This paper examines the use of microRNAs (miRNAs) and anti-miRs (antagomirs) in contemporary genetic therapies. It explains how miRNAs regulate cellular processes and how inappropriate expression is linked to disease, then outlines two main therapeutic approaches: restoring miRNA function through synthetic miRNAs or viral vectors, and inhibiting pathogenic miRNA activity using chemically modified oligonucleotides. The paper describes mechanisms of action including RNA duplex synthesis and antisense inhibition, and surveys therapeutic applications in cardiac disease, high cholesterol, and viral infections like Epstein-Barr virus. While these therapies show promise, challenges remain in optimizing inhibition levels and ensuring tissue-specific delivery.
The process of using microRNAs as a type of genetic therapy involves altering an organism's genetic patterns in a manner that could potentially have a significant impact on many individuals' lives. Scientists are able to effectively rewrite faulty genetic code by enabling new binding patterns of molecules to the RNA strand. The human genome contains more than 500 miRNAs, and each miRNA can repress hundreds of genes, regulating almost every cellular process. Inappropriate miRNA expression has been linked to a variety of diseases (Broderick & Zamore, 2011).
Conversely, appropriate miRNA expression has been linked to health promotion. For example, the let-7 miRNA prevents proliferation of cancer stem cells. miRNAs also play roles in metabolic diseases such as obesity and diabetes; differentiation of adipocytes is promoted by miR-143, and insulin secretion is regulated by miR-375 in pancreatic-islet cells (Broderick & Zamore, 2011).
MicroRNA/anti-miR therapy exploits the fact that miRNAs typically have many targets within cellular networks, which enables modulation of entire pathways in a disease state via therapeutic targeting of disease-associated miRNAs (Van Rooij & Kauppinen, 2014). Because miRNAs are typically very short and common to a number of species, the creation of preclinical trials involving animals is relatively safe and effective before the treatment is used on humans. The two main therapeutic approaches entail either restoring the original function of a damaged miRNA through the use of synthetic double-stranded miRNAs or viral vector-based overexpression, or using chemically modified antimiR oligonucleotides to inhibit negative miRNA functioning (Van Rooij & Kauppinen, 2014).
The simplest method of therapeutic action involves rewriting an RNA strand. Researchers can use synthetic RNA duplexes that harbor chemical modifications to improve stability and cellular uptake. The synthetic double-stranded miRNA can mimic the strand identical to the miRNA of interest as the guide (antisense) strand, while the opposite (passenger or sense) strand is less stable and can be linked to a molecule, such as cholesterol, to enhance cellular uptake (Van Rooij & Kauppinen, 2014).
A second method of action involves using mature miRNAs, which can be inhibited using either miRNA sponges or antisense oligonucleotides, known as antimiRs, to produce the desired genetic effect (Van Rooij & Kauppinen, 2014).
The mechanisms of miRNA are also useful in current research on a variety of pathogens. For example, one recent application of miRNA functioning involved use of genomic SELEX, a method to identify protein-binding RNAs encoded in the genome and search for further regulatory RNAs (Lorenz, 2010). In their work on mapping Escherichia coli, researchers used the global regulator protein Hfq as bait because it can interact with a large number of RNAs, promoting their interaction. The enriched SELEX pool sequences were mapped to the E. coli genome, enabling scientists to regulate the expression of a large number of genes via interaction with cis-antisense RNAs (Lorenz, 2010). This could effectively reduce the efficacy of E. coli in its negative expression in the human body.
"Clinical use in cardiac disease, cholesterol, and viral infection"
"Unresolved dosing and tissue-targeting obstacles"
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