Neurosphere

Key takeaways

Neurosphere belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Neurosphere to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Neurosphere from memory before moving on to harder problems.

Reference excerpt

A neurosphere is a culture system composed of free-floating clusters of neural stem cells. Neurospheres provide a method to investigate neural precursor cells in vitro. Putative neural stem cells are suspended in a medium lacking adherent substrates but containing necessary growth factors, such as epidermal growth factor and fibroblast growth factor. This allows the neural stem cells to form into characteristic 3-D clusters. However, neurospheres are not identical to stem cells; rather, they only contain a small percentage of neural stem cells. The predominant use of the neurosphere is in the neurosphere assay. However, in vitro and in vivo environments have shown to have different inductive effects on precursor cells. The creation of the neurosphere assay is highly sensitive; it is still unclear as to the exact differing effects that environment produces, relative to the in vivo environment.

History Reynolds and Weiss first described the neurosphere method of investigating neural precursor cells in 1992. The method was continued through the work of Angelo Viscovi and Derek van der Kooy and colleagues.

Reynolds and Weiss In 1992, Brent A. Reynolds and Samuel Weiss attempted to isolate EGF-responsive cells from an adult mouse central nervous system (CNS). They dissociated the striata of 3 to 18-month-old mice via enzymes and plated them in a serum-free culture containing 20 ng of EGF per milliliter. After two days in vitro, most of the cells had died, but 15±2 cells for each plate were undergoing cell division. This continued for two to three days, after which the proliferating clusters of cells detached and formed a sphere of proliferating cells. After this discovery of a spherical formation of cells, the two assessed the antigenic properties of the cells within these spheres. They found that cells in the spheres were nearly all immunoreactive for nestin, an intermediate filament found in neuroepithelial stem cells. The cells were not immunoreactive for neurofilament, neuron-specific enolase (NSE), and glial fibrillary acidic protein (GFAP). After more proliferation and longer days in vitro in the presence of EGF, cells eventually became immunoreactive to neurofilament, NSE, and GFAP. The cells that had this immunoreactivity were then tested for CNS neurotransmitters with indirect immunocytochemistry. Reynolds and Weiss found that, at 21 days, in vitro cultures of spheres and associated cells contained two of the major neurotransmitters of the adult striatum. These spheres of cells that Reynolds and Weiss discovered in 1992 were the first neurosphere formations created and analyzed.

Neurosphere (Stemness) Assay The neurosphere assay examines three fundamental characteristics of neural stem cells: proliferation, self-renewal, and multipotency. Self-renewal and multipotency are the requirements for cells to be considered stem cells. The neurosphere assay, or stemness assay, has been used to confirm that neurospheres contain neural stem cells. Neurospheres are dissociated and distributed into single-cell wells to examine self-renewal through clonal analysis. A small percentage of cells reform into a secondary neurosphere. The secondary neurospheres are then transferred into a culture medium containing growth factors that promote cell differentiation. The presence of varying cell types, including neurons, astrocytes, and oligodendrocytes, confirms the multipotency of these precursor cells. The evidence of self-renewal and multipotency serves to confirm the presence of neural stem cells within neurospheres, and emphasizes that neural stem cells comprise only a fraction of the neurosphere.

Clinical Applications

Since the neurosphere assay's goal is to develop neural stem cells in vitro, the clinical applications of such an achievement can be highly beneficial. Neural stem cells that are transplanted are able to cross the blood–brain barrier and integrate themselves into the host's brain without disrupting normal function. This therapeutic application of neural stem cells derived from neurospheres is still in its infancy concerning efficacy, but it has a high potential for success in treating many diseases. Another aspect of clinical applications regarding neural stem cells is versatility. There have been neural stem cell transplants into various tissues with successful differentiation and proliferation in these tissues. This broader differentiation "spectrum" would be highly exploitable in a clinical setting. Neurospheres have also been used for peripheral nerve regeneration

Auditory Restoration Researchers are exploring the use of neural stem cells (NSCs) obtained from neurospheres to aid in the regrowth of inner ear neurons and hair cells. Hu et al. transplanted adult mice NSCs into normal and deafened inner ears of guinea pigs. Before implantation, the NSCs were treated with neurogenin 2 protein to encourage the proliferation of the intended inner ear cells. They concluded that adult NSCs were indeed able to survive and differentiate in the injured inner ear and that this type of therapy could act to restore auditory function in hearing-impaired subjects. This experiment also indicates that genetic engineering can contribute to the success of generating specific progenitor cells of interest.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Neurosphere

Start with the simplest possible case. Write down what Neurosphere claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Neurosphere before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Neurosphere ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Neurosphere

In research: Neurosphere appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Neurosphere in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Neurosphere is common in secondary-school and first-year university syllabi. It links to neighbouring topics Developmental neuroscience, so understanding it makes those chapters shorter.
In everyday life: Look for Neurosphere outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Neurosphere in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Neurosphere means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Neurosphere out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Neurosphere in simple terms?

A neurosphere is a culture system composed of free-floating clusters of neural stem cells. Neurospheres provide a method to investigate neural precursor cells in vitro.

Why does Neurosphere matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Neurosphere?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Neurosphere.