Brain Cells Once Ignored Could Unlock New Neurological Treatments

The Brain’s Janitorial Staff Just Got a Promotion

For decades, if you asked a neuroscientist what makes the brain tick, they’d point to neurons. The flashy cells. The ones that fire electrical signals, build networks, and store memories. Everything else was just packing material. Structural support. Brain glue.

That glue has a name: astrocytes. Star-shaped cells that outnumber neurons in some brain regions. For most of the 20th century, they were treated as the brain’s janitorial staff. They clean up debris. They hold things together. They keep the place from collapsing.

But a 2023 paper in Signal Transduction and Targeted Therapy flips that script completely. The authors, led by Alexei Verkhratsky at the University of Manchester, along with Arthur M. Butt, Baoman Li, and Péter Illés, argue that astrocytes are not just bystanders in neurological disease. They are central players. They can drive disease, protect against it, or transform into something that does both at once. And that means we have been ignoring a whole class of potential treatments (Verkhratsky et al., 2023).

The paper is a sweeping review of astrocyte biology across dozens of human disorders. But its core argument is simple and radical: if you want to fix a broken brain, you might need to start by fixing its janitors.

What Exactly Are Astrocytes?

Astrocytes are glial cells. Glia comes from the Greek word for glue. For a long time, that name felt accurate. They fill the spaces between neurons, regulate blood flow, and maintain the chemical balance of the brain. They do not fire action potentials. They do not send signals down axons. They just sit there, quietly, doing housekeeping.

But in the last twenty years, the picture has changed. Astrocytes are now known to communicate with neurons using calcium signals. They release molecules called gliotransmitters that can modulate synaptic strength. They even form networks of their own, connected by gap junctions, like a second nervous system running underneath the first.

Verkhratsky and his colleagues take this further. They classify astrocyte dysfunction into four distinct categories, each with its own logic and its own potential for intervention. This is not a vague list of things that go wrong. It is a taxonomy of failure modes, each requiring a different fix.

The Four Ways Astrocytes Break

The authors describe four distinct pathological states. Think of them as four ways the janitorial staff can fail.

Reactive Astrogliosis: The Overzealous Janitor

This is the most common and best understood response. When the brain is injured, infected, or degenerating, astrocytes change shape. Their branches thicken. They start pumping out inflammatory signals. This is called reactive astrogliosis.

In the short term, it is protective. Reactive astrocytes wall off damaged areas, prevent the spread of infection, and help repair the blood-brain barrier. But when the response is chronic, it becomes destructive. The same cells that were trying to help start releasing toxic molecules that kill neurons.

The authors note that reactive astrogliosis is a hallmark of virtually every neurological disorder, from stroke to Alzheimer’s to multiple sclerosis. But here is the twist: it is not a simple on-off switch. Astrocytes can exist in multiple reactive states, some protective, some harmful. The same cell that is helping in one context can be killing in another.

Astroglial Atrophy: The Lazy Janitor

The opposite problem. Some astrocytes stop doing their jobs. They shrink. They lose their branches. They stop supporting neurons and regulating synapses.

This is surprisingly common in early stages of neurodegenerative disease. In Alzheimer’s, for example, astrocytes in certain brain regions show atrophy before neurons start dying. The authors describe this as a loss of function that creates vulnerability. If the janitors stop cleaning, the trash piles up. And in the brain, that trash includes toxic proteins like amyloid beta and tau.

Atrophy is also seen in depression, schizophrenia, and bipolar disorder. The authors suggest that this might explain why these conditions involve cognitive and emotional symptoms that are not easily tied to neuron death. The problem might be that the support system has gone quiet.

Astroglial Degeneration and Death: The Dead Janitor

Sometimes astrocytes just die. This happens in severe trauma, stroke, and some forms of epilepsy. When astrocytes die, they leave gaps in the brain’s support network. The blood-brain barrier leaks. Neurons lose their metabolic support. Inflammation spirals out of control.

This is the most straightforward failure mode. The janitors are dead, and the building falls apart.

Astrocytopathies: The Mutant Janitor

The most fascinating category. Some astrocytes do not just react, atrophy, or die. They change into something fundamentally different. They become aberrant.

The authors point to specific genetic disorders where mutations in astrocyte genes cause disease directly. Alexander disease, for example, is caused by mutations in the GFAP gene, which is expressed almost exclusively in astrocytes. The result is severe neurological dysfunction, even though the neurons themselves are genetically normal.

This category also includes cases where astrocytes develop pathological features that drive disease. In some forms of epilepsy, astrocytes develop abnormal calcium signaling that triggers seizures. In Huntington’s disease, astrocytes lose their ability to clear potassium from the extracellular space, making neurons hyperexcitable.

The key insight: these are not secondary effects of neuron damage. These are primary astrocyte failures that cause neuron damage.

Why This Matters for Treatment

The standard approach to neurological disease has been neuron-centric. If you want to treat Alzheimer’s, you target amyloid beta or tau. If you want to treat epilepsy, you target neurotransmitter receptors on neurons. If you want to treat stroke, you try to protect neurons from death.

This has not worked very well. The most successful Alzheimer’s drugs remove amyloid but barely slow cognitive decline. Epilepsy drugs work for some patients but not others. Stroke treatments have a narrow window of effectiveness.

The authors argue that we have been ignoring an entire dimension of pathology. Astrocytes are not just reacting to disease. They are part of the disease mechanism. And because they are separate cells with separate biology, they offer separate targets for intervention.

This is not a fringe idea. The paper has already accumulated nearly 400 citations. Major pharmaceutical companies are starting to fund astrocyte research. The field is moving from basic biology to translational work.

The Evidence Across Disorders

The paper reviews astrocyte pathology across a staggering range of conditions. Here is what the authors found in each major category.

Neurotrauma and Stroke

After a traumatic brain injury or stroke, astrocytes undergo rapid reactive changes. Within hours, they start expressing inflammatory genes and releasing molecules that attract immune cells. This is protective in the short term, but if it persists, it creates a toxic environment that prevents regeneration.

The authors note that in stroke, the penumbra (the tissue around the core infarct) is full of reactive astrocytes. Some of these cells are trying to save neurons. Others are actively killing them. The challenge is figuring out which is which and how to tip the balance.

Neuroinfection

In infections like meningitis or encephalitis, astrocytes are both victims and perpetrators. They are infected by pathogens, which can trigger their death. But they also mount a defensive response that can damage surrounding tissue.

The authors highlight a particularly interesting finding: in HIV-associated neurocognitive disorder, astrocytes can harbor the virus without dying. They become a reservoir. This might explain why the cognitive symptoms persist even when antiviral drugs suppress the virus in the blood.

Epilepsy

This is where the evidence gets concrete. In temporal lobe epilepsy, astrocytes in the hippocampus lose their ability to regulate potassium and glutamate. This makes neurons more excitable and more likely to seize.

The authors describe a specific mechanism: astrocytes normally express potassium channels that help clear excess potassium after neuronal firing. In epileptic tissue, these channels are downregulated. The potassium builds up. The neurons cannot repolarize properly. They fire again and again.

This is a clear, mechanistic link between astrocyte dysfunction and a specific symptom. And it suggests a treatment: restore potassium channel function in astrocytes.

Neurodevelopmental Disorders

The paper reviews evidence that astrocytes contribute to autism, schizophrenia, and intellectual disability. In some cases, this is genetic. Mutations in astrocyte genes have been linked to these conditions. In others, it is functional. Astrocytes from patients with schizophrenia show abnormal calcium signaling and reduced support for synapse formation.

The authors are careful not to overstate this. The evidence is correlative in many cases. But the pattern is consistent: when astrocytes are abnormal, brain development goes wrong.

Neurodegenerative Diseases

This is the biggest category. Alzheimer’s, Parkinson’s, Huntington’s, ALS. All of them involve astrocyte pathology.

In Alzheimer’s, astrocytes around amyloid plaques become reactive and lose their ability to clear amyloid. In Parkinson’s, astrocytes fail to protect dopamine neurons from oxidative stress. In ALS, astrocytes release toxic factors that kill motor neurons. In Huntington’s, astrocytes lose their ability to regulate glutamate, leading to excitotoxicity.

The authors argue that in each case, astrocyte dysfunction is not just a consequence of neuron death. It is a contributor. And it might be a target for intervention.

What This Does Not Prove

This is a review paper, not a single experiment. It synthesizes thousands of individual studies into a coherent framework. That is valuable, but it comes with limits.

First, much of the evidence comes from animal models. Mouse astrocytes are not identical to human astrocytes. The authors acknowledge this and note that human astrocytes are larger, more complex, and more diverse than their rodent counterparts. Treatments that work in mice might not work in humans.

Second, the field lacks specific tools. We can activate or inhibit neurons with optogenetics and chemogenetics. We cannot do the same for astrocytes as easily. This makes it hard to prove causation in living animals.

Third, the taxonomy of four pathological states is useful, but it is almost certainly incomplete. Astrocytes are heterogeneous. Different brain regions have different types of astrocytes. Different diseases might involve different subtypes. The authors note that the field is still working out the details.

Finally, the paper does not provide a specific treatment. It provides a framework for thinking about treatments. That is a step forward, but it is not a cure.

The Therapeutic Frontier

The authors end with a call to action. They argue that astrocyte biology represents a new frontier for therapeutic development. Here is what that looks like in practice.

Targeting Reactive Astrogliosis

If reactive astrocytes can be protective or harmful, the goal is not to eliminate them but to modulate them. This means identifying the signaling pathways that control the protective versus harmful states. The authors point to specific molecules: STAT3, NF-kB, and others. Drugs that target these pathways are in development.

Restoring Atrophic Astrocytes

If astrocytes have lost their function, the goal is to restore it. This might involve growth factors that promote astrocyte survival and branching. It might involve drugs that boost their metabolic support for neurons.

Preventing Astrocyte Death

In stroke and trauma, protecting astrocytes from death might be as important as protecting neurons. The authors note that astrocyte death often precedes neuron death in these conditions. Saving the janitors might save the building.

Correcting Astrocytopathies

For genetic disorders like Alexander disease, the goal is gene therapy. Replace the mutant GFAP gene with a normal one. For acquired astrocytopathies like epilepsy, the goal is to normalize astrocyte function. Restore potassium channels. Correct calcium signaling.

What This Actually Means

• ▸Astrocytes are not passive support cells. They are active participants in neurological disease. The old view that neurons are everything and glia are nothing is dead. Treatment strategies need to account for both cell types.

• ▸Different diseases involve different types of astrocyte failure. Reactive astrogliosis is not the same as atrophy. Degeneration is not the same as mutation. A treatment that works for one might not work for another. The taxonomy matters.

• ▸Astrocyte dysfunction can be primary. In some conditions, the astrocytes are the problem, not the neurons. This changes how we think about disease causation and opens up new genetic and therapeutic targets.

• ▸The tools to study astrocytes are improving. Single-cell RNA sequencing, calcium imaging, and chemogenetics are making it possible to study astrocytes with the same precision as neurons. The field is moving fast.

• ▸Treatments that target astrocytes are not science fiction. Several are in clinical trials. Some are already approved for other indications. The paper provides a roadmap for repurposing existing drugs and developing new ones.

The brain is not a collection of neurons with some glue holding them together. It is a complex ecosystem where different cell types interact, compete, and support each other. Astrocytes have been ignored for too long. The janitors have earned their place at the table.