Microvesicle-mediated transfer of microRNA-150 from monocytes to endothelial cells promotes angiogenesis

Microvesicles and diabetic complications--novel mediators, potential biomarkers and therapeutic targets

Microvesicles (MVs), also known as microparticles, are small membrane vesicles released from different cell types under different conditions. MVs have been detected in the circulation and in organs/tissues in various diseases, including diabetes. Patients with different types of diabetes and complications have different cellular MV patterns. Studies have shown that MVs may mediate vascular thrombosis, vascular inflammation, angiogenesis, and other pathological processes of the disease through their procoagulant, pro-inflammatory, pro-angiogenic, proteolytic, and other properties. Therefore, MVs contribute to the development of diabetic macrovascular and microvascular complications. In addition, clinical studies have indicated that changes in MV number and composition may reflect the pathophysiological conditions of disease, and therefore, may serve as potential biomarkers for diagnostic and prognostic use. Understanding MVs' involvement in the pathophysiological conditions may provide insight into disease mechanisms and would also be helpful for the development of novel therapeutic strategies in the future. Here, we review the latest publications from our group and other groups and focus on the involvement of MVs in diabetic complications.

Microvesicle-mediated delivery of transforming growth factor β1 siRNA for the suppression of tumor growth in mice

Cell-derived microvesicles (MVs) have been recently shown as an efficient carrier to deliver small RNAs into the target cells. In the present study, we characterized the inhibitory effect of TGF-β1 siRNA delivered by mouse fibroblast L929 cell-derived MVs (L929 MVs) on the growth and metastasis of murine sarcomas 180 cells both in vitro and in vivo. We found that, comparing to the same concentration of free TGF-β1 siRNA, TGF-β1 siRNA delivered by L929 MVs much more efficiently decreased the level of TGF-β1 in the recipient tumor cells. Functionally, MVs containing TGF-β1 siRNA significantly decreased the viability and migration of sarcomas 180 cells and promoted the apoptosis of tumor cells. Co-immunoprecipitation with Argonaute 2 (AGO2) via anti-AGO2 antibody indicated that the majority of TGF-β1 siRNA in the MVs were associated with AGO2 complex. A tumor implantation mouse model further showed that intravenous injection of TGF-β1 siRNA-containing MVs strongly suppressed TGF-β1 expression and TGF-β1 signaling downstream in the implanted tumor cells, and thus inhibited the growth and lung metastases of tumor cells. In conclusion, our results collectively demonstrate that the delivery of therapeutic TGF-β1 siRNA by cell-derived MVs provides an effective strategy to control tumor cell growth and metastasis.

Extracellular vesicles derived from human bone marrow mesenchymal stem cells promote angiogenesis in a rat myocardial infarction model

Mesenchymal stem cells (MSCs) have been increasingly tested experimentally and clinically for cardiac repair. However, the underlying mechanisms remain controversial due to the poor viability and considerable death of the engrafted cells in the infracted myocardium. Recent reports have suggested that extracellular vesicles (EVs) released by MSCs have angiogenesis-promoting activity; however, the therapeutic effect of MSC-EVs on an ischemic heart is unclear. In the present study, we reported that MSCs could release a large quantity of EVs around 100 nm in diameter upon hypoxia stimulation though the majority of the cells had not experienced apoptosis. MSC-EVs could be promptly uptaken by human umbilical vein endothelial cells, and the internalization resulted in dose-dependent enhancement of in vitro proliferation, migration, and tube formation of endothelial cells. Using an acute myocardial infarction rat model, we found that intramyocardial injection of MSC-EVs markedly enhanced blood flow recovery, in accordance with reduced infarct size and preserved cardiac systolic and diastolic performance compared to those treated with PBS. These data suggest that like MSCs, MSC-EVs could also protect cardiac tissue from ischemic injury at least by means of promoting blood vessel formation, though further detailed investigations should be performed to define the functionality of MSC-EVs.

KEY MESSAGES

MSCs released extracellular vesicles (EVs) upon hypoxia stimulation. MSC-EVs were a mixture of microvesicles and exosomes. MSC-EVs could be promptly uptaken by human umbilical vein endothelial cells. MSC-EVs promoted neoangiogenesis in vitro and in vivo. MSC-EVs preserved cardiac performance in an AMI model.

Trash or Treasure: extracellular microRNAs and cell-to-cell communication

Circulating RNAs in human body fluids are promising candidates for diagnostic purposes. However, the biological significance of circulating RNAs remains elusive. Recently, small non-coding RNAs, microRNAs (miRNAs), were isolated from multiple human body fluids, and these “circulating miRNAs” have been implicated as novel disease biomarkers. Concurrently, miRNAs were also identified in the extracellular space associated with extracellular vesicles (EVs), which are small membrane vesicles secreted from various types of cells. The function of these secreted miRNAs has been revealed in several papers. Circulating miRNAs have been experimentally found to be associated with EVs; however, other types of extracellular miRNAs were also described. This review discusses studies related to extracellular miRNAs, including circulating miRNAs and secreted miRNAs, to highlight the importance of studying not only secreted miRNAs, but also circulating miRNAs to determine the contribution of extracellular miRNAs especially in cancer development.