First of all, I would like to define stem cells. Stem cells are undifferentiated cells that have the ability to proliferate and differentiate into more specialized and functioning cells including inner ear stem cells.
Generally, They exist in two major types in mammals, embryonic stem cells, and adult stem cells.
The first type presents in the inner cell mass of blastocysts (endoderm), and the latter presents in various tissues.
Nowadays, Researchers are trying in laboratories to use stem cells to replace the lost body organs. They hope that patients can partially restore their hearing when stem cells injected into the ear.
The new studies of stem cells
Recently, there is a new study at the Indiana University School of Medicine. It suggested that stem cells present in bone marrow of rats can differentiate into auditory neurons (nerve cell for hearing ) that may reverse deafness.
There is also another study, conducted at the National Tokyo Medical Center. The researchers used stem cell therapy to study the effect of these cells in restoring hearing due to aging, trauma, or disease.
Researchers found that lab rats that received stem cells have a greater chance to recover from hearing loss by 23% other rats that did not receive this therapy.
Dr. Kwan said, “Hearing loss impacts about 15 percent of the American population, probably more”. “Over the years, you don’t realize that you don’t hear well until you get tested. We’re one of the few labs trying to figure out how to address the hearing loss issue.”
Dr. Kelvin Y. Kwan is a senior author of the study and an assistant professor in the Department of Cell Biology and Neuroscience in the School of Arts and Sciences.
Although, until this moment, these studies are confined to the laboratories, it is expected that stem cells (of the patient’s body) will have the ability to restore lost hearing.
The side effects of stem cells
Many scientists believe that stem cell is a double-edged weapon.
Dr. Kwan said, “People say, ‘we’ll just put stem cells in and we’re going to replace lost neurons.’ We’re saying that ‘yes, we can make neurons,’ but you have other side effects that are unanticipated, such as the increased proliferation of stem cells. So, this will guide us toward a better strategy for cell replacement therapies.”
These stem cells may produce cancerous tumors after injection.
The expected way for restoring hearing
The scientists expect a gene called NEUROG1 to turn the injected inner ear stem cells into auditory neurons. Furthermore, the gene NEUROG1 could stimulate other stem cells to make other types of neurons. However, scientists should be aware that when using this gem, they may also increase cell proliferation causing tumors.
There is a chromatin (pieces of DNA and histone proteins) can influence the function of NEUROG1. So, they can adjust this chromatin to help reduce unwanted stem cell proliferation.
According to Dr. Kwan, “we would change the chromatin state before we start overexpressing NEUROG1 and prevent unwanted stem cell proliferation,”.
Song, Z., Jadali, A., Fritzsch, B., & Kwan, K. Y. (2017). NEUROG1 Regulates CDK2 to Promote Proliferation in Otic Progenitors. Stem Cell Reports.
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