Combined Growth Factor and Gene Therapy: An Approach for Hair Cell Regeneration and Hearing Recovery

INTRODUCTION: Fibroblast growth factor, nerve growth factor neurotrophins, and insulin-like growth factor 1 are considered 3 families of growth factors that can be involved in the process of otic neurogenesis. In this respect, otic neurons can also be connected with mechanoreceptors in the ear, the hair cells (HCs), as well as the central nervous system. As a growth factor is combined with gene transfer technology, it can be used for hair cell regeneration. Gene therapy can be similarly employed to introduce genes into a system in order to induce the expression of genes for therapeutic agents, to replace defective genes, or to re-program supporting or surrounding cells to acquire the phenotype of lost or damaged cells in order to repair or regenerate the damaged tissue. OBJECTIVE: The purpose of this review article was to investigate the epigenetic and growth factors involved in the differentiation pathway of embryonic stem cells (ESCs) into HCs and auditory neurons (ANs). METHODS: To this end, the databases of Directory of Open Access Journals, Google Scholar, PubMed (NLM), LISTA (EBSCO), as well as Web of Science were searched. RESULTS: Given the results available in the related literature, the differentiation efficacy of ESCs toward the ANs and the HCs, the important role of growth factors, and 3 different strategies of application of miRNA, epigenetic regulation, and preparation of three-dimensional (3D) environments were suggested to be taken into consideration in order to improve these studies in the future. Furthermore, the role of epige-netic mechanisms and miRNA in this differentiation process became quite obvious; hence, the utilization of such procedures in the near future would be significant. CONCLUSION: Combining several techniques with a synergic effect (such as growth factor gene therapy and 3D environments) seemed to lead to obtaining the best results as a therapeutic strategy

The Effect of the MicroRNA-183 Family on Hair Cell-Specific Markers of Human Bone Marrow-Derived Mesenchymal Stem Cells

Hearing loss is considered the most common sensory disorder across the world. Nowadays, a cochlear implant can be an effective treatment for patients. Moreover, it is often believed that sensorineural hearing loss in humans is caused by loss or disruption of the function of hair cells in the cochlea. In this respect, mesenchymal cells can be a good candidate for cell-based therapeutic approaches. To this end, the potential of human bone marrow-derived mesenchymal stem cells to differentiate into hair cells with the help of transfection of microRNA in vitro was investigated. MicroRNA mimics (miRNA-96, 182, and 183) were transfected to human bone marrow-derived mesenchymal stem cells using Lipofec-tamine as a common transfection reagent following the manufacturer's instructions at 50 nM for microRNA mimics and 50 nM for the scramble. The changes in cell morphology were also observed under an inverted microscope. Then, the relative expression levels of SOX2, POU4F3, MYO7A, and calretinin were assayed using real-time polymerase chain reaction according to the ΔΔCt method. The ATOH1 level was similarly measured via real-time polymerase chain reaction and Western blotting. The results showed that increased expression of miRNA-182, but neither miRNA-96 nor miRNA-183, could lead to higher expression levels in some hair cell markers. The morphology of the cells also did not change in this respect, but the evaluation of gene expression at the levels of mRNA could promote the expression of the ATOH1, SOX2, and POU4F3 markers. Furthermore, miRNA-182 could enhance the expression of ATOH1 at the protein level. According to the results of this study, it was concluded that miRNA-182 could serve as a crucial function in hair cell differentiation by the upregulation of SOX2, POU4F3, and ATOH1 to promote a hair cell's fate