Cardiac Extracellular Matrix Modification as a Therapeutic Approach

The Utilisation of Hydrogels for iPSC-Cardiomyocyte Research

Cardiac fibroblasts' (FBs) and cardiomyocytes' (CMs) behaviour and morphology are influenced by their environment such as remodelling of the myocardium, thus highlighting the importance of biomaterial substrates in cell culture. Biomaterials have emerged as important tools for the development of physiological models, due to the range of adaptable properties of these materials, such as degradability and biocompatibility. Biomaterial hydrogels can act as alternative substrates for cellular studies, which have been particularly key to the progression of the cardiovascular field. This review will focus on the role of hydrogels in cardiac research, specifically the use of natural and synthetic biomaterials such as hyaluronic acid, polydimethylsiloxane and polyethylene glycol for culturing induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs). The ability to fine-tune mechanical properties such as stiffness and the versatility of biomaterials is assessed, alongside applications of hydrogels with iPSC-CMs. Natural hydrogels often display higher biocompatibility with iPSC-CMs but often degrade quicker, whereas synthetic hydrogels can be modified to facilitate cell attachment and decrease degradation rates. iPSC-CM structure and electrophysiology can be assessed on natural and synthetic hydrogels, often resolving issues such as immaturity of iPSC-CMs. Biomaterial hydrogels can thus provide a more physiological model of the cardiac extracellular matrix compared to traditional 2D models, with the cardiac field expansively utilising hydrogels to recapitulate disease conditions such as stiffness, encourage alignment of iPSC-CMs and facilitate further model development such as engineered heart tissues (EHTs).

Doxycycline Attenuates Doxorubicin-Induced Cardiotoxicity by Improving Myocardial Energy Metabolism in Rats

Aim: Evaluate the influence of doxycycline, an anti-inflammatory and matrix metalloproteinase (MMP) inhibitor, on the attenuation of chronic doxorubicin-induced cardiotoxicity in rats. Methods: We allocated male Wistar rats into four groups: control (C), doxorubicin (D), doxycycline (inhibitor of MMP, IM), and Dox + doxycycline (DIM). Groups IM and DIM received doxycycline (5 mg/kg, IP) once a week for 4 weeks. In addition, 48 h after every doxycycline injection, groups D and DIM received Dox (5 mg/kg, IP). We performed echocardiogram and evaluated TIMP-4 and collagen I protein expression, MMP-2 activity, and oxidative stress and myocardial metabolism. Results: Doxorubicin promotes left atrium (LA) and left ventricle (LV) dilatation and decreases in LV fractional shortening, which was improved by doxycycline. Moreover, doxycycline attenuated the LV cardiomyocyte hypertrophy and collagen type I expression. Doxorubicin increased phosphofructokinase and decreased beta-hydroxyacyl Co-A dehydrogenase, pyruvate dehydrogenase, citrate synthase, and ATP synthase activity, which was partially attenuated by doxycycline. Lastly, doxycycline improved antioxidant enzyme activity in the DIM group. Conclusion: Doxorubicin increases oxidative stress and promotes changes in myocardial energy metabolism, accompanied by structural and functional changes. Doxycycline attenuated the doxorubicin-induced cardiotoxicity, at least in part, through changes in myocardial energy metabolism.

Extracellular Matrix Coatings on Cardiovascular Materials—A Review

Vascular transplantation is an effective and common treatment for cardiovascular disease (CVD). However, the low biocompatibility of implants is a major problem that hinders its clinical application. Surface modification of implants with extracellular matrix (ECM) coatings is an effective approach to improve the biocompatibility of cardiovascular materials. The complete ECM seems to have better biocompatibility, which may give cardiovascular biomaterials a more functional surface. The use of one or several ECM proteins to construct a surface allows customization of coating composition and structure, possibly resulting in some unique functions. ECM is a complex three-dimensional structure composed of a variety of functional biological macromolecules, and changes in the composition will directly affect the function of the coating. Therefore, understanding the chemical composition of the ECM and its interaction with cells is beneficial to provide new approaches for coating surface modification. This article reviews novel ECM coatings, including coatings composed of intact ECM and biomimetic coatings tailored from several ECM proteins, and introduces new advances in coating fabrication. These ECM coatings are effective in improving the biocompatibility of vascular grafts.

Engineering of thick human functional myocardium via static stretching and electrical stimulation

Human cardiac-muscle patches (hCMPs) constructed from induced pluripotent stem cells derived cardiomyocytes (iCMs) can replicate the genetics of individual patients, and consequently be used for drug testing, disease modeling, and therapeutic applications. However, conventional hCMPs are relatively thin and contain iCMs with fetal cardiomyocyte structure and function. Here, we used our layer-by-layer (lbl) fabrication to construct thicker (>2.1 mm), triple-layered hCMPs, and then evaluated iCM maturity after ten days of standard culture (Control), static stretching (Stretched), or stretching with electrical stimulation at 15 or 22 V (Stretched+15V or Stretched+22V). Assessments of stained hCMPs suggested that expression and alignment of contractile proteins was greater in Stretched+22V, whereas quantification of mRNA abundance and protein expression indicated the Stretched+22V enhanced biomolecular maturation. Transmission electron microscope images indicated that stretching and electrical stimulation were associated with increases in development of Z-lines and gap junctions, and sarcomeres were significantly longer following any of the maturation protocols.

Possible Treatment of Myocardial Infarct Based on Tissue Engineering Using a Cellularized Solid Collagen Scaffold Functionalized with Arg-Glyc-Asp (RGD) Peptide

Currently, the clinical impact of cell therapy after a myocardial infarction (MI) is limited by low cell engraftment due to low cell retention, cell death in inflammatory and poor angiogenic infarcted areas, secondary migration. Cells interact with their microenvironment through integrin mechanoreceptors that control their survival/apoptosis/differentiation/migration and proliferation. The association of cells with a three-dimensional material may be a way to improve interactions with their integrins, and thus outcomes, especially if preparations are epicardially applied. In this review, we will focus on the rationale for using collagen as a polymer backbone for tissue engineering of a contractile tissue. Contractilities are reported for natural but not synthetic polymers and for naturals only for: collagen/gelatin/decellularized-tissue/fibrin/Matrigel™ and for different material states: hydrogels/gels/solids. To achieve a thick/long-term contractile tissue and for cell transfer, solid porous compliant scaffolds are superior to hydrogels or gels. Classical methods to produce solid scaffolds: electrospinning/freeze-drying/3D-printing/solvent-casting and methods to reinforce and/or maintain scaffold properties by reticulations are reported. We also highlight the possibility of improving integrin interaction between cells and their associated collagen by its functionalizing with the RGD-peptide. Using a contractile patch that can be applied epicardially may be a way of improving ventricular remodeling and limiting secondary cell migration.

Basement Membrane Extracellular Matrix Proteins in Pulmonary Vascular and Right Ventricular Remodeling in Pulmonary Hypertension

The extracellular matrix (ECM), a highly organized network of structural and non-structural proteins, plays a pivotal role in cellular and tissue homeostasis. Changes in the ECM are critical for normal tissue repair, while dysregulation contributes to aberrant tissue remodeling. Pulmonary arterial hypertension (PAH) is a severe disorder of the pulmonary vasculature characterized by pathologic remodeling of the pulmonary vasculature and right ventricle (RV), increased production and deposition of structural and non-structural proteins, and altered expression of ECM growth factors and proteases. Furthermore, ECM remodeling plays a significant role in disease progression as several dynamic changes in its composition, quantity, and organization are documented in both humans and animal models of disease. These ECM changes impact upon vascular cell biology and affect proliferation of resident cells. Further, ECM components determine the tissue architecture of the pulmonary and myocardial vasculature as well as the myocardium itself, and provide mechanical stability crucial for tissue homeostasis. However, little is known about the basement membrane (BM), a specialized, self-assembled conglomerate of ECM proteins, during remodeling. In the vasculature, the BM is in close physical association with the vascular endothelium and smooth muscle cells. While in the myocardium, each cardiomyocyte is enclosed by a BM that serves as the interface between cardiomyocytes and the surrounding interstitial matrix. In this review, we provide a brief overview on the current state of knowledge of the BM and its ECM composition and their impact on pulmonary vascular remodeling and RV dysfunction and failure in PAH.

Progress in cardiovascular bioprinting

Cardiovascular disease has been the leading cause of death globally for the past 15 years. Following a major cardiac disease episode, the ideal treatment would be the replacement of the damaged tissue, due to the limited regenerative capacity of cardiac tissues. However, we suffer from a chronic organ donor shortage which causes approximately 20 people to die each day waiting to receive an organ. Bioprinting of tissues and organs can potentially alleviate this burden by fabricating low cost tissue and organ replacements for cardiac patients. Clinical adoption of bioprinting in cardiovascular medicine is currently limited by the lack of systematic demonstration of its effectiveness, high costs, and the complexity of the workflow. Here, we give a concise review of progress in cardiovascular bioprinting and its components. We further discuss the challenges and future prospects of cardiovascular bioprinting in clinical applications.

Effect of cellular and ECM aging on human iPSC-derived cardiomyocyte performance, maturity and senescence

Cardiovascular diseases are the leading cause of death worldwide and their occurrence is highly associated with age. However, lack of knowledge in cardiac tissue aging is a major roadblock in devising novel therapies. Here, we studied the effects of cell and cardiac extracellular matrix (ECM) aging on the induced pluripotent stem cell (iPSC)-derived cardiomyocyte cell state, function, as well as response to myocardial infarction (MI)-mimicking stress conditions in vitro. Within 3-weeks, young ECM promoted proliferation and drug responsiveness in young cells, and induced cell cycle re-entry, and protection against stress in the aged cells. Adult ECM improved cardiac function, while aged ECM accelerated the aging phenotype, and impaired cardiac function and stress defense machinery of the cells. In summary, we have gained a comprehensive understanding of cardiac aging and highlighted the importance of cell-ECM interactions. This study is the first to investigate the individual effects of cellular and environmental aging and identify the biochemical changes that occur upon cardiac aging.

Extracellular Matrix in Regulation of Contractile System in Cardiomyocytes

The contractile apparatus of cardiomyocytes is considered to be a stable system. However, it undergoes strong rearrangements during heart development as cells progress from their non-muscle precursors. Long-term culturing of mature cardiomyocytes is also accompanied by the reorganization of their contractile apparatus with the conversion of typical myofibrils into structures of non-muscle type. Processes of heart development as well as cell adaptation to culture conditions in cardiomyocytes both involve extracellular matrix changes, which appear to be crucial for the maturation of contractile apparatus. The aim of this review is to analyze the role of extracellular matrix in the regulation of contractile system dynamics in cardiomyocytes. Here, the remodeling of actin contractile structures and the expression of actin isoforms in cardiomyocytes during differentiation and adaptation to the culture system are described along with the extracellular matrix alterations. The data supporting the regulation of actin dynamics by extracellular matrix are highlighted and the possible mechanisms of such regulation are discussed.

Decellularized extracellular matrix bioinks and the external stimuli to enhance cardiac tissue development in vitro

Engineered heart tissue (EHT) has ample potential as a model for in vitro tissue modeling or tissue regeneration. Using 3D cell printing technology, various hydrogels have been utilized as bioinks to fabricate EHT to date. However, its efficacy has remained limited due to poor functional properties of the cultured cardiomyocytes stemming from a lack of proper microenvironmental cues. Specifically, the surrounding matrix plays a key role in modulating cardiomyocyte differentiation and maturation. Recently, the use of heart tissue-derived extracellular matrix (hdECM) bioink has come to be seen as one of the most promising candidates due to its functional and structural similarities to native tissue. Here, we demonstrated a correlation between the synthesis of cardiomyocyte-specific proteins and the surrounding microenvironment irrespective of the similar material chemistry. Primary cardiomyocytes isolated from neonatal rats were encapsulated in different composition and concentration of bioinks (hdECM and collagen). The bioinks were sequentially printed using an extrusion-based 3D bioprinter and cultured either statically or dynamically. Qualitative and quantitative evaluation revealed enhanced maturation of cardiomyocytes in hdECM, unlike the collagen group under similar culture conditions. Specifically, 3D-printed EHT using a low concentration of hdECM promoted early differentiation of cardiomyocytes. Hence, the present study provides experimental insights regarding the establishment of a 3D-printed cardiac tissue model, highlighting that the matrix and the culture microenvironment can be decisive factors for cell-material interactions that affect cardiomyocyte maturation. STATEMENT OF SIGNIFICANCE: The regulation of signal transduction and responses to extracellular matrices (ECMs) is of particular relevance in tissue maturation. In particular, there is a clear need to understand the structural and phenotypical modulation in cardiomyocytes with respect to the surrounding microenvironment. Exploration of the key regulators, such as the compositional and the biophysical properties of bioinks associated directly with cell-cell and cell-matrix interactions would assist with the fabrication of cardiac tissue constructs with enhanced functionality. Hence, we documented the synergistic effects of surrounding matrices and culture conditions on the maturation of cardiomyocytes. Additionally, we highlighted the potential of using 3D bioprinting techniques to fabricate uniformly aligned cardiac constructs for mid- to high-throughput drug testing platforms that have great reproducibility and versatility.