 32% of all deaths. Due to the detrimental effects of COVID-19 on the cardiovascular system, this rate is expected to increase in the coming years. Although there has been some progress in myocardial infarction treatment, translating pre-clinical findings to the clinic remains a major challenge. One reason for this is the lack of reliable and human representative healthy and fibrotic cardiac tissue models that can be used to understand the fundamentals of ischemic/reperfusion injury caused by myocardial infarction and to test new drugs and therapeutic strategies. In this review, we first present an overview of the anatomy of the heart and the pathophysiology of myocardial infarction, and then discuss the recent developments on pre-clinical infarct models, focusing mainly on the engineered three-dimensional cardiac ischemic/reperfusion injury and fibrosis models developed using different engineering methods such as organoids, microfluidic devices, and bioprinted constructs. We also present the benefits and limitations of emerging and promising regenerative therapy treatments for myocardial infarction such as cell therapies, extracellular vesicles, and cardiac patches. This review aims to overview recent advances in three-dimensional engineered infarct models and current regenerative therapeutic options, which can be used as a guide for developing new models and treatment strategies.

A Bi-Layer Hydrogel Cardiac Patch Made of Recombinant Functional Proteins

The development of minimally invasive cardiac patches, either as hemostatic dressing or treating myocardial infarction, is of clinical significance but remains a major challenge. Designing such patches often requires simultaneous consideration of several material attributes, including bioabsorption, non-toxicity, matching the mechanic properties of heart tissues, and working efficiently in wet and dynamic environments. Using genetically engineered multi-domain proteins, a printed bi-layer proteinaceous hydrogel patch for heart failure treatments is reported. The intrinsic self-healing nature of hydrogel materials physically enables seamless interfacial integration of two disparate hydrogel layers and functionally endows the cardiac patches with the combinatorial advantages of each layer. Leveraging the biocompatibility, structural stability, and tunable drug release properties of the bi-layer hydrogel, promising effects of hemostasis, fibrosis reduction, and heart function recovery on mice is demonstrated with two myocardium damage models. Moreover, this proteinaceous patch is proved biodegradable in vivo without any additive inflammations. In conclusion, this work introduces a promising new type of minimally invasive patch based on genetically modified double-layer protein gel for treating heart-related injuries or diseases.

Nanoengineered Sprayable Therapy for Treating Myocardial Infarction

We report the development, as well as the in vitro and in vivo testing, of a sprayable nanotherapeutic that uses surface engineered custom-designed multiarmed peptide grafted nanogold for on-the-spot coating of an infarcted myocardial surface. When applied to mouse hearts, 1 week after infarction, the spray-on treatment resulted in an increase in cardiac function (2.4-fold), muscle contractility, and myocardial electrical conductivity. The applied nanogold remained at the treatment site 28 days postapplication with no off-target organ infiltration. Further, the infarct size in the mice that received treatment was found to be <10% of the total left ventricle area, while the number of blood vessels, prohealing macrophages, and cardiomyocytes increased to levels comparable to that of a healthy animal. Our cumulative data suggest that the therapeutic action of our spray-on nanotherapeutic is highly effective, and in practice, its application is simpler than other regenerative approaches for treating an infarcted heart.

Injection-Free Delivery of MSC-Derived Extracellular Vesicles for Myocardial Infarction Therapeutics

As emerging therapeutic factors, extracellular vesicles (EVs) offer significant potential for myocardial infarction (MI) treatment. Current delivery approaches for EVs involve either intra-myocardial or intravenous injection, where both have inherent limitations for downstream clinical applications such as secondary tissue injury and low delivery efficiency. Herein, an injection-free approach for delivering EVs onto the heart surface to treat MI is proposed. By spraying a mixture of EVs, gelatin methacryloyl (GelMA) precursors, and photoinitiators followed by visible light irradiation for 30 s, EVs are physically entrapped within the GelMA hydrogel network covering the surface of the heart, resulting in an enhanced retention rate. Moreover, EVs are gradually released from the hydrogel network through a combination of diffusion and/or enzymatic degradation of the hydrogel, and they are effectively taken up by the sprayed tissue area. More importantly, the released EVs further migrate deep into myocardium tissue, which exerts an improved therapeutic effect. In an MI-induced mice model, the group treated with EVs-laden GelMA hydrogels shows significant recovery in cardiac function after 4 weeks. The work demonstrates a new strategy for delivering EVs into cardiac tissues for MI treatment in a localized manner with high retention.

Alleviating Oxidative Injury of Myocardial Infarction by a Fibrous Polyurethane Patch with Condensed ROS-Scavenging Backbone Units

Excessive reactive oxygen species (ROS) generated after myocardial infarction (MI) result in the oxidative injury in myocardium. Implantation of antioxidant biomaterials, without the use of any type of drugs, is very appealing for clinical translation, leading to the great demand of novel biomaterials with high efficiency of ROS elimination. In this study, a segmented polyurethane (PFTU) with a high density of ROS-scavenging backbone units is synthesized by the reaction of poly(thioketal) dithiol (PTK) and poly(propylene fumarate) diol (PPF) (soft segments), thioketal diamine (chain extender), and 1,6-hexamethylene diisocyanate (HDI). Its chemical structure is verified by gel permeation chromatography (GPC), ¹ H nuclear magnetic resonance (¹ H NMR) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The electrospun composite PFTU/gelatin (PFTU/Gt) fibrous patches show good antioxidation capacity and ROS-responsive degradation in vitro. Implantation of the PFTU/gelatin patches on the heart tissue surface in MI rats consistently decreases the ROS level, membrane peroxidation, and cell apoptosis at the earlier stage, which are not observed in the non-ROS-responsive polyurethane patch. Inflammation and fibrosis are also reduced in the PFTU/gelatin-treated hearts, resulting in the reduced left ventricular remodeling and better cardiac functions postimplantation for 28 d.

Exosomes as a messager to regulate the crosstalk between macrophages and cardiomyocytes under hypoxia conditions

Recent studies have confirmed that cardiomyocyte‐derived exosomes have many pivotal biological functions, like influencing the progress of coronary artery disease via modulating macrophage phenotypes. However, the mechanisms underlying the crosstalk between cardiomyocytes and macrophages have not been fully characterized. Hence, this study aimed to observe the interaction between cardiomyocytes under hypoxia and macrophages through exosome communication and further evaluate the ability of exosomes derived from cardiomyocytes cultured under hypoxic conditions (Hypo‐Exo) to polarize macrophages, and the effect of alternatively activated macrophages (M2) on hypoxic cardiomyocytes. Our results revealed that hypoxia facilitated the production of transforming growth factor‐beta (TGF‐β) in H9c2 cell‐derived exosomes. Moreover, exosomes derived from cardiomyocytes cultured under normal conditions (Nor‐Exo) and Hypo‐Exo could induce RAW264.7 cells into classically activated macrophages (M1) and M2 macrophages respectively. Likewise, macrophage activation was induced by circulating exosomes isolated from normal human controls (hNor‐Exo) or patients with acute myocardial infarction (hAMI‐Exo). Thus, our findings support that the profiles of hAMI‐Exo have been changed, which could regulate the polarization of macrophages and subsequently the polarized M2 macrophages reduced the apoptosis of cardiomyocytes in return. Based on our findings, we speculate that exosomes have emerged as important inflammatory response modulators regulating cardiac oxidative stress injury.

Nanoparticles functionalized with stem cell secretome and CXCR4-overexpressing endothelial membrane for targeted osteoporosis therapy

Background

Osteoporosis is a chronic condition affecting patients’ morbidity and mortality and represents a big socioeconomic burden. Because stem cells can proliferate and differentiate into bone-forming cells, stem cell therapy for osteoporosis has been widely studied. However, cells as a live drug face multiple challenges because of their instability during preservation and transportation. In addition, cell therapy has potential adverse effects such as embolism, tumorigenicity, and immunogenicity.

Results

Herein, we sought to use cell-mimicking and targeted therapeutic nanoparticles to replace stem cells. We fabricated nanoparticles (NPs) using polylactic-co-glycolic acid (PLGA) loaded with the secretome (Sec) from mesenchymal stem cells (MSCs) to form MSC-Sec NPs. Furthermore, we cloaked the nanoparticles with the membranes from C–X–C chemokine receptor type 4 (CXCR4)-expressing human microvascular endothelial cells (HMECs) to generate MSC-Sec/CXCR4 NP. CXCR4 can target the nanoparticles to the bone microenvironment under osteoporosis based on the CXCR4/SDF-1 axis.

Conclusions

In a rat model of osteoporosis, MSC-Sec/CXCR4 NP were found to accumulate in bone, and such treatment inhibited osteoclast differentiation while promoting osteogenic proliferation. In addition, our results showed that MSC-Sec/CXCR4 NPs reduce OVX-induced bone mass attenuation in OVX rats.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01231-6.

Extruded Mesenchymal Stem Cell Nanovesicles Are Equally Potent to Natural Extracellular Vesicles in Cardiac Repair

Mesenchymal stem cells (MSCs) repair injured tissues mainly through their paracrine actions. One of the important paracrine components of MSC secretomes is the extracellular vesicle (EV). The therapeutic potential of MSC-EVs has been established in various cardiac injury preclinical models. However, the large-scale production of EVs remains a challenge. We sought to develop a scale-up friendly method to generate a large number of therapeutic nanovesicles from MSCs by extrusion. Those extruded nanovesicles (NVs) are miniature versions of MSCs in terms of surface marker expression. The yield of NVs is 20-fold more than that of EVs. In vitro, cell-based assays demonstrated the myocardial protective effects and therapeutic potential of NVs. Intramyocardial delivery of NVs in the injured heart after ischemia-reperfusion led to a reduction in scar sizes and preservation of cardiac functions. Such therapeutic benefits are similar to those injected with natural EVs from the same MSC parental cells. In addition, NV therapy promoted angiogenesis and proliferation of cardiomyocytes in the post-injury heart. In summary, extrusion is a highly efficient method to generate a large quantity of therapeutic NVs that can potentially replace extracellular vesicles in regenerative medicine applications.

Recent Advances in Cardiac Tissue Engineering for the Management of Myocardium Infarction

Myocardium Infarction (MI) is one of the foremost cardiovascular diseases (CVDs) causing death worldwide, and its case numbers are expected to continuously increase in the coming years. Pharmacological interventions have not been at the forefront in ameliorating MI-related morbidity and mortality. Stem cell-based tissue engineering approaches have been extensively explored for their regenerative potential in the infarcted myocardium. Recent studies on microfluidic devices employing stem cells under laboratory set-up have revealed meticulous events pertaining to the pathophysiology of MI occurring at the infarcted site. This discovery also underpins the appropriate conditions in the niche for differentiating stem cells into mature cardiomyocyte-like cells and leads to engineering of the scaffold via mimicking of native cardiac physiological conditions. However, the mode of stem cell-loaded engineered scaffolds delivered to the site of infarction is still a challenging mission, and yet to be translated to the clinical setting. In this review, we have elucidated the various strategies developed using a hydrogel-based system both as encapsulated stem cells and as biocompatible patches loaded with cells and applied at the site of infarction.

A Minimally Invasive Exosome Spray Repairs Heart after Myocardial Infarction

Myocardial infarction (MI) remains the most common cause of death worldwide. Many MI survivors will suffer from recurrent heart failure (HF), which has been recognized as a determinant of adverse prognosis. Despite the success of improved early survival after MI by primary percutaneous coronary intervention, HF after MI is becoming the major driver of late morbidity, mortality, and healthcare costs. The development of regenerative medicine has brought hope to MI treatment in the past decade. Mesenchymal stem cell (MSC)-derived exosomes have been established as an essential part of stem cell paracrine factors for heart regeneration. However, its regenerative power is hampered by low delivery efficiency to the heart. We designed, fabricated, and tested a minimally invasive exosome spray (EXOS) based on MSC exosomes and biomaterials. In a mouse model of acute myocardial infarction, EXOS improved cardiac function and reduced fibrosis, and promoted endogenous angiomyogenesis in the post-injury heart. We further tested the feasibility and safety of EXOS in a pig model. Our results indicate that EXOS is a promising strategy to deliver therapeutic exosomes for heart repair.

Cardiac fibrosis: Myofibroblast-mediated pathological regulation and drug delivery strategies

Cardiac fibrosis remains an unresolved problem in heart diseases. After initial injury, cardiac fibroblasts (CFs) are activated and subsequently differentiate into myofibroblasts (myoFbs) that are major mediator cells in the pathological remodeling. MyoFbs exhibit proliferative and secretive characteristics, and contribute to extracellular matrix (ECM) turnover, collagen deposition. The persistent functions of myoFbs lead to fibrotic scars and cardiac dysfunction. The anti-fibrotic treatment is hindered by the elusive mechanism of fibrosis and lack of specific targets on myoFbs. In this review, we will outline the progress of cardiac fibrosis and its contributions to the heart failure. We will also shed light on the role of myoFbs in the regulation of adverse remodeling. The communication between myoFbs and other cells that are involved in the heart injury and repair respectively will be reviewed in detail. Then, recently developed therapeutic strategies to treat fibrosis will be summarized such as i) chimeric antigen receptor T cell (CAR-T) therapy with an optimal target on myoFbs, ii) direct reprogramming from stem cells to quiescent CFs, iii) "off-target" small molecular drugs. The application of nano/micro technology will be discussed as well, which is involved in the construction of cell-based biomimic platforms and "pleiotropic" drug delivery systems.

All Roads Lead to Rome (the Heart): Cell Retention and Outcomes From Various Delivery Routes of Cell Therapy Products to the Heart

In the past decades, numerous preclinical studies and several clinical trials have evidenced the feasibility of cell transplantation in treating heart diseases. Over the years, different delivery routes of cell therapy have emerged and broadened the width of the field. However, a common hurdle is shared by all current delivery routes: low cell retention. A myriad of studies confirm that cell retention plays a crucial role in the success of cell-mediated cardiac repair. It is important for any delivery route to maintain donor cells in the recipient heart for enough time to not only proliferate by themselves, but also to send paracrine signals to surrounding damaged heart cells and repair them. In this review, we first undertake an in-depth study of primary theories of cell loss, including low efficiency in cell injection, "washout" effects, and cell death, and then organize the literature from the past decade that focuses on cell transplantation to the heart using various cell delivery routes, including intracoronary injection, systemic intravenous injection, retrograde coronary venous injection, and intramyocardial injection. In addition to a recapitulation of these approaches, we also clearly evaluate their strengths and weaknesses. Furthermore, we conduct comparative research on the cell retention rate and functional outcomes of these delivery routes. Finally, we extend our discussion to state-of-the-art bioengineering techniques that enhance cell retention, as well as alternative delivery routes, such as intrapericardial delivery. A combination of these novel strategies and more accurate assessment methods will help to address the hurdle of low cell retention and boost the efficacy of cell transplantation to the heart.

Minimally invasive delivery of therapeutic agents by hydrogel injection into the pericardial cavity for cardiac repair

Cardiac patches are an effective way to deliver therapeutics to the heart. However, such procedures are normally invasive and difficult to perform. Here, we develop and test a method to utilize the pericardial cavity as a natural "mold" for in situ cardiac patch formation after intrapericardial injection of therapeutics in biocompatible hydrogels. In rodent models of myocardial infarction, we demonstrate that intrapericardial injection is an effective and safe method to deliver hydrogels containing induced pluripotent stem cells-derived cardiac progenitor cells or mesenchymal stem cells-derived exosomes. After injection, the hydrogels form a cardiac patch-like structure in the pericardial cavity, mitigating immune response and increasing the cardiac retention of the therapeutics. With robust cardiovascular repair and stimulation of epicardium-derived cells, the delivered therapeutics mitigate cardiac remodeling and improve cardiac functions post myocardial infarction. Furthermore, we demonstrate the feasibility of minimally-invasive intrapericardial injection in a clinically-relevant porcine model. Collectively, our study establishes intrapericardial injection as a safe and effective method to deliver therapeutic-bearing hydrogels to the heart for cardiac repair.

Mesenchymal Stem Cells in Cardiac Repair: Effects on Myocytes, Vasculature, and Fibroblasts

PURPOSE

Cardiac pathologies remain a dominant cause of morbidity and mortality within the community. The drive to develop therapies capable of repairing damaged heart tissue to achieve clinically significant restoration of function has motivated the pursuit of novel approaches such as cell therapy. To this end, evidence of therapeutic benefits achieved by using mesenchymal stem cells (MSCs) has captured considerable interest despite a relative lack of information regarding the mechanisms involved. This narrative review synthesizes and interprets the current literature describing mechanisms by which MSCs can elicit cardiac repair, thereby directing attention to avenues of further inquiry.

METHODS

OVID versions of MEDLINE and EMBASE were searched for studies describing the role of MSCs in mammalian cardiac repair. Additional studies were sourced from the reference lists of relevant articles and other personal files.

FINDINGS

MSCs elicit cardiac repair in a range of in vitro systems and animal models of diseases such as myocardial infarction and heart failure. Important mechanisms include the preservation of myocardial contractility, the promotion of angiogenesis, and the modulation of fibrosis. Exposing in vitro MSCs to a microenvironment reflective of that encountered in the injured heart seems to potentiate these therapeutic mechanisms.

IMPLICATIONS

Promising results in animal studies warrant continuation of clinical MSC cardiac therapy studies. Paracrine functions of MSCs seem to be the dominant mechanism of cardiac repair over direct cellular effects. Although integral, the MSC secretome remains poorly defined. In addition, most of the mechanistic data within the literature have been derived from animal MSC research, necessitating more human MSC-based work.

Dermal exosomes containing miR-218-5p promote hair regeneration by regulating β-catenin signaling

The progression in the hair follicle cycle from the telogen to the anagen phase is the key to regulating hair regrowth. Dermal papilla (DP) cells support hair growth and regulate the hair cycle. However, they gradually lose key inductive properties upon culture. DP cells can partially restore their capacity to promote hair regrowth after being subjected to spheroid culture. In this study, results revealed that DP spheroids are effective at inducing the progression of the hair follicle cycle from telogen to anagen compared with just DP cell or minoxidil treatment. Because of the importance of paracrine signaling in this process, secretome and exosomes were isolated from DP cell culture, and their therapeutic efficacies were investigated. We demonstrated that miR-218-5p was notably up-regulated in DP spheroid-derived exosomes. Western blot and immunofluorescence imaging were used to demonstrate that DP spheroid-derived exosomes up-regulated β-catenin, promoting the development of hair follicles.

An off-the-shelf artificial cardiac patch improves cardiac repair after myocardial infarction in rats and pigs

Cell therapy has been a promising strategy for cardiac repair after injury or infarction; however, low retention and engraftment of transplanted cells limit potential therapeutic efficacy. Seeding scaffold material with cells to create cardiac patches that are transplanted onto the surface of the heart can overcome these limitations. However, because patches need to be freshly prepared to maintain cell viability, long-term storage is not feasible and limits clinical applicability. Here, we developed an off-the-shelf therapeutic cardiac patch composed of a decellularized porcine myocardial extracellular matrix scaffold and synthetic cardiac stromal cells (synCSCs) generated by encapsulating secreted factors from isolated human cardiac stromal cells. This fully acellular artificial cardiac patch (artCP) maintained its potency after long-term cryopreservation. In a rat model of acute myocardial infarction, transplantation of the artCP supported cardiac recovery by reducing scarring, promoting angiomyogenesis, and boosting cardiac function. The safety and efficacy of the artCP were further confirmed in a porcine model of myocardial infarction. The artCP is a clinically feasible, easy-to-store, and cell-free alternative to myocardial repair using cell-based cardiac patches.

In situ Enabling Approaches for Tissue Regeneration: Current Challenges and New Developments

In situ tissue regeneration can be defined as the implantation of tissue-specific biomaterials (by itself or in combination with cells and/or biomolecules) at the tissue defect, taking advantage of the surrounding microenvironment as a natural bioreactor. Up to now, the structures used were based on particles or gels. However, with the technological progress, the materials' manipulation and processing has become possible, mimicking the damaged tissue directly at the defect site. This paper presents a comprehensive review of current and advanced in situ strategies for tissue regeneration. Recent advances to put in practice the in situ regeneration concept have been mainly focused on bioinks and bioprinting techniques rather than the combination of different technologies to make the real in situ regeneration. The limitation of conventional approaches (e.g., stem cell recruitment) and their poor ability to mimic native tissue are discussed. Moreover, the way of advanced strategies such as 3D/4D bioprinting and hybrid approaches may contribute to overcome the limitations of conventional strategies are highlighted. Finally, the future trends and main research challenges of in situ enabling approaches are discussed considering in vitro and in vivo evidence.

In situ Enabling Approaches for Tissue Regeneration: Current Challenges and New Developments

In situ tissue regeneration can be defined as the implantation of tissue-specific biomaterials (by itself or in combination with cells and/or biomolecules) at the tissue defect, taking advantage of the surrounding microenvironment as a natural bioreactor. Up to now, the structures used were based on particles or gels. However, with the technological progress, the materials' manipulation and processing has become possible, mimicking the damaged tissue directly at the defect site. This paper presents a comprehensive review of current and advanced in situ strategies for tissue regeneration. Recent advances to put in practice the in situ regeneration concept have been mainly focused on bioinks and bioprinting techniques rather than the combination of different technologies to make the real in situ regeneration. The limitation of conventional approaches (e.g., stem cell recruitment) and their poor ability to mimic native tissue are discussed. Moreover, the way of advanced strategies such as 3D/4D bioprinting and hybrid approaches may contribute to overcome the limitations of conventional strategies are highlighted. Finally, the future trends and main research challenges of in situ enabling approaches are discussed considering in vitro and in vivo evidence.

Mussel-inspired conductive Ti2C-cryogel promotes functional maturation of cardiomyocytes and enhances repair of myocardial infarction

Rationale: Researches on conductive engineering cardiac patch (ECP) for myocardial infarction (MI) treatment have achieved some progress in the animal while the availability of traditional conductive materials in ECP is still limited because of their controversial cytotoxicity. Here we aim to introduce a novel hydrophilic biocompatible conductive material: MXene Ti₂C and mussel-inspired dopamine into PEGDA-GelMA cryogel to construct a bio-functional ECP of which the property closes to natural heart for the repair of MI.

Method: MXene Ti₂C was etched from MAX Ti₂AlC, then uniformly dispersed into the prepolymer composed with dopamine-N′, N′-methylene-bisacrylamide, methacrylate-gelatin, and poly (ethylene glycol) diacrylate by simple water bath sonication. The resilient conductive Ti₂C-cryogel was fabricated by chemical cryogelation. The conductive ECP was evaluated in vitro and transplanted to the MI rat model for MI treatment.

Results: In vitro, the 3D vessels-shape framework was observed in Ti₂C-8-cryogel which was seeded with rats aortic endothelial cells. When the Ti₂C-cryogels were cocultured with CMs, remarkably aligned sarcomere and the primitive intercalated disc between the mature CMs were formed on day 7. The as-prepared Ti₂C-8-cryogel ECP also demonstrated rapid calcium transients and synchronous tissue-like beating. When transplanted into the infarcted heart of the MI rat model, the Ti₂C-8-cryogel ECP could improve the cardiac function, reduce the infarct size, and inhibit the inflammatory response. Obvious vasculation especially newly formed arteriole was also found.

Conclusion: A novel conductive Ti₂C-embedded cardiac patch with suitable conductivity and the mechanical property was developed and could be served as an ideal candidate for MI repair.

Biomaterials for stem cell engineering and biomanufacturing

Recent years have witnessed the expansion of tissue failures and diseases. The uprising of regenerative medicine converges the sight onto stem cell-biomaterial based therapy. Tissue engineering and regenerative medicine proposes the strategy of constructing spatially, mechanically, chemically and biologically designed biomaterials for stem cells to grow and differentiate. Therefore, this paper summarized the basic properties of embryonic stem cells (ESCs), induced pluripotent stem cells (iPSCs) and adult stem cells. The properties of frequently used biomaterials were also described in terms of natural and synthetic origins. Particularly, the combination of stem cells and biomaterials for tissue repair applications was reviewed in terms of nervous, cardiovascular, pancreatic, hematopoietic and musculoskeletal system. Finally, stem-cell-related biomanufacturing was envisioned and the novel biofabrication technologies were discussed, enlightening a promising route for the future advancement of large-scale stem cell-biomaterial based therapeutic manufacturing.

Optimising platelet secretomes to deliver robust tissue-specific regeneration

Promoting cell proliferation is the cornerstone of most tissue regeneration therapies. As platelet-based applications promote cell division and can be customised for tissue-specific efficacy, this makes them strong candidates for developing novel regenerative therapies. Therefore, the aim of this study was to determine if platelet releasate could be optimised to promote cellular proliferation and differentiation of specific tissues. Growth factors in platelet releasate were profiled for physiological and supraphysiological platelet concentrations. We analysed the effect of physiological and supraphysiological releasate on C2C12 skeletal myoblasts, H9C2 rat cardiomyocytes, human dermal fibroblasts (HDF), HaCaT keratinocytes, and chondrocytes. Cellular proliferation and differentiation were assessed through proliferation assays, mRNA, and protein expression. We show that supraphysiological releasate is not simply a concentrated version of physiological releasate. Physiological releasate promoted C2C12, HDF, and chondrocyte proliferation with no effect on H9C2 or HaCaT cells. Supraphysiological releasate induced stronger proliferation in C2C12 and HDF cells compared with physiological releasate. Importantly, supraphysiological releasate induced proliferation of H9C2 cells. The proliferative effects of skeletal and cardiac muscle cells were in part driven by vascular endothelial growth factor alpha. Furthermore, supraphysiological releasate induced differentiation of H9C2 and C2C12, HDF, and keratinocytes. This study provides insights into the ability of releasate to promote muscle, heart, skin, and cartilage cell proliferation and differentiation and highlights the importance of optimising releasate composition for tissue-specific regeneration.

Engineering a naturally-derived adhesive and conductive cardiopatch

Myocardial infarction (MI) leads to a multi-phase reparative process at the site of damaged heart that ultimately results in the formation of non-conductive fibrous scar tissue. Despite the widespread use of electroconductive biomaterials to increase the physiological relevance of bioengineered cardiac tissues in vitro, there are still several limitations associated with engineering biocompatible scaffolds with appropriate mechanical properties and electroconductivity for cardiac tissue regeneration. Here, we introduce highly adhesive fibrous scaffolds engineered by electrospinning of gelatin methacryloyl (GelMA) followed by the conjugation of a choline-based bio-ionic liquid (Bio-IL) to develop conductive and adhesive cardiopatches. These GelMA/Bio-IL adhesive patches were optimized to exhibit mechanical and conductive properties similar to the native myocardium. Furthermore, the engineered patches strongly adhered to murine myocardium due to the formation of ionic bonding between the Bio-IL and native tissue, eliminating the need for suturing. Co-cultures of primary cardiomyocytes and cardiac fibroblasts grown on GelMA/Bio-IL patches exhibited comparatively better contractile profiles compared to pristine GelMA controls, as demonstrated by over-expression of the gap junction protein connexin 43. These cardiopatches could be used to provide mechanical support and restore electromechanical coupling at the site of MI to minimize cardiac remodeling and preserve normal cardiac function.

Optimizing Epicardial Restraint and Reinforcement Following Myocardial Infarction: Moving Towards Localized, Biomimetic, and Multitherapeutic Options

The mechanical reinforcement of the ventricular wall after a myocardial infarction has been shown to modulate and attenuate negative remodeling that can lead to heart failure. Strategies include wraps, meshes, cardiac patches, or fluid-filled bladders. Here, we review the literature describing these strategies in the two broad categories of global restraint and local reinforcement. We further subdivide the global restraint category into biventricular and univentricular support. We discuss efforts to optimize devices in each of these categories, particularly in the last five years. These include adding functionality, biomimicry, and adjustability. We also discuss computational models of these strategies, and how they can be used to predict the reduction of stresses in the heart muscle wall. We discuss the range of timing of intervention that has been reported. Finally, we give a perspective on how novel fabrication technologies, imaging techniques, and computational models could potentially enhance these therapeutic strategies.

A New Era of Cardiac Cell Therapy: Opportunities and Challenges

Myocardial infarction (MI), caused by coronary heart disease (CHD), remains one of the most common causes of death in the United States. Over the last few decades, scientists have invested considerable resources on the study and development of cell therapies for myocardial regeneration after MI. However, due to a number of limitations, they are not yet readily available for clinical applications. Mounting evidence supports the theory that paracrine products are the main contributors to the regenerative effects attributed to these cell therapies. The next generation of cell-based MI therapies will identify and isolate cell products and derivatives, integrate them with biocompatible materials and technologies, and use them for the regeneration of damaged myocardial tissue. This review discusses the progress made thus far in pursuit of this new generation of cell therapies. Their fundamental regenerative mechanisms, their potential to combine with other therapeutic products, and their role in shaping new clinical approaches for heart tissue engineering, are addressed.

NIPAM-based Microgel Microenvironment Regulates the Therapeutic Function of Cardiac Stromal Cells

To tune the chemical, physical, and mechanical microenvironment for cardiac stromal cells to treat acute myocardial infarction (MI), we prepared a series of thermally responsive microgels with different surface charges (positive, negative, and neutral) and different degrees of hydrophilicity, as well as functional groups (carboxyl, hydroxyl, amino, and methyl). These microgels were used as injectable hydrogels to create an optimized microenvironment for cardiac stromal cells (CSCs). Our results indicated that a hydrophilic and negatively charged microenvironment created from poly( N-isopropylacrylamide- co-itaconic acid) was favorable for maintaining high viability of CSCs, promoting CSC proliferation and facilitating the formation of CSC spheroids. A large number of growth factors, such as vascular endothelial growth factor (VEGF), insulin-like growth factor I (IGF-1), and stromal-derived factor-1 (SDF-1) were released from the spheroids, promoting neonatal rat cardiomyocyte activation and survival. After injecting the poly( N-isopropylacrylamide- co-itaconic acid) microgel into mice, we examined their acute inflammation and T-cell immune reactions. The microgel itself did not elicit obvious immune response. We then injected the same microgel-encapsulated with CSCs into MI mice. The result revealed the treatment-promoted MI heart repair through angiogenesis and inhibition of apoptosis with an improved cell retention rate. This study will open a door for tailoring poly( N-isopropylacrylamide)-based microgel as a delivery vehicle for CSC therapy.

Cardiac cell-integrated microneedle patch for treating myocardial infarction

We engineered a microneedle patch integrated with cardiac stromal cells (MN-CSCs) for therapeutic heart regeneration after acute myocardial infarction (MI). To perform cell-based heart regeneration, cells are currently delivered to the heart via direct muscle injection, intravascular infusion, or transplantation of epicardial patches. The first two approaches suffer from poor cell retention, while epicardial patches integrate slowly with host myocardium. Here, we used polymeric MNs to create "channels" between host myocardium and therapeutic CSCs. These channels allow regenerative factors secreted by CSCs to be released into the injured myocardium to promote heart repair. In the rat MI model study, the application of the MN-CSC patch effectively augmented cardiac functions and enhanced angiomyogenesis. In the porcine MI model study, MN-CSC patch application was nontoxic and resulted in cardiac function protection. The MN system represents an innovative approach delivering therapeutic cells for heart regeneration.

Cardiac Stem Cell Patch Integrated with Microengineered Blood Vessels Promotes Cardiomyocyte Proliferation and Neovascularization after Acute Myocardial Infarction

Cardiac stem cell (CSC) therapy has shown preclinical and clinical evidence for ischemic heart repair but is limited by low cellular engraftment and survival after transplantation. Previous versions of the cardiac patch strategy improve stem cell engraftment and encourage repair of cardiac tissue. However, cardiac patches that can enhance cardiomyogenesis and angiogenesis at the injured site remain elusive. Therapies that target cardiomyocyte proliferation and new blood vessel formation hold great potential for the protection against acute myocardial infarction (MI). Here, we report a new strategy for creating a vascularized cardiac patch in a facile and modular fashion by leveraging microfluidic hydrodynamic focusing to construct the biomimetic microvessels (BMVs) that include human umbilical vein endothelial cells (HUVECs) lining the luminal surface and then encapsulating the BMVs in a fibrin gel spiked with human CSCs. We show that the endothelialized BMVs mimicked the natural architecture and function of capillaries and that the resultant vascularized cardiac patch (BMV-CSC patch) exhibited equivalent release of paracrine factors compared to those of coculture of genuine human CSCs and HUVECs after 7 days of in vitro culture. In a rat model of acute MI, the BMV-CSC patch therapy induced profound mitotic activities of cardiomyocytes in the peri-infarct region 4 weeks post-treatment. A significant increase in myocardial capillary density was noted in the infarcted hearts that received BMV-CSC patch treatment compared to the infarcted hearts treated with conventional CSC patches. The striking therapeutic benefits and the fast and facile fabrication of the BMV-CSC patch make it promising for practical applications. Our findings suggest that the BMV-CSC patch strategy may open up new possibilities for the treatment of ischemic heart injury.

Current Progress in 3D Bioprinting of Tissue Analogs

Tissue engineering has progressed tremendously over recent decades through the generation of functional tissue analogs. Traditional approaches based on seeding cells into scaffold are limited in their capacity to produce tissues with precise biomimetic properties. Three-dimensional (3D) bioprinting is one kind of fabrication technology used to precisely dispense cell-laden biomaterials for the construction of functional tissues or organs. In recent years, much research progress has been made in 3D bioprinting technology and its application in generating tissue analogs, including skin, heart valves, blood vessels, bone, and cardiac tissue. However, it still faces many technical challenges. In this review, we introduce the current progress in 3D bioprinting technology and focus on biomaterials and their potential applications in regenerative medicine and drug discovery. Current challenges are also discussed.

Potential clinical benefits of cell therapy in coronary heart disease: an update

Cell therapy is a central issue of regenerative medicine and is raising a growing interest in the scientific community, but its full therapeutic potential in coronary heart disease (CHD) has not been reached yet. Several different methods, cell types, delivery routes, and supporting techniques have been attempted and improved to elicit cardiac regeneration in CHD, but only some of them showed a really convincing potential for the use in clinical practice. Here we provide an update on approaches and clinical trials of cell therapy applied to CHD, which are ongoing or that have been realized in the last 5 years. Moreover, we discuss the evidence collected so far in favor or against the validity of stem cell therapy for CHD. In particular, we review and comment the recent advances in cell therapy applied to CHD, the most promising cell types, delivery strategies, biochemical and engineering techniques that have been adopted in this context.

Towards a Novel Patch Material for Cardiac Applications: Tissue-Specific Extracellular Matrix Introduces Essential Key Features to Decellularized Amniotic Membrane

There is a growing need for scaffold material with tissue-specific bioactivity for use in regenerative medicine, tissue engineering, and for surgical repair of structural defects. We developed a novel composite biomaterial by processing human cardiac extracellular matrix (ECM) into a hydrogel and combining it with cell-free amniotic membrane via a dry-coating procedure. Cardiac biocompatibility and immunogenicity were tested in vitro using human cardiac fibroblasts, epicardial progenitor cells, murine HL-1 cells, and human immune cells derived from buffy coat. Processing of the ECM preserved important matrix proteins as demonstrated by mass spectrometry. ECM coating did not alter the mechanical characteristics of decellularized amniotic membrane but did cause a clear increase in adhesion capacity, cell proliferation and viability. Activated monocytes secreted less pro-inflammatory cytokines, and both macrophage polarization towards the pro-inflammatory M1 type and T cell proliferation were prevented. We conclude that the incorporation of human cardiac ECM hydrogel shifts and enhances the bioactivity of decellularized amniotic membrane, facilitating its use in future cardiac applications.

Concise Review: Is Cardiac Cell Therapy Dead? Embarrassing Trial Outcomes and New Directions for the Future

Stem cell therapy is a promising strategy for tissue regeneration. The therapeutic benefits of cell therapy are mediated by both direct and indirect mechanisms. However, the application of stem cell therapy in the clinic is hampered by several limitations. This concise review provides a brief introduction into stem cell therapies for ischemic heart disease. It summarizes cell‐based and cell‐free paradigms, their limitations, and the benefits of using them to target disease. stemcellstranslationalmedicine2018;7:354–359

Engineering Cardiac Muscle Tissue: A Maturating Field of Research

Twenty years after the initial description of a tissue engineered construct, 3-dimensional human cardiac tissues of different kinds are now generated routinely in many laboratories. Advances in stem cell biology and engineering allow for the generation of constructs that come close to recapitulating the complex structure of heart muscle and might, therefore, be amenable to industrial (eg, drug screening) and clinical (eg, cardiac repair) applications. Whether the more physiological structure of 3-dimensional constructs provides a relevant advantage over standard 2-dimensional cell culture has yet to be shown in head-to-head-comparisons. The present article gives an overview on current strategies of cardiac tissue engineering with a focus on different hydrogel methods and discusses perspectives and challenges for necessary steps toward the real-life application of cardiac tissue engineering for disease modeling, drug development, and cardiac repair.