José António Belo

Folic acid (FA) supplementation during pregnancy is the commonly accepted treatment to prevent neural tube defects. The mechanism by which FA prevents neural tube defects (NTDs) remains unclear. FA also prevents other developmental malformations, including alcohol-induced malformations in Fetal Alcohol Syndrome models. We show that FA acts through a metabolic link to retinoic acid (RA) signaling. Using a pax3 -knockdown Xenopus model of FA-rescuable NTDs, we show that RA or its precursors equally rescue these defects. Similarly, FA rescues alcohol-induced NTDs in a model previously shown to be rescued by retinoids. We identify the FA-metabolizing enzyme, formyl tetrahydrofolate dehydrogenase (ALDH1L1, FTHFD), encoded by the aldh1l1 gene, as essential for this rescue. Mechanistically, FA upregulates aldh1l1 expression, thereby increasing RA biosynthesis. Knockdown of ALDH1L1 activity using CRISPR/Cas9 abolishes the FA protective effect. To support these observations, we show that the human ALDH1L1 enzyme converts retinaldehyde to RA, and its overexpression restores neural tube closure in aldh1l1 -knockdown embryos when retinaldehyde is provided. At the cellular level, reduced RA signaling results in overproliferation of neural plate precursors and a pathological expansion of the neural tube. ALDH1L1 enables FA to restore normal neural plate proliferation, thereby preventing NTDs. These findings establish ALDH1L1 as an unexpected enzymatic link between FA (vitamin B9) and RA signaling, revealing how FA supplementation safeguards neural development and suggesting opportunities to refine strategies for NTD prevention.

Cardiovascular diseases remain a growing concern worldwide. Hence, it is critical to understand cardiac development and disease in a relevant human-based in vitro model. Human cardiac organoids are an alternative approach to studying cardiogenesis, in the context of cell–cell communication, and disease etiology, using human induced pluripotent stem cells (hiPSCs). Extracellular vesicles (EVs) are nanosized particles harboring proteins, nucleic acids, and metabolites and are implicated in intercellular communication. Since cardiac development requires a complex interplay between several cell types, we hypothesize that EVs may mediate this communication. Here, we isolated EVs from hiPSC-derived cardiac organoids (cardEVs). LC-MS/MS was performed to analyze their protein cargo and compare it with those from a cardiomyocyte cell line (AC10 CM EVs) and from human heart explants of cadaveric donors (heEVs) using a bioinformatic approach. cardEVs share 48.9% of their proteins with heEVs, with important biological processes such as “Metabolism” and “Cardiac Function” highlighted in both proteomes. This overlap between the proteomes of cardEVs and heEVs suggests a molecular similarity between the two models. Therefore, we reiterate the importance of cardiac organoids as an excellent model for studying cardiac development and disease modeling, as well as to explore the complexity of intercellular communication.

After the publication of the review article

Cardiovascular mortality remains a major health challenge. Cardiomyocyte (CM)‐based tissue engineering (TE) offers promising alternatives for developing therapies via in vitro models. However, the immature phenotype of CM in engineered tissues hampers progress. Recent studies introduce conductive materials like graphene to enhance CM maturation, but conventional graphene synthesis suffers from complexity, toxicity, and low yield. Laser‐induced graphene (LIG) provides a sustainable, cost‐effective, eco‐friendly solution with efficient conductivity and biocompatibility. A LIG‐based substrate is bioengineered in this study, hypothesizing that its conductive, anisotropic properties promote CM maturation and mimic the native cardiac niche. LIG is fabricated using a CO ₂ laser with Parylene‐C as a precursor. Stem cells (SCs) and SC‐derived embryoid bodies (EBs) are cultured on LIG substrates, and their viability, metabolic activity, morphology, and protein expression are evaluated through immunofluorescence and electron microscopy. Both SCs and EBs maintain viability and activity throughout the culture. Moreover, EB‐derived CM exhibit spontaneous contraction and express cardiac‐specific proteins, confirming functional differentiation on LIG matrices. This first report demonstrates that LIG substrates support SC culture and differentiation, highlighting their potential in developing refined in vitro cardiac models and advancing regenerative therapeutic strategies. The findings support LIG as a transformative advancement in TE.

Background: Dand5 encodes a protein that acts as an antagonist to Nodal/TGF-β and Wnt pathways. A mouse knockout (KO) model has shown that this molecule is associated with left-right asymmetry and cardiac development, with its depletion causing heterotaxia and cardiac hyperplasia. Objective: This study aimed to investigate the molecular mechanisms affected by the depletion of Dand5. Methods: DAND5-KO and wild-type embryoid bodies (EBs) were used to assess genetic expression with RNA sequencing. To complement the expression results that pointed towards differences in epithelial to mesenchymal transition (EMT), we evaluated migration and cell attachment. Lastly, in vivo valve development was investigated, as it was an established model of EMT. Results: DAND5-KO EBs progress faster through differentiation. The differences in expression will lead to differences in the expression of genes involved with Notch and Wnt signalling pathways, as well as changes in the expression of genes encoding membrane proteins. Such changes were accompanied by lower migratory rates in DAND5-KO EBs, as well as higher concentrations of focal adhesions. Within valve development, Dand5 is expressed in the myocardium underlying future valve sites, and its depletion compromises correct valve structure. Conclusion: The DAND5 range of action goes beyond early development. Its absence leads to significantly different expression patterns in vitro and defects in EMT and migration. These results have an in vivo translation in mouse heart valve development. Knowledge regarding the influence of DAND5 in EMT and cell transformation allows further understanding of its role in development, or even in some disease contexts, such as congenital heart defects.

Cardiovascular disease (CVD) remains the leading cause of death globally, with myocardial infarction (MI) being a major contributor. The current therapeutic approaches are limited in effectively regenerating damaged cardiac tissue. Up-to-date strategies for heart regeneration/reconstitution aim at cardiac remodeling through repairing the damaged tissue with an external cell source or by stimulating the existing cells to proliferate and repopulate the compromised area. Cell reprogramming is addressed to this challenge as a promising solution, converting fibroblasts and other cell types into functional cardiomyocytes, either by reverting cells to a pluripotent state or by directly switching cell lineage. Several strategies such as gene editing and the application of miRNA and small molecules have been explored for their potential to enhance cardiac regeneration. Those strategies take advantage of cell plasticity by introducing reprogramming factors that regress cell maturity in vitro, allowing for their later differentiation and thus endorsing cell transplantation, or promote in situ cell proliferation, leveraged by scaffolds embedded with pro-regenerative factors promoting efficient heart restoration. Despite notable advancements, important challenges persist, including low reprogramming efficiency, cell maturation limitations, and safety concerns in clinical applications. Nonetheless, integrating these innovative approaches offers a promising alternative for restoring cardiac function and reducing the dependency on full heart transplants.

Cardiovascular diseases (CVD) are a group of disorders that affect the heart and blood vessels. They include conditions such as myocardial infarction, coronary artery disease, heart failure, arrhythmia, and congenital heart defects. CVDs are the leading cause of death worldwide. Therefore, new medical interventions that aim to prevent, treat, or manage CVDs are of prime importance. MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the posttranscriptional level and play important roles in various biological processes, including cardiac development, function, and disease. Moreover, miRNAs can also act as biomarkers and therapeutic targets. In order to identify and characterize miRNAs and their target genes, scientists take advantage of computational tools such as bioinformatic algorithms, which can also assist in analyzing miRNA expression profiles, functions, and interactions in different cardiac conditions. Indeed, the combination of miRNA research and bioinformatic algorithms has opened new avenues for understanding and treating CVDs. In this review, we summarize the current knowledge on the roles of miRNAs in cardiac development and CVDs, discuss the challenges and opportunities, and provide some examples of recent bioinformatics for miRNA research in cardiovascular biology and medicine.

Heart failure with preserved ejection fraction (HFpEF) represents a global health challenge, with limited therapies proven to enhance patient outcomes. This makes the elucidation of disease mechanisms and the identification of novel potential therapeutic targets a priority. Here, we performed RNA sequencing on ventricular myocardial biopsies from patients with HFpEF, prospecting to discover distinctive transcriptomic signatures. A total of 306 differentially expressed mRNAs (DEG) and 152 differentially expressed microRNAs (DEM) were identified and enriched in several biological processes involved in HF. Moreover, by integrating mRNA and microRNA expression data, we identified five potentially novel miRNA–mRNA relationships in HFpEF: the upregulated hsa-miR-25-3p, hsa-miR-26a-5p, and has-miR4429, targeting HAPLN1; and NPPB mRNA, targeted by hsa-miR-26a-5p and miR-140-3p. Exploring the predicted miRNA–mRNA interactions experimentally, we demonstrated that overexpression of the distinct miRNAs leads to the downregulation of their target genes. Interestingly, we also observed that microRNA signatures display a higher discriminative power to distinguish HFpEF sub-groups over mRNA signatures. Our results offer new mechanistic clues, which can potentially translate into new HFpEF therapies.

(1) Background: The contribution of gene-specific variants for congenital heart disease, one of the most common congenital disabilities, is still far from our complete understanding. Here, we applied a disease model using human-induced pluripotent stem cells (hiPSCs) to evaluate the function of DAND5 on human cardiomyocyte (CM) differentiation and proliferation. (2) Methods: Taking advantage of our DAND5 patient-derived iPSC line, we used CRISPR-Cas9 gene-editing to generate a set of isogenic hiPSCs (DAND5-corrected and DAND5 full-mutant). The hiPSCs were differentiated into CMs, and RT-qPCR and immunofluorescence profiled the expression of cardiac markers. Cardiomyocyte proliferation was analysed by flow cytometry. Furthermore, we used a multi-electrode array (MEA) to study the functional electrophysiology of DAND5 hiPSC-CMs. (3) Results: The results indicated that hiPSC-CM proliferation is affected by DAND5 levels. Cardiomyocytes derived from a DAND5 full-mutant hiPSC line are more proliferative when compared with gene-corrected hiPSC-CMs. Moreover, parallel cardiac differentiations showed a differential cardiac gene expression profile, with upregulated cardiac progenitor markers in DAND5-KO hiPSC-CMs. Microelectrode array (MEA) measurements demonstrated that DAND5-KO hiPSC-CMs showed prolonged field potential duration and increased spontaneous beating rates. In addition, conduction velocity is reduced in the monolayers of hiPSC-CMs with full-mutant genotype. (4) Conclusions: The absence of DAND5 sustains the proliferation of hiPSC-CMs, which alters their electrophysiological maturation properties. These results using DAND5 hiPSC-CMs consolidate the findings of the in vitro and in vivo mouse models, now in a translational perspective. Altogether, the data will help elucidate the molecular mechanism underlying this human heart disease and potentiates new therapies for treating adult CHD.