Transgenic minipig model of Huntington's disease exhibiting gradually progressing neurodegeneration

Abstract

Recently developed therapeutic approaches for the treatment of Huntington's disease (HD) require preclinical testing in large animal models. The minipig is a suitable experimental animal because of its large gyrencephalic brain, body weight of 70-100 kg, long lifespan, and anatomical, physiological and metabolic resemblance to humans. The Libechov transgenic minipig model for HD (TgHD) has proven useful for proof of concept of developing new therapies. However, to evaluate the efficacy of different therapies on disease progression, a broader phenotypic characterization of the TgHD minipig is needed. In this study, we analyzed the brain tissues of TgHD minipigs at the age of 48 and 60-70 months, and compared them to wild-type animals. We were able to demonstrate not only an accumulation of different forms of mutant huntingtin (mHTT) in TgHD brain, but also pathological changes associated with cellular damage caused by mHTT. At 48 months, we detected pathological changes that included the demyelination of brain white matter, loss of function of striatal neurons in the putamen and activation of microglia. At 60-70 months, we found a clear marker of neurodegeneration: significant cell loss detected in the caudate nucleus, putamen and cortex. This was accompanied by clusters of structures accumulating in the neurites of some neurons, a sign of their degeneration that is also seen in Alzheimer's disease, and a significant activation of astrocytes. In summary, our data demonstrate age-dependent neuropathology with later onset of neurodegeneration in TgHD minipigs.

Longitudinal study revealing motor, cognitive and behavioral decline in a transgenic minipig model of Huntington's disease

“…Brain degeneration was manifested by the loss of DARPP32-positive cells, activated microglia, increased level of GFAP and demyelination. The same markers of neurodegeneration were detected in a TgHD minipig model but much later, starting at 16-70 months of age (Baxa et al, 2013;Vidinská et al, 2018;Ardan et al, 2020). Enlarged ventricles were revealed in an HD knock-in model at 5 months of age.…”

“…Significant decline in walking was observed in TgHD sows at 4-5.9 years of age. We assume that this relates to the lower animal body mass index (ABMI, calculated as a ratio of an animal's weight, height and length) of TgHD sows at 6-7 years compared to that of WT sows (Ardan et al, 2020). Weight loss is a prominent feature of HD and it could facilitate the movement process in TgHD females.…”

“…Furthermore, perturbed mitochondrial function was detected in TgHD minipig muscle tissue starting at 36 months, before alteration in muscle mitochondria ultrastructure and first locomotor decline at the age of 48 months (Askeland et al, 2018;Rodinova et al, 2019). TgHD-genotype-specific significant cellular loss in the striatum and cortex, together with inclusions in the axons of some neurons, were detected at 60-70 months (5-5.8 years) (Ardan et al, 2020).…”

“…The phenotype development of the model was rather slow, and the first clear phenotype preceding the neurodegenerative one was sperm and testicular degeneration linked with mitochondria metabolism and glycolytic impairment starting at 13 months of age (Krizova et al, 2017;Macakova et al, 2016). However, reduction of DARPP32 (also known as PPP1R1B), a marker of proper function of spiny neurons, has been detected from 16 to 70 months (Baxa et al, 2013;Vidinská et al, 2018;Ardan et al, 2020). Also, other markers of neurodegeneration, such as activation of microglia and demyelination of white matter, together with mHTT gradual fragmentation, were revealed at 24 months (Vidinská et al, 2018).…”

Recent Overview of the Use of iPSCs Huntington’s Disease Modeling and Therapy

“…The known genetic mutation in HD allows researchers to create various types of disease models. Widely used animal models ranging from roundworms [24] and Drosophila [25] to large animals, such as sheep, pig [26,27], mouse [28,29], and monkey [30], have been applied to HD modeling. Among these, the most common are murine models, including both knock-in and transgenic models.…”