Stem Cell Therapy and Alzheimer’s Disease
As you sit here reading this article, tens of billions of nerve cells in your brain are busy at work, signalling to other neighboring neuron cells and generating electrical impulses in communication networks responsible for your comprehension of these very words. 100 billion nerve cells connected at 100 trillion points- a neuron forest that supports the hypothesis of ‘strength in numbers’, powered by signals that form the basis of your identity, thoughts and memories. Microscopic changes in the brain are happening all the time but you feel nothing of these changes, oblivious to the intrinsic action of one neuron connecting to the other, one electrical impulse passing from top to bottom, one neurotransmitter released from side A to side B. Every cell in your brain is working akin to a well-oiled factory responsible for a steady stream of production. But what if one machine breaks down and delays the production process? What if communication in the factory is delayed and leads to machinery damage over time? What will happen if the neurons in your brain are harmed and are no longer able to communicate with each other effectively?
What is Alzheimer’s?
Alzheimer’s disease is a progressive disease of the brain in which memory, thinking and behavior are impaired over time as a result of nerve cell damage and brain tissue loss. It is a form of dementia- a general term for “impaired ability to remember, think, or make decisions that interferes with doing everyday activities”. The disease eradicates the ability to think, to remember, to make informed decisions. Common symptoms normally include memory loss, difficulty reasoning, mood swings and social withdrawal. A diagnosis of Alzheimer’s is akin to a death sentence in which the patient is stripped of their very identity. It erodes away at their cognitive skills, an invasive breach made even more frightening by the patient’s unawareness of their body cells turning against them. This condition normally affects those of ages 60 and over and is believed to have a strong genetic etiology with lifestyle and environment acting as possible factors.
Nerve Cell Damage
Our brain is composed of brain cells called neurons which communicate with each other and transmit electrical impulses to other parts of the body such as organs and muscles. They communicate with each other by releasing chemical messages called neurotransmitters across synapses, which are small gaps between one neuron and the next.
In Alzheimer’s disease, as neurons are injured and break down, there is a loss of neuronal connections and a breakdown of communication, resulting in portions of the brain shrinking. Although the exact cause of neuronal cell damage is still unknown, scientists predict that the main suspects are plaques and tangles in the brain.
1. Plaques are clumps of protein fragments from beta amyloid which collect and build up between nerve cells. Beta amyloid is formed from the breakdown of a larger protein (amyloid precursor protein) and is chemically ‘sticky’, allowing them to form clumps. These clumps can disrupt and block neurotransmitters from travelling across synapses, leading to nerve cell deterioration.
2. Tangles are caused from the abnormal accumulation of another protein called tau, which forms twisted fibres. In healthy cells, straight microtubule strands in neurons help the cell transport substances but in Alzheimer’s, the strands become twisted and block synaptic communication between neurons.
Stem Cell Therapy
Currently, there is no cure for Alzheimer’s; however, scientists have found a unique approach to treating this condition with the use of stem cell therapy. Stem cells are undifferentiated cells that have the potential to develop and differentiate along different pathways into any cell type. For example, stem cells used in leukemia treatment can grow and differentiate into healthy bone marrow cells, and divide to produce copious copies of these bone marrow cells to replace the damaged ones. Therefore, their versatility and ability for autonomous cell division makes stem cells valuable for tissue growth and cell replacement.
Researchers are currently using induced pluripotent stem cells (adult stem cells that have been modified to replicate embryonic stem cells) in order to study Alzheimer’s in more detail. These stem cells can be used to grow neurons resembling those who suffer from Alzheimer’s, aiding researchers in their search towards finding new drugs to reduce tau or beta amyloid levels responsible for neuronal plaques and tangles. Another possible area of exploration is the use of mesenchymal stem cells- adult stem cells limited in their ability to differentiate. When they are introduced into the body, they have the ability to hone to injured or inflamed sites, making them strong contenders for therapeutic drug carriers. This unique ability makes mesenchymal stem cells a promising possible method to treat Alzheimer’s disease by repairing damaged neuron cells.
Challenges of stem cell therapy
However, no stem cell treatments are currently approved for Alzheimer’s despite some successful clinical trials on mice. There are a multitude of diverse neuronal functions affected by the disease and every neuron is a unique case in its own right, making it challenging for researchers to target specific problem areas collectively. As different neurons may be affected differently for each individual, successful stem cell treatments must introduce stem cells safely into the body, wire them correctly to other neurons and combine new cells into the pre-existing stem cell network. This means that there may need to be specific custom-made stem cell therapy treatments for each Alzheimer’s patient: something that researchers are still trying to find out more about.
By Palida (Pammy) Leenabanchong (Year 13 Student at Bangkok Patana School)
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