Kai Kang

Myocardial infarction (MI) remains the leading cause of death worldwide. Cardiomyocytes, being terminally differentiated cells, have limited regenerative capacity. Following an MI, myocyte necrosis and ventricular dilation can lead to heart failure. While current treatments for heart disease—such as pharmaceuticals, coronary interventions, coronary artery bypass grafting, cellular therapy, and heart transplantation—offer some relief, their effectiveness is limited, particularly in patients with severe myocardial damage. Recent advancements in cardiac tissue engineering have introduced a range of materials aimed at repairing the heart, with conductive hydrogels emerging as a promising approach. These materials, which include metallic nanomaterials, conductive polymers, carbon-based conductive materials, and other specialized types of conductive substances, exhibit excellent electrical conductivity, tunable mechanical properties, and biomimetic features. As a result, they are increasingly being considered for myocardial repair. This review explores the application of conductive hydrogels in treating myocardial infarction, highlighting recent research in various types of conductive hydrogels. These are categorized by their nanomaterial composition, including hydrogels designed for cell culture scaffolds, patch-type hydrogels, and injectable conductive hydrogels. Additionally, electrophysiological monitoring during MI is gaining importance in understanding disease progression and prognosis. In recent years, conductive hydrogels have rapidly evolved to serve as tools for real-time monitoring of signal changes, while their electroresponsive properties open new possibilities for targeted drug delivery in infarct therapy.

BACKGROUND Mesenchymal stem cell (MSC)-based therapy may be a future treatment for myocardial infarction (MI). However, few studies have assessed the therapeutic efficacy of adipose tissue-derived MSCs (ADSCs) obtained from elderly patients in comparison to that of bone marrow-derived MSCs (BMSCs) from the same elderly patients. The metabolomics results revealed a significantly higher L-arginine excretion from aged ADSCs vs BMSCs in hypoxic conditions. This was hypothesized as the possible mechanism that ADSCs showed an improved angiogenic capacity and enhanced the therapeutic effect on ischemic heart diseases. AIM To investigate the role of L-arginine in enhancing angiogenesis and cardiac protection by comparing ADSCs and BMSCs in hypoxic conditions for MI therapy. METHODS Metabolomic profiling of supernatants from ADSCs and BMSCs under hypoxic conditions were performed. Then, arginine succinate lyase (ASL) overexpression and short hairpin RNA plasmid were prepared and transfected into BMSCs. Subsequently, in vitro wound healing and Matrigel tube formation assays were used to verify the proangiogenetic effects of ADSC positive control, BMSCs, BMSCs ASL short hairpin RNA, BMSCs ASL overexpressed, and BMSC negative control on cocultured human umbilical vein endothelial cells. All sample sizes, which were determined to meet the statistical requirements and be greater than 3, were established on the basis of previously established literature standards. The protein levels of vascular endothelial growth factor (VEGF), basic fibroblast growth factor, etc . were detected. In vivo , the five types of cells were transplanted into the infarcted area of MI rat models, and the therapeutic effects of the transplanted cells were evaluated by echocardiography on cardiac function and by Masson’s staining/terminal-deoxynucleotidyl transferase mediated nick end labeling assay/immunofluorescence detection on the infarcted area. RESULTS Metabolomic analysis showed that L-arginine was increased. Using ASL gene transfection, we upregulated the production of L-arginine in aged patient-derived BMSCs in vitro , which in turn enhanced mitogen activated protein kinase and VEGF receptor 2 protein expression, VEGF and basic fibroblast growth factor secretion, and inductive angiogenesis to levels comparable to donor-matched ADSCs. After the cell transplantation in vivo , the modified BMSCs as well as ADSCs exhibited decreased apoptotic cells, enhanced vessel formation, reduced scar size, and improved cardiac function in the MI rat model. The therapeutic efficacy decreased by inhibiting L-arginine synthesis. CONCLUSION L-arginine is important for inducing therapeutic angiogenesis for ADSCs and BMSCs in hypoxic conditions. ADSCs have higher L-arginine secretion, which leads to better angiogenesis induction and cardiac protection. ADSC transplantation is a promising autologous cell therapy strategy in the context of the present aging society.

Diabetes mellitus (DM) is a risk factor for the development of atrial fibrillation (AF). The action potential duration (APD) has been demonstrated to be prolonged in the atrium of diabetic mice. In contrast, the APD is generally shortened in AF patients. It is unclear what change occurs in the atrial APD of diabetic patients. In this study, we explore the APD change of atrial myocytes from diabetic patients and the underlying molecular mechanisms. The whole-cell patch-clamp technique is used to detect single-cell electrical activity in diabetic and nondiabetic human samples. The results show that APD₅₀ and APD₉₀, the APD at both 50% and 90% repolarization, are increased in diabetic patients compared with nondiabetic controls. The density of I_NaL in the atrial myocytes of diabetic patients is greater than that in the myocytes of nondiabetic patients. The expression of RAGE is increased in the atria of diabetic patients. In cultured HL-1 cells, high glucose (HG) treatment increases I_NaL, and the expression of the receptor for advanced glycation end products (RAGE) prolongs APD. The siRNA-mediated knockdown of RAGE reduces the late sodium current and shortens the APD. The APD is prolonged in the atria of diabetic patients because of the upregulation of RAGE and the subsequent increase in I_NaL. Our findings provide novel insights into atrial electrical remodeling in diabetic patients.

Myocardial ischemia/reperfusion (IR) injury is a common adverse event in the clinical treatment of myocardial ischemic disease. Autosis is a form of cell d

Objective: Cold regions exhibit a high prevalence of cardiovascular disease, particularly acute myocardial infarction (AMI), which is one of the leading causes of death associated with cardiovascular conditions. Cardiovascular disease is closely linked to the abnormal expression of long non-coding RNA (lncRNA). This study investigates whether circulating levels of lncRNA cardiac conduction regulatory RNA (CCRR) could serve as a biomarker for AMI. Materials and methods: We measured circulating CCRR from whole blood samples collected from 68 AMI patients and 69 non-AMI subjects. An AMI model was established using C57BL/6 mice. Quantitative reverse transcription PCR (qRT-PCR) was used to assess CCRR expression. Exosomes were isolated from cardiomyocytes, and their characteristics were evaluated using electron microscope and nanoparticle tracking analysis. The exosome inhibitor GW4869 was employed to examine the effect of exosomal CCRR on cardiac function using echocardiography. Protein expression was detected using Western blot and immunofluorescence staining. Results: The circulating level of CCRR was significantly higher in AMI patients (1.93 ± 0.13) than in non-AMI subjects (1.00 ± 0.05, P < 0.001). The area under the ROC curve (AUC) of circulating CCRR was 0.821. Similar changes in circulating CCRR levels were consistently observed in an AMI mouse model. Exosomal CCRR derived from hypoxia-induced cardiomyocytes and cardiac tissue after AMI were increased, a change that was reversed by GW4869. Additionally, CCRR-overexpressing exosomes improved cardiac function in AMI. Conclusion: Circulating lncRNA CCRR is a potential predictor of AMI. Exosomal CCRR plays a role in the communication between the heart and other organs through circulation.

Background: Morbidity and mortality associated with cardiovascular diseases, such as myocardial infarction, stem from the inability of terminally differentiated cardiomyocytes to regenerate, and thus repair the damaged myocardial tissue structure. The molecular biological mechanisms behind the lack of regenerative capacity for those cardiomyocytes remains to be fully elucidated. Recent studies have shown that c-Jun serves as a cell cycle regulator for somatic cell fates, playing a key role in multiple molecular pathways, including the inhibition of cellular reprogramming, promoting angiogenesis, and aggravation of cardiac hypertrophy, but its role in cardiac development is largely unknown. This study aims to delineate the role of c-Jun in promoting early-stage cardiac differentiation. Methods: The c-Jun gene in mouse embryonic stem cells (mESCs) was knocked out with CRISPR-Cas9, and the hanging drop method used to prepare the resulting embryoid bodies. Cardiac differentiation was evaluated up to 9 days after c-Jun knockout (ko) via immunofluorescence, flow cytometric, and qPCR analyses. Results: Compared to the wild-type control group, obvious beating was observed among the c-Jun-ko mESCs after 6 days, which was also associated with significant increases in myocardial marker expression. Additionally, markers associated with mesoderm and endoderm cell layer development, essential for further differentiation of ESCs into cardiomyocytes, were also up-regulated in the c-Jun-ko cell group. Conclusions: Knocking out c-Jun directs ESCs toward a meso-endodermal cell lineage fate, in turn leading to generation of beating myocardial cells. Thus, c-Jun plays an important role in regulating early cardiac cell development.

Reprogramming of human dermal fibroblasts (HDFs) into induced cardiomyocyte-like cells (iCMs) represents a promising strategy for human cardiac regeneration. Different cocktails of cardiac transcription factors can convert HDFs into iCMs, although with low efficiency and immature phenotype. Here, GATA4, MEF2C, TBX5, MESP1, and MYOCD (GMTMeMy for short) were used to reprogram HDFs by retrovirus infection. We found that the exogenous expression stoichiometry of GATA4 (GATA4 stoichiometry) significantly affected reprogramming efficiency. When 1/8 dosage of GATA4 virus (GATA4 dosage) plus MTMeMy was used, the reprogramming efficiency was obviously improved compared with average pooled virus encoding each factor, which measured, by the expression level of cardiac genes, the percentage of cardiac troponin T and alpha-cardiac myosin heavy-chain immunopositive cells and the numbers of iCMs showing calcium oscillation or beating synchronously in co-culture with mouse CMs. In addition, we prepared conditioned maintenance medium (CMM) by CM differentiation of H9 human embryonic stem cell line. We found that compared with traditional maintenance medium (TMM), CMM made iCMs show well-organized sarcomere formation and characteristic calcium oscillation wave earlier. These findings demonstrated that appropriate GATA4 stoichiometry was essential for cardiac reprogramming and some components in CMM were important for maturation of iCMs.

Background Morbidity and mortality associated with cardiovascular diseases, such as myocardial infarction, stem from the inability of terminally differentiated cardiomyocytes to regenerate, and thus repair the damaged myocardial tissue structure. The molecular biological mechanisms behind the lack of regenerative capacity for those cardiomyocytes remains to be fully elucidated. Recent studies have shown that c-Jun serves as a cell cycle regulator for somatic cell fates, playing a key role in multiple molecular pathways, including the inhibition of cellular reprogramming, promoting angiogenesis, and aggravation of cardiac hypertrophy, but its role in cardiac development is largely unknown. This study aims to delineate the role of c-Jun in promoting early-stage cardiac differentiation. Methods The c-Jun gene in mouse embryonic stem cells (mESCs) was knocked out with CRISPR-Cas9, and the hanging drop method used to prepare the resulting embryoid bodies. Cardiac differentiation was evaluated up to 9 days after c-Jun knockout (ko) via immunofluorescence, flow cytometric, and qPCR analyses. Results Compared to the wild-type control group, obvious beating was observed among the c-Jun-ko mESCs after 6 days, which was also associated with significant increases in myocardial marker expression. Additionally, markers associated with mesoderm and endoderm cell layer development, essential for further differentiation of ESCs into cardiomyocytes, were also up-regulated in the c-Jun-ko cell group. Conclusions Knocking out c-Jun directs ESCs towards a meso-endodermal cell lineage fate, in turn leading to generation of beating myocardial cells. Thus, c-Jun plays an important role in regulating early cardiac cell development.

Despite direct reprogramming of human cardiac fibroblasts into induced cardiomyocytes (iCM) holds great potential for heart regeneration, the mechanisms are poorly understood. Whether other human somatic cells could be reprogrammed into cardiomyocytes is also unknown. Here, we report human urine cells (hUCs) could be converted into CM-like cells from different donors and the related chromatin accessibility dynamics (CAD) by assay for transposase accessible chromatin(ATAC)-seq. hUCs transduced by MEF2C, TBX5, MESP1 and MYOCD but without GATA4 expressed multiple cardiac specific genes, exhibited Ca²⁺ oscillation potential and sarcomeric structures, and contracted synchronously in coculture with mouse CM. Additionally, we found that MYOCD is required for both closing and opening critical loci, mainly by hindering the opening of loci enriched with motifs for the TEAD and AP1 family and promoting the closing of loci enriched with ETS motifs. These changes differ partially from CAD observed during iCM induction from human fibroblasts. Collectively, our study offers one practical platform for iCM generation and insights into mechanisms for iCM fate determination.