The central portion of the midbody, a cytoplasmic bridge between nascent daughter cells at the end of cell division, has generally been thought to be retained by one of the daughter cells, but has, recently, also been shown to be released into the extracellular space. The significance of midbody-retention versus -release is unknown. Here we show, by quantitatively analysing midbody-fate in various cell lines under different growth conditions, that the extent of midbody-release is significantly greater in stem cells than cancer-derived cells. Induction of cell differentiation is accompanied by an increase in midbody-release. Knockdown of the endosomal sorting complex required for transport family members, Alix and tumour-suppressor gene 101, or of their interaction partner, centrosomal protein 55, impairs midbody-release, suggesting mechanistic similarities to abscission. Cells with such impaired midbody-release exhibit enhanced responsiveness to a differentiation stimulus. Taken together, midbody-release emerges as a characteristic feature of cells capable of differentiation.

Human prominin-1 (CD133) is expressed by various stem and progenitor cells originating from diverse sources. In addition to stem cells, its mouse ortholog is expressed in a broad range of adult epithelial cells, where it is selectively concentrated in their apical domain. The lack of detection of prominin-1 in adult human epithelia might be explained, at least in part, by the specificity of the widely used AC133 antibody, which recognizes an epitope that seems dependent on glycosylation. Here we decided to re-examine its expression in adult human tissues, particularly in glandular epithelia, using a novel monoclonal antibody (80B258) generated against the human prominin-1 polypeptide. In examined tissues, we observed 80B258 immunoreactivity at the apical or apicolateral membranes of polarized cells. For instance, we found expression in secretory serous and mucous cells as well as intercalated ducts of the large salivary and lacrimal glands. In sweat glands including the gland of Moll, 80B258 immunoreactivity was found in the secretory (eccrine and apocrine glands) and duct (eccrine glands) portion. In the liver, 80B258 immunoreactivity was identified in the canals of Hering, bile ductules, and small interlobular bile ducts. In the uterus, we detected 80B258 immunoreactivity in endometrial and cervical glands. Together these data show that the overall expression of human prominin-1 is beyond the rare primitive cells, and it seems to be a general marker of apical or apicolateral membrane of glandular epithelia. This manuscript contains online supplemental material at http://www.jhc.org . Please visit this article online to view these materials.

The differentiation of stem cells is a fundamental process in cell biology and understanding its mechanism might open a new avenue for therapeutic strategies. Using an ex vivo co‐culture system consisting of human primary haematopoietic stem and progenitor cells growing on multipotent mesenchymal stromal cells as a feeder cell layer, we describe here the exosome‐mediated release of small membrane vesicles containing the stem and cancer stem cell marker prominin‐1 (CD133) during haematopoietic cell differentiation. Surprisingly, this contrasts with the budding mechanism underlying the release of this cholesterol‐binding protein from plasma membrane protrusions of neural progenitors. Nevertheless, in both progenitor cell types, protein–lipid assemblies might be the essential structural determinant in the release process of prominin‐1. Collectively, these data support the concept that prominin‐1‐containing lipid rafts may host key determinants necessary to maintain stem cell properties and their quantitative reduction or loss may result in cellular differentiation.

We investigated the phenotype of hepatocellular carcinoma (HCC) in livers removed during transplantation after local ablation therapy by transarterial chemoembolization (TACE). This study involved 80 HCC nodules (40 treated with TACE and 40 not treated with local ablation before transplantation) observed in 64 explanted livers and included clinicopathological evaluations as well as single and double immunohistochemistry and reverse-transcription polymerase chain reaction (RT-PCR) for cytokeratin 19 (CK19), epithelial cell adhesion molecule (EpCAM), neural cell adhesion molecule (NCAM), and CD133. HCCs with complete necrosis post-TACE without viable tumors were excluded from the analysis. Cholangiolar, glandular, or spindle cell areas suggestive of a mixed hepatocholangiocellular phenotype were seen in 14 post-TACE HCCs and in none of the non-TACE HCCs (P < 0.001). According to single-epitope immunohistochemistry of post-TACE HCCs, CD133, CK19, EpCAM, and NCAM were expressed in 14 (35%), 8 (20%), 12 (30%), and 8 (20%), respectively. Only EpCAM was detected in 4 non-TACE HCC cases (10%). RT-PCR experiments using tissues obtained by laser microdissection showed that 4 of 5 investigated post-TACE HCCs expressed at least 1 of the markers, which were coexpressed in 3 of 5 tumors, whereas CD133 and EpCAM were individually expressed in 2 non-TACE HCCs. Double immunostaining showed that CD133⁺ cells frequently coexpressed CK19, EpCAM, or NCAM. Interestingly, the recurrence rate for patients with CD133⁺ post-TACE HCC was significantly higher than the rate for patients with CD133⁻ post-TACE HCC (P = 0.025). In conclusion, HCC with the combined hepatocholangiocellular phenotype appears to be more frequent in post-TACE HCC versus untreated HCC. Further studies are needed to investigate the potential relationships between TACE and HCC subpopulations with a chemoembolization-resistant phenotype and their clinical significance. Liver Transpl 17:943–954, 2011. © 2011 AASLD.

We isolated and expanded stem cells from dental pulp from extracted third molars using an innovative culture method consisting of low serum-containing medium supplemented with epidermal growth factor and platelet-derived growth factor BB. We evaluated the differentiation potential of these cells when they were growing either adherently or as micromass/spheroid cultures in various media. Undifferentiated and differentiated cells were analyzed by flow cytometry, immunocytochemistry and immunoblotting. The flow cytometry results showed that the dental pulp stem cells (DPSCs) were positive for mesenchymal stromal cell markers, but negative for hematopoietic markers. Immunocytochemical and/or immunoblotting analyses revealed the expression of numerous stem cell markers, including nanog, Sox2, nestin, Musashi-1 and nucleostemin, whereas they were negative for markers associated with differentiated neural, vascular and hepatic cells. Surprisingly, the cells were only slightly positive for α-smooth muscle actin, and a heterogeneous expression of CD146 was observed. When cultured in osteogenic media, they expressed osteonectin, osteopontin and procollagen I, and in micromass cultures, they produced collagen I. DPSCs cultured in TGF-β1/3-supplemented media produced extracellular matrix typical of cartilaginous tissue. The addition of vascular endothelial growth factor to serum-free media resulted in the expression of endothelial markers. Interestingly, when cultured in neurogenic media, DPSCs exhibited de novo or upregulated markers of undifferentiated and differentiated neural cells. Collectively, our data show that DPSCs are self-renewing and able to express markers of bone, cartilage, vascular and neural tissues, suggesting their multipotential capacity. Their easy accessibility makes these cells a suitable source of somatic stem cells for tissue engineering.

Extracellular membrane vesicles (EVs) are emerging as new vehicles in intercellular communication, but how the biological information contained in EVs is shared between cells remains elusive. Several mechanisms have been described to explain their release from donor cells and the initial step of their uptake by recipient cells, which triggers a cellular response. Yet, the intracellular routes and subcellular fate of EV content upon internalization remain poorly characterized. This is particularly true for EV-associated proteins and nucleic acids that shuttle to the nucleus of host cells. In this review, we will describe and discuss the release of EVs from donor cells, their uptake by recipient cells, and the fate of their cargoes, focusing on a novel intracellular route wherein small GTPase Rab7⁺ late endosomes containing endocytosed EVs enter into nuclear envelope invaginations and deliver their cargo components to the nucleoplasm of recipient cells. A tripartite protein complex composed of (VAMP)-associated protein A (VAP-A), oxysterol-binding protein (OSBP)-related protein-3 (ORP3), and Rab7 is essential for the transfer of EV-derived components to the nuclear compartment by orchestrating the particular localization of late endosomes in the nucleoplasmic reticulum.