Microvesicles Derived from Human Umbilical Cord Mesenchymal Stem Cells Stimulated by Hypoxia Promote Angiogenesis Both In Vitro and In Vivo

Abstract

Although mesenchymal stem cells (MSCs) have been increasingly trialed to treat a variety of diseases, the underlying mechanisms remain still elusive. In this study, human umbilical cord (UC)-derived MSCs were stimulated by hypoxia, and the membrane microvesicles (MVs) in the supernatants were collected by ultracentrifugation, observed under an electron microscope, and the origin was identified with the flow cytometric technique. The results showed that upon hypoxic stimulus, MSCs released a large quantity of MVs of *100 nm in diameter. The MVs were phenotypically similar to the parent MSCs, except that the majority of them were negative for the receptor of platelet-derived growth factor. DiI-labeling assay revealed that MSC-MVs could be internalized into human UC endothelial cells (UC-ECs) within 8 h after they were added into the culture medium. Carboxyfluorescein succinimidyl ester-labeling technique and MTT test showed that MSC-MVs promoted the proliferation of UC-ECs in a dose-dependent manner. Further, MVs could enhance in vitro capillary network formation of UC-ECs in a Matrigel matrix. In a rat hindlimb ischemia model, both MSCs and MSC-MVs were shown to improve significantly the blood flow recovery compared with the control medium (P < 0.0001), as assessed by laser Doppler imaging analysis. These data indicate that MV releasing is one of the major mechanisms underlying the effectiveness of MSC therapy by promoting angiogenesis.

Therapeutic effects of mesenchymal stem cell-derived microvesicles on pulmonary arterial hypertension in rats

“…Accumulating evidence has indicated that MVs could modulate various processes, such as vascular function, angiogenesis, cell proliferation, inflammation, and coagulation [10,23,24] . Cord blood-derived MSC-MVs may promote angiogenesis in vitro and in vivo [25] . A recent study showed that the administration of MSC-exosomes can promote functional recovery and neurovascular plasticity in a stroke model [10] .…”

Therapeutic and diagnostic applications of extracellular vesicles

“…MSCs are stromal cells with multipotent differentiation capacity and have been intensively investigated for their potential regenerative and immunosuppressive effects in many animal models and clinical trials. Although originally believed to be the result of MSC homing to and engraftment at injured tissues, it is now becoming increasingly clear that the biological effect of these cells is mainly attributed to their secretome, including EVs [93,94]. In this respect, MSCderived EVs have been studied in dedicated mouse models for their tissue-protective effects following acute kidney failure [93], myocardial infarct [95], liver injury [96] and neural injury after middle cerebrate artery occlusion [97].…”

Mesenchymal stem cell-based therapy for ischemic stroke

“…Several studies demonstrate that small cellularly secreted vesicles called exosomes mediate much of MSCs' tissue healing capabilities [15][16][17][18][19][20][21][22][23][24][25][26][27][28]. MSC derived exosomes are internalized by target cells and transfer proteins, RNA, lipids and metabolites [29].…”