Stem Cells and Nanotechnology
Stavros Hatzopoulos, Andrea Ciorba, Mark Krumm in Advances in Audiology and Hearing Science, 2020
The human inner ear is divided into two main parts, the auditory system (the cochlea) and the vestibular system. The cochlea is a bony spiral canal, about 30-mm long and divided into three fluid-filled compartments, the scala tympani, the scala media, and the scala vestibuli. The round window membrane (RWM) and the blood inner ear barrier (BB) are two physical barriers that isolate the cochlea, respectively, from the middle ear and from the circulatory system. The RWM is a three-layer semipermeable membrane, composed of an outer epithelial cell layer, a middle connection layer, and an inner connection layer facing the perilymph of the scala tympani (Banerjee and Parnes, 2004). In humans, the variable thickness of RWM affects the response of patients to DD treatments. In animal models, its thickness is different among species but its composition is similar (Goycoolea and Lundman, 1997).
Mitochondrial Dysfunction and Hearing Loss
Shamim I. Ahmad in Handbook of Mitochondrial Dysfunction, 2019
The function of the cochlea is to convert the sound waves into an electrochemical stimulus that can be transmitted to the Central Nervous System (CNS). The receptor of this sensory function is the inner hair cells (IHC) which stereocilia movement produces ion channels opening to allow entry of K+ and Ca++. This result in a transduction current that generates the activation the calcium channels which are in the wall and the base of the IHC. The glutamate neurotransmitter is released and it binds afferent nerve terminals surrounding the HC, then an action potential is propagated for the afferent nerve. The outer hair cells (OHC) provide the amplification of the signal, this happen because of the elongation and contraction of these cells that cause depolarization and hyperpolarization of the cell augmenting the displacement of the basilar membrane.12,13
The Role of the Audiologist in Life Care Planning
Roger O. Weed, Debra E. Berens in Life Care Planning and Case Management Handbook, 2018
In older children (and adults), one of the most preventable is noise-induced hearing loss. Most people will have reduced hearing as they grow older (especially after the age of 60); however, there are things individuals can do to try to preserve their hearing. Noise-induced hearing loss, once called “blacksmith's deafness” from the continual clanging of metal on metal, dates back hundreds of years. During World War II, it received much more attention because of the heavy artillery used in the war. Acoustic trauma from a single exposure may cause permanent hearing loss. Gradual hearing loss from repeated exposure to excessive sound can damage or destroy the delicate hair cells in the cochlea. Hearing conservation programs and hearing research programs (ASHA, 2006) have developed public education campaigns to alert people, especially adolescents and teenagers, to the damage caused to hearing with loud music. Wearing ear plugs or ear muffs to help block the loud sounds or music, limiting the time of an iPod session with breaks to allow your hearing to rest, and keeping the volume reduced are just a few suggestions included in a hearing conservation program. Table 10.3 shows the readers the decibel levels of some of the most common environmental sounds, and Table 10.4 lists the decibel levels of some musical instruments, as well as some types of music. Table 10.5 shows the noise exposure of sound in decibels for certain periods of time that may create hearing risk.
Sustained delivery of triamcinolone acetonide from a thermosensitive microemulsion gel system for the treatment of sensorineural hearing loss
Published in Drug Delivery, 2023
Thu Nhan Nguyen, So-Yeol Yoo, Warisraporn Tangchang, Jae-Young Lee, Hwa-Young Son, Jeong-Sook Park
Hearing is one of the most important senses, as it allows humans to be aware of surrounding airborne sounds. The cochlea is an organ dedicated to hearing that transfers mechanical stimuli as electrical signals and then transduces them to the brain, where they can be processed to cause auditory sensation (Brownell, 1997; Fettiplace, 2017; Sohmer, 1997). Any damage to the sensory hair cells or auditory nerves of the cochlea caused by external stimuli (such as excessive noise (Yang & Chung, 2016), infection (Cohen et al., 2014) or ototoxic drugs (Rizk et al., 2020)) or intrinsic causes such as genetic mutations (Vona & Haaf, 2016), aging (Cardin, 2016) and Meniere’s disease (Gacek, 2021) gives rise to sensorineural hearing loss (SNHL), the most frequent inner ear impairment in humans. However, the treatment of SNHL has been challenging, as it is difficult to achieve therapeutic drug concentrations in the inner ear due to anatomical and physiological barriers. Poor penetration of the blood-labyrinth barrier that separates the blood from the inner ear fluids and the limited blood supply to the inner ear leads to subtherapeutic concentrations of drugs after systemic administration (Nyberg et al., 2019). Compared to systemic administration, intratympanic (IT) administration not only offers higher levels of drug in the perilymph but also minimizes undesired systemic side effects (Bird et al., 2011). This makes drug delivery via the IT route more attractive in the treatment of inner ear disorders.
The applications of targeted delivery for gene therapies in hearing loss
Published in Journal of Drug Targeting, 2023
Melissa Jones, Bozica Kovacevic, Corina Mihaela Ionescu, Susbin Raj Wagle, Christina Quintas, Elaine Y. M. Wong, Momir Mikov, Armin Mooranian, Hani Al-Salami
The complex structure of the mammalian ear is divided into three primary sections, classified as the outer, middle, and inner ear, with all parts required to work in an organised, controlled synergistic nature for hearing to occur. Focus here will be on the inner ear, which has roles in both hearing and balance [38]. The inner ear contains the cochlea where auditory signals are transduced. Located within the cochlea are three ducts, termed the scala vestibule, scala media, and scala tympani. Within the scala media of the cochlea, the organ of Corti is positioned, with the primary function of transducing auditory signals. The organ of Corti contains both inner and outer hair cells, being mechanosensory hair cells arranged in rows, with three rows of outer hair cells and one row of inner hair cells in the luminal half of the organ. Also located within are supporting cells of a non-sensory nature, positioned throughout the basement membrane to the luminal surface in a highly organised pattern [23,39,40].
Experimental drugs for the prevention or treatment of sensorineural hearing loss
Published in Expert Opinion on Investigational Drugs, 2023
Judith S Kempfle, David H. Jung
The cochlea, a portion of the inner ear, is a snail-shaped, fluid-filled compartment within the petrous portion of the temporal bone. It is divided into three chambers, two of which, the scala tympani, and scala vestibuli, are filled with perilymph (resembling cerebrospinal fluid and low in potassium chloride and high in sodium chloride), and the scala media, which contains endolymph (high in potassium chloride and low in sodium chloride). The scala media also harbors the cochlear duct, which is home to the organ of Corti with the sensory cells (hair cells) of the cochlea (Figure 1). Its unique structure allows frequency tuning along the cochlear axis – high frequencies are perceived at the base, while low frequencies are detected at the apex [10]. Along the organ of Corti, one row of inner hair cells and three rows of outer hair cells are flanked by nonsensory supporting cells and connect to the peripheral neurites of spiral ganglion neurons (SGNs). The cell bodies of the SGNs are located in Rosenthal’s canal, and their central axons project along the modiolus to the brainstem (Figure 1). Approximately 25 000 to 33 000 SGNs are found in the modiolus and connect with 3 500 inner and 12 000 outer hair cells [11].
Related Knowledge Centers
- Bony Labyrinth
- Hearing
- Inner Ear
- Modiolus
- Organ of Corti
- Oval Window
- Perilymph
- Organ of Corti
- Vestibular Duct
- Tympanic Duct
- Round Window