Noise-induced hearing loss restored in mice

searchers from the University of Michigan and Harvard Medical School in Boston, MA, may be well on the way to finding new therapies that restore noise-induced and age-related hearing loss in humans. In a new study, the team describes how they recovered hearing in mice partially deafened by noise.

 

The researchers, led by Gabriel Corfas, PhD, of the University of Michigan, publish their findings online in the journal eLife.

Approximately 50 million Americans have hearing loss in at least one ear, with around 26 million Americans aged 20-69 experiencing high-frequency hearing loss as a result of noise exposure. Hearing loss is also common as we age, affecting around 30% of adults aged 65-74 and 47% of adults aged 75 and over.

In their study, the researchers explain how they were able to increase production of a protein called Neurotrophin-3 (NT3) in mice, which they found plays a key role in communication between the ears and the brain.

NT3 allows sound signals to be sent from the ear to the brain. The protein is crucial in establishing a super-fast connection between the ear’s hair cells and nerve cells – a connection the researchers call the “ribbon synapse.” But this ribbon synapse can become damaged as a result of noise exposure or normal aging, which can lead to hearing loss.

Boosting NT3 production in mice

In their study, the researchers identified supporting cells in the inner ear that produce NT3. They set out to see what would happen if they increased production of NT3 through these supporting cells.

Fast facts about hearing loss

• Hearing loss is more common among men than women
• Around 60% of veterans returning from Iraq or Afghanistan have some form of hearing loss ortinnitus – ringing in the ears
• Approximately 2-3 in every 1,000 children in the US are born with detectable levels of hearing loss in one or both ears.

Learn more about hearing loss

They adopted a method called conditional gene recombination. This allows researchers to activate genes in particular cells by administering a drug that prompts the cells to “read” additional copies of a gene that have been inserted into them.

For this study, the team used the technique to activate additional NT3 genes that had been introduced to the supporting cells of the inner ear in mice that had been partially deafened by loud noise.

The drug tamoxifen was introduced to the supporting cells in the inner ear, which prompted them to produce extra NT3 protein. The researchers then tested the hearing of the mice through a test normally used in humans – the auditory brainstem response (ABR).

The researchers found the mice that had experienced boosted NT3 production regained their hearing over a 2-week period, compared with mice that had not had additional NT3 production.

According to the team, these findings indicate that NT3 production is important for making ribbon synapses, and that boosting production of this protein may restore noise-induced and age-related hearing loss.

The potential to restore hearing loss in humans

Corfas and his team say they now plan to investigate the role of NT3 in human ears and identify drugs that produce the same effect as the protein, offering the potential to restore hearing loss in humans.

The researchers note that the gene therapy technique used in this study has the potential to work in humans, but that a drug-based method would be “simpler” and a drug could be repeatedly administered for as long as it takes for hearing to be restored. Corfas says he already has some drug candidates in mind.

The researchers stress, however, that since the mice in this study were only partially deaf, it is unclear whether increased NT3 production would restore hearing in subjects that are fully deaf.

But the team believes their findings are promising. Corfas says:

“It has become apparent that hearing loss due to damaged ribbon synapses is a very common and challenging problem, whether it’s due to noise or normal aging. We began this work 15 years ago to answer very basic questions about the inner ear, and now we have been able to restore hearing after partial deafening with noise, a common problem for people. It’s very exciting.”

Their findings may even reach further than hearing loss. The researchers say they may offer new strategies to treat neurodegenerative diseases, in which nerve cell connections are impaired.

Medical News Today recently reported on a study from the University of Leicester in the UK, in which researchers reveal how loud noises damage hearing in more detail.

Written by Honor Whiteman

http://www.medicalnewstoday.com/articles/284159.php

 

 

Effectiveness of treatment to reduce blood clots in otolaryngology patients admitted for surgery examined

The effectiveness of a treatment to reduce blood clots among otolaryngology patients admitted for surgery appears to differ based on patient risk and the procedure.

Blood clots (venous thromboembolism [VTE], which includes deep vein thrombosis [DVT] and pulmonary embolism[PE]) are common complications in surgical patients. Treatment (primary thromboprophylaxis with anticoagulant medication [chemoprophylaxis]) can help reduce the incidence of VTE in surgical patients. But treatment should be considered in light of the risk of VTE and bleeding complications. The American College of Chest Physician’s guidelines for thromboprophylaxis do not specifically apply to otolaryngology. The authors sought to examine the effectiveness and safety of VTE chemoprophylaxis for otolaryngology patients admitted for surgery.

How the Study Was Conducted:

The study included 3,498 patients treated by surgeons at an academic medical center between September 2003 and June 2010. The authors analyzed the incidence of VTE and bleeding complications within 30 days after surgery.

Results:

Of the 1,482 patients who received VTE chemoprophylaxis, 18 (1.2 percent) developed a VTE compared with 27 of 2,016 patients (1.3 percent) who did not receive treatment. Patients with higher scores on a risk assessment were less likely to have a VTE with perioperative chemoprophylaxis (5.3 percent vs. 10.4 percent). Of the patients who underwent treatment, 3.5 percent developed a bleeding complication compared with 1.2 percent of patients without treatment. Among patients who underwent free tissue transfer, treatment decreased the incidence of VTE (2.1 percent vs. 7.7 percent) and increased bleeding complications (11.9 percent vs. 4.5 percent). In all other patients, treatment did not significantly influence the likelihood of VTE (1 percent vs. 0.6 percent) or bleeding (1.5 percent vs. 0.9 percent).

Discussion:

“Results from this study provide the basis for future research. … An examination of additional benefits and harms of VTE prophylaxis is warranted, including its impact on mortality due to PE. Free tissue transfer patients merit special analysis when developing recommendations for VTE prophylaxis because of the high risk of both VTE and bleeding. … Finally, further tests of the incidence of VTE by risk level and of the effectiveness and safety of chemoprophylaxis should be conducted for other otolaryngology patients, in populations large enough to produce sufficiently powered analyses.”

http://www.medicalnewstoday.com/releases/283314.php