Move towards treatment for hereditary deafness


Deafness is the most common sensory impairment in newborns – about 1 in 1,000 children are born with hearing loss or develop it in infancy. Half of these cases have a genetic cause; very often, this type of deafness is linked to a mutation in a gene called “gap junction beta 2 (GJB2)”, which codes for a protein called “connexin 26 (CX26)”. This protein is found in the cells of the cochlea, the part of the inner ear that allows hearing. One way to treat GJB2-related deafness would be to reproduce properly functioning cochlear cells and insert them into the inner ear. Today, Kazusaku Kamiya from Juntendo University and his colleagues took an important step forward in making this treatment possible: Using a stem cell technique, they were able to reproduce cochlear support cells, a type of cell known to contain CX26 proteins.

The researchers started with human-induced pluripotent stem cells (iPSCs) – artificially generated cells that can differentiate into any other type of cell in the human body. By applying a special set of culture techniques, including exposing the cultures to insulin, they were able to get their iPSCs to produce the CX26 protein. Another similarity to cochlear support cells was investigated by checking for the presence of proteins expressed by other “marker genes” typical of the cochlea. The cells themselves formed intercellular junctions – composed in part of the CX26 protein – characteristic of normal support cells in the cochlea.

Kamiya and his colleagues also examined the outcome of iPSC production from cells taken from GJB2 deaf patients. the cells generated this way differed from healthy iPSCs: intercellular junctions did not form as they should. It is this malformation that can be directly associated with hearing loss – in other words, scientists have reproduced the pathology of deafness linked to GJB2.

It should be emphasized that the cochlea is anatomically complex, which makes traditional and invasive procedures such as biopsies (to take samples) or direct administration of drugs (for treatment) difficult as there is a risk of loss of ‘hearing. The results of Kamiya and her colleagues are therefore important in two respects. First, being able to reproduce cochlear support cells via the iPSC method can lead to hereditary deafness treatment in which the defective cells are replaced with normally functioning cells. Second, reproducing the pathology by generating iPSCs derived from patients with GJB2 mutations is useful for testing drugs and for developing treatments for each mutation that occurs. Quoting the scientists: “Such iPSC-derived cells are expected to be particularly useful for drug screening and inner ear cell therapies with genome editing targeting GJB2-related hearing loss and the disease condition could be reproduced with the iPS derived from a typical patient “.


Induced pluripotent stem cells (iPSC)

Stem cells are cells that have the ability to differentiate – that is, to become cells of a specialized type. An important attribute of a stem cell is its potency, indicating into which types of cells the stem cell can differentiate. So-called pluripotent stem cells (PSCs) can develop into organisms because they can differentiate into cells of one of three different germ layers characteristic of organisms.

An induced pluripotent stem cell (iPSC) is an artificially generated PSC from a non-PSC. The procedure for creating iPSC was discovered in 2006 by Shinya yamanaka (for which he received the 2012 Nobel Prize in Physiology or Medicine). The iPSC generation is today a promising technique in the field of regenerative medicine: damaged or defective human cells can be replaced by cells regenerated using the iPSC technique.

Kazusaku Kamiya of Juntendo University and his colleagues have now applied the iPSC technique to provide information on a common type of deafness in newborns. They succeeded in creating cells that function as cochlear support cells, a promising step in the development of replacement therapy for defective support cells. They have also been successful in producing iPSC-derived cell cultures from GJB2-related deafness patients; artificially reproducing the pathology is useful for drug testing and treatment development.


Ichiro Fukunaga, Yoko Oe, Keiko Danzaki, Sayaka ohta, Cheng Chen, Kyoko Shirai, Atsushi Kawano, Katsuhisa Ikeda And Kazusaku Kamiya. Modeling of deafness linked to the beta gene of the gap junction with human iPSC. Human molecular genetics Posted online May 17, 2021.

DOI: 10.1093 / hmg / ddab097


Further information:

Juntendo University
2-1-1, Hongo, Bunkyo-ku, Tokyo 113-8421 JAPAN
E-mail: [email protected]

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Mission statement

The mission of Juntendo University is to strive for the advancement of society through education, research and healthcare, guided by the motto “Jin – I exist as you exist” and the principle of ” Fudan Zenshin – Continuously Moving Forward “. The spirit of “Jin”, which is the ideal of all who gather at Juntendo University, involves being kind and considerate to others. The principle of “Fudan Zenshin” expresses the conviction of the founders that education and research activities will prosper only in an environment of free competition. Our academic environment allows us to educate exceptional students to become healthcare professionals in whom patients can believe, scientists capable of innovative discoveries and inventions, and global citizens willing to serve society.

History of Juntendo University

Juntendo was originally founded in 1838 as a Dutch medical school at a time when Western medical education was not yet integrated into Japanese society. With the creation of Juntendo, the founders hoped to create a place where people could come together for the common purpose of helping society through the powers of education and medical practices. Their aspirations led to the creation of Juntendo Hospital, the first private hospital in Japan. Over the years, the institution’s experience and perspective as a higher education institution and place of clinical practice has enabled Juntendo University to play a pivotal role in shaping education and Japanese medical practices. Along the way, the focus of the institution has also broadened, now consisting of four undergraduate and three graduate programs, the university specializes in the areas of health and sports, nursing and health sciences, and medicine. Today, Juntendo University continues to pursue innovative approaches to education and research at the international level with the aim of applying the results to society.

SOURCE Juntendo University


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