ADAMTS13 is a circulating zinc metalloprotease that cleaves the hemostatic glycoprotein von Willebrand factor (VWF) in a shear-dependent manner. Deficiency in ADAMTS13, owing to genetic mutations or autoimmune inhibitors, causes thrombotic thrombocytopenic purpura (TPP). Northern blot analysis has shown that ADAMTS13 is expressed primarily in the liver. By using real-time RT-PCR, we confirmed that in mice the liver had the highest level of the ADAMTS13 transcript. To identify the liver cell-type-specific origin of ADAMTS13, we used in situ hybridization techniques to investigate the pattern of ADAMTS13 expression in the liver; analyzed the ADAMTS13 proteolytic activity in the culture media of fractionated liver cells; and confirmed ADAMTS13 expression with RT-PCR analysis and cloning of the mouse ADAMTS13 gene. The results revealed that ADAMTS13 was expressed primarily in cell fractions enriched in hepatic stellate cells. The mouse ADAMTS13 cloned from primary hepatic stellate cells was similar to its human counterpart in digesting VWF and was susceptible to suppression by EDTA or the IgG inhibitors of patients with TTP. Since hepatic stellate cells are believed to play a major role in the development of hepatic fibrosis and cirrhosis, the identification of the liver cell-type expressing ADAMTS13 will have important implications for understanding pathophysiological mechanisms regulating ADAMTS13 expression. The von Willebrand factor (VWF) is a multimeric glycoprotein that mediates adhesion and aggregation of platelets at sites of vascular injury. A metalloprotease cleaves VWF at the Tyr1605-Met1606 bond, generating homodimers of the 176 and 140 kDa fragments. 1,2 The VWF-cleaving protease is essential for preventing platelet aggregation in the circulation, and deficiency of the protease is associated with thrombotic thrombocytopenic purpura (TTP), a disease characterized by the development of VWF-platelet-rich thrombi in the arterioles and capillaries. 3 Recent studies identified this protease as ADAMTS13, a member of the reprolysin-type zinc metalloprotease family. [4][5][6] The human ADAMTS13 gene, spanning 37 kb on human chromosome 9q34, comprises 29 exons that encode a polypeptide of 1427-amino-acid residues and possibly several splicing isoforms. Although it shares with other members of the ADAMTS family a common domain architecture consisting of metalloprotease, disintegrin-like sequence, thrombospondin type 1 repeat, cysteine-rich and spacer regions, ADAMTS13 exhibits several distinct features, such as an RGDS sequence in the spacer domain and two copies of CUB domains at the carboxyl terminus. Substitution of the D residue in the RGDS sequence does not appear to diminish the proteolytic activity of ADAMTS13. 7 Unlike other ADAMTS proteases, pro-ADAMTS13 is proteolytically active. 8 These unique features of ADAMTS13 are consistent with

No abstract

Understanding the biological potential of fetal stem/progenitor cells will help define mechanisms in liver development and homeostasis. We isolated epithelial fetal human liver cells and established phenotype-specific changes in gene expression during continuous culture conditions. Fetal human liver epithelial cells displayed stem cell properties with multilineage gene expression, extensive proliferation and generation of mesenchymal lineage cells, although the initial epithelial phenotype was rapidly supplanted by meso-endodermal phenotype in culture. This meso-endodermal phenotype was genetically regulated through cytokine signaling, including transforming growth factor β, bone morphogenetic protein, fibroblast growth factor and other signaling pathways. Reactivation of HNF3α (FOXA1) transcription factor, a driver of hepatic specification in the primitive endoderm, indicated that the meso-endodermal phenotype represented an earlier developmental stage of cells. We found that fetal liver epithelial cells formed mature hepatocytes in vivo, including after genetic manipulation using lentiviral vectors, offering convenient assays for analysis of further cell differentiation and fate. Taken together, these studies demonstrate plasticity in fetal liver epithelial stem cells, offer paradigms for defining mechanisms regulating lineage switching in stem cells, and provide potential avenues for regulating cell phenotypes for applications of stem cells, such as for cell therapy.

A novel Asfarvirus-like virus is proposed as the etiological agent responsible for mass mortality in abalone. The disease, called abalone amyotrophia, originally was recognized in the 1980s, but efforts to identify a causative agent were unsuccessful. We prepared a semi-purified fraction by nuclease treatment and ultracentrifugation of diseased abalone homogenate, and the existence of the etiological agent in the fraction was confirmed by a challenge test. Using next-generation sequencing and PCR-based epidemiological surveys, we obtained a partial sequence with similarity to a member of the family Asfarviridae. BLASTP analysis of the predicted proteins against a virus database resulted in 48 proteins encoded by the novel virus with top hits against proteins encoded by African swine fever virus (ASFV). Phylogenetic analyses of predicted proteins of the novel virus confirmed that ASFV represents the closest relative. Comparative genomic analysis revealed gene-order conservation between the novel virus and ASfV. In situ hybridization targeting the gene encoding the major capsid protein of the novel virus detected positive signals only in tissue from diseased abalone. The results of this study suggest that the putative causative agent should be considered a tentative new member of the family Asfarviridae, which we provisionally designate abalone asfa-like virus (AbALV). African swine fever virus (ASFV) is the causative agent of African swine fever (ASF). The virus causes a hemorrhagic fever with high mortality, with rates approaching 100% in domestic pigs 1. The virus infects domestic pigs and their relatives and ticks 2. ASF outbreaks had been recorded in Africa and Europe, but in recent years the disease has spread to China, Vietnam, Cambodia, Mongolia, Hong Kong, and Korea, becoming a threat to the swine industry worldwide 3. ASFV is a member of nucleocytoplasmic large DNA viruses (NCLDVs) with an average diameter of 200 nm. Although some related viruses, such as faustovirus 4 , kaumoebavirus 5 , and pacmanvirus 6 , have been reported, ASFV is the only member of the Asfarviridae family 7. In the present paper, we describe a virus likely to be the closest ASFV relative found to date; this novel virus was isolated as the presumptive causative agent of abalone amyotrophia. Mass mortalities of abalone have been reported since the early 1980s, during seed production in Japan. The disease was designated abalone amyotrophia because diseased abalone develop muscle atrophy in the mantle and foot 8. Diseased abalone show reduced ability to adhere to the substrate, and some diseased abalone exhibit incisions on the front margin of the shell and brown pigmentation inside of the shell 9. Histopathological evaluation has revealed the presence of abnormal cell masses that are produced extensively, primarily in the ganglion and peripheral nerve of the foot muscle 9. Cumulative mortality can reach 50% and higher 10. Abalone herpesvirus (AbHV) 11,12 and abalone shriveling syndrome-associated virus (AbSV) 13 also cause mortality ac...

No abstract

Purpose Regulated expression of cell adhesion molecules could be critical in the proliferation, sequestration, and maintenance of stem/progenitor cells. Therefore, we determined fetal and adult stage-specific roles of cell adhesion in liver cell compartments. Methods We performed immunostaining for the adhesion molecules, E-cadherin and Ep-CAM, associated proteins, b-catenin and a-actinin, hepatobiliary markers, albumin, a-fetoprotein, and cytokeratin-19, and the proliferation marker, Ki-67. Expression of albumin was verified by in situ mRNA hybridization. Results In the fetal liver, hepatoblasts showed extensive proliferation with wide expression of E-cadherin, b-catenin, and a-actinin, although Ep-CAM was expressed in these cells less intensely and focally in the cell membrane to indicate weak cell adhesion. Hepatoblasts in ductal plate and bile ducts showed less proliferation and Ep-CAM was intensely expressed in these cells throughout the cell membrane, indicating strong adhesion. In some ductal plate cells, b-catenin was additionally in the cytoplasm and nucleus, suggesting active cell signaling by adhesion molecules. In adult livers, cells were no longer proliferating and E-cadherin, b-catenin, and a-actinin were expressed in hepatocytes throughout, whereas Ep-CAM was expressed in only bile duct cells. Some cells in ductal structures of the adult liver with Ep-CAM coexpressed albumin and cytokeratin-19, indicating persistence of fetal-like stem/progenitor cells. Conclusions Regulated expression of Ep-CAM supported proliferation in fetal hepatoblasts through weak adhesion and helped in biliary morphogenesis by promoting stronger adhesion in hepatoblasts during this process. Restriction of Ep-CAM expression to bile ducts in the adult liver presumably facilitated sequestration of stem/progenitor cells. This stage-specific and cell compartment-related regulation of adhesion molecules should be relevant for defining how liver stem/progenitor cells enter, exit, and remain in hepatic niches during both health and disease.

Doxorubicin-induced hepatic endothelial damage enhanced cell engraftment, which should be useful in cell therapy strategies.

No abstract