Hair Cell Regeneration After ATOH1 Case Study

Hearing loss continues to linger in the elderly population of today’s society. Yet, the onset of hearing loss can occur at any age and at any point in

Twenty-six percent of infants ears demonstrated hearing loss during the first year of life, and 78% of children’s ears demonstrated hearing loss during the study period. Of the children’s ears with hearing loss, 100% had a conductive component and 26% had an additional sensorineural component (mixed hearing loss…Common temporal bone findings included thickening and sclerosis of the

Another study looked at the effects of acoustic trauma in adult Cotirnix quail, and if hair cell regeneration was possible (Ryals and Rubel, 1988). The quail is used because, similarly to humans, it cannot reproduce hair cells after birth and are sensitive to ototoxicity and acoustic trauma. The animals are also relatively quick developing enough to use for such a study and allow researchers more examine the cochlea. This early paper was looking more towards physical damage to the hair cells as opposed to the chemical damage caused during development. They believed that the recovery process was age related, and that belief had been supported in the previous research that only young birds could have hearing restored. They set out to see if ototoxic

The neural processes required to hear a phone ring may surprise some people. The neuron’s cell body (the part of the neuron which contains the nucleus) contains branch-like structures known as dendrites, which receive information from the axon—a long tail-like portion of the neuron. This information then travels to other neurons via chemicals called neurotransmitters (Pastorino & Doyle-Portile, 2015). The axon is coated by a wax-like substance called myelin, composed of segments known as myelin sheaths. Corrosion of the myelin sheaths may adversely affect a sensory input, in this case

Cochlear implants are biomedical devices that help individuals with severe hearing impairments with auditory sensation. In order to process sound cochlear implants include external and internal components. A microphone, which is part of the external component gathers sound (Petersona, Pisonia, & Miyamoto, 2010). These sound waves from the environment are transferred into electrical signals (Petersen, Gjedde, Wallentin, & Vuust, 2013). The electrical signals are then organized through a series of filters. After this step is completed, the signals are conveyed across the skin to a receiver within the internal components. In the implanted device, further conversion occurs and the signals are delivered to an array of electrodes within the cochlea. Each signal is directed to a specific electrode, this method utilizes tonotopic representation and coding of frequency. Lastly, the electrodes stimulate the auditory nerve (Petersona et al., 2010). These are the main processes involved in the application of cochlear implants. This paper explores some of the current research related to the application of cochlear implants including: language abilities, plasticity and areas for further research.

The cochlear implant is a incredible device that all started out in the 1950s, when "Lundberg performed one of the first recorded attempts to simulate the auditory nerve with a sinusoidal current during a neurosurgical operation"(MAJOR BREAKTHROUGHS! (n.d.). Retrieved April 25, 2015, from http://biomed.brown.edu/Courses/BI108/BI108_2001_Groups/Cochlear_Implants/history.html ). After the operation his patient was able to hear noise. This device as been changing peoples lives for a long time, with time it has improved. there are other things in this world that changed people lives, that benefits them, so

et al. used two different thyroid hormone receptor knock-in mutations, TRβΔ337T/Δ337T and TRβE457A/E457A, to test how triiodothyronine regulates cochlear development. They introduced the mutations in the same way for both trial groups and followed the same procedure for mice maintenance, surgery and cochlea tuning as well as using the same sound system of testing. Data was collected for auditory brainstem responses by subtracting the value measured from an electrode placed on the mastoid process from the ipsilateral electrode in the vertex, relative to the ground electrode placed in the neck and measuring, through direct instructions, the morphology of the cochlea. The researchers also measured compound action potential threshold in the cochlear by using a modified tracking system and threshold was defined as the level needed for a 20-µV N1/P1 amplitude at each frequency. Results show that TRβΔ337T/Δ337T mutants had significant increases in auditory brainstem responses, more than 60dB, and that TRβ E457A/E457A mutants had moderate elevations of approximately 20dB. Also, TRβE457A/E457A mutants show an increase in sound pressure required to raise compound action potential amplitude to the defined level and that gross morphology was normal in both groups. The results suggest that disrupted triiodothyronine leads to improper tectorial membrane development which allows for increased thresholds and decreased action potentials of inner hair cell potassium channels.

The mammalian cochlea is located within the inner ear and is responsible for the transduction of auditory stimuli from an organism’s external environment to the brain. The neurons that mediate this signal transduction are spiral ganglion neurons (SGN), a bipolar cell type with peripheral axons extending to mechanically sensitive hair cells (HC) in the organ of Corti (OC) and central axons that bifurcate and project to the dorsal and ventral cochlear nuclei (DCN, VCN) (Coate, et al., 2013). SGNs are divided into two classes determined by the hair cells to which they project: 90-95% of SGNs innervate inner hair cells (IHCs), whereas the remaining 5-10%

Hair cells are the auditory receptors of the auditory system. Inner hair cells are those located between the modiolus and the rods of the Corti. They are positioned with 3500 in one row. The outer hair cells on the other hand are located farther out than the rods of Corti and are arranged in three rows of a total of 15,000 to 20,000 hair cells. The stereocilia extend with their tips ending at either the outer hair cells’ gelatinous substance or below the tectorial membrane in the inner hair cells. Outer hair cells are found only in mammals and function by vibtrating to produce a sound in our ears, while the inner hair cells are geared towards a release of neurotransmitter to the synapses which allows them to react quickly to any mechanical

Cisplatin is a platinum-based chemotherapeutic agent with proven efficacy against solid tumors. However, the clinical use of cisplatin is limited by the development of permanent hearing loss in cancer patients. There is currently no drug approved by the US Food and Drug Administration for cisplatin-induced hearing loss (1, 2). Multiple studies have shown that cisplatin profoundly damages outer hair cells (OHCs) present in the hook region, basal and middle turns of the cochlea (3, 4) with relative sparing of inner hair cells (IHCs) in these regions. Other regions of the cochlea such as the spiral ligament (SL), stria vascularis (SV) and spiral ganglion neuron (SGN) are also susceptible to cisplatin-induced damage (5-9).

The hair follicle is maintained by continuous cycles of generation and degeneration, which are highly controlled by molecular signals that induce cell proliferation, differentiation, and death. Wnt, BMP, SHH, and Notch are a few of the signaling pathways that have been involved in regulating the hair cycle [28]. The hair cycle is divided into three stages, which are telogen, anagen, and catagen. Telogen is a quiescent period where the dermal papilla rests under the bulge stem cell compartment [14]. The dermal papilla is a group of mesenchymal cells that control hair follicle development and serve as a stem cell reservoir [11]. After receiving the necessary signals, the follicle enters the active state of hair growth, anagen. During this stage,

They found that the canonical Notch pathway is not active to any significant degree in the

The etiology of Otosclerosis of most patients is usually a genetic mutation or inherited from a parent. Otosclerosis is known to be a in an autosomal dominant pattern with variable penetrance. Which means that a child has a 50% chance of inheriting the gene if one parent is a carrier. Scientists have found that it can be multiple genes on the chromosomes that are affected that cause Otosclerosis. Showing that the disease does not just occur on one specific gene. Scientist where able to find in one case that a family had a mutation in a gene for collagen and antibodies against collagen, suggesting an autoimmune mechanism (Niedermeyer & Arnold 2002). Although, scientist found this information they cannot automatically say that this is the sole cause for Otosclerosis, because they have also found that in some cases of this diseases that it can be onset by an infection of the measles virus. A recent hypothesis suggests that otosclerosis requires a combination of a specific gene with exposure to a specific virus (for example measles) for it to be expressed and for hearing loss to occur (McGuirt et al, 1998). Scientists continue to work on this hypothesis because they have reason to believe that the measles virus predisposes patients to Otosclerosis. They have found viral material in the nucleic acid of the otosclerotic stapes footplates (Karosi et al 2008) and increased levels of antibodies to

The ear is sectioned off into three parts, the outer, the middle, and the inner ear. Each section serves its own function to the hearing of an individual. The external portion of the ear includes the auricle, the auditory canal, and the eardrum outer layer. The auricle is the cartilage that is covered by skin on opposite sides of the head, the auditory canal, more commonly called the ear canal, is the tunnel in which sound waves travel down, and the ear drum, also known as the tympanic membrane. The function of the auricle is to collect sound and act as a funnel that amplifies that sound down into the auditory canal (Middlebrooks and Green, 1991). The ear canal serves to transfer sound to the ear drum and the secretion of earwax which helps protect the ear from bacteria, fungi, and insects (Okuda, et al., 1991). The eardrums main purpose is to transmit sound from air to the ossicles in the middle ear and then to the oval window in the fluid-filled cochlea. The ossicles are the common name for the three middle ear bones that transmit sound from the air to the fluid-filled cochlea. The ossicles consist of the malleus, incus, and stapes bones in that order respectively. These bones contribute to the amplification and transmission of sound to the inner ear. Our main focus is on the inner and its function in hearing and ultimately hearing loss. The inner ear consists of two main parts: the cochlea, which detects sound, and the vestibular system, that is dedicated to balance

The ear is an extraordinary human organ that many people take for granted until it doesn’t function. It is the only device that allows the human to hear sounds in their environment. The ear is made up of many parts that distinguish various sounds through different means. The ear anatomy and physiology along with how sound waves are transmitted into meaningful sounds will help one understand how hearing loss occurs.