Characterization of Human Huntington's Disease Cell Model from Induced Pluripotent Stem Cells

Abstract

Huntington’s disease (HD) is a dominantly inherited neurodegenerative disease caused by a CAG repeat expansion in the first exon of the gene Huntingtin (Htt). A dramatic pathological change in HD is the massive loss of striatal neurons as the disease progresses. A useful advance in HD would be the generation of a human-derived HD model to use for drug screening and understanding mechanisms of HD. We utilized the recently established human iPS cell line derived from HD patient fibroblasts to derive neuronal precursors and human striatal neurons. To achieve this goal, the differentiation of the HD-iPS cells into striatal fate required several steps. First, we generated nestin+/PAX6+/SOX1+/OCT4- neural stem cells (NSCs) from HD-iPS cells using the method of embryoid body formation. HD-NSCs were then subjected to a differentiation condition combining morphogens and neurotrophins to induce striatal lineage commitment. Striatal neuronal precursors/immature neurons stained with β-III tubulin, calbindin and GABA but not DARPP-32 (dopamine- and cyclic AMP-regulated phosphoprotein, Mr = 32,000) were produced in this step. Finally, maturation and terminal differentiation of the striatal neuronal precursors/immature neurons resulted in striatal neurons expressing markers like DARPP-32. The HD-iPS cells derived striatal neurons and neuronal precursors contain the same CAG expansion as the mutation in the HD patient from whom the iPS cell line was established. Moreover, the HD-NSCs showed enhanced caspase activity upon growth factor deprivation compared to normal NSCs (from iPS or H9 NSCs). Therefore, these differentiated cells may produce a human HD cell model useful in the study of HD mechanisms and drug screening.

Cellular Therapy and Induced Neuronal Replacement for Huntington's Disease

“…A variety of disease-specific iPS cells, including those for HD, have been generated and have already found uses in drug screening and in the investigation of disease-specific molecular pathways [58][59][60][61]. Yet these cells also comprise an important source of cells for phenotype-specific cell replacement and tissue repair.…”

Huntington's disease: Dancing in a dish

“…In the HD iPSC-based model, the derivation method, clonal discrepancy as well as the culture conditions may affect the manifestation of phenotypes. Indeed, in previously reported HD iPSC lines, only slight increases in caspase and lysosomal activity were observed [7][8][9]. Although in both reports of HD iPSCs, significant phenotypes in electrophysiology, energy metabolism and cell death were recorded, other typical HD-associated phenotypes such as oligomeric mutant HTT aggregation, formation of nuclear inclusions and preferential striatal degeneration were not observed.…”

Stem Cell Therapy: In Treatment of Neurodegenerative Diseases

“…Expansion of a CAG repeat alters the transport and release of BDFN and increases glutamate receptors, producing toxicity and oxidative stress in neuron and glial cells. 18,19 Stem-cell therapy aims to restore or preserve brain function by replacing and protecting striatal neurons. At this time, using stem cells from the delivery of trophic factors and neuroprotection to prevent disease progression seems a more achievable clinical goal in HD than neuronal replacement.…”