Heart Uses Exosomes to Send SOS Signal to Bone Marrow (BM) Cells After Heart Attack; In BM, Exosomes Release Heart-Specific MicroRNAs That Down-Regulate CXCR4 & Stimulate BM Progenitor Cells to Enter Blood Stream & Travel to Heart to Attempt Repairs

Human cells release exosomes. These tiny, membrane-bound vesicles can carry cargo for cell-to-cell communication, with the ability to ferry diverse loads of proteins, lipids, and/or nucleic acids. Researchers at the University of Alabama at Birmingham (UAB) and in China now report that exosomes are key to the SOS signal that the heart muscle sends out after a heart attack. After the heart attack, the exosomes in the bloodstream carry greatly increased amounts of heart-specific microRNAs — an observation seen in both mice and humans. These exosomes preferentially carry the microRNAs to progenitor cells in the bone marrow. Inside those progenitor cells, the microRNAs turn off a specific gene that allows the progenitor cells to leave the bone marrow and enter the bloodstream. The cells then travel to the heart to attempt repairs. The investigators say discovery of this novel pathway — a signal from the damaged heart to a systemic response by the reparative bone marrow cells — can now be leveraged to improve cell-based cardiovascular repair after heart attacks. The study — led by Gangjian Qin, MD, Professor in the UAB Department of Biomedical Engineering and Director of the Molecular Cardiology Program, and Min Cheng, MD, PhD, Huazhong University of Science and Technology, Wuhan, China — was published online on February 27, 2019 in Nature Communications. The open-access article is titled “Circulating Myocardial MicroRNAs from Infarcted Hearts Are Carried in Exosomes and Mobilize Bone Marrow Progenitor Cells.” For 15 years, it had been known that progenitor cells are released from the bone marrow after a heart attack. These cells move to the damaged heart muscle to attempt repairs. However, many efforts to improve that repair have yielded only modest efficacies, at best.
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