Advances in the Differentiation of hiPSCs into Cerebellar Neuronal Cells

The cerebellum has historically been primarily associated with the regulation of precise motor functions. However, recent findings suggest that it also plays a pivotal role in the development of advanced cognitive functions, including learning, memory, and emotion regulation. Pathological changes in the cerebellum, whether congenital hereditary or acquired degenerative, can result in a diverse spectrum of disorders, ranging from genetic spinocerebellar ataxias to psychiatric conditions such as autism, and schizophrenia. While studies in animal models have significantly contributed to our understanding of the genetic networks governing cerebellar development, it is important to note that the human cerebellum follows a protracted developmental timeline compared to the neocortex. Consequently, employing animal models to uncover human-specific molecular events in cerebellar development presents significant challenges. The emergence of human induced pluripotent stem cells (hiPSCs) has provided an invaluable tool for creating human-based culture systems, enabling the modeling and analysis of cerebellar physiology and pathology. hiPSCs and their differentiated progenies can be derived from patients with specific disorders or carrying distinct genetic variants. Importantly, they preserve the unique genetic signatures of the individuals from whom they originate, allowing for the elucidation of human-specific molecular and cellular processes involved in cerebellar development and related disorders. This review focuses on the technical advancements in the utilization of hiPSCs for the generation of both 2D cerebellar neuronal cells and 3D cerebellar organoids.

Mesenchymal Stem Cell Therapy in the Treatment of Neurodegenerative Cerebellar Ataxias: a Systematic Review and Meta-analysis

The objective of this study is to synthesise the findings of clinical studies in order to derive evidence for use of the mesenchymal stem cell (MSC) therapy in the treatment of neurodegenerative cerebellar ataxias. In order to find relevant studies for the systematic review, we searched through Medline (1985 to July 2020), PubMed and Clinical trial register. We included both single-arm and comparative studies in which MSCs were given as intervention in neurodegenerative ataxia patients at any time after the diagnosis. We used Joanna Briggs Institute (JBI) quality scale to evaluate the methodological qualities of the included studies. Our literature search obtained 81 publications. Three articles comprising a total of 47 patients were included in the meta-analysis. None of them were randomised controlled trials (RCTs). Pooled analysis noted that there was a decrease in the Berg Balance Scale (BBS)/Scale for the Assessment and Rating of Ataxia (SARA) score from pre to post assessment; however, the difference was statistically not significant (standardised mean difference (SMD) - 0.20; 95% CI - 0.78 to 0.38). No significant side effects were reported in any of the studies. We did not observe any statistically significant difference in the pooled mean difference in the International Cooperative Ataxia Rating Scale (ICARS) score between pre and post assessment in patients with ataxia after receiving the stem cells (SMD 0.36, 95% CI - 0.08 to 0.81). Our systematic review and meta-analysis concluded that MSC cell therapy appeared safe but provided insufficient evidence to support the use of MSCs to treat patients with neurodegenerative cerebellar ataxia at present. No l RCTs was available in the literature to test efficacy; therefore, well-designed RCTs are needed to ascertain the effectiveness of MSCs in patients with neurodegenerative cerebellar ataxias.

In Vitro Models of the Human Blood-Brain Barrier Utilising Human Induced Pluripotent Stem Cells: Opportunities and Challenges

The blood-brain barrier (BBB) is a component of the neurovascular unit formed by specialized brain microvascular endothelial cells surrounded by astrocytes end-feet processes, pericytes, and a basement membrane. The BBB plays an important role in the maintenance of brain homeostasis and has seen a growing involvement in the pathophysiology of various neurological diseases. On the other hand, the presence of such a barrier remains an important challenge for drug delivery to treat such illnesses.Since the pioneering work describing the isolation and cultivation of primary brain microvascular cells about 50 years ago until now, the development of an in vitro model of the BBB that is scalable, capable to form tight monolayers, and predictive of drug permeability in vivo remained extremely challenging.The recent description of the use of induced pluripotent stem cells (iPSCs) as a modeling tool for neurological diseases raised momentum into the use of such cells to develop new in vitro models of the BBB. This chapter will provide an exhaustive description of the use of iPSCs as a source of cells for modeling the BBB in vitro, describe the advantages and limitations of such model, as well as describe their prospective use for disease modeling and drug permeability screening platforms.

Short Review: Investigating ARSACS: models for understanding cerebellar degeneration

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is an early-onset neurodegenerative disease that includes progressive cerebellar dysfunction. ARSACS is caused by an autosomal recessive loss-of-function mutation in the SACS gene, which encodes for SACSIN. Although animal models are still necessary to investigate the role of SACSIN in the pathology of this disease, more reliable human cellular models need to be generated to better understand the cerebellar pathophysiology of ARSACS. The discovery of human induced pluripotent stem cells (hiPSC) has permitted the derivation of patient-specific cells. These cells have an unlimited self-renewing capacity and the ability to differentiate into different neural cell types, allowing studies of disease mechanism, drug discovery and cell replacement therapies. In this study, we discuss how the hiPSC-derived cerebellar organoid culture offers novel strategies for targeting the pathogenic mutations related to ARSACS. We also highlight the advantages and challenges of this 3D cellular model, as well as the questions that still remain unanswered.

Recent advances in modelling of cerebellar ataxia using induced pluripotent stem cells

The cerebellar ataxias are a group of incurable brain disorders that are caused primarily by the progressive dysfunction and degeneration of cerebellar Purkinje cells. The lack of reliable disease models for the heterogeneous ataxias has hindered the understanding of the underlying pathogenic mechanisms as well as the development of effective therapies for these devastating diseases. Recent advances in the field of induced pluripotent stem cell (iPSC) technology offer new possibilities to better understand and potentially reverse disease pathology. Given the neurodevelopmental phenotypes observed in several types of ataxias, iPSC-based models have the potential to provide significant insights into disease progression, as well as opportunities for the development of early intervention therapies. To date, however, very few studies have successfully used iPSC-derived cells to model cerebellar ataxias. In this review, we focus on recent breakthroughs in generating human iPSC-derived Purkinje cells. We also highlight the future challenges that will need to be addressed in order to fully exploit these models for the modelling of the molecular mechanisms underlying cerebellar ataxias and the development of effective therapeutics.