Small Extracellular Vesicles Derived from Induced Pluripotent Stem Cells in the Treatment of Myocardial Injury

Abstract

Induced pluripotent stem cell (iPSC) therapy brings great hope to the treatment of myocardial injuries, while extracellular vesicles may be one of the main mechanisms of its action. iPSC-derived small extracellular vesicles (iPSCs-sEVs) can carry genetic and proteinaceous substances and mediate the interaction between iPSCs and target cells. In recent years, more and more studies have focused on the therapeutic effect of iPSCs-sEVs in myocardial injury. IPSCs-sEVs may be a new cell-free-based treatment for myocardial injury, including myocardial infarction, myocardial ischemia-reperfusion injury, coronary heart disease, and heart failure. In the current research on myocardial injury, the extraction of sEVs from mesenchymal stem cells induced by iPSCs was widely used. Isolation methods of iPSCs-sEVs for the treatment of myocardial injury include ultracentrifugation, isodensity gradient centrifugation, and size exclusion chromatography. Tail vein injection and intraductal administration are the most widely used routes of iPSCs-sEV administration. The characteristics of sEVs derived from iPSCs which were induced from different species and organs, including fibroblasts and bone marrow, were further compared. In addition, the beneficial genes of iPSC can be regulated through CRISPR/Cas9 to change the composition of sEVs and improve the abundance and expression diversity of them. This review focused on the strategies and mechanisms of iPSCs-sEVs in the treatment of myocardial injury, which provides a reference for future research and the application of iPSCs-sEVs.

Keywords: exosome; extracellular vesicles; heart; induced pluripotent stem cells; mechanisms; myocardial injury.

Figure 1

Biogenesis of EVs and schematic of exosomal molecular compositions. (A). EVs contain apoptotic bodies, microvesicles, and exosomes. Apoptotic bodies are formed by membrane folding, invagination, and shedding with organelles and nuclear debris. MVs are formed by the direct outward budding of plasma membranes. As for exosomes, at the very beginning, the invagination of the plasma membrane forms a cup-shaped structure termed early endosome containing cell surface proteins and other biological substances. Early endosomes then develop into late endosomes, which invaginate to form multivesicular bodies (MVBs) that finally fuse with the plasma membrane and release the exosomes. (B). Exosome contains various important biomarkers, such as proteins, lipids, and miRNAs.

Figure 2

Exosome separation diagram. (A). Ultracentrifugation. First, the samples are centrifuged at 300× g, 2000× g, and 10,000× g to remove larger cells, cell debris, and dead cells. Secondly, the exosomes are isolated via ultracentrifugation twice at a speed of more than 100,000× g. (B). Isopycnic density gradient centrifugation. Impurities are firstly removed via low-speed centrifugation, and then, the separated samples are added to the constructed density medium (3%, 35%, 45%, and 90%) for separation. (C). Size-exclusion chromatography.

Figure 3

Biogenesis and information exchange of exosomes. The invagination of the plasma membrane forms a cup-shaped structure, which includes proteins on the cell surface and some components in the extracellular environment, such as proteins, lipids and metabolites, making up the early endosomes. Early endosomes then develop into late endosomes and invaginate to form intraluminal vesicles, and the cytoplasmic components also enter intraluminal vesicles, and then, late endosomes form multivesicular body. Finally, multivesicular body fuses with the plasma membrane and the exosomes are released. The receptor cells mainly interact with the exosomes through three ways: (1) the exosomes bind to the receptors on the cell membrane; (2) the exosomes fuse directly with the cell membrane to release the contents; (3) the exosomes directly enter the cytoplasm in a complete form through cellular pinocytosis or phagocytosis.