As presented last week at Hearing International, the politics of stem cell research is volatile in the United States. Thus, most of the research is being conducted in countries where this is less political.
Ever since human embryonic stem cells were first cultivated by Dr. James Thompson at the University of Wisconsin, Madison in 1998, they have been at the center of one of the most promising, and controversial, areas of modern medicine. Dr. Thompson headed the group of scientists that reported the first isolation of embryonic stem cell lines from a non-human primate in 1995, and the first successful isolation of human embryonic stem cell lines in 1998. He was awarded patents related to a method of “isolating embryonic stem cells of humans and primates.” These history-making patents are considered the primary intellectual property rights to the politically controversial embryonic stem cell research within the United States. Although much research has been conducted in the U.S., the up and down politics surrounding these studies have led to substantial research being conducted elsewhere. This week our story continues by looking at the specifics of hearing research in various countries and where we are with results on various hearing disorders.
Auditory Neuropathy is one area where there is significant progress. Auditory neuropathy is a hearing disorder in which sound enters the inner ear normally but the transmission of signals from the inner ear to the brain is impaired. It can affect people of all ages, from infancy through adulthood.
The number of people affected by auditory neuropathy is not known, but the condition affects a relatively small percentage of people who are deaf or hearing-impaired. People with auditory neuropathy may have “normal” hearing evaluations, or hearing losses ranging from mild to severe, but they always have poor speech-perception. Their difficulty understanding speech clearly results in low word-recognition scores (note the flat ABR and OAE in the presence of “normal” hearing). Usually, speech perception is significantly worse than would be predicted by the degree of hearing loss. For example, a person with auditory neuropathy may be able to hear sounds, but still have difficulty recognizing spoken words. For these individuals, sound may fade in and out and seem out of sync. The frustration is that these individuals have difficulty using amplification effectively and find it difficult to function normally.
Researchers at the University of Sheffield in the UK, led by Dr. Marcelo Rivolta, may have some hope to offer those with auditory neuropathy A study from the University of Sheffield, published last month in the prestigious scientific journal Nature (1) – suggests that human embryonic stem cells )hESC) may be able to restore hearing as well as vision. The scientists found that auditory nerve cells derived from hESCs could restore hearing in deaf gerbils.
While this is not the first time that auditory nerve cells have been created from hESCs, it is the first time that it has been demonstrated that they can restore the connection between the sensory hair cells that convert sound vibration into electrical signals and the brain, and lead to measurable improvements to hearing. Dr. Rivolta’s team took human embryonic stem cells, which can grow into many different tissue types, and transformed them with chemical growth factors into both early-stage auditory neurons and sensory hair cells found in the cochlea. Tests on cells created in the lab found they processed electrical signals in a similar way to healthy adult auditory cells, a sign that they should perform normally when implanted.
The UK scientists tried the auditory neurons on gerbils because they have a hearing range close to that of humans. The animals were first given a drug in one ear that caused deafness by damaging the auditory nerves. The team then cut an incision behind the ear, drilled a small hole in the temporal bone to get into the cochlea, and injected about 50,000 of the early-stage auditory neurons. After 10 weeks, the 18 animals that received cell implants had regained 46% of their hearing ability on average, measured by the volume of sound to which they responded.
Next week Hearing International will look at another UK researcher’s investigation into “old age hearing loss” and the effects of human embryonic stem cells on the impairment.
Addendum to October 2……
The Results of Audiology Outreach to the Northern Communities – Part III – Jack Scott, Ph.D.
There are several funding opportunities available. In 2012, the Hear The World Foundation provided funds to a grant application with the purpose of improving the hearing healthcare in Attawapiskat, Ontario. The initiative is designed to provide FM soundfield systems to the elementary school, provide personal amplification systems (i.e., pocket talkers) to the hospital, allow for in-service instructional programs at the hospital on cerumen management, and allow for the presentation of Sound Sense to Grade 6 students. Sound Sense is a program designed to educate students on the dangers of noise-induced hearing loss and possible ways of protective themselves now and in the future from noise exposure. The grant provided funds to allow for two students to attend the trip and provided enough funds for two trips. Search the web and contact hearing instrument manufacturers that may be interested in providing assistance in such a humanitarian endeavor.