Tumor initiating cells (TICs) are being extensively studied for their role in tumor etiology, maintenance and resistance to treatment. We describe a novel approach to generate TICs by transduction of human primary breast cell preparations with exogenous expression of the OCT4 transcription factor. The OCT4 transduced breast colonies (OTBCs) underwent an immortalization process, as reflected by loss of p16 and enhanced telomerase expression. OTBCs exhibited cancer stem cell antigens, such as CD44high/CD24low/‐. These cells generated subcutaneous tumors in nude mice with colonization capabilities with 1–50 cells, thereby exhibiting TIC properties. Histological analysis of these tumors revealed poorly differentiated breast carcinomas. RNAi‐mediated knock‐down of OCT4 and downstream embryonic targets of OCT4 resulted in suppression of the self‐renewal ability. OCT4 over‐expression in these clones was molecularly associated with Epithelial‐to‐Mesenchymal Transition (EMT) gene signatures and strongly correlated with the claudin‐low intrinsic subtype of breast cancer. Our experimental approach provides a novel model system to dissect genes that could be used to effectively target breast cancer self‐renewal and tumor initiation.

The pathogenesis of osteoporosis is considered extremely intricate. Osteoblast differentiation and angiogenesis can greatly affect bone development and formation, given their coupling role in these processes. Exosome-mediated miRNA regulates cellular senescence, proliferation, and differentiation. However, whether senescent osteoblasts can regulate the senescence of vascular endothelial cell by miRNA through exosomal pathway remains unclear. In this study, senescent osteoblasts could regulate endothelial cell function, promote cell senescence and apoptosis, and decrease cell proliferation via exosomal pathway. miR-139-5p showed high expression in senescent osteoblasts and their exosomes. After senescent osteoblast-derived exosome treatment, miR-139-5p was also upregulated in endothelial cells. Furthermore, transfection of miR-139-5p mimic promoted the senescence and apoptosis of vascular endothelial cells and inhibited their proliferation and migration, whereas transfection of miR-139-5p inhibitor rescued the effect of D-galactose. Using double luciferase assay, TBX1 was confirmed to be a direct target gene of miR-139-5p. In conclusion, senescent osteoblast-derived exosome-mediated miR-139-5p regulated endothelial cell function via exosomal pathway. Our study revealed the role of osteoblast-derived exosomes in the bone environment during aging, providing a clue for inventing a new target therapy.

Backgrounds. Skin aging could be regulated by the aberrant expression of microRNAs. In this manuscript, we explain that endothelial cell-derived extracellular vesicles could act as supporters to deliver exogenous miR-326-3p to accelerate skin fibroblasts senescence. Methods. β-galactosidase senescence staining assay, Hoechst 33258 apoptosis staining assay, and Ki67 staining assay were used to evaluate the biological function of mouse skin fibroblasts. Real-time PCR was applied to assay miRNAs and mRNAs expressions. Western blot was used to detect TLR4 protein expression. The target gene of miRNA were identified using a double luciferase reporter assay. miR-326-3p mimic/inhibitor and siRNA-TLR4 can demonstrate a nonnegligible link between miR-326-3p-TLR4 and skin aging. Results. In coculture experiment, senescence endothelial cells could promote the skin fibroblasts senescence and apoptosis via extracellular vesicles pathway. In contrast, miR-326-3p mimics accelerated senescence and apoptosis of skin fibroblasts, while miR-326-3p inhibitor could dramatically delay skin fibroblasts senescence and apoptosis. TLR4 was proved to be a miR-326-3p directly target gene via double luciferase assay. After skin fibroblasts transfected with siRNA-TLR4, cellular senescence and apoptosis were significantly increased. Furthermore, the skin tissues of aging mice were shown with overexpression of miR-326-3p and decrease of TLR4 gene and protein expression levels. Conclusions. Endothelial cell-derived extracellular vesicles delivery of miR-326-3p was found to have a function in skin fibroblasts via target TLR4. Therefore, endothelial cell-derived extracellular vesicles in antiaging therapies might be a new treatment way for delaying skin aging.

Skin aging is a complicated physiological process, and microRNA-mediated regulation has been shown to contribute to this process. Exosomes mediate intercellular communication through miRNAs, mRNAs and proteins, and participate in many physiological and pathological processes. Vascular endothelial cell-derived exosomes have been confirmed to be involved in the development of many diseases, however, their effects on skin aging have not been reported. In this study, senescent endothelial cells could regulate skin fibroblast functions and promote cell senescence through exosomal pathway. miR-767 was highly expressed in senescent vascular endothelial cells and their exosomes, and miR-767 is also upregulated in skin fibroblasts after treatment with exosomes derived from senescent vascular endothelial cells. In addition, transfection with miR-767 mimic promoted senescence of skin fibroblasts, while transfection with miR-767 inhibitor reversed the effect of D-galactose. Double luciferase analysis confirmed that TAB1 was a direct target gene of miR-767. Furthermore, miR-767 expression was increased and TAB1 expression was decreased in D-galactose induced aging mice. In mice that overexpressed miR-767, HE staining showed thinning of dermis and senescence appearance. In conclusion, senescent vascular endothelial cell-derived exosome mediated miR-767 regulates skin fibroblasts through the exosome pathway. Our study reveals the role of vascular endothelial cell-derived exosomes in aging in the skin microenvironment and contributes to the discovery of new targets for delaying senescence.