Current and Future Treatment Options for Hearing Loss

Hearing loss is caused by several factors, such as genetic, aging, drug, infection and exposure to loud sound and around 360 million people worldwide have disabling hearing loss. Here, we discuss the current and future strategies for the treatment of hearing loss

Approaches of auditory hair cells induction from stem cells

Hair cells are the sensory epithelial cells of both the auditory and the vestibular systems in the inner ear of all vertebrates. Auditory hair cells are located in the organ of corti on a thin layer of basement membrane in the cochlea of the inner ear. Damage to hair cells decreases hearing sensitivity. When these delicate hair cells in the cochlea are damaged, sound signals cannot be sent to the brain. In general, damage to the mammalian inner ear, is not returnable. In fact, a key goal in the treatment of sensorineural hearing loss is to find appropriate procedures to replace the missing hair cells. Cell therapy is one of the treatment options for hearing loss. In this regard, studies focus on ways which hair cells can be provided from exogenous and endogenous stem cells. This review identified ways to induce auditory hair cells regeneration from stem cells as the potential therapeutic approaches for the hearing loss

Signaling Pathways Involved in Auditory Hair Cells Development

Auditory hair cells (HCs) cannot be spontaneously regenerated or replaced in mammalian damaged cochlea which leads to permanent deafness. On the other hand, regenerative ability of HCs in lower vertebrates such as birds and amphibians causes that researchers investigate underlying mechanisms and pathways which can possibly induce mammalian cochlear HCs regeneration and hearing recovery. Signaling cascades of HCs regeneration in lower vertebrate can be considered as the potential therapeutic option for the hearing loss in human. This paper reviews current knowledge about the main signaling pathways involved in HCs development in the mammalian cochlea

Gene Therapy in Hearing Loss Treatment: A Review

Background Hearing loss, which is highly heterogeneous, is the most common sensorineural disorder in humans. More than 50% of the causes of deafness are attributed to genetic factors. Numerous studies have shown the persistent negative impact of deafness on communication and quality of life. Therefore, action to optimize performance and maintain or improve hearing ability seems necessary. In so doing, interventions are performed after assessing hearing loss. The most important intervention is gene therapy; For several genetic diseases, gene therapy is a potential treatment that is being investigated. Gene therapy will restore the ability to hear by overcoming functional defects caused by genetic mutations. Furthermore, gene therapy might potentially be used to trigger the regeneration of hair cells by transferring genes required in the cochlea for hair cell differentiation. Aim: We review recent research about hereditary hearing loss and technologies in animal. Methods: In this study, we review current reports in clarifying genomics of hereditary hearing loss and technologies between 2014 and 2020 in PubMed, Scopus, and Google Scholar to create a gene therapy that may soon become a treatment choice. We also discuss recent research applied to animal models of hearing loss by gene therapy. Conclusion: Gene therapy allows for the treatment of sensorineural hearing loss by restoring and/or preserving the inner ear cells functioning. Hopeful results from recent research have contributed to cochlear gene therapies being created for end-use in patients

Trehalose increase proliferation and decrease apoptosis in hair cells induced by Hydrogen peroxides

BACKGROUND: Hydrogen peroxide (H2O2) a key reactive oxygen species, which is made through redox procedure, can induce oxidative damage to several biological macromolecules and play critical role in neurodegenerative diseases. Aim: The current study examined the neuroprotective effect of Trehalose on hair cells death induced by H2O2. Material and method: Hair cells were co-treated by Trehalose and H2O2. The effects of Trehalose on BAX/BCL2 expression ratio and cell viability were assessed by Real time PCR and MTT assay, respectively.  Result:  The results of Real time PCR and MTT assay indicated that H2O2 induce cell death, and Trehalose have neuroprotective effect and decreases cell death. Conclusion: Our data showed that Trehalose has the protective effect on hair cells death induced by H20

The effects of modern therapies on noise pollution affecting hearing loss: challenges and novelty

Background: Human reactions to noise pollution can have detrimental consequences for physical and mental health. Increased infection in the workplace or the surrounding area can cause deafness and its disorders, tinnitus, high blood pressure, coronary artery disease, and sleep disorders. Changes in the immune system and birth defects have also been attributed to exposure to noise pollution. Adverse effects and cardiovascular complications due to constant exposure to noise pollution prevent human blood pressure from experiencing a regular cycle of increase and decrease around the clock. The most important sources of such pollution are cars, airplanes, long-term exposure to loud music, and industrial noise. In the European Union, more than 10,000 people die each year due to the effects of noise pollution. The level of noise pollution during the night causes the production and permanent increase of cortisol, which increases the risk of heart attack. Aim: The aim of this study was to review the results of research on the role of antioxidants and other protective agents against the destructive effects of free radicals on hearing loss and deafness. Methods: In this research, using the desired keywords in valid databases (PubMed, Scopus, and Medline), articles from 2016 to 2020 were performed and then this study was written by studying the selected articles. Results: The results showed that most of the pollution is caused by cars, airplanes, long-term exposure to loud music and industrial sounds, as well as protection and training methods, as well as the use of neurotrophic agents and antioxidants and cell therapy. Gene therapy is effective in treating deafness caused by infection. Conclusion: The most appropriate method in the treatment of noise pollution and deafness is the prevention of areas with high noise and the use of antioxidants

Ribbon Synapse Reformation: A Key Role for the Hearing Restoration; A Review

Background: Auditory sensory epithelium of mammals has two types of mechanosensory cells including the inner hair cells (IHC) and outer hair cells (OHC). IHC in the mammalian inner ear is an important component for the sound perception. Information about the frequency, intensity, and timingof acoustic signals is transmitted rapidly and precisely via ribbon synapses of the IHCs to the type 1 spiral ganglion neurons (SGNs). Even in the absence of stimulation, these synapses drive spontaneous spiking into the afferent neuron. Evidence has shown that cochlear neuropathy leading to hearing loss may be a result of the damage to ribbon synapses Aim:Here, we review how these synapses promote the rapid neurotransmitter release and sustained signal transmission. We also discuss the mechanisms involved in ribbon synapse reformation for hearing restoration. Conclusion:Although cochlear ribbon synapses fail to regenerate spontaneously when injured, recent studies have provided evidence for cochlear synaptogenesis that will be relevant to regenerative methods for cochlear neural loss. A better understanding of mechanisms underlying synaptic reformation would be helpful in achieving reversal of sensorineural hearing loss

Effects of Lordegan Thyme endophytes on Shigella sonnei and Candida albicans

The aim of this study was to investigate the effects of thyme endophytes belonging to the Lordegan region on Shigella sonnei and Candida albicans.  Thyme components were immersed in 70% ethanol (2 minutes), 3.5% sodium hypochlorite (5 minutes), and 75% ethanol (30 seconds), respectively, and lastly washed with sterile distilled water. Subsequently, they were cultured on YEA and PA medium, and the endophytes were isolated. A total of 8 bacterial endophytes were taken from different parts of the Lordegan thyme plant (stem, leaves, and roots) and examined. The endophytes isolated from thyme were bacilli, coccobacilli, and cocci. Antimicrobial and inhibitory properties of endophytes isolated from Lordegan thyme were studied in two methods: structural factors and secretory metabolites of endophytes. The results of this study showed the beneficial effects of thyme endophytes on Shigella sonnei and Candida albicans. Bacterial endophytes isolated from thyme (roots stems and leaves) showed stronger inhibitory effects than the study of secretory metabolites against S. sonnei and C. albicans. In general, thyme could be a good alternative to chemical drugs in the treatment of Candida infections, especially cutaneous mucosal candidiasis, and shigellosis, and can be used in therapeutic cases, food, health, and pharmaceutical industries

Contamination of chicken eggs supplied in Tehran by heavy metals and calculation of their daily intake

Background and Aims: Chicken eggs, owing to richness in protein and essential minerals, are used in many communities and for all age groups. Metals are considered as one of the most important environmental pollutants which may lead to egg contamination. The consumption of contaminated eggs can harm human health. The aim of this study was to evaluate heavy metal (arsenic, cadmium, lead, nickel, copper, zinc and iron) contents in chicken eggs supplied in Tehran. Daily intake rates of heavy metals were also calculated.Materials and Methods: A total of 29 chicken eggs were sampled from various food stores in Tehran. Sample preparation was performed using wet acid digestion. Heavy metals concentrations were determined using ICP-OES. Data analysis was carried out by means of the statistical software SPSS as well as Excel (V.2.26). Kruskal Wallis and ANOVA tests were executed to compare heavy metal concentrations between different brands. Results: Mean concentrations of cadmium, lead, arsenic, nickel, copper, iron and zinc in collected chicken eggs were 0.01, 0.074, 0.03, 0.014, 1.46, 34.37 and 12.55 mg/kg, respectively. Iron and cadmium respectively showed the highest and lowest daily intake through chicken egg consumption. Conclusion: It was concluded that the levels of heavy metals in sampled chicken eggs were less than permissible limits and thus are considered safe. However, due to the importance of food contamination in public health, the continuous monitoring of these contaminants in food is recommended.Key words: Chicken Eggs, Heavy Metals, Food Safety, Tehra

Chronic Noise Exposure Activates Apoptosis Signaling Pathway in the Rat Auditory Cortex

Background: Today, hearing disorders are one of the most common problems in an industrial society. High-intensity sounds can induce apoptosis and metabolic changes in the auditory neural pathway and auditory cortex.Aim: In this study, we investigated the effect of chronic noise exposure on Bax, Bcl-2 and Caspase-3 genes expression in the auditory cortex of rats.Methods: Chronic exposure to 110 dB white noise was applied in male rats for 6 hours for 5 consecutive days. Superoxide dismutase (SOD) activity was measured in the serum of rats prior to and following noise exposure. Bax, Bcl-2 and Caspase-3 genes expression in the auditory cortex was determined by Real time PCR assay. Results: Our results showed that the serum SOD level was significantly decreased in rats exposed to noise. In addition, the gene expression of Caspase-3 and Bax/Bcl-2 ratio was markedly increased in the auditory cortex of rats were subjected to chronic noise exposure compared to control rats.Conclusion: Chronic noise exposure can activate apoptosis signaling pathway in the auditory cortex of rat