Développement d'un modèle murin de la maladie de Parkinson par augmentation compensatoire de l'arborisation axonale dopaminergique-nigrostriée
Dopaminergic neurons of the substantia nigra (SNc) are amongst the most vulnerable to neurodegeneration in Parkinson's disease and its animal models. According to previous work and preliminary results in our laboratory, our present hypothesis postulates that the large axonal arborisation size of SNc neurons is a key driving factor in their vulnerability, since this characteristic is associated with increased oxidative phosphorylation levels and free radicals production. In agreement with this hypothesis, other dopaminergic populations with smaller axonal arbors better resist to experimental lesions and to the disease process in humans. The current project aims to develop a mouse model in which SNc neurons present an axonal arborisation of increased size, closer to what is encountered in humans, thus reproducing their vulnerability, which could represent an important breakthrough in the identification of new therapeutic approaches. Based on compensatory axonal sprouting of dopaminergic neurons following partial lesions, the method used was the unilateral intranigral injection of the toxin 6-hydroxydopamine (6-OHDA) at an early age (P5), to induce the loss of approximately 50% of SNc neurons. Immunostaining against tyrosine hydroxylase (TH), an enzyme required for the synthesis of dopamine, TH signal quantification in the striatum and stereological counting of neurons allowed for the quantification of the partial lesion and demonstrated compensatory axonal sprouting at 10 and 90 days post-lesion, with our results suggesting an early compensation. To better characterize the origin of axonal sprouting, we injected an AAV viral vector encoding a fluorescent protein (EYFP) in either the SNc or the VTA of adult animals. Our results confirm the presence of nigrostriatal neurons with increased arborisation sizes following early unilateral lesion using 6-OHDA, whose increased vulnerability will be evaluated in future experiments through lesion protocols using MPTP, a toxin used to model Parkinson's disease in mice.
Dopamine 6-hydroxydopamine Animal Model Parkinson's disease Animal Model Vulnerability Axonal Arborisation Substantia Nigra Ventral Tegmental Area Compensatory Sprouting