Characterization of subventricular zone-derived progenitor cells from mild and late symptomatic YAC128 mouse model of Huntington's disease

Huntington's disease (HD) is caused by an expansion of CAG repeats in the HTT gene, leading to expression of mutant huntingtin (mHTT) and selective striatal neuronal loss, frequently associated with mitochondrial dysfunction and decreased support of brain-derived neurotrophic factor (BDNF). New neurons derived from the subventricular zone (SVZ) are apparently not able to rescue HD pathological features. Thus, we analyzed proliferation, migration and differentiation of adult SVZ-derived neural stem/progenitor cells (NSPC) from mild (6 month-old (mo)) and late (10 mo) symptomatic HD YAC128 mice expressing full-length (FL)-mHTT versus age-matched wild-type (WT) mice. SVZ cells derived from 6 mo YAC128 mice exhibited higher migratory capacity and a higher number of MAP2 + and synaptophysin + cells, compared to WT cells; MAP2 labeling was enhanced after exposure to BDNF. However, BDNF-evoked neuronal differentiation was not observed in 10 mo YAC128 SVZ-derived cells. Interestingly, 6 mo YAC128 SVZ-derived cells showed increased intracellular Ca²⁺ levels in response to KCl, which was potentiated by BDNF, evidencing the presence of differentiated neurons. In contrast, KCl depolarization-induced intracellular Ca²⁺ increase in 10 mo YAC128 SVZ-derived cells was shown to be increased only in BDNF-treated YAC128 SVZ-derived cells, suggestive of decreased differentiation capacity. In addition, BDNF-untreated NSPC from 10 mo YAC128 mice exhibited lower mitochondrial membrane potential and increased mitochondrial Ca²⁺ accumulation, in relation with NSPC from 6 mo YAC128 mice. Data evidence age-dependent reduced migration and decreased acquisition of a neuronal phenotype, accompanied by decreased mitochondrial membrane potential in SVZ-derived cells from YAC128 mice through HD symptomatic phases.