Astrocytes generated from patient induced pluripotent stem cells recapitulate features of Huntington’s disease patient cells

Abstract

BackgroundHuntington’s Disease (HD) is a devastating neurodegenerative disorder that clinically manifests as motor dysfunction, cognitive impairment and psychiatric symptoms. There is currently no cure for this progressive and fatal disorder. The causative mutation of this hereditary disease is a trinucleotide repeat expansion (CAG) in the Huntingtin gene that results in an expanded polyglutamine tract. Multiple mechanisms have been proposed to explain the preferential striatal and cortical degeneration that occurs with HD, including non-cell-autonomous contribution from astrocytes. Although numerous cell culture and animal models exist, there is a great need for experimental systems that can more accurately replicate the human disease. Human induced pluripotent stem cells (iPSCs) are a remarkable new tool to study neurological disorders because this cell type can be derived from patients as a renewable, genetically tractable source for unlimited cells that are difficult to acquire, such as neurons and astrocytes. The development of experimental systems based on iPSC technology could aid in the identification of molecular lesions and therapeutic treatments.ResultsWe derived iPSCs from a father with adult onset HD and 50 CAG repeats (F-HD-iPSC) and his daughter with juvenile HD and 109 CAG repeats (D-HD-iPSC). These disease-specific iPSC lines were characterized by standard assays to assess the quality of iPSC lines and to demonstrate their pluripotency. HD-iPSCs were capable of producing phenotypically normal, functional neurons in vitro and were able to survive and differentiate into neurons in the adult mouse brain in vivo after transplantation. Surprisingly, when HD-iPSCs were directed to differentiate into an astrocytic lineage, we observed the presence of cytoplasmic, electron clear vacuoles in astrocytes from both F-HD-iPSCs and D-HD-iPSCs, which were significantly more pronounced in D-HD-astrocytes. Remarkably, the vacuolation in diseased astrocytes was observed under basal culture conditions without additional stressors and increased over time. Importantly, similar vacuolation phenotype has also been observed in peripheral blood lymphocytes from individuals with HD. Together, these data suggest that vacuolation may be a phenotype associated with HD.ConclusionsWe have generated a unique in vitro system to study HD pathogenesis using patient-specific iPSCs. The astrocytes derived from patient-specific iPSCs exhibit a vacuolation phenotype, a phenomenon previously documented in primary lymphocytes from HD patients. Our studies pave the way for future mechanistic investigations using human iPSCs to model HD and for high-throughput therapeutic screens.

Astrocyte pathology and the absence of non-cell autonomy in an induced pluripotent stem cell model of TDP-43 proteinopathy

“…Propagating NPCs with LIF and EGF, but without FGF2, promoted glial commitment and expansion and resulted in efficient APC fate specification within 6 wk (33)(34)(35)(36). A number of methodologies derive astroglia from pluripotent cells with varying levels of function and purity (37)(38)(39)(40). The protocol described here achieves functional astrocyte differentiation without serum supplementation, presenting a more chemically defined and comparatively faster alternative to other methods (37).…”

“…A number of methodologies derive astroglia from pluripotent cells with varying levels of function and purity (37)(38)(39)(40). The protocol described here achieves functional astrocyte differentiation without serum supplementation, presenting a more chemically defined and comparatively faster alternative to other methods (37). The resulting astroglial populations have low numbers of neuronal cells (<2%), enabling the study of astroglial survival, function, and biochemistry in near-homogenous populations.…”

Astrocytic transporters in Alzheimer's disease

“…In recent years investigators have developed methods to derive and maintain astrocytes from patient iPSCs (261)(262)(263). The question as to whether these cells truly represent functioning astrocytes in aged human brains remains to be answered (264).…”

Experimental Models for Identifying Modifiers of Polyglutamine-Induced Aggregation and Neurodegeneration

“…In addition, embryonic and neural stem cells from HD mouse models have also been characterized and could serve as critical bridging tools for supporting preclinical translational studies [132,133]. Initial studies showed no differences in the ability of HD iPSCs to differentiate into neurons [123,134,135].…”