Charakterisierung der Oligodendroglia in akuten und chronischen Entmarkungsläsionen der Maus
Characterization of oligodendroglia in acute and chronic demyelinated lesions in the mouse
by Nadine Katharina Theresia Seitz
Date of Examination:2022-10-10
Date of issue:2022-09-05
Advisor:Prof. Dr. Christine Stadelmann-Nessler
Referee:Prof. Dr. Christine Stadelmann-Nessler
Referee:Prof. Dr. Francesca Odoardi
Referee:PD Dr. Sabine Sennhenn-Kirchner
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EnglishMS is a chronic inflammatory autoimmune disease of the CNS of unknown etiology associated with demyelinating lesions. In addition to chronic demyelinated lesions, there are also remyelinated areas in the CNS. Therapeutically, promoting this remyelination process is an important approach to mitigate or counteract long-term damage after relapses. Animal models can be used to elucidate certain mechanisms of MS. To study remyelination acute demyelinating animal models are largely used, in which remyelination is often very efficient. However, there is a lack of chronic models, which are important to better understand chronic MS lesions or to test remyelination-promoting or axon-protective therapies. To develop such a chronic model, we used a spontaneous double-transgenic mouse model of EAE. It is based on crossing single-transgenic mice with MOG-specific T cells and MOG antibodies. Approximately 50% of the mice spontaneously developed EAE at the age of four to eight weeks, and after disease onset they were examined at various time points. Examination after two to six days was used to assess the acute stage of disease, and examination after one, three, six, and nine months was used to assess the chronic stage of disease. After that I used histological and immunohistochemical staining to examine the demyelinating lesions within the white matter of the spinal cord. In this work, the lesion development of acute and chronic EAE lesions was analyzed. For this purpose, I determined the size of the demyelinated lesions using LFB-PAS staining. It was found that the demyelinated areas were largest in the acute stage and with increasing disease duration there was a continuous reduction in lesion extent. To determine the density of mature oligodendrocytes and their progenitor cells in the lesions, I used the markers NogoA and Olig2. When considering the acute stage, I found a loss of mature NogoA-positive oligodendrocytes. The late chronic stages were characterized by a very low density of oligodendrocytes as well as their progenitor cells. This may indicate that chronic EAE lesions no longer remyelinate. Furthermore, I examined the inflammatory activity of the lesions to find clues for possible repeated demyelination in chronic lesions. In the acute stage, I observed a high density of freshly infiltrated S100A9-positive macrophages/monocytes and foamy-cell Mac3-positive macrophages/activated microglia with phagocytosed MBP. However, the late chronic lesions showed hardly any S100A9-positive cells and phagocytosing macrophages/activated microglia. To detect possible axonal loss, I also determined axonal density using the staining Bielschowsky. In the acute stage, axonal density was decreased compared with controls. As the disease progressed, there was a further decrease in axonal density within the lesions. Inactive MS lesions are also characterized by hypocellularity, like that of oligodendroglia and macrophages/microglia, and by reduction in axon density. In conclusion, there is much to be said for an atrophy of large areas of chronic EAE lesions. However, with the methods used here, I cannot confidently rule out remyelination of small lesions or areas of lesions, particularly at their lesion margin. Further studies are needed to conclusively clarify the extent of possible remyelination during the course of EAE. Overall, the spontaneous double-transgenic mouse model of EAE offers itself as an experimental tool to study the progression from active lesions to chronic lesions and to test possible remyelination-promoting or axon-protective substances in this context.
Keywords: axon; MS; oligodendroglia; remyelination; lesion; white matter; double-transgenic mouse model; spontaneous EAE