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.

Stroke can cause permanent neurological damage, complications, and even death. However, there is no treatment exists to restore its lost function. Human embryonic stems transplantation therapy was a novel and potential therapeutic approach for stroke. However, as we have seen, the ethical controversy pertains to embryonic stem cell research. Human induced pluripotent stem cells (iPSCs) are the latest generation of stem cells that may be a solution to the controversy of using embryonic cells. In our study, we generated iPSCs from adult human fibroblasts by introduction of four defined transcription factors (Oct4, Sox2, Nanog, and Lin-28). And then, we investigated the efficacy of iPSCs transplantation therapy for stroke on the animal models of middle cerebral artery occlusion. Surprisingly, we found that transplanted iPSCs migrated to injured brain areas, and differentiated into neuron-like cells successfully. After 4-16 days iPSCs grafting, sensorimotor function of rats has been improved significantly. In one word, we may prove that iPSCs therapy in stroke to be an effective form of treatment.

SummaryThe development of human erythroid cells has been mostly examined in models of adult hematopoiesis, while their early derivation during embryonic and fetal stages is largely unknown. We observed the development and maturation of erythroblasts derived from human pluripotent stem cells (hPSCs) by an efficient co-culture system. These hPSC-derived early erythroblasts initially showed definitive characteristics with a glycophorin A+ (GPA+) CD34lowCD36− phenotype and were distinct from adult CD34+ cell-derived ones. After losing CD34 expression, early GPA+CD36− erythroblasts matured into GPA+CD36low/+ stage as the latter expressed higher levels of β-globin along with a gradual loss of mesodermal and endothelial properties, and terminally suppressed CD36. We establish a unique in vitro model to trace the early development of hPSC-derived erythroblasts by serial expression of CD34, GPA, and CD36. Our findings may provide insight into the understanding of human early erythropoiesis and, ultimately, therapeutic potential.

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