viral-transgene-expression-rodent-hearts-assessment-cardiac

Viral Transgene Expression in Rodent Hearts and the Assessment of Cardiac Arrhythmia Risk

Heart disease is the leading cause of morbidity and mortality worldwide. Due to the ease of handling&#160;and abundance of transgenic strains, rodents ...

University of Ottawa Heart Institute

University of Ottawa

Wnt/β-catenin signaling is activated in the heart after myocardial infarction (MI). This study aims to investigate if β-catenin deletion affects post-MI ion channel gene alterations and ventricular tachycardias (VT). MI was induced by permanent ligation of left anterior descending artery in wild-type (WT) and cardiomyocyte-specific β-catenin knockout (KO) mice. KO mice showed reduced susceptibility to VT (18% vs. 77% in WT) at 8 weeks after MI, associated with reduced scar size and attenuated chamber dilation. qPCR analyses of both myocardial tissues and purified cardiomyocytes demonstrated upregulation of Wnt pathway genes in border and infarct regions after MI, including Wnt ligands (such as Wnt4) and receptors (such as Fzd1 and Fzd2). At 1 week after MI, cardiac sodium channel gene (Scn5a) transcript was reduced in WT but not in KO hearts, consistent with previous studies showing Scn5a inhibition by Wnt/β-catenin signaling. At 8 weeks after MI when Wnt genes have declined, Scn5a returned to near sham levels and K channel gene downregulations were not different between WT and KO mice. This study demonstrated that VT susceptibility in the chronic phase after MI is reduced in mice with cardiomyocyte-specific β-catenin deletion primarily through attenuated structural remodeling, but not ion channel gene alterations.

Cardiomyocyte-specific deletion of β-catenin protects mouse hearts from ventricular arrhythmias after myocardial infarction.

Previous studies have established that transmural gradients of the fast transient outward K current () correlate with regional differences in action potential (AP) profile and excitation-contraction coupling (ECC) with high  expression in the epimyocardium (EPI) being associated with short APs and low contractility and vice versa. Herein, we investigated the effects of altering the  gradients on transmural contractile properties using mice lacking  (Irx5-KO) or lacking  (K4.2-KO) or both. Irx5-KO mice exhibited decreased global LV contractility in association with elevated , as well as reduced cell shortening and Ca transient amplitudes in cardiomyocytes isolated from the endomyocardium (ENDO) but not in cardiomyocytes from the EPI. Transcriptional profiling revealed that the primary effect of  ablation on ECC-related genes was to increase  gene expression (i.e.,  and ) in the ENDO, but not the EPI. By contrast, K4.2-KO mice showed selective increases in cell shortening and Ca transients in isolated EPI cardiomyocytes, leading to enhanced ventricular contractility and mice lacking both  and  displayed elevated ventricular contractility, comparable to K4.2-KO mice, demonstrating a dominant role of -dependent modulation of  in the regulation of contractility. Our findings show that the transmural electromechanical heterogeneities in the healthy ventricles depend on the -dependent  gradients. These observations provide a useful framework for assessing the molecular mechanisms underlying the alterations in contractile heterogeneity seen in the diseased heart. Irx5 is a vital transcription factor that establishes the transmural heterogeneity of ventricular myocyte contractility, thereby ensuring proper contractile function in the healthy heart. Regional differences in excitation-contraction coupling in the ventricular myocardium are primarily mediated through the inverse relationship between Irx5 and the fast transient outward K current () across the ventricular wall.

Irx5 and transient outward K currents contribute to transmural contractile heterogeneities in the mouse ventricle.

The unique ability of piezoelectric materials to generate electricity spontaneously has attracted widespread interest in the medical field. In addition to the ability to convert mechanical stress into electrical energy, piezoelectric materials offer the advantages of high sensitivity, stability, accuracy and low power consumption. Because of these characteristics, they are widely applied in devices such as sensors, controllers and actuators. However, piezoelectric materials also show great potential for the medical manufacturing of artificial organs and for tissue regeneration and repair applications. For example, the use of piezoelectric materials in cochlear implants, cardiac pacemakers and other equipment may help to restore body function. Moreover, recent studies have shown that electrical signals play key roles in promoting tissue regeneration. In this context, the application of electrical signals generated by piezoelectric materials in processes such as bone healing, nerve regeneration and skin repair has become a prospective strategy. By mimicking the natural bioelectrical environment, piezoelectric materials can stimulate cell proliferation, differentiation and connection, thereby accelerating the process of self-repair in the body. However, many challenges remain to be overcome before these concepts can be applied in clinical practice, including material selection, biocompatibility and equipment design. On the basis of the principle of electrical signal regulation, this article reviews the definition, mechanism of action, classification, preparation and current biomedical applications of piezoelectric materials and discusses opportunities and challenges for their future clinical translation.

From electricity to vitality: the emerging use of piezoelectric materials in tissue regeneration.

Macrophages are primary immune cells that play a crucial role in tissue regeneration during the early stages of biomaterial implantation. They create a microenvironment that facilitates cell infiltration, angiogenesis, and tissue remodeling. In the field of vascular tissue engineering, numerous studies have been conducted to modulate the macrophage phenotype by designing various biomaterials, which in turn enhances the regenerative capacity and long-term patency of vascular grafts. However, the mechanism underlying the different phenotypes of macrophages involved in the tissue regeneration of vascular grafts remains unclear. In this study, vascular grafts loaded with various macrophage phenotypes were developed, and their effects were evaluated both in vivo and in vitro. The RAW 264.7 macrophages (M0) were initially treated with LPS or IL-4/IL-10 and polarized into M1 and M2 phenotypes. Subsequently, M0, M1, and M2 macrophages were seeded onto electrospun PCL scaffolds to obtain macrophage-loaded vascular grafts (PCL-M0, PCL-M1, and PCL-M2). As prepared vascular grafts were implanted into the mouse carotid artery for up to one month. The results indicate that the loading of M2 macrophages effectively enhances the patency rate and neotissue formation of vascular grafts. This is achieved through the development of a well-defined endothelium and smooth muscle layer. RNA sequencing was used to investigate the mechanisms of action of different macrophages on tissue regeneration. The study found that M1 macrophages inhibited tissue regeneration by mediating angiogenesis and chronic inflammation through upregulation of VEGFa, IL-1β, and IL-6 expression. In contrast, M2 macrophages regulate the immune microenvironment by upregulating the expression of IL-4 and TGF-β, thereby promoting tissue regeneration. In conclusion, our study demonstrates how different macrophage phenotypes contribute to the initial inflammatory microenvironment surrounding vascular grafts, thereby modulating the biological process of vascular remodeling. STATEMENT OF SIGNIFICANCE: Regulating the biophysical and biochemical characteristics of biomaterials can induce macrophage polarization and enhance vascular remodeling. In previous work, we fabricated a vascular graft with a macroporous structure that promoted macrophage infiltration and polarization into a pro-regenerative phenotype. To illustrate the mechanism, we established a new mouse model and evaluated the effects of different macrophages on vascular regeneration. The study revealed that tuning macrophage phenotype can impact the initial inflammatory microenvironment by secreting cytokines, which can increase the patency rate and regenerative capacity of vascular grafts. These findings provide essential theoretical support for the development of immunoregulatory scaffolds for vascular and other tissue regeneration.

Article	Year
Cardiomyocyte-specific deletion of β-catenin protects mouse hearts from ventricular arrhythmias after myocardial infarction. Scientific reports\| PubMed ID: 34489488	2021
Irx5 and transient outward K currents contribute to transmural contractile heterogeneities in the mouse ventricle. American journal of physiology. Heart and circulatory physiology\| PubMed ID: 35245131	2022
From electricity to vitality: the emerging use of piezoelectric materials in tissue regeneration. Burns & trauma\| PubMed ID: 38957661	2024
Tuning macrophage phenotype for enhancing patency rate and tissue regeneration of vascular grafts. Acta biomaterialia\| PubMed ID: 40158766	2025

Ying Xia

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