Human iPS-derived pre-epicardial cells direct cardiomyocyte aggregation expansion and organization in vitro

Injectable ECM-mimetic dynamic hydrogels abolish ferroptosis-induced post-discectomy herniation through delivering nucleus pulposus progenitor cell-derived exosomes

Discectomy-induced ferroptosis of nucleus pulposus cells (NPCs) contributes to postoperative lumbar disc herniation (LDH) recurrence and intervertebral disc degeneration (IDD). We discover that nucleus pulposus progenitor cells (NPPCs) could imprint ferroptosis resistance into NPCs through exosome-dependent intercellular transmission of miR-221-3p. Based on these findings, we first develop synthetically-tailored NPPC-derived exosomes with enhanced miR-221-3p expression and NPC uptake capacity, which are integrated into an injectable hydrogel based on extracellular matrix (ECM) analogues. The ECM-mimetic hydrogel (HACS) serves as a biomimetic filler for the post-operative care of herniated discs, which could be facilely injected into the discectomy-established nucleus pulposus (NP) cavity for localized treatment. HACS-mediated in-situ exosome release in the NP cavity enables marked ferroptosis inhibition in NPCs that not only prevents LDH recurrence but also reverses the IDD symptoms, leading to robust restoration of NP structure and functions. In summary, this study offers a promising approach for treating disc herniation.

Human epicardial organoids from pluripotent stem cells resemble fetal stage with potential cardiomyocyte- transdifferentiation

Epicardium, the most outer mesothelium, exerts crucial functions in fetal heart development and adult heart regeneration. Here we use a three-step manipulation of WNT signalling entwined with BMP and RA signalling for generating a self-organized epicardial organoid that highly express with epicardium makers WT1 and TCF21 from human embryonic stem cells. After 8-days treatment of TGF-beta following by bFGF, cells enter into epithelium-mesenchymal transition and give rise to smooth muscle cells. Epicardium could also integrate and invade into mouse heart with SNAI1 expression, and give birth to numerous cardiomyocyte-like cells. Single-cell RNA seq unveils the heterogeneity and multipotency exhibited by epicardium-derived-cells and fetal-like epicardium. Meanwhile, extracellular matrix and growth factors secreted by epicardial organoid mimics the ecology of subepicardial space between the epicardium and cardiomyocytes. As such, this epicardial organoid offers a unique ground for investigating and exploring the potential of epicardium in heart development and regeneration.

The molecular mechanisms of cardiac development and related diseases

Cardiac development is a complex and intricate process involving numerous molecular signals and pathways. Researchers have explored cardiac development through a long journey, starting with early studies observing morphological changes and progressing to the exploration of molecular mechanisms using various molecular biology methods. Currently, advancements in stem cell technology and sequencing technology, such as the generation of human pluripotent stem cells and cardiac organoids, multi-omics sequencing, and artificial intelligence (AI) technology, have enabled researchers to understand the molecular mechanisms of cardiac development better. Many molecular signals regulate cardiac development, including various growth and transcription factors and signaling pathways, such as WNT signaling, retinoic acid signaling, and Notch signaling pathways. In addition, cilia, the extracellular matrix, epigenetic modifications, and hypoxia conditions also play important roles in cardiac development. These factors play crucial roles at one or even multiple stages of cardiac development. Recent studies have also identified roles for autophagy, metabolic transition, and macrophages in cardiac development. Deficiencies or abnormal expression of these factors can lead to various types of cardiac development abnormalities. Nowadays, congenital heart disease (CHD) management requires lifelong care, primarily involving surgical and pharmacological treatments. Advances in surgical techniques and the development of clinical genetic testing have enabled earlier diagnosis and treatment of CHD. However, these technologies still have significant limitations. The development of new technologies, such as sequencing and AI technologies, will help us better understand the molecular mechanisms of cardiac development and promote earlier prevention and treatment of CHD in the future.

SMAD3 mediates the specification of human induced pluripotent stem cell-derived epicardium into progenitors for the cardiac pericyte lineage

Understanding the molecular mechanisms of epicardial epithelial-to-mesenchymal transition (EMT), particularly in directing cell fate toward epicardial derivatives, is crucial for regenerative medicine using human induced pluripotent stem cell (iPSC)-derived epicardium. Although transforming growth factor β (TGF-β) plays a pivotal role in epicardial biology, orchestrating EMT during embryonic development via downstream signaling through SMAD proteins, the function of SMAD proteins in the epicardium in maintaining vascular homeostasis or mediating the differentiation of various epicardial-derived cells (EPDCs) is not yet well understood. Our study reveals that TGF-β-independent SMAD3 expression autonomously predicts epicardial cell specification and lineage maintenance, acting as a key mediator in promoting the angiogenic-oriented specification of the epicardium into cardiac pericyte progenitors. This finding uncovers a novel role for SMAD3 in the human epicardium, particularly in generating cardiac pericyte progenitors that enhance cardiac microvasculature angiogenesis. This insight opens new avenues for leveraging epicardial biology in developing more effective cardiac regeneration strategies.

Heart-on-a-Chip Model of Epicardial-Myocardial Interaction in Ischemia Reperfusion Injury

Epicardial cells (EPIs) form the outer layer of the heart and play an important role in development and disease. Current heart-on-a-chip platforms still do not fully mimic the native cardiac environment due to the absence of relevant cell types, such as EPIs. Here, using the Biowire II platform, engineered cardiac tissues with an epicardial outer layer and inner myocardial structure are constructed, and an image analysis approach is developed to track the EPI cell migration in a beating myocardial environment. Functional properties of EPI cardiac tissues improve over two weeks in culture. In conditions mimicking ischemia reperfusion injury (IRI), the EPI cardiac tissues experience less cell death and a lower impact on functional properties. EPI cell coverage is significantly reduced and more diffuse under normoxic conditions compared to the post-IRI conditions. Upon IRI, migration of EPI cells into the cardiac tissue interior is observed, with contributions to alpha smooth muscle actin positive cell population. Altogether, a novel heart-on-a-chip model is designed to incorporate EPIs through a formation process that mimics cardiac development, and this work demonstrates that EPI cardiac tissues respond to injury differently than epicardium-free controls, highlighting the importance of including EPIs in heart-on-a-chip constructs that aim to accurately mimic the cardiac environment.

Liquid-liquid reactions performed by cellular reactors

Liquid-liquid reactions play a significant role in organic synthesis. However, control of the phase interface between incompatible two-phase liquids remains challenging. Moreover, separating liquid acid, base and oxidants from the reactor takes a long time and high cost. To address these issues, we draw inspiration from the structure and function of cells in living organisms and develop a biomimetic 3D-printed cellular reactor. The cellular reactor houses an aqueous phase containing the catalyst or oxidant while immersed in the organic phase reactant. This setup controls the distribution of the phase interface within the organic phase and increases the interface area by 2.3 times. Notably, the cellular reactor and the aqueous phase are removed from the organic phase upon completing the reaction, eliminating additional separation steps and preventing direct contact between the reactor and acidic, alkaline, or oxidizing substances. Furthermore, the cellular reactor offers the advantages of digital design feasibility and cost-effective manufacturing.

P53 Activation Promotes Maturational Characteristics of Pluripotent Stem Cell-Derived Cardiomyocytes in 3-Dimensional Suspension Culture Via FOXO-FOXM1 Regulation

BACKGROUND

Current protocols generate highly pure human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) in vitro that recapitulate characteristics of mature in vivo cardiomyocytes. Yet, a risk of arrhythmias exists when hiPSC-CMs are injected into large animal models. Thus, understanding hiPSC-CM maturational mechanisms is crucial for clinical translation. Forkhead box (FOX) transcription factors regulate postnatal cardiomyocyte maturation through a balance between FOXO and FOXM1. We also previously demonstrated that p53 activation enhances hiPSC-CM maturation. Here, we investigate whether p53 activation modulates the FOXO/FOXM1 balance to promote hiPSC-CM maturation in 3-dimensional suspension culture.

METHODS AND RESULTS

Three-dimensional cultures of hiPSC-CMs were treated with Nutlin-3a (p53 activator, 10 μM), LOM612 (FOXO relocator, 5 μM), AS1842856 (FOXO inhibitor, 1 μM), or RCM-1 (FOXM1 inhibitor, 1 μM), starting 2 days after onset of beating, with dimethyl sulfoxide (0.2% vehicle) as control. P53 activation promoted hiPSC-CM metabolic and electrophysiological maturation alongside FOXO upregulation and FOXM1 downregulation, in n=3 to 6 per group for all assays. FOXO inhibition significantly decreased expression of cardiac-specific markers such as TNNT2. In contrast, FOXO activation or FOXM1 inhibition promoted maturational characteristics such as increased contractility, oxygen consumption, and voltage peak maximum upstroke velocity, in n=3 to 6 per group for all assays. Further, by single-cell RNA sequencing of n=2 LOM612-treated cells compared with dimethyl sulfoxide, LOM612-mediated FOXO activation promoted expression of cardiac maturational pathways.

CONCLUSIONS

We show that p53 activation promotes FOXO and suppresses FOXM1 during 3-dimensional hiPSC-CM maturation. These results expand our understanding of hiPSC-CM maturational mechanisms in a clinically-relevant 3-dimensional culture system.

Retinoic acid modulation guides human-induced pluripotent stem cell differentiation towards left or right ventricle-like cardiomyocytes

BACKGROUND

Cardiomyocytes (CMs) derived from human induced pluripotent stem cells (hiPSCs) by traditional methods are a mix of atrial and ventricular CMs and many other non-cardiomyocyte cells. Retinoic acid (RA) plays an important role in regulation of the spatiotemporal development of the embryonic heart.

METHODS

CMs were derived from hiPSC (hi-PCS-CM) using different concentrations of RA (Control without RA, LRA with 0.05μM and HRA with 0.1 μM) between day 3-6 of the differentiation process. Engineered heart tissues (EHTs) were generated by assembling hiPSC-CM at high cell density in a low collagen hydrogel.

RESULTS

In the HRA group, hiPSC-CMs exhibited highest expression of contractile proteins MYH6, MYH7 and cTnT. The expression of TBX5, NKX2.5 and CORIN, which are marker genes for left ventricular CMs, was also the highest in the HRA group. In terms of EHT, the HRA group displayed the highest contraction force, the lowest beating frequency, and the highest sensitivity to hypoxia and isoprenaline, which means it was functionally more similar to the left ventricle. RNAsequencing revealed that the heightened contractility of EHT within the HRA group can be attributed to the promotion of augmented extracellular matrix strength by RA.

CONCLUSION

By interfering with the differentiation process of hiPSC with a specific concentration of RA at a specific time, we were able to successfully induce CMs and EHTs with a phenotype similar to that of the left ventricle or right ventricle.

Engineered Cardiac Microtissue Biomanufacturing Using Human Induced Pluripotent Stem Cell Derived Epicardial Cells

Epicardial cells are a crucial component in constructing in vitro 3D tissue models of the human heart, contributing to the ECM environment and the resident mesenchymal cell population. Studying the human epicardium and its development from the proepicardial organ is difficult, but induced pluripotent stem cells can provide a source of human epicardial cells for developmental modeling and for biomanufacturing heterotypic cardiac tissues. This study shows that a robust population of epicardial cells (approx. 87.7% WT1+) can be obtained by small molecule modulation of the Wnt signaling pathway. The population maintains WT1 expression and characteristic epithelial morphology over successive passaging, but increases in size and decreases in cell number, suggesting a limit to their expandability in vitro. Further, low passage number epicardial cells formed into more robust 3D microtissues compared to their higher passage counterparts, suggesting that the ideal time frame for use of these epicardial cells for tissue engineering and modeling purposes is early on in their differentiated state. Additionally, the differentiated epicardial cells displayed two distinct morphologic sub populations with a subset of larger, more migratory cells which led expansion of the epicardial cells across various extracellular matrix environments. When incorporated into a mixed 3D co-culture with cardiomyocytes, epicardial cells promoted greater remodeling and migration without impairing cardiomyocyte function. This study provides an important characterization of stem cell-derived epicardial cells, identifying key characteristics that influence their ability to fabricate consistent engineered cardiac tissues.

The role of metabolism in cardiac development

Metabolism is the fundamental process that sustains life. The heart, in particular, is an organ of high energy demand, and its energy substrates have been studied for more than a century. In recent years, there has been a growing interest in understanding the role of metabolism in the early differentiation of pluripotent stem cells and in cancer research. Studies have revealed that metabolic intermediates from glycolysis and the tricarboxylic acid cycle act as co-factors for intracellular signal transduction, playing crucial roles in regulating cell behaviors. Mitochondria, as the central hub of metabolism, are also under intensive investigation regarding the regulation of their dynamics. The metabolic environment of the fetus is intricately linked to the maternal metabolic status, and the impact of the mother's nutrition and metabolic health on fetal development is significant. For instance, it is well known that maternal diabetes increases the risk of cardiac and nervous system malformations in the fetus. Another notable example is the decrease in the risk of neural tube defects when pregnant women are supplemented with folic acid. These examples highlight the profound influence of the maternal metabolic environment on the fetal organ development program. Therefore, gaining insights into the metabolic environment within developing fetal organs is critical for deepening our understanding of normal organ development. This review aims to summarize recent findings that build upon the historical recognition of the environmental and metabolic factors involved in the developing embryo.

Supramolecular Assemblies of Glycopeptides Enhance Gap Junction Maturation of Human Induced Pluripotent Stem Cell-Derived Cardiomyocytes via Inducing Spheroids Formation to Optimize Cardiac Repair

Stem cell-based therapies have demonstrated significant potential for use in heart regeneration. An effective paradigm for heart repair in rodent and large animal models is the transplantation of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Despite this, the functional and phenotypical immaturity of 2D-cultured hiPSC-CMs, particularly their low electrical integration, poses a caveat for clinical translation. In this study, a supramolecular assembly of a glycopeptide containing a cell adhesion motif-RGD, and saccharide-glucose (Bio-Gluc-RGD) is designed to enable the 3D spheroid formation of hiPSC-CMs, promoting cell-cell and cell-matrix interactions that occur during spontaneous morphogenesis. HiPSC-CMs in spheroids are prone to be phenotypically mature and developed robust gap junctions via activation of the integrin/ILK/p-AKT/Gata4 pathway. Monodispersed hiPSC-CMs encapsulated in the Bio-Gluc-RGD hydrogel are more likely to form aggregates and, therefore, survive in the infarcted myocardium of mice, accompanied by more robust gap junction formation in the transplanted cells, and hiPSC-CMs delivered with the hydrogels also displayed angiogenic effect and anti-apoptosis capacity in the peri-infarct area, enhancing their overall therapeutic efficacy in myocardial infarction. Collectively, the findings illustrate a novel concept for modulating hiPSC-CM maturation by spheroid induction, which has the potential for post-MI heart regeneration.

iPSC-derived mesenchymal stem cells attenuate cerebral ischemia-reperfusion injury by inhibiting inflammatory signaling and oxidative stress

Induced pluripotent stem cell-derived mesenchymal stem cells (iMSCs) hold great promise as a cell source for transplantation into injured tissues to alleviate inflammation. However, the therapeutic efficacy of iMSC transplantation for ischemic stroke remains unknown. In this study, we evaluated the therapeutic effects of iMSC transplantation on brain injury after ischemia-reperfusion using a rat transient middle cerebral artery occlusion model and compared its therapeutic efficacy with that of bone marrow mesenchymal stem cells (BMMSCs). We showed that iMSCs and BMMSCs reduced infarct volumes after reperfusion and significantly improved motor function on days 3, 7, 14, 28, and 56 and cognitive function on days 28 and 56 after reperfusion compared with the vehicle group. Furthermore, immunological analyses revealed that transplantation of iMSCs and BMMSCs inhibited microglial activation and expression of proinflammatory cytokines and suppressed oxidative stress and neuronal cell death in the cerebral cortex at the ischemic border zone. No difference in therapeutic effect was observed between the iMSC and BMMSC groups. Taken together, our results demonstrate that iMSC therapy can be a practical alternative as a cell source for attenuation of brain injury and improvement of neurological function because of the unlimited supply of uniform therapeutic cells.

Recent advances in regulating the proliferation or maturation of human-induced pluripotent stem cell-derived cardiomyocytes

In the last decade, human-induced pluripotent stem cell-derived cardiomyocyte (hiPSC-CM)-based cell therapy has drawn broad attention as a potential therapy for treating injured hearts. However, mass production of hiPSC-CMs remains challenging, limiting their translational potential in regenerative medicine. Therefore, multiple strategies including cell cycle regulators, small molecules, co-culture systems, and epigenetic modifiers have been used to improve the proliferation of hiPSC-CMs. On the other hand, the immaturity of these proliferative hiPSC-CMs could lead to lethal arrhythmias due to their limited ability to functionally couple with resident cardiomyocytes. To achieve functional maturity, numerous methods such as prolonged culture, biochemical or biophysical stimulation, in vivo transplantation, and 3D culture approaches have been employed. In this review, we summarize recent approaches used to promote hiPSC-CM proliferation, and thoroughly review recent advances in promoting hiPSC-CM maturation, which will serve as the foundation for large-scale production of mature hiPSC-CMs for future clinical applications.

Primary cardiac sarcomas: A clinicopathologic study in a single institution with 25 years of experience with an emphasis on MDM2 expression and adjuvant therapy for prognosis

BACKGROUND

Primary cardiac sarcomas are rare and their clinicopathologic features are heterogeneous. Among them, particularly intimal sarcoma is a diagnostic challenge due to nonspecific histologic features. Recently, MDM2 amplification reported to be a characteristic genetic event in the intimal sarcoma. In this study, we aimed to identify the types and incidence of primary cardiac sarcomas that occurred over 25 years in tertiary medical institutions, and to find clinicopatholgical significance through reclassification of diagnoses using additional immunohistochemistry (IHC).

METHODS

We reviewed the primary cardiac sarcoma cases between January 1993 and June 2018 at Asan Medical Center, South Korea, with their clinicopathologic findings, and reclassified the subtypes, especially using IHC for MDM2 and then, analyzed the significance of prognosis.

RESULTS

Forty-eight (6.8%) cases of a primary cardiac sarcoma were retrieved. The tumors most frequently involved the right atrium (n = 25, 52.1%), and the most frequent tumor subtype was angiosarcoma (n = 23, 47.9%). Seven cases (53.8%) were newly reclassified as an intimal sarcoma by IHC for MDM2. Twenty-nine (60.4%) patients died of disease (mean, 19.8 months). Four patients underwent a heart transplantation and had a median survival of 26.8 months. This transplantation group tended to show good clinical outcomes in the earlier stages, but this was not statistically significant (p = 0.318). MDM2 positive intimal sarcoma showed the better overall survival (p = 0.003) than undifferentiated pleomorphic sarcoma. Adjuvant treatment is beneficial for patient survival (p < 0.001), particularly in angiosarcoma (p < 0.001), but not in intimal sarcoma (p = 0.154).

CONCLUSION

Our study supports the use of adjuvant treatment in primary cardiac sarcoma, as it was associated with a significantly better overall survival rate. Further consideration of tumor histology may be important in determining the optimal use of adjuvant treatment for different types of sarcomas. Therefore, accurate diagnosis by MDM2 test is important condsidering patient's prognosis and treatment.

Biotechnological advances and applications of human pluripotent stem cell-derived heart models

In recent years, significant biotechnological advancements have been made in engineering human cardiac tissues and organ-like models. This field of research is crucial for both basic and translational research due to cardiovascular disease being the leading cause of death in the developed world. Additionally, drug-associated cardiotoxicity poses a major challenge for drug development in the pharmaceutical and biotechnological industries. Progress in three-dimensional cell culture and microfluidic devices has enabled the generation of human cardiac models that faithfully recapitulate key aspects of human physiology. In this review, we will discuss 3D pluripotent stem cell (PSC)-models of the human heart, such as engineered heart tissues and organoids, and their applications in disease modeling and drug screening.

Induced pluripotent stem cell technology in bone biology

Technologies on the development and differentiation of human induced pluripotent stem cells (hiPSCs) are rapidly improving, and have been applied to create cell types relevant to the bone field. Differentiation protocols to form bona fide bone-forming cells from iPSCs are available, and can be used to probe details of differentiation and function in depth. When applied to iPSCs bearing disease-causing mutations, the pathogenetic mechanisms of diseases of the skeleton can be elucidated, along with the development of novel therapeutics. These cells can also be used for development of cell therapies for cell and tissue replacement.

Animal Disease Models and Patient-iPS-Cell-Derived In Vitro Disease Models for Cardiovascular Biology-How Close to Disease?

Currently, zebrafish, rodents, canines, and pigs are the primary disease models used in cardiovascular research. In general, larger animals have more physiological similarities to humans, making better disease models. However, they can have restricted or limited use because they are difficult to handle and maintain. Moreover, animal welfare laws regulate the use of experimental animals. Different species have different mechanisms of disease onset. Organs in each animal species have different characteristics depending on their evolutionary history and living environment. For example, mice have higher heart rates than humans. Nonetheless, preclinical studies have used animals to evaluate the safety and efficacy of human drugs because no other complementary method exists. Hence, we need to evaluate the similarities and differences in disease mechanisms between humans and experimental animals. The translation of animal data to humans contributes to eliminating the gap between these two. In vitro disease models have been used as another alternative for human disease models since the discovery of induced pluripotent stem cells (iPSCs). Human cardiomyocytes have been generated from patient-derived iPSCs, which are genetically identical to the derived patients. Researchers have attempted to develop in vivo mimicking 3D culture systems. In this review, we explore the possible uses of animal disease models, iPSC-derived in vitro disease models, humanized animals, and the recent challenges of machine learning. The combination of these methods will make disease models more similar to human disease.

Wnt signaling directs human pluripotent stem cells into vascularized cardiac organoids with chamber-like structures

Heart diseases are leading cause of death around the world. Given their unique capacity to self-renew and differentiate into all types of somatic cells, human pluripotent stem cells (hPSCs) hold great promise for heart disease modeling and cardiotoxic drug screening. hPSC-derived cardiac organoids are emerging biomimetic models for studying heart development and cardiovascular diseases, but it remains challenging to make mature organoids with a native-like structure in vitro. In this study, temporal modulation of Wnt signaling pathway co-differentiated hPSCs into beating cardiomyocytes and cardiac endothelial-like cells in 3D organoids, resulting in cardiac endothelial-bounded chamber formation. These chambered cardiac organoids exhibited more mature membrane potential compared to cardiac organoids composed of only cardiomyocytes. Furthermore, a better response to toxic drugs was observed in chamber-contained cardiac organoids. In summary, spatiotemporal signaling pathway modulation may lead to more mature cardiac organoids for studying cardiovascular development and diseases.

Trends in research on sick sinus syndrome: A bibliometric analysis from 2000 to 2022

Sick sinus syndrome (SSS) is a refractory arrhythmia disease caused by the pathological changes of sinoatrial node and its adjacent tissues. 2,251 publications related to SSS were retrieved from Web of Science database from 2000 to 2022 and analyzed by using VOS viewer and CiteSpace software. The results showed the United States dominated the field, followed by Japan, Germany, and China. SSS was closely related to risk factors such as atrial fibrillation and aging. Sick sinus syndrome, atrial fibrillation and sinus node dysfunction were the top three keywords that had the strongest correlation with the study. Pacemaker implantation, differentiation and mutation are research hotspots currently. Clinical studies on SSS found that sick sinus syndrome, atrial fibrillation, and pacemakers were the top three keywords that had the largest nodes and the highest frequency. In the field of basic applied research and basic research, atrial fibrillation and pacemaker cells were the focus of research. In conclusion, bibliometric analysis provided valuable information for the prevention, treatment and future research trends of SSS.

RA signaling pathway combined with Wnt signaling pathway regulates human-induced pluripotent stem cells (hiPSCs) differentiation to sinus node-like cells

BACKGROUND

The source of SAN is debated among researchers. Many studies have shown that RA and Wnt signaling are involved in heart development. In this study, we investigated the role of retinoic acid (RA) and Wnt signaling in the induction of sinus node-like cells.

METHODS

The experimental samples were divided into four groups: control group (CHIR = 0), CHIR = 3, RA + CHIR = 0 andRA + CHIR = 3. After 20 days of differentiation, Western blot, RT-qPCR, immunofluorescence and flow cytometry were performed to identify sinus node-like cells. Finally, whole-cell patch clamp technique was used to record pacing funny current and action potential (AP) in four groups.

RESULTS

The best intervention method used in our experiment was RA = 0.25 µmol/L D5-D9 + CHIR = 3 µmol/L D5-D7. Results showed that CHIR can increase the expression of ISL-1 and TBX3, while RA mainly elevated Shox2. Immunofluorescence assay and flow cytometry further illustrated that combining RA with CHIR can induce sinus node-like cells (CTNT+Shox2+Nkx2.5-). Moreover, CHIR might reduce the frequency of cell beats, but in conjunction with RA could partly compensate for this side effect. Whole cell patch clamps were able to record funny current and the typical sinus node AP in the experimental group, which did not appear in the control group.

CONCLUSIONS

Combining RA with Wnt signaling within a specific period can induce sinus node-like cells.

Injectable conductive gelatin methacrylate / oxidized dextran hydrogel encapsulating umbilical cord mesenchymal stem cells for myocardial infarction treatment

Umbilical cord mesenchymal stem cells (UCMSCs) transplantation has been proposed as a promising treatment modality for myocardial infarction (MI), but the low retention rate remains a considerable challenge. Injectable natural polymer hydrogels with conductivity ability are highly desirable as cell delivery vehicles to repair infarct myocardium and restore the cardiac function. In this work, we developed a hydrogel system based on gelatin methacrylate (GelMA) and oxidized dextran (ODEX) as cell delivery vehicles for MI. And dopamine could be used as a reductant of graphene oxide (GO) to form reductive GO (rGO). By adjusting the amount of rGO, the conductivity of hydrogels with 0.5 mg/mL rGO concentration (≈10⁻⁴ S/cm) was similar to that of natural heart tissue. In vitro cell experiments showed that the prepared hydrogels had excellent biocompatibility and cell delivery ability of UCMSCs. More importantly, GelMA-O5/rGO hydrogel could promote UCMSCs growth and proliferation, improve the myocardial differentiation ability of UCMSCs, and up-regulate the expression of cTnI and Cx43. Further in vivo experiments demonstrated that GelMA-O5/rGO/UCMSCs Hydrogel could significantly improve the ejection fraction (EF) of rats and significantly reduce myocardial infarct area compared to PBS group, promote the survival of UCMSCs, enhance the expression level of cTnI and Cx43, and decrease the expression level of caspase-3. The findings of this study suggested that the injectable conductive GelMA-O5/rGO hydrogel encapsulating UCMSCs could improve damaged myocardial tissue and reconstruct myocardial function, which will be a promising therapeutic strategy for cardiac repair.

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Conducting interpenetrating polymer network (IPN) hydrogels were synthesized for myocardial infarction treatment.

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The conductivity of hydrogel with 0.5 mg/mL rGO concentration (≈10⁻⁴ S/cm) was similar to that of natural heart tissue.

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The hydrogel could promote the growth and proliferation of UCMSCs, and improve the myocardial differentiation ability of UCMSCs.

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The hydrogel could reduce infarct size and cardiac fibrosis in the infarct zone, increase ventricular ejection fraction.

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The hydrogel could promote the survival of UCMSCs, up-regulate the expression level of cTnI and Cx43, down-regulate the expression level of caspase-3.

Sympathetic Neurons Regulate Cardiomyocyte Maturation in Culture

Embryos devoid of autonomic innervation suffer sudden cardiac death. However, whether autonomic neurons have a role in heart development is poorly understood. To investigate if sympathetic neurons impact cardiomyocyte maturation, we co-cultured phenotypically immature cardiomyocytes derived from human induced pluripotent stem cells with mouse sympathetic ganglion neurons. We found that 1) multiple cardiac structure and ion channel genes related to cardiomyocyte maturation were up-regulated when co-cultured with sympathetic neurons; 2) sarcomere organization and connexin-43 gap junctions increased; 3) calcium imaging showed greater transient amplitudes. However, sarcomere spacing, relaxation time, and level of sarcoplasmic reticulum calcium did not show matured phenotypes. We further found that addition of endothelial and epicardial support cells did not enhance maturation to a greater extent beyond sympathetic neurons, while administration of isoproterenol alone was insufficient to induce changes in gene expression. These results demonstrate that sympathetic neurons have a significant and complex role in regulating cardiomyocyte development.

The relationship between vascular endothelial growth factor expression and the risk of childhood nephroblastoma: systematic review and meta-analysis

BACKGROUND

This study explores the correlation between vascular endothelial growth factor expression and the risk of childhood nephroblastoma.

METHODS

PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), Wanfang database were searched to collect independent study data published in China between 2010 and 2021 on the expression and significance of VEGF in childhood nephroblastoma, and literature heterogeneity was tested. The odds ratio (OR) value was used as the effect indicator. Meta-analysis software RevMan 4.2.2 was used, and the original data of each study were statistically processed to calculate the combined OR value and 95% confidence interval (CI).

RESULTS

Twelve studies involving 1,226 cases of pediatric nephroblastoma were included for systematic evaluation. The 12 randomized controlled studies reported the expression of VEGF in childhood nephroblastoma (OR =9.06, 95% CI: 6.97-11.78, P<0.00001). There was a statistically significant difference in expression of VEGF between the unfavorable histology (UH) group and the favorable histology (FH) group (OR =1.17, 95% CI: 1.07-1.27, P=0.0006) and expression of VEGF in different clinical stages of nephroblastoma, including stage I-II and III-IV (OR =0.49, 95% CI: 0.42-0.58, P<0.00001). Positive expression of VEGF showed no significant statistical difference between cases with and without tumor metastasis (OR =1.08, 95% CI: 0.86-1.36, P=0.50).

CONCLUSIONS

The expression of VEGF may play an important role in the occurrence and development of childhood nephroblastoma and could help guide clinicians to judge disease and treatment.

Cardiac Organoids and Gastruloids to Study Physio-Pathological Heart Development

Ethical issues restrict research on human embryos, therefore calling for in vitro models to study human embryonic development including the formation of the first functional organ, the heart. For the last five years, two major models have been under development, namely the human gastruloids and the cardiac organoids. While the first one mainly recapitulates the gastrulation and is still limited to investigate cardiac development, the second one is becoming more and more helpful to mimic a functional beating heart. The review reports and discusses seminal works in the fields of human gastruloids and cardiac organoids. It further describes technologies which improve the formation of cardiac organoids. Finally, we propose some lines of research towards the building of beating mini-hearts in vitro for more relevant functional studies.

Retinoic acid signaling in heart development: Application in the differentiation of cardiovascular lineages from human pluripotent stem cells

Retinoic acid (RA) signaling plays an important role during heart development in establishing anteroposterior polarity, formation of inflow and outflow tract progenitors, and growth of the ventricular compact wall. RA is also utilized as a key ingredient in protocols designed for generating cardiac cell types from pluripotent stem cells (PSCs). This review discusses the role of RA in cardiogenesis, currently available protocols that employ RA for differentiation of various cardiovascular lineages, and plausible transcriptional mechanisms underlying this fate specification. These insights will inform further development of desired cardiac cell types from human PSCs and their application in preclinical and clinical research.