The Expression Of FGFR2 In The Adult Mouse Inner Ear And It's Relationship With Hearing Function

Cytokine is one of the factors which regulate the growth and development of cell. When it binds with its special receptors of cell membrane, a series of biochemical reactions in cells will happen and cause the synthesis of DNA. Fibroblast growth factors (FGFs) are one of the heparin binding growth factor (HBGF) families, which are multifunctional and non-special polypeptide and can regulate the proliferation, differentiation and other functions of cells. FGFs can enhance the synthesis of DNA and mitosis, and delay aging of cells coming from neural ectoderm or mesoderm such as endothelial cells, fibroblast and epithelial cells. Fibroblast growth factor receptors (FGFRs) are a kind of immunoglobulin-like tyrosine kinase receptors. To date, the functions of this important gene family in multiple biological processes have been known. These include mesoderm induction and patterning; cell growth, migration and differentiation; organ formation and maintenance; neuronal differentiation and survival; wound healing; and malignant. The inner ear, which mediates hearing and equilibrium, develops from an ectodermal placode located adjacent to the developing hindbrain. Induction of the placode and its subsequent morphogenesis and differentiation into the inner ear epithelium and its sensory neurons, involves signaling interactions within and between otic and non-otic tissues. A lot of studies have been shown that members of the fibroblast growth factor (FGF) gene family control formation of the body plan and organogenesis in vertebrates. FGFs and their receptors play an important role in the processes of inner ear development, structure and function maintenance, injury repair.FGFR2 is expressed in embryonic inner ear, which is very important for the formation of inner ear, but there is no report about its expression and function after birth.To study the expression of FGFR2 in inner ear of adult mouse and its effect on hearing, we carried out our study by three steps. First step is to observe hearing of the twoanimal models (one month old littermate): one with lower FGFR2 expression (Genetype: FGFR2-Neo-250 Mutation, MT), and the other with normal expression (wild type, WT), and to study changes of hearing function in the two groups after gentamycin given by intraperitoneal injection. Second step is to study the expression of FGFR2 mRNA in inner ear with in situ hybridization (ISH). Third step is to study the histomorphological changes of inner ear in the two animal models, and to study the inner ear cell hyperplasy after Brdu given by intraperitoneal injection. Results:1. Acoustic electrophysiological change: there is no significant difference between the two groups: MT, WT. There is a tendency that audibility threshold of MT group maybe better than WT group after gentamycin 2 weeks.2. The expression of FGFR2 mRNA: The expression is strong in spiral ganglion (SG) and week in spiral ligament (SL). After GM given, there is no significant difference between the two groups: MT, WT.3. Histomorphological changes: No obvious histomorphologyical change has been found in the two groups. Spiral ganglion cells in cochlea and fibroblasts in SL proliferate obviously.Conclusion:1. Cochleas of mice decreased expression of FGFR2 have no abnormalities on mass and the histomorphology of inner ear has no abnormality.2. The expression of FGFR2 is mainly in SG of inner ear.3. Partly decreased expression of FGFR2 has no obvious influence on the hearing function.4. Spiral ganglion cells in cochlea and fibroblasts in SL proliferate obviously in MT adult mouse.