Liver failure, which is the result of liver injury and pathological inflammation, is currently only successfully treated by organ transplantation. However donor organ shortages preclude transplantation for many patients in need. Thus, bioartificial liver systems (BALS) are being developed as a bridge to transplantation, or to create an environment conducive to liver regeneration. Hepatocytes, the main functional cells of the liver, are the cells of choice for BALSs, but in standard conditions ex vivo, they rapidly suffer from a reduction of their functionality and viability. Coculture with stromal cells, for example bone marrow mesenchymal stromal cells (BM-MSC), has been shown to improve, and extend, hepatocyte function ex vivo up to 21 days. But, only small numbers of BM-MSCs can be harvested from adult volunteers. We have previously described an alternative, more plentiful, source of MSCs — human umbilical cord perivascular cells (HUCPVC) — that are easily expanded and non-alloreactive. Our hypothesis was that HUCPVCs are putative stromal cells for hepatocytes. Our results show that HUCPVCs improved hepatocyte albumin secretion, urea synthesis and maintained hepatocyte cytochrome activity and the expression of hepato-specific genes. Furthermore, there was a net proliferation of hepatocytes, which were polarized in coculture with HUCPVCs, as judged by functional bile canaliculi that were present for up to 40 days. We found that both soluble and non-soluble factors contributed to these effects, while neither was able to allow net proliferation individually. Moreover, HUCPVCs expressed both hepato-trophic and anti-inflammatory factors, at different levels to BM-MSCs, indicating the potential for differential hepato-therapeutics. We conclude that HUCPVCs are putative stromal cells for hepatocytes; they improve hepatocyte functionality, polarity, morphology and net proliferation, and thus present an opportunity for the improvement of both BALS function and liver therapy.

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Diss. (sammanfattning) Stockholm : Karol. inst., 2004. / Härtill 5 uppsatser.

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La transition cellulaire Mésenchymo-Amiboïde (MAT) est requise pour l’échappement métastasique, cependant elle n’a encore jamais été associée à une situation physiopathologique précise. PAI-1, l’inhibiteur de l’activateur du plasminogène de type-1, est une molécule du microenvironnement tumoral considérée comme facteur de mauvais pronostic et localisée en forte concentration autour des tumeurs les plus invasives. Nous montrons que, sous sa forme matricielle active, PAI-1 est capable d’entretenir, au cours du temps et de façon dose-dépendante, la morphologie amiboïde de cellules cancéreuses colorectales et mammaires, et que celle-ci est associée à une adhérence faible intégrines-indépendante, une migration de type amiboïde et à l’activation de la voie RhoA/ROCK-1/MLC-P. Le mécanisme moléculaire mis en jeu a partiellement été mis en évidence : nous montrons que l’immobilisation de PAI-1 et sa liaison à l’uPA sont indispensables, et nous suggérons la possibilité que le récepteur membranaire uPAR participe à la transmission de signaux maintenant la voie RhoA/ROCK-1/MLC-P active. La compatibilité des effets du PAI-1 matriciel vis-à-vis des principales voies de signalisation impliquées dans la régulation de la transition MAT est établie in silico grâce à une méthode fondée sur la modélisation de la dynamique des réseaux d’interactions. L’ensemble de ces résultats permet pour la première fois de caractériser une situation physiopathologique microenvironnementale favorable à la transition MAT ; et bien que la forme matricielle de PAI-1 n’ait pas encore livré tous ses secrets, elle semble être une cible thérapeutique intéressante. / The Mesenchymal-Amoeboid transition (MAT) is required for metastatic escape, however it has not been associated with a precise physiopathological requirement yet. PAI-1, type-1 plasminogen activator inhibitor, is a tumor matrix molecule considered as marker of bad prognosis and found in high amount in the most aggressive tumors. We show that, in its activated matrix form, PAI-1 is able to maintain, in time and with concentration-dependence, the amoeboid morphology of colorectal and mammary cancer cells, and that this one is associated with a weak integrin-independant adhesion, an amoeboid migration and the activation of RhoA/ROCK-1/MLC-P pathway. The involved molecular mechanism has been partially underlined: we show that immobilization of PAI-1 and its link with uPA are essential, and we assume that the membrane receptor uPAR participates in the transmission of signals maintaining activated the RhoA/ROCK-1/MLC-P pathway. The compatibility of matrix PAI-1 effects towards the main signaling pathways involved in MAT regulation is established in silico with a method based on the modeling of interaction network dynamics. All this results enable for the first time to characterize a matrix physiopathological situation supporting MAT; and although the matrix form of PAI-1 has not been revealed all its secrets yet, it seems to be an interesting therapeutic target.

The cost of drug development is high with many drugs failing during toxicity testing. This is a particular problem in veterinary medicine where the pharmaceutical market size is so small that it may not be economically viable to develop drugs. The liver and specifically hepatocytes have a crucial role in drug metabolism via oxidation by cytochrome enzymes (CYP), conjugation and excretion into the biliary system. This drug metabolism is unpredictable between species as each has unique CYP profiles. Furthermore there is breed variation of CYP profiles within the canine species. The ability to produce an in vitro source of canine hepatocytes to model drug metabolism in this species and in different breeds would greatly reduce the expense of candidate drug testing. If an unlimited supply could be produced in vitro this would reduce the number of animals required in pre-clinical testing. The aim of this thesis was to produce an in vitro supply of canine hepatocyte-like cells from stem cell sources, namely hepatic progenitor cells (HPC), mesenchymal stem cells (MSC) or induced pluripotent stem cells (iPSC). Cultures of canine primary hepatocytes were produced to use as a gold standard, but also to develop and refine tests of hepatocyte characterisation and function. A panel of primers was developed for use in real time polymerase chain reaction (PCR) as well as optimising tests for low density lipoprotein (LDL) and indocyanine green uptake, albumin production, periodic acid- Schiff staining for glycogen and CYP activity using a luciferase-based system. As primary hepatocytes rapidly lost their defining characteristics and function in vitro, methods of maintaining function using CYP inducers and culture substrates were assessed. Isodensity centrifugation and magnetic-activated cell sorting was employed to isolate HPCs. Selection of cells from the non-parenchymal cell fraction with stem cell marker Prominin 1 demonstrated that these were keratin 7 positive, a HPC marker. Cells morphologically consistent with HPC appeared and expanded in culture after 2 weeks. On passaging, these cells failed to continue expanding, despite plating onto collagen, laminin, SNL feeder cells or using Kubota’s medium (known to allow rapid expansion of rodent and human HPCs). Canine adipose (Ad-MSC) and bone marrow-derived mesenchymal stromal cells (BM-MSC) were isolated post mortem. These were characterised as CD45, 105 and STRO-1 positive, CD11b, 19 and 45 negative cells which could be differentiated into adipocytes, chondrocytes and osteocytes based on staining characteristics and relative gene expression. Protocols published for other species were used to differentiate both Ad-MSC and BM-MSC towards a hepatocyte phenotype. Although a dramatic change in morphology and a reduction in vimentin gene expression were noted, suggesting a loss of mesenchymal phenotype, these protocols did not induce a hepatocyte phenotype. Pre-treatment with 5-Aza-2′-deoxycytidine to cause DNA demethylation and valproic acid to inhibit histone deacetylation also failed to allow transdifferentiation. A polycistronic vector containing Oct-4, c-Myc, Sox2 and Klf4 was successfully transfected into canine epidermal keratinocyte progenitor cells which became alkaline phosphatase positive and assumed a morphology consistent with iPSC. After colony selection and expansion, PCR evidence of plasmid presence was lost, colony morphology changed, and alkaline phosphatase activity reduced, consistent with vector expression factor and pluripotency loss. Canine iPSCs produced by lentiviral method were then differentiated towards hepatocyte phenotype using a published protocol for mouse and human iPSC. These cells were then assessed for hepatocyte characteristics using the developed reagents and primers. These cells demonstrated increased gene expression and morphology consistent with differentiation towards a hepatocyte-like phenotype. This thesis demonstrates successful culture of canine primary hepatocytes and validation of tests of hepatocyte phenotype. This provides a basis for optimising primary hepatocyte function in vitro and assessment of the success of differentiation protocols on stem cell sources. Canine mesenchymal stromal cells do not appear to transdifferentiate towards a hepatocyte-like phenotype using published protocols for other species. Canine iPSC are a promising candidate for an in-vitro source of hepatocyte-like cells.

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"The effectiveness of exogenous cellular therapies has been limited by the ability to efficiently and locally deliver cells to a region of interest. We have developed biological sutures, formed from fibrin microthreads, to overcome these delivery issues and demonstrated increased cell engraftment compared to the current gold standard. However, the cell seeding efficiency onto the sutures is low and during implantation cells are subjected to shear forces as the sutures are pulled through the tissue. As a result, cells go unused after seeding and an uneven distribution of cells from the entry point to exit of the suture. By adding cell attachment and adhesion promoters and increasing culture time we proposed to overcome these issues. We have developed a shear loading method to evaluate the changes in cellular adhesion. Either poly-l-lysine or vitronectin was used to coat sutures. Uncoated control and coated sutures were then seeded with 100,000 human mesenchymal stem cells (hMSCs) for 24hrs or control sutures were seeded for 48hrs. An in vitro shear stress model was created by spinning seeded sutures with a centrifuge. Cell number per unit length prior to and post spinning were compared. To compare the effect of modifications on cell morphology cells were qualitatively assessed and nuclear alignment was evaluated as a robust measurement for overall cellular angle. Control sutures were found to have 6,821±739cells/cm prior to spinning, while sutures modified with poly-l-lysine resulted in 4,226±1,003cells/cm and vitronectin had 19,604±1,829cells/cm (p<0.05 vs. control and poly-l-lysine). 48hrs seeding resulted in a cell number to 4,417±2,266 cells/cm. Spinning resulted in relative decreases in cell number for control and coated sutures. Cells remained attached after sutures were spun after increased incubation time. Cells aligned along the long axis of individual microthreads; the alignment on control sutures was significantly different from all modifications. There was no difference in alignment between modifications, although they were significantly different compared to cells grown on topographically flat tissue culture plastic. These results demonstrated increased cell seeding efficiency and cell number for vitronectin coated biological sutures and increased cell adhesion following increased incubation time. The combination of these two modifications may lead to increased quantity and more evenly distributed cells delivered to diseased tissues by increasing initial cell number, increasing cell engraftment, and increased resistance to shear."