Neurons can be cultured outside a living organism in a laboratory setting, a process known as in vitro neuronal culture. This technique provides researchers with a controlled environment to investigate the nervous system’s complexities. Studying neurons in isolation allows for observations and manipulations often unfeasible within a living animal or human body. Maintaining these delicate nerve cells outside their natural environment requires precise conditions and intricate procedures.
Sources of Neurons for Culture
Scientists obtain neurons for culturing from various sources, each offering distinct advantages. One common method involves primary neuronal cultures, where cells are harvested directly from animal tissue, often from the embryonic or neonatal brains of rodents like mice or rats. Using embryonic or young tissue is beneficial because the neurons are in developmental stages, making them adaptable to the artificial culture environment and capable of forming new connections.
A newer source for neuron cultures comes from stem cells, especially induced Pluripotent Stem Cells (iPSCs). These iPSCs can be generated from adult human cells, like those found in skin or blood, through genetic reprogramming. Once created, these patient-specific iPSCs can be guided to differentiate and mature into various types of neurons. This allows researchers to create human neuron models reflecting individual genetic backgrounds, addressing ethical and species-specific limitations of animal-derived cultures.
Creating a Viable In Vitro Environment
After neurons are acquired, establishing a suitable in vitro environment is paramount to keeping them alive and functional. Neurons require specific physical and chemical conditions to thrive, as they cannot simply grow on plain plastic surfaces. Culture dishes are coated with adhesive molecules, such as poly-L-lysine or laminin, which mimic the body’s extracellular matrix. These coatings provide a sticky substrate that allows neurons to attach, spread, and form intricate networks.
The cells are submerged in a specialized nutrient solution known as culture medium. This medium usually begins with a basal solution like Neurobasal, enriched with a blend of supplements including amino acids, vitamins, and glucose to provide energy and building blocks. Specific growth factors like Brain-Derived Neurotrophic Factor (BDNF) and Glial Cell Line-Derived Neurotrophic Factor (GDNF) are also added. These factors are important for supporting neuronal survival, promoting their maturation, and encouraging synaptic connections.
Maintaining these cultures demands a controlled atmospheric environment within an incubator. The temperature must be kept at 37°C to match physiological conditions. High humidity is maintained to prevent medium evaporation, and the carbon dioxide (CO2) level is regulated, often at 5%, to buffer the medium and maintain a stable pH. These cultures are delicate, as most mature neurons are post-mitotic, meaning they do not divide and replace themselves, making them susceptible to contamination and environmental fluctuations.
Applications of Cultured Neurons
Cultured neurons serve as tools across various fields of neuroscience, providing platforms for investigation. One application is in disease modeling, where researchers can replicate aspects of neurological disorders in a dish. For example, iPSC-derived neurons from patients with conditions such as Alzheimer’s disease, Parkinson’s disease, or Amyotrophic Lateral Sclerosis (ALS) allow scientists to observe how the disease manifests and progresses at a cellular level. This provides direct insights into the underlying mechanisms of neurodegeneration and cellular dysfunction associated with these complex conditions.
These in vitro neuronal systems are used in drug discovery and toxicology screening. They provide a controlled environment to test thousands of potential therapeutic compounds for their efficacy or to assess their neurotoxic effects. This high-throughput screening capability allows researchers to identify promising drug candidates or harmful substances before moving to more complex and costly animal models. Such preliminary testing is efficient and reduces the need for animal experimentation.
Cultured neurons are important for fundamental neuroscience research, enabling scientists to dissect the basic biology of nerve cells. These simplified, controlled systems facilitate studies on how synapses, the communication junctions between neurons, form and function. Researchers can investigate the mechanisms of electrical signal transmission, how neural networks develop their intricate architecture, and how these networks process information. This foundational research advances our understanding of brain function and development.