MicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression by binding to messenger RNAs (mRNAs), thereby influencing various biological processes. In cardiovascular biology, miRNAs play crucial roles in development and disease. They modulate the expression of multiple mRNAs, often with related functions, to control complex processes. The functions of miRNAs in the cardiovascular system have provided new insights into disease mechanisms and have revealed potential therapeutic targets and diagnostics for cardiovascular disorders. Cardiovascular diseases are the most common congenital birth defects and major causes of adult morbidity and mortality. While the cellular mechanisms and gene mutations responsible for many cardiovascular disorders have been studied, it has become clear that miRNAs also play key roles in cardiovascular development and disease. The sensitivity of the cardiovascular system to subtle gene expression changes means that miRNAs can significantly impact disease outcomes. MiRNAs are involved in the 'fine-tuning' of gene expression to control development and tissue homeostasis. Under stress conditions, their functions become more pronounced, highlighting their roles in disease. Specific miRNA expression patterns correlate with various cardiovascular disorders, and studies in mice have shown both pathogenic and protective functions of miRNAs. MiRNAs are integrated into introns of protein-coding genes, allowing their expression to be coordinated with the mRNA of the host gene. This integration enables the regulation of biological processes related to the host gene. Genetic deletions of miRNAs in various organisms show that few developmental processes are absolutely dependent on a single miRNA, indicating redundancy in miRNA function. MiRNAs typically exert modest inhibitory effects on many mRNAs, which often encode proteins involved in the same biological process. The cumulative effect of miRNA-mRNA interactions can significantly influence gene regulatory networks. The multiplicity of miRNA targets allows for combinatorial regulation, which can be crucial for biological responses. Oligonucleotide-based techniques, such as antisense oligonucleotides and miRNA mimics, allow for the manipulation of miRNA function, offering potential therapeutic applications. Studies in mice and zebrafish have shown that miRNAs are essential for cardiovascular development and function, with miR-1 and miR-133 playing significant roles in heart development. In vascular and blood development, miRNAs regulate processes such as angiogenesis and vascular patterning. miR-126, for example, is involved in angiogenic sprouting and vascular integrity. miR-143 and miR-145 regulate smooth muscle cell function and vascular tone. In cardiovascular disease, miRNAs are involved in processes such as heart failure, fibrosis, and vascular disease. miR-21, miR-29, and miR-133 are implicated in various pathological conditions. miRNAs can also influence the re-expression of fetal gene programs in heart failure. MiRNA mutations can affectMicroRNAs (miRNAs) are small non-coding RNA molecules that regulate gene expression by binding to messenger RNAs (mRNAs), thereby influencing various biological processes. In cardiovascular biology, miRNAs play crucial roles in development and disease. They modulate the expression of multiple mRNAs, often with related functions, to control complex processes. The functions of miRNAs in the cardiovascular system have provided new insights into disease mechanisms and have revealed potential therapeutic targets and diagnostics for cardiovascular disorders. Cardiovascular diseases are the most common congenital birth defects and major causes of adult morbidity and mortality. While the cellular mechanisms and gene mutations responsible for many cardiovascular disorders have been studied, it has become clear that miRNAs also play key roles in cardiovascular development and disease. The sensitivity of the cardiovascular system to subtle gene expression changes means that miRNAs can significantly impact disease outcomes. MiRNAs are involved in the 'fine-tuning' of gene expression to control development and tissue homeostasis. Under stress conditions, their functions become more pronounced, highlighting their roles in disease. Specific miRNA expression patterns correlate with various cardiovascular disorders, and studies in mice have shown both pathogenic and protective functions of miRNAs. MiRNAs are integrated into introns of protein-coding genes, allowing their expression to be coordinated with the mRNA of the host gene. This integration enables the regulation of biological processes related to the host gene. Genetic deletions of miRNAs in various organisms show that few developmental processes are absolutely dependent on a single miRNA, indicating redundancy in miRNA function. MiRNAs typically exert modest inhibitory effects on many mRNAs, which often encode proteins involved in the same biological process. The cumulative effect of miRNA-mRNA interactions can significantly influence gene regulatory networks. The multiplicity of miRNA targets allows for combinatorial regulation, which can be crucial for biological responses. Oligonucleotide-based techniques, such as antisense oligonucleotides and miRNA mimics, allow for the manipulation of miRNA function, offering potential therapeutic applications. Studies in mice and zebrafish have shown that miRNAs are essential for cardiovascular development and function, with miR-1 and miR-133 playing significant roles in heart development. In vascular and blood development, miRNAs regulate processes such as angiogenesis and vascular patterning. miR-126, for example, is involved in angiogenic sprouting and vascular integrity. miR-143 and miR-145 regulate smooth muscle cell function and vascular tone. In cardiovascular disease, miRNAs are involved in processes such as heart failure, fibrosis, and vascular disease. miR-21, miR-29, and miR-133 are implicated in various pathological conditions. miRNAs can also influence the re-expression of fetal gene programs in heart failure. MiRNA mutations can affect