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Implications of Stem Cell Therapy for Huntington’s Disease

By: Vamshikrishna Pothireddy

When the brain and the nervous system are unable to communicate properly, the body’s motor skills sufficiently decrease. Even in the 21st century, researchers are trying to find cures for neurological disorders. This led to researchers turning to gene therapy to reverse gene flips causing these neurological diseases.

Specifically, Huntington’s disease is a neurological disease that affects the whole body. Huntington's disease (HD) is an autosomal dominant, late‐onset, neurodegenerative disorder, which primarily affects the caudate and putamen regions of the brain. The symptoms of Huntington’s can be considered in the categories as motor, cognitive, and psychological classes. HD neurological disease is a unique disease stemming from the central nervous system.

The disease results from a combination of the sequence triploid of a CAG trinucleotide repeat in the HTT gene. The HTT gene represents Huntington's disease gene. The disease is easily recognized by its main symptoms in the motor, cognitive and psychiatric disorders.

This disease leads to a progressive decline of the patient’s cognitive state. Research states that after 20 years from the onset of symptoms of Huntington’s disease, the majority of the patients die due to the loss of mental and physical capabilities. Since the first citing of Huntington’s disease, there is no proper treatment for the disease to cure all patients. However, there are smaller treatments that treat symptoms with only palliative treatments. This method of systematic management of Huntington’s disease has not properly been utilized as documentation has led to variations and different scenarios in the clinical trials.

Huntington’s disease is a disease that can worsen through external stimuli such as stress, fatigue, and infectious cuts and scars. Researchers are investigating methods to find patterns to mitigate the repeat of the CAG triploid of Huntington’s disease. The Huntington gene leads to toxic effects on the neurological degeneration of the brain’s neurons. The loss of the brain’s neurons leads to an impairment in the cell’s functions throughout the whole body.

Current preventative measures to Huntington’s disease involve maintaining physical exercise and low input exercises in order to maintain physically and mentally strong-willed. Helping Huntington’s disease patients currently will require various rehabilitation methods in order to greatly stabilize vital organs in the diagnosed patients.

The CRISPR Cas9 complex was accomplished through the pioneering work by Doudna and Charpentier in 2012. The aim of CRISPR is to efficiently aim and target a sequence in the gene with a guide RNA.in order to replace the targeted gene triploid with the new RNA sequence. As CRISPR started to improve and become more precise, genetics and targeting technologies proved more extensive to reverse genomics in order to prevent neurological diseases.

The repeat of the Huntingtin gene results in the synthesis of a misfolded form of the identifiable protein, mHTT, a harmful gene expression. Huntington’s disease treatments are only palliative, sedating pain without curing the incident of the disease. Current palliative solutions to Huntington’s disease include the use of CRISPR-Cas 9 complex with stem cells therapy.

Stem cell therapy allows cells to reprogram themselves in order to replace lost or damaged cells through grafts. However, the recent work of Cicchetti and colleagues identified HD’s patients whose graft resulted in clusters of mHTT in the surrounding areas of the graft through the “prion-like mechanism”.

Recent studies from Cicchetti’s research display “prion-like” behavior as the growth occurs from the original host location to the new graft area for the stem cells in order to be placed in the brain during Huntington’s disease.


The study resulted in a progressive decrease in the production of mHTT, the toxic production of Huntington’s disease. Thus, there was a reduction of the conglomerates thus reducing inflammation in the brain and cellular damage. The mice that received the new gene therapy showed vast improvements in motor skills. According to the study, MRI monitoring is used in order to monitor any acute or long term symptoms of Huntington’s disease.


Specifically, Cicchetti’s research group identified that the introduction of the CRISPR-Cas9 complex resulted in the interruption of the toxic mHTT gene resulted in a 50% decrease of the neurological symptoms of Huntington’s disease and thus significantly improved the patient’s lifespan and a certain decrease in motor deficits. The final tests of Huntington’s disease occurred in mice with immunofluorescence lights to tracks the effects of the reduced symptoms of Huntington’s disease.

In order to statistically analyze the results, the researchers used a 2 way ANOVA analysis with a comparison to the wildtype strain. However, the results of gene therapy in order to find a long-lasting solution to Huntington’s disease needs more research investigation to ensure a transparent understanding of the mHTT gene after stem cell therapy.



References:

1. Bachoud Lévi, Ferreira J, Massart R. International guidelines for the treatment of Huntington's disease. Frontiers in Neurology. 2019.

2. Bhairavi Srinageshwar,Robert B. Petersen,Gary L. Dunbar, Julien Rossignol. Prion‐like mechanisms in neurodegenerative disease: Implications for Huntington's disease therapy. Stem Cells Translational Medicine. 2019.

3. Freja K Ekman, David S Ojala, Maroof M Adil, Paola A Lopez, David V Schaffer, Thomas Gaj. CRISPR-Cas9-Mediated Genome Editing Increases Lifespan and Improves Motor Deficits in a Huntington's Disease Mouse Model. Molecular Therapy-Nucleic Acids. 2019.

4. Odatha W. Kotagama, Chanika D. Jayasinghe, Thelma Abeysinghe. Era of Genomic Medicine: A Narrative Review on CRISPR Technology as a Potential Therapeutic Tool for Human Diseases. Biomedical Research International. 2019.

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