Multimodally trackable and clinically translatable platform for modelling human demyelinating brain diseases by temporally dispersed chemically induced lesions in thepig brain

Abstract

BackgroundDespite advances in therapy, inflammatory demyelinating diseases of the central nervous system, such as multiple sclerosis, remain important causes of morbidity among young adults. Translation of remyelinating paradigms from current murine models is encumbered by the small size and low white matter content of the brains, limiting the spatial resolution of diagnostic imaging. Large animal models might be more suited for this purpose but pose significant technological, ethical and logistical challenges. MethodWe induced reversible and targeted cerebral demyelinating lesions by controlled injection of lysophosphatidylcholine in the minipig brain. One strength of the approach is the serial induction, allowing parallel imaging of successive stages of de-/remyelination. FindingsWe demonstrate controlled, clinically unapparent, reversible and multimodally trackable brain white matter demyelination in a large animal model. Lesions were amenable to follow-up using the same clinical imaging modalities (3T magnetic resonance imaging, 11C-PIB positron emission tomography) and standard histopathology protocols as for human diagnostics, as well as electron microscopy to compare against biopsy data from two patients with cerebral demyelination. InterpretationBy employing human diagnostic tools and validating the model against data from related human diseases, our platform overcomes one important translational barrier of current animal brain demyelination models while having the potential for developing diagnostic procedures and imaging biomarkers. Remyelination and axon preservation dynamics diverge from classical rodent models. FundingThis work was supported by the DFG under Germanys Excellence Strategy within the framework of the Munich Cluster for Systems Neurology (EXC 2145 SyNergy, ID 390857198) and TRR 274/1 2020, 408885537 (projects B03 and Z01). Research in contextO_ST_ABSEvidence before this studyC_ST_ABSInflammatory demyelinating diseases of the central nervous system (CNS), targeting primarily the white matter (WM) of the brain and spinal cord, such as multiple sclerosis (MS), still represent some of the most important non-traumatic causes of disability in young adults. Current animal models based on murine species, for example, experimental autoimmune encephalomyelitis, have been demonstrated to reliably depict pathophysiological facets of human disease. However, they are nevertheless encumbered by the low WM content and the small size of murine brains, which still pose a translational barrier to diagnostic imaging tools used in a clinical context in human patients. Minipigs are increasingly being used to model human neurological diseases, as yet primarily in the context of neurodegenerative disorders. Added value of this studyHere, we establish a platform for Minipig Stereotactic White-matter Injection using Navigation by Electromagnetism (MiniSWINE) and validate such a tool in a clinical multimodal imaging and microscopy setting against biopsy and imaging data from human demyelinating disorders across different disease stages, as well as against existing and potentially emerging human diagnostic imaging. Moreover, in order to overcome the neuroanatomical challenges of stereotactic injection in the pig brain, we designed a new electromagnetic-guided tracking system whose key advantage is the direct measurement of the injection cannula tip position in situ. Another strength of our study lies in its setup, characterized by the serial induction of successive stages of de- and remyelination, allowing for multimodal assessment via imaging and histopathology or electron microscopy of multiple stages in parallel. The remyelination dynamics inferred in this context diverge from the classical rodent studies, by exhibiting incomplete remyelination at the subacute stage, persistent astroglial and microglial activation as well as a minor degree of secondary axonal degeneration. Thus, they more closely resemble human inflammatory demyelinating brain plaques. Implications of all the available evidenceWe believe that MiniSWINE links evidence from well-established demyelination-induction methods from rodent models of CNS demyelinating disorders, as well as from human imaging and biopsy data, while at the same time providing a novel platform for the potential development of diagnostic procedures, discovery of imaging biomarkers and testing of remyelinating agents in diseases such as MS. Thus, it can have particular relevance to human health in the context of future translational animal model-based research in inflammatory demyelinating disorders of the CNS. Additionally, our electromagnetic-guided injection technique may enhance stereotactic substance delivery in human neurosurgery.