Portal venous repopulation of decellularised rat liver scaffolds with syngeneic bone marrow stem cells

Liver transplantation is the only life-saving treatment for end-stage liver failure but is limited by the organ shortage and consequences of immunosuppression. Repopulation of decellularised scaffolds with recipient cells provides a theoretical solution, allowing reliable and timely organ sourcing without the need for immunosuppression. Recellularisation of the vasculature of decellularised liver scaffolds was investigated as an essential prerequisite to the survival of other parenchymal components. Liver decellularisation was carried out by portal vein perfusion using a detergent-based solution. Decellularised scaffolds were placed in a sterile perfusion apparatus consisting of a sealed organ chamber, functioning at 37°C in normal atmospheric conditions. The scaffold was perfused via portal vein with culture medium. A total of 10⁷ primary cultured bone marrow stem cells, selected by plastic adherence, were infused into the scaffold, after which repopulated scaffolds were perfused for up to 30 days. The cultured stem cells were assessed for key marker expression using fluorescence-activated cell sorting (FACS), and recellularised scaffolds were analysed by light, electron and immunofluorescence microscopy. Stem cells were engrafted in portal, sinusoidal and hepatic vein compartments, with cell alignment reminiscent of endothelium. Cell surface marker expression altered following engraftment, from haematopoietic to endothelial phenotype, and engrafted cells expressed sinusoidal endothelial endocytic receptors (mannose, Fc and stabilin receptors). These results represent one step towards complete recellularisation of the liver vasculature and progress towards the objective of generating transplantable neo-organs.

Synthetic mimetics of the endogenous gastrointestinal nanomineral: Silent constructs that trap macromolecules for intracellular delivery

Amorphous magnesium-substituted calcium phosphate (AMCP) nanoparticles (75-150nm) form constitutively in large numbers in the mammalian gut. Collective evidence indicates that they trap and deliver luminal macromolecules to mucosal antigen presenting cells (APCs) and facilitate gut immune homeostasis. Here, we report on a synthetic mimetic of the endogenous AMCP and show that it has marked capacity to trap macromolecules during formation. Macromolecular capture into AMCP involved incorporation as shown by STEM tomography of the synthetic AMCP particle with 5nm ultra-fine iron (III) oxohydroxide. In vitro, organic cargo-loaded synthetic AMCP was taken up by APCs and tracked to lysosomal compartments. The AMCP itself did not regulate any gene, or modify any gene regulation by its cargo, based upon whole genome transcriptomic analyses. We conclude that synthetic AMCP can efficiently trap macromolecules and deliver them to APCs in a silent fashion, and may thus represent a new platform for antigen delivery.

Experimental heart failure modelled by the cardiomyocyte-specific loss of an epigenome modifier, DNMT3B

Differential DNA methylation exists in the epigenome of end-stage failing human hearts but whether it contributes to disease progression is presently unknown. Here, we report that cardiac specific deletion of Dnmt3b, the predominant DNA methyltransferase in adult mouse hearts, leads to an accelerated progression to severe systolic insufficiency and myocardial thinning without a preceding hypertrophic response. This was accompanied by widespread myocardial interstitial fibrosis and myo-sarcomeric disarray. By targeted candidate gene quantitative RT-PCR, we discovered an over-activity of cryptic splice sites in the sarcomeric gene Myh7, resulting in a transcript with 8 exons missing. Moreover, a region of differential methylation overlies the splice site locus in the hearts of the cardiac-specific conditional knockout (CKO) mice. Although abundant and complex forms of alternative splice variants have been reported in diseased hearts and the contribution of each remains to be understood in further detail, our results demonstrate for the first time that a link may exist between alternative splicing and the cardiac epigenome. In particular, this gives the novel evidence whereby the loss of an epigenome modifier promotes the development and progression of heart disease.

An investigation of the carbon nanotube--Lipid interface and its impact upon pulmonary surfactant lipid function

Multiwalled carbon nanotubes (MWCNTs) are now synthesized on a large scale, increasing the risk of occupational inhalation. However, little is known of the MWCNT-pulmonary surfactant (PS) interface and its effect on PS functionality. The Langmuir-Blodgett trough was used to evaluate the impact of MWCNTs on fundamental properties of PS lipids which influence PS function, i.e. compression resistance and maximum obtainable pressure. Changes were found to be MWCNT length-dependent. 'Short' MWCNTs (1.1 μm, SD = 0.61) penetrated the lipid film, reducing the maximum interfacial film pressure by 10 mN/m (14%) in dipalmitoylphosphatidylcholine (DPPC) and PS, at an interfacial MWCNT-PS lipid mass ratio range of 50:1 to 1:1. 'Long' commercial MWCNTs (2.1 μm, SD = 1.2) caused compression resistance at the same mass loadings. 'Very long' MWCNTs (35 μm, SD = 19) sequestered DPPC and were squeezed out of the DPPC film. High resolution transmission electron microscopy revealed that all MWCNT morphologies formed DPPC coronas with ordered arrangements. These results provide insight into how nanoparticle aspect ratio affects the interaction mechanisms with PS, in its near-native state at the air-water interface.

A scale down process for the development of large volume cryopreservation

The process of ice formation and propagation during cryopreservation impacts on the post-thaw outcome for a sample. Two processes, either network solidification or progressive solidification, can dominate the water–ice phase transition with network solidification typically present in small sample cryo-straws or cryo-vials. Progressive solidification is more often observed in larger volumes or environmental freezing. These different ice phase progressions could have a significant impact on cryopreservation in scale-up and larger volume cryo-banking protocols necessitating their study when considering cell therapy applications.

This study determines the impact of these different processes on alginate encapsulated liver spheroids (ELS) as a model system during cryopreservation, and develops a method to replicate these differences in an economical manner.

It was found in the current studies that progressive solidification resulted in fewer, but proportionally more viable cells 24 h post-thaw compared with network solidification. The differences between the groups diminished at later time points post-thaw as cells recovered the ability to undertake cell division, with no statistically significant differences seen by either 48 h or 72 h in recovery cultures.

Thus progressive solidification itself should not prove a significant hurdle in the search for successful cryopreservation in large volumes. However, some small but significant differences were noted in total viable cell recoveries and functional assessments between samples cooled with either progressive or network solidification, and these require further investigation.

Differential localisation of PARP-1 N-terminal fragment in PARP-1(+/+) and PARP-1(-/-) murine cells

Human PARP family consists of 17 members of which PARP-1 is a prominent member and plays a key role in DNA repair pathways. It has an N-terminal DNA-binding domain (DBD) encompassing the nuclear localisation signal (NLS), central automodification domain and C-terminal catalytic domain. PARP-1 accounts for majority of poly-(ADP-ribose) polymer synthesis that upon binding to numerous proteins including PARP itself modulates their activity. Reduced PARP-1 activity in ageing human samples and its deficiency leading to telomere shortening has been reported. Hence for cell survival, maintenance of genomic integrity and longevity presence of intact PARP-1 in the nucleus is paramount. Although localisation of full-length and truncated PARP-1 in PARP-1 proficient cells is well documented, subcellular distribution of PARP-1 fragments in the absence of endogenous PARP-1 is not known. Here we report the differential localisation of PARP-1 N-terminal fragment encompassing NLS in PARP-1(+/+) and PARP-1(-/-) mouse embryo fibroblasts by live imaging of cells transiently expressing EGFP tagged fragment. In PARP-1(+/+) cells the fragment localises to the nuclei presenting a granular pattern. Furthermore, it is densely packaged in the midsections of the nucleus. In contrast, the fragment localises exclusively to the cytoplasm in PARP-1(-/-) cells. Flourescence intensity analysis further confirmed this observation indicating that the N-terminal fragment requires endogenous PARP-1 for its nuclear transport. Our study illustrates the trafficking role of PARP-1 independently of its enzymatic activity and highlights the possibility that full-length PARP-1 may play a key role in the nuclear transport of its siblings and other molecules.

Sulfidation of silver nanowires inside human alveolar epithelial cells: a potential detoxification mechanism

Silver nanowires (AgNWs) are being developed for use in optoelectronics. However before widespread usage, it is crucial to determine their potential effects on human health. It is accepted that Ag nanoparticles (AgNPs) exert toxic effects by releasing Ag(+) ions, but much less is known about whether Ag(+) reacts with compounds, or any downstream bioactive effects of transformed AgNPs. Analytical high-resolution transmission electron microscopy has been employed to elucidate cellular uptake and reactivity of AgNWs inside human alveolar epithelial type 1-like cells. AgNWs were observed in the cytoplasm and membrane-bound vesicles, and precipitation of Ag2S within the cell occurred after 1 h exposure. Cell viability studies showed no evidence of cytotoxicity and reactive oxygen species were not observed on exposure of cells to AgNWs. We suggest that Ag2S formation acts as a 'trap' for free Ag(+), significantly limiting short-term toxicological effects - with important consequences for the safety of Ag-nanomaterials to human health.

'Insect aquaplaning' on a superhydrophilic hairy surface: how Heliamphora nutans Benth. pitcher plants capture prey

Trichomes are a common feature of plants and perform important and diverse functions. Here, we show that the inward-pointing hairs on the inner wall of insect-trapping Heliamphora nutans pitchers are highly wettable, causing water droplets to spread rapidly across the surface. Wetting strongly enhanced the slipperiness and increased the capture rate for ants from 29 to 88 per cent. Force measurements and tarsal ablation experiments revealed that wetting affected the insects' adhesive pads but not the claws, similar to the 'aquaplaning' mechanism of (unrelated) Asian Nepenthes pitcher plants. The inward-pointing trichomes provided much higher traction when insects were pulled outwards. The wetness-dependent capture mechanisms of H. nutans and Nepenthes pitchers present a striking case of functional convergence, whereas the use of wettable trichomes constitutes a previously unknown mechanism to make plant surfaces slippery.

Abstract 100: An Altered Epigenomic Mark Predisposes to Dilated Cardiomyopathy Through Alternative Splicing of Sarcomeric Gene Expression in Mice

Distinct epigenomic patterns of DNA methylation exist in important elements of the cardiac genome in human end-stage cardiomyopathy but whether these contribute to disease progression is unknown. We examined and found that the main DNA methyltransferase expressed in the adult mammalian heart is DNMT3B. We therefore generated a conditional inducible Dnmt3b knockout mouse to test the effect of altered DNA methylation in the heart. Upon induction in the adult mouse, Dnmt3b knockout (CKO) led rapidly to severe systolic insufficiency and myocardial thinning. Examination of myocyte nuclei reflected a loss of homogeniety and re-distribution of heterochromatin. This was accompanied by widespread myocardial interstitial fibrosis and myofibrillary disarray. We examined the myocardial transcriptome of CKO mice by RNA-seq and discovered significant changes in levels of transcript splicing isoforms especially those of sarcomeric genes. When subjected to pressure overload, CKO mice failed to mount a compensatory hypertrophic response and instead developed accelerated fulminant dilated cardiomyopathy. Our results demonstrate that DNA methylation has a distinct role with regulating transcript isoform splicing apart from gene expression. In particular, we have highlighted a mechanism by which the epigenome may mediate the development and progression of a complex disease.

Selenium-enhanced electron microscopic imaging of different aggregate forms of a segment of the amyloid β peptide in cells

The aggregation of misfolded proteins is a common feature underlying a wide range of age-related degenerative disorders, including Alzheimer's and Parkinson's diseases. A key aspect of understanding the molecular origins of these conditions is to define the manner in which specific types of protein aggregates influence disease pathogenesis through their interactions with cells. We demonstrate how selenium-enhanced electron microscopy (SE-EM), combined with tomographic reconstruction methods, can be used to image, here at a resolution of 5-10 nm, the interaction with human macrophage cells of amyloid aggregates formed from Aβ(25-36), a fragment of the Aβ peptide whose self-assembly is associated with Alzheimer's disease. We find that prefibrillar aggregates and mature fibrils are distributed into distinct subcellular compartments and undergo varying degrees of morphological change over time, observations that shed new light on the origins of their differential toxicity and the mechanisms of their clearance. In addition, the results show that SE-EM provides a powerful and potentially widely applicable means to define the nature and location of protein assemblies in situ and to provide detailed and specific information about their partitioning and processing.

With a flick of the lid: a novel trapping mechanism in Nepenthes gracilis pitcher plants

Carnivorous pitcher plants capture prey with modified leaves (pitchers), using diverse mechanisms such as ‘insect aquaplaning’ on the wet pitcher rim, slippery wax crystals on the inner pitcher wall, and viscoelastic retentive fluids. Here we describe a new trapping mechanism for Nepenthes gracilis which has evolved a unique, semi-slippery wax crystal surface on the underside of the pitcher lid and utilises the impact of rain drops to ‘flick’ insects into the trap. Depending on the experimental conditions (simulated ‘rain’, wet after ‘rain’, or dry), insects were captured mainly by the lid, the peristome, or the inner pitcher wall, respectively. The application of an anti-slip coating to the lower lid surface reduced prey capture in the field. Compared to sympatric N. rafflesiana, N. gracilis pitchers secreted more nectar under the lid and less on the peristome, thereby directing prey mainly towards the lid. The direct contribution to prey capture represents a novel function of the pitcher lid.

A FRET sensor for non-invasive imaging of amyloid formation in vivo

Misfolding and aggregation of amyloidogenic polypeptides lie at the root of many neurodegenerative diseases. Whilst protein aggregation can be readily studied in vitro by established biophysical techniques, direct observation of the nature and kinetics of aggregation processes taking place in vivo is much more challenging. We describe here, however, a Förster resonance energy transfer sensor that permits the aggregation kinetics of amyloidogenic proteins to be quantified in living systems by exploiting our observation that amyloid assemblies can act as energy acceptors for variants of fluorescent proteins. The observed lifetime reduction can be attributed to fluorescence energy transfer to intrinsic energy states associated with the growing amyloid species. Indeed, for a-synuclein, a protein whose aggregation is linked to Parkinson's disease, we have used this sensor to follow the kinetics of the self-association reactions taking place in vitro and in vivo and to reveal the nature of the ensuing aggregated species. Experiments were conducted in vitro, in cells in culture and in living Caenorhabditis elegans. For the latter the readout correlates directly with the appearance of a toxic phenotype. The ability to measure the appearance and development of pathogenic amyloid species in a living animal and the ability to relate such data to similar processes observed in vitro provides a powerful new tool in the study of the pathology of the family of misfolding disorders. Our study confirms the importance of the molecular environment in which aggregation reactions take place, highlighting similarities as well as differences between the processes occurring in vitro and in vivo, and their significance for defining the molecular physiology of the diseases with which they are associated.

Modeling inherited metabolic disorders of the liver using human induced pluripotent stem cells

Human induced pluripotent stem (iPS) cells hold great promise for advancements in developmental biology, cell-based therapy, and modeling of human disease. Here, we examined the use of human iPS cells for modeling inherited metabolic disorders of the liver. Dermal fibroblasts from patients with various inherited metabolic diseases of the liver were used to generate a library of patient-specific human iPS cell lines. Each line was differentiated into hepatocytes using what we believe to be a novel 3-step differentiation protocol in chemically defined conditions. The resulting cells exhibited properties of mature hepatocytes, such as albumin secretion and cytochrome P450 metabolism. Moreover, cells generated from patients with 3 of the inherited metabolic conditions studied in further detail (alpha1-antitrypsin deficiency, familial hypercholesterolemia, and glycogen storage disease type 1a) were found to recapitulate key pathological features of the diseases affecting the patients from which they were derived, such as aggregation of misfolded alpha1-antitrypsin in the endoplasmic reticulum, deficient LDL receptor-mediated cholesterol uptake, and elevated lipid and glycogen accumulation. Therefore, we report a simple and effective platform for hepatocyte generation from patient-specific human iPS cells. These patient-derived hepatocytes demonstrate that it is possible to model diseases whose phenotypes are caused by pathological dysregulation of key processes within adult cells.

Prelamin A acts to accelerate smooth muscle cell senescence and is a novel biomarker of human vascular aging

BACKGROUND

Hutchinson-Gilford progeria syndrome is a rare inherited disorder of premature aging caused by mutations in LMNA or Zmpste24 that disrupt nuclear lamin A processing, leading to the accumulation of prelamin A. Patients develop severe premature arteriosclerosis characterized by vascular smooth muscle cell (VSMC) calcification and attrition.

METHODS AND RESULTS

To determine whether defective lamin A processing is associated with vascular aging in the normal population, we examined the profile of lamin A expression in normal and aged VSMCs. In vitro, aged VSMCs rapidly accumulated prelamin A coincidently with nuclear morphology defects, and these defects were reversible by treatment with farnesylation inhibitors and statins. In human arteries, prelamin A accumulation was not observed in young healthy vessels but was prevalent in medial VSMCs from aged individuals and in atherosclerotic lesions, where it often colocalized with senescent and degenerate VSMCs. Prelamin A accumulation correlated with downregulation of the lamin A processing enzyme Zmpste24/FACE1, and FACE1 mRNA and protein levels were reduced in response to oxidative stress. Small interfering RNA knockdown of FACE1 reiterated the prelamin A-induced nuclear morphology defects characteristic of aged VSMCs, and overexpression of prelamin A accelerated VSMC senescence. We show that prelamin A acts to disrupt mitosis and induce DNA damage in VSMCs, leading to mitotic failure, genomic instability, and premature senescence.

CONCLUSIONS

This study shows that prelamin A is a novel biomarker of VSMC aging and disease that acts to accelerate senescence. It therefore represents a novel target to ameliorate the effects of age-induced vascular dysfunction.

Investigation into the intragranular structures of microcrystalline cellulose and pre-gelatinised starch

The internal structures of commercial spheronised microcrystalline cellulose (s-MCC) and pre-gelatinised starch (PGS) granules were investigated, using a range of methods. Results from scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM) revealed hierarchical structures, with dimensions ranging from nanometres to a few micrometres, for both materials. Residual fragments of plant cell walls, consisting largely of crystalline fibrillar bundles, were indicated within s-MCC granules, while PGS granules appeared to consist of densely packed spherical features. The lack of any obvious regular periodicity associated with the intragranular sub-structures was entirely consistent with the power-law behaviour of the small-angle X-ray scattering (SAXS) patterns from these materials. The presence of intragranular porosity was inferred from TEM, AFM and N(2)-adsorption measurements, while the ability to deform these structures was clearly indicated by the irregular force-displacement curves recorded by AFM on the granule surfaces. Hence, the intragranular sub-structures observed for s-MCC and PGS appeared to be consistent with the possibility of entire granules undergoing affine deformation during compaction. Since this mechanism was postulated to explain changes in SAXS patterns from these materials following compaction, as reported elsewhere, the work reported here provides a considerably stronger basis for using 2D-SAXS to investigate powder compaction behaviour.

Imaging amyloid fibrils within cells using a Se-labelling strategy

The process of aggregation leading to amyloid formation by peptides and proteins is associated with diseases ranging from systemic amyloidoses to neurodegenerative disorders such as Alzheimer's disease. A key question in understanding the link between amyloid formation and its pathological consequences is the ultrastructural localisation and morphological form of amyloid species within the cellular environment. The acquisition of such information has proven to be challenging, but we report here a novel approach that enables amyloid fibrils to be visualised directly within a cell. First, fibrils are assembled from selenium analogues of the sulfur-containing cysteine peptides, and then, atomic number contrast transmission electron microscopy is used to detect the selenium doped species selectively within the carbon-rich background of the cell. We demonstrate the power of this approach by imaging human monocyte-derived macrophage cells that have been exposed to fibrils from an amyloidogenic fragment of the disease-associated protein transthyretin. The ready incorporation of seleno-cysteine and methionine instead of their natural sulfur-containing analogues, a feature that is already commonly used in X-ray diffraction studies of proteins, suggests that this method can be used as a general strategy to image specific peptides and proteins within the cellular environment using electron microscopy.

Vascular development in embryoid bodies: quantification of transgenic intervention and antiangiogenic treatment

It has become increasingly clear that the investigation of vascular development is best considered in the context of a whole tissue environment since in vivo endothelial cells interact closely with other cell types. Murine embryoid bodies have been used as a model for the early development of a vascular network and are amenable to genetic manipulation and treatment with soluble modulators. However, quantifying morphological changes in these complex three-dimensional structures is challenging. In this paper we describe protocols to culture embryoid bodies on a large scale to study vascular development together with methods to quantify changes seen when antiangiogenic agents or endothelial cell-specific transgenes are introduced.

Vascular development is disrupted by endothelial cell-specific expression of the anti-apoptotic protein Bcl-2

Endothelial cell (EC) apoptosis has been detected in remodelling blood vessels in vivo, and inhibition of EC apoptosis appears to alter vascular morphogenesis in vitro, suggesting that EC apoptosis may play a role in blood vessel remodelling. However, apoptotic EC are difficult to quantify in vivo, and studies of the incidence of EC apoptosis and the sites at which it occurs in vivo have produced contradictory results. Therefore, the specific biological roles played by EC apoptosis remain unclear. Here, we have used a transgenic approach to determine the biological function of EC apoptosis in vivo. Anti-apoptotic Bcl-2 transgenes were expressed in mice under control of the EC-specific tie2 promoter. These transgenic mice died during the second half of gestation. While the development and remodelling of large vessels including aortic arch arteries and great veins proceeded normally, abnormally dense and disorganised networks of small vessels were present in the skin and internal organs. In addition, vessel organisation and lumen formation were disrupted in the placental labyrinth. This study provides direct experimental evidence that endothelial cell apoptosis plays an essential role during embryogenesis. Our results suggest that EC apoptosis plays an important role in determining the structure of the microcirculation but may be dispensable for large vessel development.

Identification of a potential structural marker for embryogenic competency in the Brassica napus spp. oleifera embryogenic tissue

The Brassica napus secondary embryogenesis system requires no exogenous growth regulator to stimulate embryo development. It is stable embryogenically over a long period of culture and has a distinct pre-embryogenic stage. This system was used to investigate the morphological and cellular changes occurring in the embryogenic tissue compared to non-embryogenic tissue using various microscopy techniques. A unique ultrastructural feature designated the extracellular matrix (ECM) was observed on the surface of pre-embryogenic embryoids but not on the non-embryogenic individuals. The ECM layer was found to be dominant in the pre-embryogenic stage and reduced to fragments during embryo growth and development in mature embryogenic tissue. This is a novel aspect of the phenotype previously unreported in the Brassica system. This structure might be linked to acquisition of embryogenic competence.

Uptake of C60 by human monocyte macrophages, its localization and implications for toxicity: studied by high resolution electron microscopy and electron tomography

Despite great interest in the engineering applications of carbon-based nanoparticles, recent studies have raised concerns about their potential toxicity and safety. The release of C(60) into the environment has been suggested to be a potential risk with possible ecological implications. Here we evaluate energy-filtered transmission electron microscopy (EFTEM) and scanning transmission electron microscopy (STEM)-based electron tomography as techniques for imaging the three-dimensional (3-D) distribution of nanoparticles within cells. Our aim was to establish if human monocyte macrophages internalise nanoparticles and to assess whether nanoparticles are modified by cells following uptake. Using these techniques we were able to show a marked increased in the amount of information gained from 3-D imaging. 3-D electron tomography revealed several sub-cellular compartments containing C(60) within the cell: secondary lysosomes, along the outer and nuclear membrane and most notably inside the nucleus of the cell. Using EFTEM and STEM-based techniques we were able to visualize cell structures such as membranes, the mitochondria, ribosomes and the nucleus, without the need for traditional staining techniques. In particular we demonstrate the potential of electron tomography for whole cell studies to enable 3-D distributions of particles within cells. The concentrations of C(60) used in this study were not toxic and were chosen to study which sub-cellular compartments accumulated C(60). Knowledge of the sites of accumulation of nanoparticles will allow us to predict vulnerability if the nanoparticles can generate free radicals.

The effect of dietary restriction on mitochondrial protein density and flight muscle mitochondrial morphology in Drosophila

Dietary restriction (DR) extends life span in diverse organisms and may do so by attenuating production of mitochondrial reactive oxygen species (ROS). However, measurements of ROS production from isolated mitochondria of organisms subjected to DR have produced inconsistent results. In the fruit fly Drosophila, DR does not reduce production of ROS from isolated mitochondria. In this study, we used Drosophila to test whether DR lowered mitochondrial density. We assessed mitochondrial densities of flies on DR and Control diets using (a) the activities of mitochondrial enzymes and (b) electron microscopy. Both methods showed no overall effect of DR on mitochondrial density; however, mitochondrial enzyme activities and morphology differed significantly between DR and Control flies. We concluded that life-span extension by DR in Drosophila is not mediated through a reduction in mitochondrial density. If DR in Drosophila extends life span by reducing ROS production, then it does so through mechanisms that operate only in vivo.

Syncollin is required for efficient zymogen granule exocytosis

Syncollin is a 13 kDa protein that is present in the exocrine pancreas, where the majority of the protein is tightly attached to the luminal surface of the zymogen granule membrane. We have addressed the physiological role of syncollin by studying the phenotype of syncollin KO (knockout) mice. These mice show pancreatic hypertrophy and elevated pancreatic amylase levels. Further, secretagogue-stimulated amylase release from pancreatic lobules of syncollin KO mice was found to be reduced by about 45% compared with wild-type lobules, and the delivery of newly synthesized protein to zymogen granules was delayed, indicating that the mice have a pancreatic secretory defect. As determined by two-photon imaging, the number of secretagogue-stimulated exocytotic events in acini from syncollin KO mice was reduced by 50%. This reduction was accounted for predominantly by a loss of later, 'secondary' fusion events between zymogen granules and other granules that had already fused with the plasma membrane. We conclude that syncollin is required for efficient exocytosis in the pancreatic acinar cell, and that it plays a particularly important role in compound exocytosis.

Cyclooxygenase-2-selective nonsteroidal anti-inflammatory drugs inhibit hepatocyte growth factor/scatter factor-induced angiogenesis

Epidemiological studies have indicated a reduced risk of malignancies with the use of nonsteroidal anti-inflammatory drugs (NSAIDs), although the exact mechanisms are debated. NSAIDs inhibit angiogenesis, which is a key step for tumor growth. Hepatocyte growth factor/scatter factor (HGF/SF), a potent and independent angiogenic factor, has been implicated in tumorigenesis, but limited knowledge exists on the potential targets for inhibiting HGF/SF-induced pathological angiogenesis. The current study was designed to elucidate the possible role of cyclooxygenase (COX) downstream of HGF/SF during angiogenesis and to evaluate the potential for harnessing NSAIDs as a therapeutic strategy. Known NSAIDs were classified as COX-1 or COX-2 selective based on their activity in a platelet aggregation experiment. The inhibitors were administered into a polyether polyurethane scaffold implant in mice at the selected doses, and the total neovascularization after the administration of HGF/SF was quantified using a (133)Xenon clearance technique, vessel counts, and immunohistochemistry. Angiogenesis was also quantized into chemoinvasion, migration, proliferation, and tube formation events in vitro, and the effects of the NSAIDs were evaluated on HGF/SF-induced activity of human umbilical vein endothelial cells (HUVECs). HGF/SF accelerated the angiogenic process in the murine implant, and this activity was inhibited by COX-2-selective meloxicam and NS398. The COX-1 inhibitors ketoprofen and SC560 failed to inhibit the HGF/SF-induced angiogenic events in vitro and in vivo. A COX-2 blockade inhibited the HGF/SF-induced chemoinvasion and migration of human umbilical vein endothelial cells, without affecting the proliferative or tubulogenic responses. Western blots revealed the induction COX-2 expression after HGF/SF treatment, and the pharmacological inhibition of COX-2 executed a temporal inhibition of phosphorylation of the mitogen-activated protein kinases. The current study, for the first time, implicates COX-2 as a downstream signal during HGF/SF-induced angiogenesis, temporally impinging on the mitogen-activated protein kinase signaling. However, the mediation is restricted to only the early events of the angiogenic process, emphasizing the chemopreventive role for NSAIDs. Few therapeutic options currently exist for HGF/SF-induced pathological angiogenesis, and the vast knowledge on COX-2 inhibitors can be harnessed to design a newer therapeutic approach.

Porcine livers perfused with human blood mount a graft-versus-"host" reaction

BACKGROUND

A major focus of xenotransplantation research is the interaction between human immune effector mechanisms and porcine tissues. We present evidence that a transplanted porcine organ might also mount a significant immune response to a human recipient.

METHODS

Isolated porcine livers were perfused with fresh human blood. Plasma samples were analyzed for complement production by reverse CH50 analysis. ELISA was used to determine the amount and class of porcine immunoglobulin in human blood after xenoperfusion. Flow cytometry was used to determine the specificity and class of porcine immunoglobulin in human blood after xenoperfusion and to determine whether porcine immunoglobulins had bound to the human lymphocytes in the blood perfusing the porcine livers. Electron microscopy was used to evaluate the interaction of porcine Kupffer cells and human erythrocytes.

RESULTS

Over the course of 72 hr of extracorporeal perfusion of porcine livers with human blood, the hematocrit fell progressively to as low as 2.5% of starting values, a phenomenon not seen in experiments using porcine blood. We have demonstrated both porcine complement and immunoglobulin in the human blood after xenoperfusion. The porcine antibodies in the human blood have specificity for human lymphocyte antigens. In fact, with increasing duration of perfusion, 40% of the xenoperfusions showed increasing titers of porcine antibodies with specificity for human lymphocyte antigens suggesting a response by primed porcine lymphocytes. However, the majority of erythrocytes are extracted directly by Kupffer cells in the liver.

CONCLUSIONS

These data demonstrate the ability of porcine livers to generate both a humoral and cellular graft versus host response to human cells.

Disassembly of nuclear inclusions in the dividing cell--a novel insight into neurodegeneration

Spinocerebellar ataxias and Huntington's disease are examples of neurodegenerative diseases caused by a trinucleotide repeat expansion. One hallmark of such diseases is the formation of inclusion bodies (IBs) within neuronal tissue. Although these inclusions may play a pivotal role in the disease process, the reasons underlying their specific accumulation remain obscure. By studying intranuclear IBs in dividing cells we demonstrate for the first time that inclusions such as those of ataxin-1 disperse during mitosis, thus reducing the nuclear aggregate burden. IBs reform in the interphase nucleus. By high-resolution confocal microscopy we also show that inclusions comprise ordered structures capable of homotypic interactions. Unlike those of a non-pathologic protein, ataxin-1 inclusions were shown to be capable of non-specific protein sequestration. Our studies indicate that the specific accumulation of inclusions in terminally differentiated cells such as neurons is a direct consequence of their inability to divide and therefore provides a key to explaining their persistence in neurodegenerative disease.

Restricted growth potential of rat neural precursors as compared to mouse

Epidermal growth factor (EGF) responsive precursors isolated from the developing mouse striatum could be continually expanded in culture as free-floating spheres of cells for over 50 days. Under identical conditions, EGF-responsive precursors from the developing rat striatum could only be expanded for between 21 and 28 days, after which crisis ensued and there was a reduction in cell number at each passage. The outer regions of 28-day-old rat spheres contained a heterogeneous population of both dividing and dying cells while the cores were full of dying cells, many of which showed features consistent with apoptosis. Fibroblast growth factor-2 (FGF-2) alone did not lead to an expansion in rat striatal precursor cell number under the conditions used here. EGF combined with FGF-2 acted synergistically on cell growth, but did not prevent the final senescence and death of the rat precursors.

Guidance of oligodendrocytes and their progenitors by substratum topography

Oligodendrocyte progenitors arise in subventricular zones and migrate extensively during development before differentiating into mature oligodendrocytes, which myelinate nerve tracts in the central nervous system. We have used microfabricated substrata, containing periodic patterns of contours similar to those of central nervous system axons to assess the influence in vitro of substratum topography on oligodendrocytes isolated from 7 day rat optic nerve. Antiganglioside antibody A2B5 positive oligodendrocyte-type 2 astrocyte progenitors, and galactocerebroside positive and myelin basic protein positive oligodendrocytes, were highly aligned by surface contours as small as 100 nm depth and 260 nm repeat spacing. Rat optic nerve astrocytes also aligned on surface contours, but rat hippocampal and cerebellar neurons were unresponsive. Oligodendrocytes demonstrated enhanced parallel extension of their processes on narrow repeating topography in an arrangement similar to that found in the intact optic nerve. This is in marked contrast to the phenotype displayed by this cell type on planar substrata. Neither oligodendrocytes nor oligodendrocyte-type 2 astrocyte progenitors showed high-order F-actin cytoskeletal networks; thus their alignment on gratings is unlikely to result from deformation of actin cables and focal contacts. In contrast, aligned astrocytes showed striking arrangements of actin stress fibres. These results establish glial cells as potentially the most topographically sensitive cell types within the central nervous system. Furthermore, the topographical pattern inducing maximal alignment of oligodendrocyte lineage cells corresponds to the diameters of single axons within the 7 day optic nerve. Thus the migration of oligodendrocyte-type 2 astrocyte progenitors and axonal ensheathment by oligodendrocytes may be guided by axonal topography within the developing nerve.

Human oligodendrocytes are not sensitive to complement. A study of CD59 expression in the human central nervous system

BACKGROUND

One or more components of the oligodendrocyte-myelin unit are the target of immune attack in multiple sclerosis. The role of complement in this process has been suggested by the demonstration in vitro that rat oligodendrocytes are sensitive to lysis by Ab-independent complement attack, partly because of a lack of the complement regulatory protein molecule, CD59.

EXPERIMENTAL DESIGN

This study assessed the sensitivity in vitro of human oligodendrocytes derived from neurosurgical specimens to complement attack and analyzed CD59 expression on their surface. The presence of CD59 was also examined in the human central nervous system during myelination and in both the normal and diseased adult brain.

RESULTS

Human oligodendrocytes are insensitive in vitro to complement attack in the absence of Ab and using the Ab YTH 53.1 and were shown to possess CD59 on their surface. CD59 is absent from the human central nervous system before myelination, at which stage strong expression occurs in areas of myelin production. CD59 expression is then normally down-regulated but is particularly strong in reactive astrocytes in diseases such as multiple sclerosis.

CONCLUSIONS

The findings suggest that the previous demonstration of rat oligodendrocyte complement sensitivity and lack of CD59 expression do not extend to the human central nervous system. There may be a role for CD59 in normal human myelination.