Our understanding of the central nervous system (CNS) has grown significantly in recent years. The advent of new technologies and products have enabled us to explore not only the molecular mechanisms involved in learning, development, memory formation, electrical conductivity and synaptic function but also the onset and deterioration of these systems in neurological disorders such as epilepsy, amyotrophic lateral sclerosis (ALS), Alzheimer’s, Huntington’s and Parkinson’s diseases as well as psychiatric conditions.
Modeling neural networks: from animal models to human cells
Animal models have helped elucidate primary findings in the neuroscience field however, the use of human cells has been limited due to restricted access and resources. The Nobel-prize winning discovery of induced pluripotent stem cell (iPSC) methodology in 2012 has created new opportunities. Cells derived using these protocols are typically sourced from fibroblasts or peripheral blood mononuclear cells (PBMCs). Reprogramming can then take place using either footprint-free non-integrating episomal vectors or viral transduction (e.g. Sendai) to introduce factors OCT4, SOX2, KLF4 and MYC, which induce pluripotency. Following this, cells may be differentiated into numerous cell types including several neural and glial lineages.
Human iPSCs offer a virtually unlimited resource of healthy- and patient-specific neural and glial cells for biomedical research, drug evaluation and toxicological screening. This has allowed researchers to gain a greater understanding of the characteristics of each cell type throughout the differentiation process and factors that govern the mature cell phenotype. Additionally, mature terminally-differentiated cells provide a human cell-based platform to identify novel therapeutic targets and assess the efficacy of current treatments for neurological conditions. Consequently, improving drug safety and increasing the possibility of reaching an effective regenerative medicine.
Complete complementary iPSC-derived neural cell culture systems
In all systems it is important that the in vitro differentiation mimics in vivo development. This may be achieved by culturing cells under fully-defined, xeno-free conditions while expanding stem cells, differentiating them into high-purity neuronal cell types and maintaining them long-term in vitro .
The availability of human iPSC-derived neural stem cells (NSCs), neurons, astrocytes and culture reagents such as those offered by Axol, enable researchers to generate pure cell populations for use in drug discovery and disease modeling. Cultures such as this could be used to determine the direct effect of compounds on these specific cells, or elucidate the mechanisms that occur in neuronal development or precede the onset of neurodegenerative conditions. Alternatively, they may be co-cultured for more complex analysis of the CNS in vitro .
Further precision may be achieved by generating isogenic cell lines with disease-specific mutations using technologies such as CRISPR/Cas9 gene editing. This enables a direct comparison of the cells without any confounding environmental or genetic factors that might otherwise be present in samples derived from different individuals.
Human iPSC-derived cell types in disease modeling & drug discovery
NSCs give rise to more advanced cell types such as astrocytes, oligodendrocytes and neurons that connect to form networks in the brain and spinal cord.These networks control inhibitory, modulatory or excitatory responses in the body by transmitting chemical signals (dopamine, acetylcholine, gamma aminobutyric acid (GABA), serotonin, or glutamate) across synaptic junctions.
NSCs can be differentiated into cerebral cortical neurons (CCNs). These are found in the outer layer of the brain and play an important role in learning and memory formation. Hence, degeneration of these neurons may lead to Alzheimer’s disease.
Dopaminergic neurons play an important role in network formation and dopamine transmission. The majority of these cells are located in the substantia nigra and ventral tegmental areas of the midbrain. These neurons control multiple brain functions and a broad array of behavioral processes such as mood, reward, addiction and stress. As such, a decrease in cell number or an imbalance in dopamine levels may result in motor dysfunction and deterioration such as Parkinson’s disease, attention deficit hyperactivity disorder (ADHD), psychosis or drug addiction.
Astrocytes are glial cells that function to support both the metabolic and trophic development of neurons. These cells serve a variety a well-established stage-specific functions in synaptogenesis, myelination and neuronal migration as they mature. Astrocyte dysfunction has been reported in Rett and fragile X syndromes, and Alexander’s and Alzheimer’s diseases. In addition, some conditions are associated with astrocytes from specific regions e.g. midbrain in Parkinson’s disease or ventral–spinal in ALS.
Axol offer iPSC-Derived Neural Stem Cells and Cerebral Cortical Neurons from controls and Alzheimer’s and Huntington’s disease patients. They also provide a fully-defined Xeno-Free Neural Cell Culture System that has been optimized for long-term culture of pure neuronal cell populations. Furthermore, Axol have an iPSC-Derived Dopaminergic Neuron Precursor Kit and a range of iPSC-derived astrocytes at various developmental stages including an iPSC-Derived Astrocyte Progenitor Kit and iPSC-Derived Mature Astrocytes Kit . Axol also provide a complete suite of custom cell sourcing, reprogramming, differentiation and gene-editing services for creating isogenic cell lines.