Cardiovascular diseases represent a significant public health challenge and are responsible for more than 4 million deaths annually in Europe alone (45% of all deaths). Among these, coronary-related heart diseases are a leading cause of mortality, accounting for 20% of all deaths. Cardiac tissue engineering has emerged as a promising strategy to address the limitations encountered after myocardial infarction. This approach aims to improve regulation of the inflammatory and cell proliferation phases, thereby reducing scar tissue formation and restoring cardiac function. In cardiac tissue engineering, biomaterials serve as hosts for cells and therapeutics, supporting cardiac restoration by mimicking the native cardiac environment. Various bioengineered systems, such as 3D scaffolds, injectable hydrogels, and patches play crucial roles in cardiac tissue repair. In this context, self-healing hydrogels are particularly suitable substitutes, as they can restore structural integrity when damaged. This structural healing represents a paradigm shift in therapeutic interventions, offering a more native-like environment compared to static, non-healable hydrogels. Herein, we sharply review the most recent advances in self-healing hydrogels in cardiac tissue engineering and their potential to transform cardiovascular healthcare.

Many studies support the idea that long noncoding RNAs (lncRNAs) are significantly involved in the process of cardiomyocyte (CM) regeneration following a myocardial infarction (MI). This study aimed to systematically review the emerging role of lncRNAs in cardiac regeneration by promoting CM proliferation after MI. Furthermore, the review summarized potential targets and the underlying mechanisms of lncRNAs to induce heart regeneration, suggesting utilizing lncRNAs as innovative therapeutic targets for mitigating MI injuries. We searched the PubMed, Scopus, and Web of Science databases for studies on lncRNAs that play a role in heart regeneration after MI. We used search terms that included MI, lncRNAs, CM, and proliferation. Relevant English articles published until June 11, 2023, were systematically reviewed based on inclusion and exclusion criteria. A total of 361 publications were initially identified, and after applying the inclusion and exclusion criteria, nine articles were included in this systematic review. These studies investigated the role of critical lncRNAs in cardiac regeneration after MI, including five upregulated and four downregulated lncRNAs. Acting as a competitive endogenous RNA is one of the main roles of lncRNAs in regulating genes involved in CM proliferation through binding to target microRNAs. The main molecular processes that greatly increase CM proliferation are those that turn on the Hippo/YAP1, PI3K/Akt, JAK2-STAT3, and E2F1-ECRAR-ERK1/2 signaling pathways. This systematic review highlights the significant role of lncRNAs in heart regeneration after MI and their impact on CM proliferation. The findings suggest that lncRNAs could serve as potential targets for therapeutic interventions aiming to enhance cardiac function.

With heart failure (HF) being one of the leading causes of hospitalization and death worldwide, multiple stem cell therapies have been attempted to accelerate the regeneration of the infarct zone. Versatile strategies have emerged to establish the cell candidates of cardiomyocyte lineage for regenerative cardiology. This article illustrates critical insights into the emerging technologies, current approaches, and translational promises on the programming of diverse cell types for cardiac regeneration.

Transplantation of pluripotent stem cell-derived cardiomyocytes is a novel promising cell-based therapeutic approach for patients with heart failure. However, engraftment arrhythmias are a predictable life-threatening complication and represent a major hurdle for clinical translation. Thus, we wanted to experimentally study whether impulse generation by transplanted cardiomyocytes can propagate to the host myocardium and overdrive the recipient rhythm. We transplanted human induced pluripotent stem cell-derived cardiomyocytes expressing the optogenetic actuator Bidirectional Pair of Opsins for Light-induced Excitation and Silencing (BiPOLES) in a guinea pig injury model. Eight weeks after transplantation ex vivo, Langendorff perfusion was used to assess electrical coupling. Pulsed photostimulation was applied to specifically activate the engrafted cardiomyocytes. Photostimulation resulted in ectopic pacemaking that propagated to the host myocardium, caused non-sustained arrhythmia, and stimulated the recipient heart with higher pacing frequency (4/9 hearts). Our study demonstrates that transplanted cardiomyocytes can (1) electrically couple to the host myocardium and (2) stimulate the recipient heart. Thus, our results provide experimental evidence for an important aspect of engraftment-induced arrhythmia induction and thereby support the current hypothesis that cardiomyocyte automaticity can serve as a trigger for ventricular arrhythmias.

UNASSIGNED: Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) show tremendous promise for cardiac regeneration following myocardial infarction (MI), but their transplantation gives rise to transient ventricular tachycardia (VT) in large-animal MI models, representing a major hurdle to translation. Our group previously reported that these arrhythmias arise from a focal mechanism whereby graft tissue functions as an ectopic pacemaker; therefore, we hypothesized that hPSC-CMs engineered with a dominant negative form of the pacemaker ion channel HCN4 (dnHCN4) would exhibit reduced automaticity and arrhythmogenic risk following transplantation.
UNASSIGNED: We used CRISPR/Cas9-mediated gene-editing to create transgenic dnHCN4 hPSC-CMs, and their electrophysiological behavior was evaluated in vitro by patch-clamp recordings and optical mapping. Next, we transplanted WT and homozygous dnHCN4 hPSC-CMs in a pig MI model and compared post-transplantation outcomes including the incidence of spontaneous arrhythmias and graft structure by immunohistochemistry.
UNASSIGNED: In vitro dnHCN4 hPSC-CMs exhibited significantly reduced automaticity and pacemaker funny current (I f ) density relative to wildtype (WT) cardiomyocytes. Following transplantation with either dnHCN4 or WT hPSC-CMs, all recipient hearts showed transmural infarct scar that was partially remuscularized by scattered islands of human myocardium. However, in contrast to our hypothesis, both dnHCN4 and WT hPSC-CM recipients exhibited frequent episodes of ventricular tachycardia (VT).
UNASSIGNED: While genetic silencing of the pacemaker ion channel HCN4 suppresses the automaticity of hPSC-CMs in vitro, this intervention is insufficient to reduce VT risk post-transplantation in the pig MI model, implying more complex mechanism(s) are operational in vivo.

Revascularization of ischemic myocardium following cardiac damage is an important step in cardiac regeneration. However, the mechanism of arteriogenesis has not been well described during cardiac regeneration. Here we investigated coronary artery remodeling and collateral growth during cardiac regeneration. Neonatal MI was induced by ligature of the left descending artery (LAD) in postnatal day (P) 1 or P7 pups from the Cx40-GFP mouse line and the arterial tree was reconstructed in 3D from images of cleared hearts collected at 1, 2, 4, 7 and 14 days after infarction. We show a rapid remodeling of the left coronary arterial tree induced by neonatal MI and the formation of numerous collateral arteries, which are transient in regenerating hearts after MI at P1 and persistent in non-regenerating hearts after MI at P7. This difference is accompanied by restoration of a perfused or a non-perfused LAD following MI at P1 or P7 respectively. Interestingly, collaterals ameliorate cardiac perfusion and drive LAD repair, and lineage tracing analysis demonstrates that the restoration of the LAD occurs by remodeling of pre-existing arterial cells independently of whether they originate in large arteries or arterioles. These results demonstrate that the restoration of the LAD artery during cardiac regeneration occurs by pruning as the rapidly forming collaterals that support perfusion of the disconnected lower LAD subsequently disappear on restoration of a unique LAD. These results highlight a rapid phase of arterial remodeling that plays an important role in vascular repair during cardiac regeneration.

OBJECTIVE: Heritable dilated cardiomyopathy (DCM) or DCM associated with congenital or acquired left ventricular diseases carries a significant mortality risk. Pulmonary artery banding (PAB) has been proposed as an alternative to heart transplantation. This study aimed to delineate the clinical development, ventricular reverse remodelling, and functional regeneration of the dilated left ventricle, presenting as a pioneering approach in China.
RESULTS: This prospective study was initiated in November 2021, involving paediatric patients with a significant dilated left ventricle and preserved right ventricle who underwent surgical PAB. The baseline characteristics and clinical information during follow-up were collected. Seven patients (five boys) with a median age of 240 (148, 1028) days have been included thus far. No procedural or follow-up mortality was observed. The modified Ross functional class improved from treatment to follow-up of 348 (200, 629) days, and the median left ventricular ejection fraction increased from 27.0 (15.0, 34.0) % before surgery to 61.0 (52.0, 68.0) % (P < 0.05); the median left ventricular end-diastolic diameter and corresponding Z-scores decreased from 43.0 (40.0, 55.0) mm [+9.4 (+7.7, +11.7)] to 33.0 (29.0, 39.0) mm [+1.8 (+1.3, +3.8)] (P < 0.05). Functional regeneration of the left ventricle was observed in five patients. Three of them underwent balloon dilation of the PAB to relieve excessively elevated right ventricular pressures.
CONCLUSIONS: The application of PAB should adhere to strict criteria. Initial results are promising for infants and even toddlers with a dilated left ventricle and limited probability of spontaneous recovery. PAB can be an alternative when there is a shortage of donor transplants and assist devices, especially for low- and middle-income countries.

Non-human primates (NHP) are valuable models for late translational pre-clinical studies, often seen as a last step before clinical application. The unique similarity between NHPs and humans is often the subject of ethical concerns. However, it is precisely this analogy in anatomy, physiology, and the immune system that narrows the translational gap to other animal models in the cardiovascular field. Cell and gene therapy approaches are two dominant strategies investigated in the research field of cardiac regeneration. Focusing on the cell therapy approach, several xeno- and allogeneic cell transplantation studies with a translational motivation have been realized in macaque species. This is based on the pressing need for novel therapeutic options for heart failure patients. Stem cell-based remuscularization of the injured heart can be achieved via direct injection of cardiomyocytes (CMs) or patch application. Both CM delivery approaches are in the late preclinical stage, and the first clinical trials have started. However, are we already ready for the clinical area? The present review concentrates on CM transplantation studies conducted in NHPs, discusses the main sources and discoveries, and provides a perspective about human translation.

Finding novel treatments for cardiovascular diseases (CVDs) is a hot topic in medicine; cell-based therapies have reported promising news for controlling dangerous complications of heart disease such as myocardial infarction (MI) and heart failure (HF). Various progenitor/stem cells were tested in various in-vivo, in-vitro, and clinical studies for regeneration or repairing the injured tissue in the myocardial to accelerate the healing. Fetal, adult, embryonic, and induced pluripotent stem cells (iPSC) have revealed the proper potency for cardiac tissue repair. As an essential communicator among cells, exosomes with specific contacts (proteins, lncRNAs, and miRNAs) greatly promote cardiac rehabilitation. Interestingly, stem cell-derived exosomes have more efficiency than stem cell transplantation. Therefore, stem cells induced pluripotent stem cells (iPSCs), embryonic stem cells (ESCs), cardiac stem cells (CDC), and skeletal myoblasts) and their-derived exosomes will probably be considered an alternative therapy for CVDs remedy. In addition, stem cell-derived exosomes have been used in the diagnosis/prognosis of heart diseases. In this review, we explained the advances of stem cells/exosome-based treatment, their beneficial effects, and underlying mechanisms, which will present new insights in the clinical field in the future.

Cell therapy is a potential novel treatment for cardiac regeneration and numerous studies have attempted to transplant cells to regenerate the myocardium lost during myocardial infarction. To date, only minimal improvements to cardiac function have been reported. This is likely to be the result of low cell retention and survival following transplantation. This study aimed to improve the delivery and engraftment of viable cells by using an injectable microcarrier that provides an implantable, biodegradable substrate for attachment and growth of cardiomyocytes derived from induced pluripotent stem cells (iPSC). We describe the fabrication and characterisation of Thermally Induced Phase Separation (TIPS) microcarriers and their surface modification to enable iPSC-derived cardiomyocyte attachment in xeno-free conditions is described. The selected formulation resulted in iPSC attachment, expansion, and retention of pluripotent phenotype. Differentiation of iPSC into cardiomyocytes on the microcarriers is investigated in comparison with culture on 2D tissue culture plastic surfaces. Microcarrier culture is shown to support culture of a mature cardiomyocyte phenotype, be compatible with injectable delivery, and reduce anoikis. The findings from this study demonstrate that TIPS microcarriers provide a supporting matrix for culturing iPSC and iPSC-derived cardiomyocytes in vitro and are suitable as an injectable cell-substrate for cardiac regeneration.