| 1. |
- Klassen, Henry, et al.
(författare)
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Isolation of progenitor cells from GFP-Transgenic pigs and transplantation to the retina of allorecipients
- 2008
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Ingår i: Cloning and Stem Cells. - : Mary Ann Liebert Inc. - 1536-2302 .- 1557-7457. ; 10:3, s. 391-402
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Tidskriftsartikel (refereegranskat)abstract
- Work in rodents has demonstrated that progenitor transplantation can achieve limited photoreceptor replacement in the mammalian retina; however, replication of these findings on a clinically relevant scale requires a large animal model. To evaluate the ability of porcine retinal progenitor cells to survival as allografts and integrate into the host retinal architecture, we isolated donor cells from fetal green fluorescent protein (GFP)transgenic pigs. Cultures were propagated from the brain, retina, and corneo-scleral limbus. GFP expression rapidly increased with time in culture, although lower in conjunction with photoreceptor markers and filial fibrillary acid protein (GFAP), thus suggesting downregulation of GFP during differentiation. Following transplantation, GFP expression allowed histological visualization of integrated cells and extension of fine processes to adjacent plexiform layers. GFP expression in subretinal grafts was high in cells expressing vimentin and lower in cells expressing photoreceptor markers, again consistent with possible downregulation during differentiation. Cells survived transplantation to the injured retina of allorecipients at all time points examined (up to 10 weeks) in the absence of exogenous immune suppression without indications of rejection. These findings demonstrate the feasibility of allogeneic progenitor transplantation in a large mammal and the utility of the pig in ocular regeneration studies.
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| 2. |
- Klassen, Henry, et al.
(författare)
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Neural precursors isolated from the developing cat brain show retinal integration following transplantation to the retina of the dystrophic cat
- 2007
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Ingår i: Veterinary Ophthalmology. - : Wiley. - 1463-5216 .- 1463-5224. ; 10:4, s. 245-253
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Tidskriftsartikel (refereegranskat)abstract
- The cat has served as an important nonrodent research model for neurophysiology and retinal degenerative disease processes, yet very little is known about feline neural precursor cells. To culture these cells and evaluate marker expression, brains were dissected from 45-day-old fetuses, enzymatically dissociated, and grown in the presence of EGF, bFGF and PDGF. Expanded cells widely expressed nestin, Sox2, Ki-67, fusin (CXCR4) and vimentin, while subpopulations expressed A2B5, GFAP, or beta-III tubulin. Precursors prelabeled with BrdU and/or transduced with a recombinant lentivirus that expresses GFP were transplanted subretinally in five dystrophic Abyssinian cats. Two to 4 weeks following surgery, histology showed survival of grafted cells in three of the animals. Labeled cells were found in the neuroretina and RPE layer, as well as in the vitreous and the vicinity of Bruch's membrane. There was no evidence of an immunologic response in any of the eyes. Neural precursor cells can therefore be cultured from the developing cat brain and survive as allografts for up to 4 weeks without immune suppression. The feasibility of deriving and transplanting feline neural precursor cells, combined with the availability of the dystrophic Abyssinian cat, provide a new feline model system for the study of retinal repair.
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| 3. |
- Klassen, Henry, et al.
(författare)
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Progenitor cells from the porcine neural retina express photoreceptor markers after transplantation to the subretinal space of allorecipients
- 2007
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Ingår i: Stem Cells. - : Oxford University Press (OUP). - 1549-4918 .- 1066-5099. ; 25:5, s. 1222-1230
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Tidskriftsartikel (refereegranskat)abstract
- Work in rodents has shown that cultured retinal progenitor cells (RPCs) integrate into the degenerating retina, thus suggesting a potential strategy for treatment of similar degenerative conditions in humans. To demonstrate the relevance of the rodent work to large animals, we derived progenitor cells from the neural retina of the domestic pig and transplanted them to the laser-injured retina of allorecipients. Prior to grafting, immunocytochemical analysis showed that cultured porcine RPCs widely expressed neural cell adhesion molecule, as well as markers consistent with immature neural cells, including nestin, Sox2, and vimentin. Subpopulations expressed the neurodevelopmental markers CD-15, doublecortin, beta-III tubulin, and glial fibrillary acidic protein. Retina-specific markers expressed included the bipolar marker protein kinase C alpha and the photoreceptor-associated markers recoverin and rhodopsin. In addition, reverse transcription-polymerase chain reaction showed expression of the transcription factors Dach1, Hes1, Lhx2, Pax6, Six3, and Six6. Progenitor cells prelabeled with vital dyes survived as allografts in the subretinal space for up to 5 weeks (11 of 12 recipients) without exogenous immune suppression. Grafted cells expressed transducin, recoverin, and rhodopsin in the pig subretinal space, suggestive of differentiation into photoreceptors or, in a few cases, migrated into the neural retina and extended processes, the latter typically showing radial orientation. These results demonstrate that many of the findings seen with rodent RPCs can be duplicated in a large mammal. The pig offers a number of advantages over mice and rats, particularly in terms of functional testing and evaluation of the potential for clinical translation to human subjects.
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| 4. |
- Kyhn, Maria Voss, et al.
(författare)
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Acute retinal ischemia caused by controlled low ocular perfusion pressure in a porcine model. Electrophysiological and histological characterisation
- 2009
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Ingår i: Experimental Eye Research. - : Elsevier BV. - 0014-4835. ; 88:6, s. 1100-1106
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to establish, and characterize a porcine model of acute, controlled retinal ischemia. The controlled retinal ischemia was produced by clamping the ocular perfusion pressure (OPP) in the left eye to 5 mm Hg for 2 h. The OPP was defined as mean arterial blood pressure (MAP) minus the intraocular pressure (IOP). It was clamped to 0-30 mm Hg by continuous monitoring of MAP and adjustment of the IOP, which was controlled by cannulation of the anterior chamber. Inner retinal function was assessed by induced multifocal electroretinography (mfERG) with comparisons of the amplitudes obtained in the experimental, left eye, and the control, right eye. Quantitative histology was performed to measure the survival of ganglion cells, amacrine cells and horizontal cells 2-6 weeks after the ischemic insult. An OPP of 5 mm Hg for 2 h induced significant reductions in the amplitudes of iN1 to 20% (CI: 13-30%), and iPr2 to 14% (95% CI: 8-22%) of their baseline values. No signs of recovery were found within the 6-week observation period. Quantitative histology revealed a highly significant reduction in the number of ganglion cells, amacrine cells and horizontal cells after the ischemic insult. This model seems to be suitable for investigations of therapeutic initiatives in diseases involving acute retinal ischemia. (C) 2009 Elsevier Ltd. All rights reserved.
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| 5. |
- Kyhn, Maria Voss, et al.
(författare)
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Delayed administration of glial cell line-derived neurotrophic factor (GDNF) protects retinal ganglion cells in a pig model of acute retinal ischemia
- 2009
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Ingår i: Experimental Eye Research. - : Elsevier BV. - 0014-4835 .- 1096-0007. ; 89:6, s. 1012-1020
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Tidskriftsartikel (refereegranskat)abstract
- This study investigates whether intravitreal administration of glial cell line-derived neurotrophic factor (GDNF) enhances survival of NeuN positive retinal cells in a porcine model of retinal ischemia. 16 pigs were subjected to an ischemic insult where intraocular pressure was maintained at 5 mmHg below mean arterial blood pressure for 2 h. The mean IOP during the ischemic insult was 79.5 mmHg (s.e.m. 2.1 mmHg, n = 15). Three days after the insult the pigs received an intravitreal injection of GDNF microspheres or blank microspheres. The pigs were evaluated by way of multifocal electroretinography (mfERG), quantification of NeuN positive cells and evaluation of the degree of retinal perivasculitis and inflammation 6 weeks after the insult. In the post-injection eyes (days 14, 28 and 42), the ratios of the iN1 and the iP2 amplitudes were 0.10 (95% CI: 0.05-0.15) and 0.09 (95% CI: 0.04-0.16) in eyes treated with blank microspheres, and 0.24 (95% CI: 0.18-0.32) and 0.23 (95% CI: 0.15-0.33) in eyes treated with GDNF microspheres. These differences were statistically significant (P < 0.05). The number of NeuN positive cells in the area of the visual streak area was significantly higher in eyes injected with GDNF microspheres compared to eyes injected with blank microspheres. In eyes injected with GDNF microspheres the ganglion cell count was 9.5/field (s.e.m.: 2.1, n = 8), in eyes injected with blank microspheres it was 3.5/field (s.e.m.: 1.2, n = 7). This difference was statistically significant (P < 0.05). There was also a significant difference (P < 0.01) in the degree of perivasculiitis between GDNF treated eyes (median perivasculitis score 1.5) and blank treated eyes (median perivasculitis score 3.0). In conclusion, injection of GDNF microspheres 3 days after an ischemic insult results in functional and morphological rescue of NeuN positive cells in a porcine model of acute ocular ischemia. (C) 2009 Elsevier Ltd. All rights reserved.
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| 6. |
- Lavik, EB, et al.
(författare)
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Fabrication of degradable polymer scaffolds to direct the integration and differentiation of retinal progenitors
- 2005
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Ingår i: Biomaterials. - : Elsevier BV. - 1878-5905 .- 0142-9612. ; 26:16, s. 3187-3196
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Tidskriftsartikel (refereegranskat)abstract
- Retinal progenitor cells (RPCs) are self-renewing cells capable of differentiating into the different retinal cell types including photoreceptors, and they have shown promise as a source of replacement cells in experimental models of retinal degeneration. We hypothesized that a biodegradable polymer scaffold could deliver these cells to the subretinal space in a more organized manner than bolus injections, while also providing the graft with laminar organization and structural guidance channels. We fabricated highly porous scaffolds from blends of poly(L-lactic acid) and poly(lactic-co-glycolic acid) using a variety of techniques to produce pores oriented normal to the plane of the scaffold. RPCs were seeded on the polymer scaffolds and cultured for 14 days. Seeded scaffolds were then either fixed for characterization or used in an explant or in vivo rat model. The, scaffolds were fully covered by RPCs in 3 days. Attachment of RPCs to the polymer scaffold was associated with down-regulation of immature markers and up-regulation of markers of differentiation. This suggests that the scaffold may promote differentiation of RPCs. The seeded cells elaborated cellular processes and aligned in the scaffold in conjunction with degenerating retinal explants. The cells also exhibited morphologies consistent with photoreceptors including a high degree of polarization of the cells. This data suggests that the scaffold may be a means to assist in the promotion of photoreceptor phenotypes. Implantation of the seeded scaffold into the rat eye is associated with increased RPC survival. Taken together, these data suggest that these polymer scaffolds provide a useful means for delivering RPCs to the subretinal space and may assist in the formation of retinal cell phenotypes, although it is clear that more cues are needed to direct the differentiation of RPCs into functional photoreceptors.
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| 7. |
- Warfvinge, Karin, et al.
(författare)
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Retinal progenitor cell xenografts to the pig retina: immunological reactions.
- 2006
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Ingår i: Cell Transplantation. - 1555-3892. ; 15:7, s. 603-612
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Tidskriftsartikel (refereegranskat)abstract
- We evaluated the host response to murine retinal progenitor cells (RPCs) following transplantation to the subretinal space (SRS) of the pig. RPCs from GFP mice were transplanted subretinally in 18 nonimmunosuppressed normal or laser-treated pigs. Evaluation of the SRS was performed on hematoxylin-cosin (H&E)-stained sections. Serum samples were taken from naive and RPC-grafted pigs and mouse-reactive antibody responses were assessed. At 1 week, histology showed a few perivascular lymphocytes consistent with a mild retinal vasculitis, and depigmentation of the RPE with large numbers of mononuclear inflammatory cells in the choroid near the transplantation site. Large choroidal infiltrates were evident at 2-5 weeks. Serum from naive and RPC-xenografted pigs contained significant levels of preformed IgG and IgM antibodies against murine antigens. Xenogeneic RPCs transplanted to the porcine SRS induced mononuclear infiltration in the choroid with graft rejection occurring over 2-5 weeks. Serum analysis confirmed that mice and pigs are discordant species; however, a cell-mediated acute mechanism appears to be responsible, rather than an antibody-mediated rejection.
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| 8. |
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