Modelling of Progressive Multiple Sclerosis like cortical pathology in mice

Bhavya Ojha

Research output: ThesisPh.D. thesis

Abstract

Multiple sclerosis (MS) is an autoimmune demyelinating disease of the central nervous system (CNS). MS is an inflammatory disease mediated by infiltrating B cells, T cells and macrophages. The pathology of the CNS in MS includes axonal damage, demyelinated lesions in both white and gray matter, with varying degrees of gliosis. There are three different clinical courses for the disease. These are relapsing-remitting
MS (RRMS), secondary progressive MS (SPMS) and primary progressive MS (PPMS). RRMS and SPMS are thought to not be isolated, but are considered a continuum with transition from one to another. Most patients diagnosed with RRMS will develop SPMS. Progression from RRMS to SPMS involves reduction of neuroinflammation, relative restoration of blood-brain barrier (BBB) integrity, and loss of brain volume. Leptomeningeal inflammation, which also contributes to the exacerbation of subpial cortical demyelinated lesions, is also a hallmark of PMS. The treatments approved for RRMS are largely ineffective against PMS, reflecting differing underlying pathological mechanisms. Current knowledge of PMS is largely based on autopsy material, and our understanding of disease triggers and mechanisms is limited. Animal models contribute to understanding disease pathology and development of therapeutic agents. It is difficult to model a multifaceted and complex disease like MS in a single animal model. The aim of this PhD project was to develop models for cortical pathology supplemented with meningeal inflammation in mice.

In the first study, I have developed a model to investigate subpial cortical pathology and focal demyelination in mice. Feeding mice with cuprizone causes cortical inflammation as well as diffuse demyelination. These were exacerbated by injection of a mixture of proinflammatory cytokines into the subarachnoid space. Injection of proinflammatory cytokines induced meningeal inflammation. Lesions were localized to the subpial cortex, and were characterized by activated microglia and astrocytes. This novel model included gliosis, demyelinated focal subpial cortical lesions, and meningeal inflammation.

A second model was developed using laser irradiation, which created a focal burn injury in the cortex. Resulting lesions were characterized by activated microglia and astrocytes. Lesions resolved after a few days. To create a more persistent lesion, a viral vector expressing IFN-gamma was injected into cerebrospinal fluid (CSF). This resulted in lesions that lasted longer with persistent activation of microglia and astrocytes in the lesion periphery. Histological examination revealed BBB breakdown and infiltration of CD45-positive cells in the lesion. Flow cytometry analysis showed the presence of monocytes, suggesting a role for these blood-derived cells. The laserinduced lesion model is dynamic and shows progression with activated microglia and astrocytes, closely resembling PMS pathology. This provides a platform to test agents
that promote remyelinating processes in chronic models.

Finally, the role of the chemokine CXCL13 and B cells recruited to the CSF was examined. CXCL13 attracts CXCR5-positive cells, such as B cells and T-follicular helper (Tfh) cells. These cells are seen in ectopic immune aggregates present in the brain sulci of PMS patients. Although their role remains uncertain, these aggregates are implicated in PMS. Induced pluripotent stem cells (iPSC)-derived neurospheroids composed of neurons and astrocytes were used to determine the efficacy of an adenoassociated virus expressing CXCL13. Production of CXCL13 protein following transfection of neurospheroids was verified. Interaction between neurospheroids and splenocytes that include B cells and Tfh cells was also evaluated.

Efficacy of intrathecally-administered AAV vector to express CXCL13 in the CSF of mice was examined. Although infection by reporter virus was seen, CXCL13 protein was not detected in CSF, in preliminary studies. This study is continuing, with a view to understanding the role of CXCL13 in the recruitment and formation of ectopic aggregates in the leptomeninges and its role in the aggravation of cortical lesions in
PMS.

Conclusion: in this thesis I have used different methods to induce PMS pathology in mice and mouse-based models. This provides a platform for future testing of remyelinating therapies and drug delivery systems.
Translated title of the contributionModellering af progressiv multipel sklerose-lignende kortikal patologi hos mus
Original languageEnglish
Awarding Institution
  • University of Southern Denmark
Supervisors/Advisors
  • Owens, Trevor, Principal supervisor
  • Khorooshi, Reza M. H., Co-supervisor
  • Asgari, Nasrin, Co-supervisor
  • Steckelings, Muscha, Co-supervisor
Date of defence21. Feb 2024
Publisher
DOIs
Publication statusPublished - 11. Dec 2023

Note re. dissertation

Print copy of the thesis is restricted to reference use in the Library. 

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