Pied, Valentin
(2023)
Iris Pigmented Epithelial Stem Cells as a Strategy to Treat Age-related Macular Degeneration.
PhD thesis, University of Liverpool.
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Abstract
The existence of iris pigmented epithelial stem cells has been hypothesised in the end of the 90s when ophthalmologists and scientists started to compare the iris pigmented epithelium (IPE) and the retinal pigmented epithelium (RPE). Early investigations demonstrated functional similarities between both tissues in various models, in which IPE cells were able to integrate the RPE without subsequent issues and proved RPE rescue effect. Over investigations, IPE cells demonstrated a certain phenotypic plasticity as neurons and photoreceptors were also generated in vitro. These early works brought the possibility that IPE cells could replace RPE cells in non-exudative age-related macular degeneration (AMD), a progressive and permanent loss of vision without therapeutic options until our days. However, no IPE stem cells were identified so far and their existence remain hypothetic until today. Stem cells therapies aim to replace degraded tissues with cell grafts developed in vitro. Intense research is dedicated to develop RPE grafts with some clinical trials already completed, which demonstrated abilities to stabilise the vision. Therefore, the identification of IPE stem cells is of interest in a clinical perspective as it is biologically close to the RPE, so potential development would not have prohibitive cost while a therapy could be developed in a personalised manner, so the patient would provides its own stem cells to treat its affection. Histological investigations defined some native features of the porcine IPE. Smooth muscle proteins composed the anterior layer, conjugated with a global flexible cytoskeleton. The basal lamina surrounds the porcine IPE, its composition varying according to the cell functions. Finally, cell proliferation occurs mainly in and near the ciliary body-IPE junction, where proteins associated with multipotency were observed. IPE cells were then processed in vitro as neurospheres. Spheres obtained were resulting from cell aggregation and not clonal proliferation. Specific neuronal proteins were observed in some aggregates. Follow-up investigations revealed the upregulation of cell transformation-associated pathways and the downregulation of RPE development associated ones after the switch from generic FBS & adherent-based conditions to a specific neurosphere culture environment. Neuronal cell culture using B27 supplement was then used. Four subsequent cell types were commonly observed: epithelial-like cells/fibroblasts-like, neurons-like and a third undefined group. Small epithelial-like cells morphologically close to induced-pluripotent stem cells (iPSC) were observed in medium supplemented with 2X B27. However, lab constraints did not allow to characterise them more. Collectively, these data confirmed that the porcine IPE tissue conducts smooth muscular functions in vivo. The tissue seems to preserve its homeostasis by maintaining proliferation in its periphery, where cells express neuronal multipotent-associated proteins. The ability to transform into other cells was then observed in vitro. No stem cells were identified but further investigations shall follow this work as the small epithelial-like may be IPE stem cells.
| Item Type: | Thesis (PhD) |
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| Uncontrolled Keywords: | Iris pigmented epithelium; stem cells; characterisation |
| Divisions: | Faculty of Health and Life Sciences Faculty of Health and Life Sciences > Institute of Life Courses and Medical Sciences |
| Depositing User: | Symplectic Admin |
| Date Deposited: | 13 Feb 2024 16:00 |
| Last Modified: | 13 Feb 2024 16:00 |
| DOI: | 10.17638/03177800 |
| Supervisors: |
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| URI: | https://livrepository.liverpool.ac.uk/id/eprint/3177800 |
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