Cell replacement therapies
One treatment option being investigated is stem cell therapy, which attempts to replace dead tissue by transplanting stem cells into affected region and either stimulating them to differentiate into the desired cell types or allowing them to stimulate endogenous regenerative mechanisms. These techniques are of interest to researchers as a possible treatment for neurodegenerative diseases, but currently are of limited success in animal models, and in in-vitro cell culture studies. The ability for grafted cells to integrate into the desired tissue and adjust for the unique pathologies of different neurodegenerative disorders can be a severe limitation on the development of stem cell based treatments. Further, the tissues in the brain often rely on intricate and complicated arrangements of neurons; regions of the brain that do not require precision in these patterns to function, like the striatum affected by Parkinsons disease which uses paracrine signaling, tend to have better results in stem cell therapies than systems that require precision, like the cerebellum and pons. Stem cell therapies can be especially difficult in replacing Purkinje neuron loss as unaffected granule cells can prevent axons reaching the deep cerebellar nuclei with which Purkinje cells interface. Despite these difficulties, grafted neural precursor cells have been shown to be viable and to successfully migrate into desired location in SCA1 transgenic mice models and mesenchymal stem cells have been shown to mitigate loss of dendritic arborization SCA1 mice.
Spinocerebellar ataxia type 1 (SCA1) is a rare autosomal dominant disorder, which, like other spinocerebellar ataxias, is characterized by neurological symptoms including dysarthria, hypermetric saccades, and ataxia of gait and stance. This cerebellar dysfunction is progressive and permanent. First onset of symptoms is normally between 30 and 40 years of age, though juvenile onset can occur. Death typically occurs within 10 to 30 years from onset. SCA1 is typically inherited from the parents in an autosomal dominant regime; the children of a person with the disease have a 50% chance of inheriting it themselves, and new mutations can occur in some cases. It is caused by an expanded number of trinucleotide repeats in the polyglutamine tract of the ATXN1 gene, which encodes the ataxin 1 protein. This expansion results in a larger than normal number of repeats of the nucleotide sequence cytosine, adenine, guanine, or CAG, in the gene which, in turn, results in a larger than normal number of consecutive glutamine amino acid residues in the protein. This mutant protein causes degradation in certain types of neurons, like Purkinje neurons, which are common in the cerebellum, spinal cord, and related parts of the brain. While the mechanism is not fully understood, it is suspected that changes in the interactions between ataxin 1 and other proteins result in a toxic gain of function. The mutation can be detected before or after the onset of symptoms by genetic testing.