The SH-SY5Y cell line is a human-derived model frequently used in laboratories to study the nervous system and its disorders. These cells originate from a neuroblastoma, a type of childhood cancer, but they possess characteristics that allow them to mimic neurons in a controlled environment. Its use provides a consistent and accessible platform for exploring the complex cellular processes underlying human neurological function and dysfunction, making it a foundational tool for investigating neurodegenerative diseases and screening for neurotoxic compounds.
Origin and Identity of SH-SY5Y
The SH-SY5Y cell line has a specific and well-documented lineage, beginning with a bone marrow biopsy taken from a four-year-old female patient with neuroblastoma in 1970. This initial sample led to the establishment of the parent cell line, known as SK-N-SH. Neuroblastoma is a cancer of immature nerve cells, or neuroblasts, often originating in the adrenal glands or sympathetic nervous system.
The SH-SY5Y line is not the original SK-N-SH line, but rather a subclone isolated through a rigorous process of selection. Researchers performed three successive subcloning steps, first producing SH-SY, then SH-SY5, and finally the SH-SY5Y line, which was first described in 1978. This selection process aimed to isolate cells that exhibited the most pronounced neuroblast-like characteristics.
These cells are genetically female and maintain a neuroblast-like phenotype. They exhibit some key enzymatic activities characteristic of catecholaminergic neurons, such as moderate dopamine-beta-hydroxylase activity.
Unique Cellular Characteristics
The most distinguishing feature of the SH-SY5Y cell line is its plasticity, or the capacity to undergo neuronal differentiation. In their undifferentiated state, the cells are highly proliferative, growing in clumps and expressing markers indicative of immature neurons. However, researchers can manipulate the culture conditions to induce a shift to a more mature, neuron-like phenotype.
This differentiation process is commonly achieved by treating the cells with compounds like retinoic acid (RA), a derivative of vitamin A. Retinoic acid induces morphological changes, causing the cells to cease rapid division and extend long, branching structures known as neurites, which resemble axons and dendrites. The differentiated cells also begin to express mature neuronal markers, such as the growth-associated protein GAP-43 and synaptophysin, a protein found in synaptic vesicles.
Different differentiation protocols can be used to select for specific neuronal subtypes, which is a significant advantage for targeted research. For instance, treatment with retinoic acid followed by brain-derived neurotrophic factor (BDNF) can yield a more cholinergic phenotype, which is relevant for Alzheimer’s disease research. Conversely, other methods involving phorbol esters can promote a more dopaminergic phenotype, which is highly useful for Parkinson’s disease models.
Primary Roles in Neuroscience Research
The SH-SY5Y cell line is extensively utilized to model human neurodegenerative diseases because of its human origin and ability to differentiate into neuron-like cells. Researchers often use these cells to study Parkinson’s disease, as the differentiated line can express dopaminergic markers like tyrosine hydroxylase, the enzyme responsible for synthesizing dopamine. By treating the cells with neurotoxins such as 6-hydroxydopamine or rotenone, scientists can induce cellular damage that mimics the mitochondrial dysfunction and oxidative stress observed in Parkinson’s pathology.
For Alzheimer’s disease research, SH-SY5Y cells are employed to investigate the mechanisms of amyloid-beta toxicity. Researchers can introduce the toxic amyloid-beta peptide into the culture medium to observe its effects on cell viability, apoptosis, and the regulation of key proteins involved in the disease. The cells’ response to this induced toxicity provides insights into the molecular pathways that lead to neuronal death in Alzheimer’s patients.
The cell line is also a standard model for neurotoxicity screening, allowing for the rapid assessment of environmental toxins, pesticides, and new drug candidates for potential harmful effects on the nervous system. For example, studies have used SH-SY5Y cells to test the cytotoxic effects of herbicides like glyphosate, providing evidence of their impact on neuronal development and pathways related to oxidative stress.
Culturing and Experimental Considerations
The practical use of SH-SY5Y cells requires attention to specific culture conditions to ensure experimental consistency. Cells are typically grown in a mixture of Dulbecco’s Modified Eagle Medium (DMEM) and Ham’s F12 medium, supplemented with fetal bovine serum (FBS) to provide necessary growth factors. The cells are maintained in a standard incubator environment at 37 degrees Celsius with five percent carbon dioxide.
A significant challenge in working with this line is the inherent heterogeneity of the culture. Even in their undifferentiated state, the cells can exhibit two distinct morphologies: neuroblast-like cells and epithelial-like cells, which can interconvert spontaneously. Furthermore, SH-SY5Y cells are known to be genetically unstable, possessing an abnormal chromosome 1, which can lead to variability in results across different laboratories or even between different passages of the same cell line.
Researchers must also be mindful of the passage number, as the cells can lose some neuronal characteristics, such as noradrenaline uptake, after too many cycles of propagation. To mitigate this variability, it is recommended to conduct experiments with cells at low passage numbers and to routinely verify the expression of specific neuronal markers. The ability to differentiate the cells also helps to synchronize the cell cycle, leading to a more homogenous population for experiments targeting mature neuronal function.