Albumin synthesis by rat hepatocytes cultured on collagen gels is sustained specifically by heparin

Two novel InDels within the Promoter of SIRT1 are associated with growth traits in chickens

1. The objectives of the present study were to elucidate the relationship between novel variations of the SIRT1 gene and chicken growth traits. In total, 1,429 chickens, including six breeds and a Gushi ×Anka F2 resource population, were genotyped using PCR-RFLP.

2. Two novel InDels (c.-1552_-1553insCG and c.-450_-451delCG) in the promoter of the chicken SIRT1 gene were identified. An association study showed that c.-1552_-1553insCG was significantly correlated with growth traits and serum lipid indicators.

3. The insertion genotype was most highly associated with body weight at day old, two- and four-week-old chickens, and with shank circumference at four and eight weeks of age. The wild type genotype at this site was most highly associated with serum lipid indicators.

4. In contrast, c.-450_-451delCG was significantly correlated with muscle fibre diameter. The SIRT1 gene expression in chickens with different InDel genotypes was analysed and was significantly higher with heterozygous genotypes at both sites in muscle and fat tissue, relative to expression in chickens with the corresponding homozygous genotypes.

5. The effects of different haplotypes on SIRT1 promoter activity showed that promoter activity depends on haplotype, with haplotype HapII exhibiting the highest activity.

6. It was concluded that the SIRT1 gene is associated with chicken growth traits and that the two InDels influence SIRT1 promoter activity in chickens.

A biphasic response of polymerized Type 1 collagen architectures to dermatan sulfate

Collagen I, the most abundant extracellular matrix (ECM) protein in vertebrate tissues provides mechanical durability to tissue microenvironments and regulates cell function. Its fibrillogenesis in biological milieu is predominantly regulated by dermatan sulfate proteoglycans, proteins conjugated with iduronic acid-containing dermatan sulfate (DS) glycosaminoglycans (GAG). Although DS is known to regulate tissue function through its modulation of Coll I architecture, a precise understanding of the latter remains elusive. We investigated this problem by visualizing the fibrillar pattern of fixed Coll I gels polymerized in the presence of varying concentrations of DS using second harmonic generation microscopy. Measuring mean second harmonic generation signal (which estimates the ordering of the fibrils), and surface occupancy (which estimates the space occupied by fibrils) supported by confocal reflectance microscopy, our observations indicated that the effect on fibril pattern of DS is contextual upon the latter's concentrations: Lower levels of DS resulted in sparse disorganized fibrils; higher levels restore organization, with fibrils occupying greater space. An appropriate change in elasticity as a result of DS levels was also observed through atomic force microscopy. Examination of dye-based GAG staining and scanning electron microscopy suggested distinct constitutions of Coll I gels when polymerized with higher and lower levels of DS. We observed that adhesion of the invasive ovarian cancer cells SKOV3 decreased for lower DS levels but was partially restored at higher DS levels. Our study shows how the Coll I gel pattern-tuning of DS is of relevance for understanding its biomaterial applications and possibly, pathophysiological functions.

Emerging In Vitro Liver Technologies for Drug Metabolism and Inter-Organ Interactions

In vitro liver models provide essential information for evaluating drug metabolism, metabolite formation, and hepatotoxicity. Interfacing liver models with other organ models could provide insights into the desirable as well as unintended systemic side effects of therapeutic agents and their metabolites. Such information is invaluable for drug screening processes particularly in the context of secondary organ toxicity. While interfacing of liver models with other organ models has been achieved, platforms that effectively provide human-relevant precise information are needed. In this concise review, we discuss the current state-of-the-art of liver-based multiorgan cell culture platforms primarily from a drug and metabolite perspective, and highlight the importance of media-to-cell ratio in interfacing liver models with other organ models. In addition, we briefly discuss issues related to development of optimal liver models that include recent advances in hepatic cell lines, stem cells, and challenges associated with primary hepatocyte-based liver models. Liver-based multiorgan models that achieve physiologically relevant coupling of different organ models can have a broad impact in evaluating drug efficacy and toxicity, as well as mechanistic investigation of human-relevant disease conditions.

Recent advances in 2D and 3D in vitro systems using primary hepatocytes, alternative hepatocyte sources and non-parenchymal liver cells and their use in investigating mechanisms of hepatotoxicity, cell signaling and ADME

This review encompasses the most important advances in liver functions and hepatotoxicity and analyzes which mechanisms can be studied in vitro. In a complex architecture of nested, zonated lobules, the liver consists of approximately 80 % hepatocytes and 20 % non-parenchymal cells, the latter being involved in a secondary phase that may dramatically aggravate the initial damage. Hepatotoxicity, as well as hepatic metabolism, is controlled by a set of nuclear receptors (including PXR, CAR, HNF-4α, FXR, LXR, SHP, VDR and PPAR) and signaling pathways. When isolating liver cells, some pathways are activated, e.g., the RAS/MEK/ERK pathway, whereas others are silenced (e.g. HNF-4α), resulting in up- and downregulation of hundreds of genes. An understanding of these changes is crucial for a correct interpretation of in vitro data. The possibilities and limitations of the most useful liver in vitro systems are summarized, including three-dimensional culture techniques, co-cultures with non-parenchymal cells, hepatospheres, precision cut liver slices and the isolated perfused liver. Also discussed is how closely hepatoma, stem cell and iPS cell-derived hepatocyte-like-cells resemble real hepatocytes. Finally, a summary is given of the state of the art of liver in vitro and mathematical modeling systems that are currently used in the pharmaceutical industry with an emphasis on drug metabolism, prediction of clearance, drug interaction, transporter studies and hepatotoxicity. One key message is that despite our enthusiasm for in vitro systems, we must never lose sight of the in vivo situation. Although hepatocytes have been isolated for decades, the hunt for relevant alternative systems has only just begun.

Alginate/galactosylated chitosan/heparin scaffold as a new synthetic extracellular matrix for hepatocytes

Formation of multicellular hepatocyte spheroids in the three-dimensional culture is a potential approach for enhancing liver-specific functions in bioartificial liver (BAL) devices. In this study, as a synthetic extracellular matrix (ECM) for hepatocytes, a highly porous hydrogel (sponge-like) scaffold, 150-200 microm pore size in diameter, was fabricated with alginate (AL), galactosylated chitosan (GC), and heparin through electrostatic interaction. We attempt to select the best condition of AL/GC/heparin sponges for coculture with NIH3T3, as well as compare the liver-specific functions with monoculture. Cell adhesion to GC based on AL film was significantly increased with increasing GC concentration, but not to chitosan regardless of its concentration. The optimal concentration of GC and heparin in AL/GC/heparin sponges to perform the best liver-specific function was 1 and 6 wt% to AL contents, respectively, where albumin secretion were maintained with maximal rates. The mechanical properties in tensile strength of three types of sponges were very slightly different from one another. Cell viabilities performed on AL, AL/GC, and AL/GC/heparin sponges were 68.5, 83.3, and 90.4 % of control, respectively, after 15 days of incubation. Hepatocyte spheroids were more rapidly formed in the AL/GC and AL/GC/heparin sponges, with diameter enlarged to about 100 microm, than in AL sponges. Connexin32 and E-cadherin genes correlated with cell-to-cell adhesion were expressed in hepatocytes within AL/GC and AL/GC/heparin sponges at 36 h after incubation, but not in AL sponges. Treatment of a gap junctional intercellular communication (GJIC) inhibitor, 18beta-glycyrrhetinic acid, indicates that cell aggregation without GJIC does not perform the liver-specific functions for long periods. In the presence of HGF, the level of albumin secretion in AL/GC/heparin sponges was markedly elevated compared to that in AL/GC sponges. Coculture of hepatocytes in AL/GC/heparin sponges with NIH3T3 in a transwell insert resulted in significant increase of liver-specific functions, such as improved albumin secretion rates, ammonia elimination rates, and ethoxyresorufin-O-deethylase activity by cytochrome P4501A1 compared to those in hepatocyte monoculture. The results suggest that hepatocytes as stable spheroids enhance liver-specific functions in AL/GC/heparin sponges, providing a new synthetic ECM to design BAL devices.

[Studies on the activation of complement by encapsulated and non-encapsulated staphylococci after their extraction with guanidinium chloride (author's transl)]

All demonstrable enzymes and toxins of encapsulated staphylococci (KS) were removed by extraction with guanidinium chloride. The capsules, however, remained apparently intact on the extracted (KS-Gu) staphylococci (fig. 1), as well as clumping factor and protein A. KS and KS-Gu failed to activate complement in the absence of specific antibodies. They showed neither immunadherence (table 1) nor agglutination by an antiserum against C3 (table 2). KS and KS-Gu had no significant chemotactic effects in vitro upon bovine granulocytes (fig. 2).

The influence of glycosaminoglycans and crosslinking agents on the phenotype of hepatocytes cultured on collagen gels

The use of primary hepatocyte cultures as in vitro models for studying xenobiotic metabolism and toxicity is limited by the loss of liver-specific differentiated functions with time in culture and the inability of the cells to proliferate. The aim of this study was to investigate the effect of incorporating 20% chondroitin-6-sulphate (Ch6SO4), a glycosaminoglycan (GAG), into collagen gels (0.3% w/v) and crosslinking the gels with either 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDAC) or 1,6-diaminohexane (DAH) on the expression of glutathione-S-transferases (GSTs) and the activity of cytochrome P450 in hepatocytes cultured for 48 hours and 7 days. Hepatocytes were isolated from male Sprague-Dawley rats by collagenase perfusion. Cell homogenates were immunoblotted against class alpha and pi GST subunits. To measure cytochrome P450 activity, testosterone hydroxylation was assessed. Viability of the cultured cells was assessed by confocal laser scanning microscopy using the vital stain carboxyfluorescein diacetate (CFDA). Cells cultured on gels crosslinked with EDAC were dead by 48 hours as judged by lack of CFDA-derived fluorescence and absence of GST bands on the immunoblots. The viability and morphology of the cells were unaffected by any of the other components of the substrata tested. Expression of GSTs indicated that the hepatocyte phenotype was stable for at least 48 hours. The addition of GAG did not improve the phenotype at either 48 hours or 7 days in culture, but the combination of GAG and DAH crosslinking improved GST expression in the 7-day cultures. However, the hepatocyte cytochrome P450 activity did not show any improvement on any of the gels. The combination of GAG and DAH crosslinking provided the most stable substratum environment in terms of GST expression in hepatocytes.

Synergistic induction by collagen and fibronectin of liver-specific genes in rat primary cultured hepatocytes

The extracellular matrix plays an important role for maintaining liver functions. We examined the effects of type I collagen and fibronectin on the expression of liver-specific genes in rat primary hepatocytes. When primary culture hepatocytes were overlaid with a type I collagen-gel, the expression of liver-specific genes (tyrosine aminotransferase, aldolase B, and albumin) increased by 4-5 times, compared with not overlaid hepatocytes. In contrast, the expression of non-liver-specific genes (GAPDH and beta-actin) was suppressed under the same conditions. The addition of fibronectin together with type I collagen-gel further enhanced the expression of liver-specific genes by 1.4-1.8 times. The addition of GRGDS peptide instead of fibronectin with the collagen-gel had a similar effect on hepatic gene expression to that of fibronectin. Addition of fibronectin alone exhibited had no effect on gene expression. These results suggest that type I collagen and fibronectin synergistically induce liver-specific genes.