Notes on Extracellular Vesicles and miRNA in Stroke Treatments

Extracellular Vesicles (EVs): Small membrane-bound structures released from cells, playing a critical role in intercellular communication.
MicroRNA (miRNA): Small non-coding RNA molecules that regulate gene expression at the post-transcriptional level. They are involved in numerous biological processes and can be significantly altered in various diseases, including stroke.

Understand the role of EVs and miRNA in cellular communication and gene regulation.
Explore potential therapeutic applications of EV-packaged miRNA in stroke treatment and their usefulness as biomarkers.

Discovered by Victor Ambros and Gary Ruvkun, leading to the 2024 Nobel Prize in Physiology or Medicine for unveiling the role of miRNA in gene regulation.
miRNA can conduct significant post-transcriptional gene regulation, making them vital in both health and disease contexts.

Clinical Observations: MiRNAs circulate in bodily fluids (plasma, serum, CSF) and exhibit unique expression patterns in stroke.
Studies have highlighted various miRNAs (e.g., miR-125, miR-181, miR-210) that may serve as biomarkers for acute ischemic stroke, indicating major differences in expression between stroke patients and controls.

A comprehensive review identified numerous miRNAs with altered expression in different studies related to stroke:
- Circulating Biomarkers: miR-145, miR-223, miR-19a, etc. have been shown to be involved in both clinical and preclinical settings, indicating their potential diagnostic relevance.
- Variable Expression: MiRNAs may be differentially regulated depending on the type of stroke (ischemic vs. hemorrhagic).

Types of EVs:
- Exosomes: Smaller vesicles (30-100 nm) derived from endosomes containing proteins, lipids, and genetic material including miRNAs.
- Microvesicles: Larger vesicles (0.1-1 μm) produced directly from the cell membrane.
Mechanisms of Action in Stroke:
- EVs can cross the blood-brain barrier (BBB) and interact with target cells, affecting cell signaling, neurogenesis, and overall neuronal recovery after stroke.
- They contain proteins and miRNAs that may promote angiogenesis and tissue repair.

Therapeutic Effects:
- Post-Stroke Recovery: MSC-derived secretome, including EVs, has been linked to decreased neuroinflammation, improved functional recovery, and reduced infarct volume.
- Studies demonstrated that EVs from MSCs and other progenitor cells can enhance neurogenesis and remodelling, hence facilitating recovery after ischemic events.

Animal Models: EVs administered in rat models demonstrated improvements in neurological function, neurogenesis, and reduced infarct size.
Human Studies: Clinical trials have indicated that specific miRNAs like miR-9, miR-124, and miR-223 are associated with stroke severity and may serve as potential biomarkers for acute ischemic stroke. Elevated levels were found to correlate with clinical outcomes.

Stroke remains a significant health concern, with current treatments focusing on reperfusion strategies. However, miRNAs encapsulated in EVs show promise as novel therapeutic agents and biomarkers, illustrating the potential of targeting these molecules for improved stroke management.