Home About us Contact
|
Home About us Contact | ||
|
|
||
Hepatocyte Function (hepatocyte + function)
Selected AbstractsHepatocyte Function in a Radial-flow Bioreactor Using a Perfluorocarbon Oxygen CarrierARTIFICIAL ORGANS, Issue 11 2005Martin J. Nieuwoudt Abstract:, The aims of this study were, first, to indicate the metabolic activity of hepatocytes in a radial-flow polyurethane foam matrix bioreactor relative to monocultures, and second, to evaluate the effect on the hepatocytes of including a synthetic perfluorocarbon (PFC) oxygen carrier to the recirculating medium. The efficient O2 -carrying ability of PFCs may be beneficial to bioreactors employed in stressed cellular environments. Thus, they may also be useful in the treatment of an acute liver failure patient with a bioartificial liver support system (BALSS). Data on the function of three-dimensional (3-D) hepatocyte cultures exposed to emulsified PFCs are lacking. Results: the metabolic functions of the 3-D hepatocyte cultures were improved relative to monocultures. Three-dimensional cultures with and without PFC behaved similarly, and no adverse effects could be detected when PFC was included in the recirculating medium. The addition of PFC significantly improved lidocaine clearance possibly due to the presence of higher O2 tension in the medium. Imaging indicated that large aggregates formed and that seeding had followed flow through the matrix. Simulations indicated first, that the cell numbers used in this study had been insufficient to challenge the bioreactor O2 supply explaining the similarity in performance of the 3-D cultures, and second, that the benefit of adding PFC would be more pronounced at the cell densities likely to be used in a BALSS bioreactor. [source] Identification of hepatocytic and bile ductular cell lineages and candidate stem cells in bipolar ductular reactions in cirrhotic human liver,HEPATOLOGY, Issue 3 2007Hongchao Zhou Hepatocyte function and regeneration are severely compromised in severe liver disease, and a common sequela is cirrhosis. Structural changes caused by cirrhosis create a cellular environment conducive to the formation of ductular reactions (DRs). Ductular reactions are primarily composed of oval cells also known as "intermediate hepatobiliary cells". We have conducted single, double, and triple staining to study lineages of oval cells present in DRs. Staining with NCAM, CK19, and HepPar1 has revealed a distinctly bipolar structure to DRs that are embedded in cirrhotic tissue. Spatial analysis of cells that are singly HepPar1-positive, or CK19-positive, has revealed hepatocytic and biliary poles, respectively, in the DRs. Also, the location of singly NCAM-positive cells in DRs suggests that they may be bipotent liver stem/progenitor cells. The locations of other intermediate hepatobiliary cells, which have combinations of markers, suggest that CK19+/NCAM+ cells are transitional cells in the biliary lineage and that rare cells that are negative for all three markers are transitional cells in the hepatocytic lineage. A working cell lineage model for DRs is presented. (HEPATOLOGY 2007;45:716,724.) [source] In vitro liver model using microfabricated scaffolds in a modular bioreactorBIOTECHNOLOGY JOURNAL, Issue 2 2010Bruna Vinci Abstract Hepatocyte function on 3-D microfabricated polymer scaffolds realised with the pressure-activated microsyringe was tested under static and dynamic conditions. The dynamic cell culture was obtained using the multicompartment modular bioreactor system. Hepatocyte cell density, glucose consumption, and albumin secretion rate were measured daily over a week. Cells seeded on scaffolds showed an increase in cell density compared with monolayer controls. Moreover, in dynamic culture, cell metabolic function increased three times in comparison with static monolayer cultures. These results suggest that cell density and cell-cell interactions are mediated by the architecture of the substrate, while the endogenous biochemical functions are regulated by a sustainable supply of nutrients and interstitial-like flow. Thus, a combination of 3-D scaffolds and dynamic flow conditions are both important for the development of a hepatic tissue model for applications in drug testing and regenerative medicine. [source] Manganese cell labeling of murine hepatocytes using manganese(III)-transferrin,CONTRAST MEDIA & MOLECULAR IMAGING, Issue 3 2008Christopher H. Sotak Abstract Manganese(III)-transferrin [Mn(III),Tf] was investigated as a way to accomplish manganese-labeling of murine hepatocytes for MRI contrast. It is postulated that Mn(III),Tf can exploit the same transferrin-receptor-dependent and -independent metabolic pathways used by hepatocytes to transport the iron analog Fe(III),Tf. More specifically, it was investigated whether manganese delivered by transferrin could give MRI contrast in hepatocytes. Comparison of the T1 and T2 relaxation times of Mn(III),Tf and Fe(III),Tf over the same concentration range showed that the r1 relaxivities of the two metalloproteins are the same in vitro, with little contribution from paramagnetic enhancement. The degree of manganese cell labeling following incubation for 2,7,h in 31.5,µm Mn(III),Tf was comparable to that of hepatocytes incubated in 500,µm Mn2+ for 1,h. The intrinsic manganese tissue relaxivity between Mn(III),Tf-labeled and Mn2+ -labeled cells was found to be the same, consistent with Mn(III) being released from transferrin and reduced to Mn2+. For both treatment regimens, manganese uptake by hepatocytes appeared to saturate in the first 1,2,h of the incubation period and may explain why the efficiency of hepatocyte cell labeling by the two methods appeared to be comparable in spite of the ,16-fold difference in effective manganese concentration. Hepatocytes continuously released manganese, as detected by MRI, and this was the same for both Mn2+ - and Mn(III),Tf-labeled cells. Manganese release may be the result of normal hepatocyte function, much in the same way that hepatocytes excrete manganese into the bile in vivo. This approach exploits a biological process,namely receptor binding, endocytosis and endosomal acidification,to initiate the release of an MRI contrast agent, potentially conferring more specificity to the labeling process. The ubiquitous expression of transferrin receptors by eukaryotic cells should make Mn(III),Tf particularly useful for manganese labeling of a wide variety of cells both in culture and in vivo. Published in 2008 by John Wiley & Sons, Ltd. [source] Temporary amelioration of bilirubin conjugation defect in Gunn rats by transplanting conditionally immortalized hepatocytesJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 6 2002BYUNG-HO KIM Abstract Background: Conditionally immortalized hepatocytes (CIH) have been used in hepatocyte transplantation as an alternative to primary hepatocytes to cope with the shortage of donor organs. However, CIH are known to undergo apoptosis at body temperature and survive in vivo for a short period. In the present study, we investigated whether CIH function or not and how long their function is maintained in vivo. Methods: Various CIH cell lines that were established with temperature-sensitive Simian virus 40 large T antigen were transplanted into the spleen of Gunn rats, which are defective in bilirubin uridine diphosphate glucuronoside transferase (BUGT). Then, we measured biological changes over 3 months. Results: Serum bilirubin of the syngeneic CIH recipients decreased by 30%, which was maintained for 8 weeks. Thereafter, it began to rise to basal levels. The recipients of allogeneic CIH showed a minor reduction of bilirubin, although this was not statistically significant. However, there was no significant change in the bilirubin level in recipients of BUGT-defective congeneic CIH throughout the study period. Bilirubin monoglucuronides in the bile were not detected in the recipients of BUGT-defective CIH. However, they appeared in recipients of non-defective CIH and made up approximately 41% of total bile pigments. Conclusions: Conditionally immortalized hepatocytes expressed hepatocyte function in vivo as well as in vitro, but the function lasted for a couple of months. According to our previous study, the limited functional duration may be related to the inevitable occurrence of apoptosis of these cells at body temperature. These data suggest that CIH can be used in hepatocyte transplantation only for temporary hepatic support. © 2002 Blackwell Publishing Asia Pty Ltd [source] Expression and Cytoskeletal Association of Integrin Subunits Is Selectively Increased in Rat Perivenous Hepatocytes After Chronic Ethanol AdministrationALCOHOLISM, Issue 12 2001Courtney S. Schaffert Background: For normal function and survival, hepatocytes require proper cell,extracellular matrix (ECM) contacts mediated by integrin receptors and focal adhesions. Previous studies have shown that chronic ethanol consumption selectively impairs perivenous (PV) hepatocyte attachment and spreading on various ECM substrates but increases expression of the ,1 integrin subunit, the common , subunit for two major hepatocyte-ECM receptors, ,1,1 and ,5,1 integrins. This study examined the effects of ethanol treatment on the expression and cytoskeletal distribution of ,1, ,5, and ,1 integrin subunits, the epidermal growth factor receptor (EGF-R), and the cytoskeletal proteins focal adhesion kinase, paxillin, vinculin, and actin in periportal and PV hepatocytes. Methods: Periportal and PV hepatocytes were isolated from control and ethanol-fed rats. For expression analysis, lysates were examined by SDS-PAGE and immunoblotting procedures. For cytoskeletal distribution studies, Triton-soluble and -insoluble (cytoskeletal) fractions from hepatocytes cultured on collagen IV were analyzed by SDS-PAGE and immunoblotting. Results: Chronic ethanol administration caused PV-specific increases in expression and cytoskeletal association of the integrin subunits. Although ethanol treatment did not affect expression of the EGF-R in either cell type, it did increase the association of the EGF-R with the cytoskeleton selectively in PV hepatocytes. Ethanol treatment had no significant effect on either the expression or the cytoskeletal distribution of focal adhesion kinase, paxillin, vinculin, or actin in either cell type. Conclusions: The increases in integrin expression and cytoskeletal association observed after chronic ethanol administration suggest that a process downstream of integrin-ECM interactions is impaired selectively in PV hepatocytes, possibly involving altered focal adhesion assembly or turnover, processes essential for efficient cell-ECM adhesion. Alterations in these processes could contribute to the impaired hepatocyte function and structure observed after chronic ethanol administration. [source] Transdifferentiation of adipose-derived stem cells into hepatocytes: a new approachLIVER INTERNATIONAL, Issue 6 2010James Lue Abstract Background: Several studies have demonstrated techniques in differentiating human adipose-derived stem cells (hADSCs) into hepatocytes. Unfortunately, transdifferentiation is inefficient, and the function of these induced hepatocyte-like cells (which we termed ,iHeps') is low compared with that of real hepatocytes. Aims: We aimed to identify transcriptional deficiencies in iHeps that are critical to hepatocyte development, which may provide insights into improving the efficiency of transdifferentiation. Methods: hADSCs were differentiated into iHeps, and iHeps were assayed for hepatocyte-like activity. iHeps were then screened for expression of several growth factors, receptors and transcription factors (TFs) critical to liver development using reverse transcription-polymerase chain reaction (RT-PCR). Deficient TFs were transduced into hADSCs and hepatocyte function was reassessed after hepatic differentiation. Results: Differentiation of hADSCs into iHeps resulted in the upregulation of hepatic proteins. However, the levels of expression of hepatocyte-specific proteins in these iHeps were well below those of Huh 7.5 hepatoma cells, used in comparison. Five developmental TFs were notably absent on the RT-PCR screen. Lentiviral transduction of these TFs into hADSCs followed by culture in hepatocyte induction medium resulted in increased albumin expression compared with untransduced hADSCs treated in a parallel fashion. Conclusions: These five missing TFs are known to regulate hepatocyte differentiation and some are required to establish the competence of the foregut endoderm. Presumably due to their mesenchymal lineage, hADSCs do not express these endodermal TFs and are not fully competent to respond to critical developmental signals. Supplementation of these TFs may induce competency and enhance the differentiation of hADSCs into hepatocytes. [source] Human embryonic stem cells and liver diseases: From basic research to future clinical applicationJOURNAL OF DIGESTIVE DISEASES, Issue 1 2008Zheng WANG Human embryonic stem cells (hESC) provide access to the earliest stages of human development and because of their high proliferation capability, pluripotency and low immunogenicity may serve as a potential source of specialized cells for regenerative medicine. hESC-derived hepatocyte-like cells exhibit characteristic hepatocyte morphology, express hepatocyte markers and are capable of executing a range of hepatocyte functions. However, there are many challenges and obstacles to be overcome before the use of hESC and hESC-derived hepatocyte-like cells in clinical practice can be realized. Here, we highlight some of the recent efforts in this area, in hope of providing insights toward this complex yet important area of therapeutical modality for treating patients with liver disease. [source] Hepatocyte dynamics in a three-dimensional rotating bioreactorJOURNAL OF GASTROENTEROLOGY AND HEPATOLOGY, Issue 11 2007Mitsuo Miyazawa Abstract Background and Aims:, The use of an artificial liver system with extracorporeal circulation or a three-dimensional bioreactor perfused with liquid culture medium inevitably exposes hepatocytes to fluid mechanical stress (MS). The expression of liver-specific hepatocyte functions seems to be modulated by the magnitude of MS. Nonetheless, few studies have focused on the direct effects of MS on hepatocytes. We subjected hepatocytes to MS using an MS loading device and investigated the effects on the cytoskeleton and hepatocyte dynamics inside three-dimensional scaffolds by monitoring the changes in actin fiber, one of the components of the cytoskeleton. We also assessed the influence of MS on specific hepatocyte functions. Methods:, We subjected hepatocytes to MS by a rotating radial flow bioreactor (RRFB) and examined the effects by comparing the MS-loaded culture cells with cells cultured under stationary conditions without MS loading. The hepatocytes (1 × 106/cm3) were seeded on gauze without collagen coating and examined to determine morphological changes after 60 h incubation. Actin filaments in samples from the MS-loaded hepatocyte culture were stained by fluorescein isothiocyanate-labeled phalloidin. Results:, Hepatocyte aggregation was observed in the MS-loaded culture, but not in the unloaded stationary culture. Better albumin products were observed in the MS-loaded group than in the stationary culture group at all measurement points. Actin filaments extended toward the scaffold after the start of MS loading incubation and polymerized around the hepatocytes. The hepatocyte aggregation eventually advanced to the formation of spheroids. Conclusion:, These results suggest that MS-induced polymerization of actin filaments stimulate hepatocyte aggregation and thereby improve hepatocyte-specific function. [source] | ||||||||||