The role of the immune system in Parkinson’s Disease: from neuropathology to treatment.

Parkinson’s Disease (PD) is a progressive neurodegenerative disorder characterised by progressive loss of dopaminergic neurons (DAn) in the substantia nigra. In the first part of this thesis (chapters 3-4) I describe the immune characterisation of a human embryonic stem cell (hESC)-derived dopamine neuron progenitor cell (NPC) ahead of its use in the STEM-PD clinical trial for PD. Several groups have shown that hESC-NPCs can generate mature DAn when grafted into rodent models of PD - providing targeted physiological dopamine replacement and improving motor function. hESCs offer a better source of cells than previously used foetal ventral midbrain (fVM) tissue, which provided proof of principle for the replacement of DAn in PD but was associated with ethical and logistical issues. Work using the hESC-derived NPCs has now matured into early clinical trials (including STEM-PD, a collaboration between the Barker lab, Cambridge, and Parmar lab, Lund), however it remains unclear whether grafts of this type will trigger a host immune response leading to rejection. Immune characterisation was performed comparing the NPCs to the undifferentiated RC17 hESCs and the mature DAn, as well as previously well-tolerated fVM tissue. I observed no significant immune response to the NPCs in several *in vitro* assays (PBMC/T cell co-cultures or monocyte-derived dendritic cell co-culture assays), despite their low expression of MHC-class I (which is up-regulated in response to IFNγ). Instead, NPCs appeared immunosuppressive; reducing T cell proliferation and CD25 expression in vitro. While I was not successful in determining the mechanism of suppression, I found it to be largely contact dependent, direct (not requiring T regulatory cells or antigen presentation cells) and not due to IDO-1/tryptophan metabolism, the production of immunoregulatory adenosine or expression of any of the tested co-inhibitory molecules, as has been reported for other PSC-derived products. Cytokine assays revealed some evidence of a T cell response to co-culture with the different cell types, though definitive results were limited by large variability seen across biological replicates. Transcriptomic analysis of the NPCs through their differentiation from ESC to mature DAn (+/- inflammatory stimuli) and the fVM revealed similarities between the NPCs and fVM confirmed by hierarchical clustering analyses, with both cell types mounting a strong upregulation of MHC-I antigen presentation pathways in response to IFNγ stimulation. Differences in the expression of potentially immunoregulatory and immunogenic molecules across cell type, differentiation stage and baseline/inflammatory conditions were also observed. In the second part of this thesis (chapter 5) I explored the regional inflammatory environment of the PD brain using post-mortem samples. While the immune system has been heavily associated with PD pathogenesis and progression, it is still not well defined, and most studies have focused on the local environment around DAn loss and the substantia nigra. Here, I examined four regions of the brain: the prefrontal cortex (PFC; thought to be relatively unaffected in PD), the amygdala (in which microglial activation has been previously reported), the putamen (the site of transplant for the hESC-NPCs in PD cell therapy and more broadly the site innervated by the A9 dopamine neurones typically lost in PD), and the substantia nigra (SN; the major region of neurodegeneration in PD). Using two Nanostring nCounter panels for neuroinflammation and glial profiling (totalling ~1300 genes), I found regional differences in the immune signatures of the PD brain compared to controls, with the strongest inflammatory signature seen in the amygdala and evidence of microglial activation in the putamen, which has not been previously reported. Gene expression and pathway analysis suggested a switch from homeostatic, protective microglia to activated, pro-inflammatory microglia. The PFC and SN showed little to no immune signatures, and instead showed upregulation of genes associated with cell stress, damage, and hypoxia. While further exploration is required (and will be performed throughout my planned post-doctoral projects), these data confirm evidence of regional pathology and immune involvement in PD.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2023

Author dc:creator

• Curle, Annabel

Advisor dc:contributor.advisor

• Jones, Joanne

• Cell therapy
• Immune response
• Microglia
• Neuroinflammation
• Parkinson's

Licence

• https://www.repository.cam.ac.uk/bitstreams/610aa6a4-23ed-4d9d-81e8-ce2d6a2f7073/download
• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.101955

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/358163