Protective Effect of [Pyr1]-apelin-13 on Oxidative Stress-induced Apoptosis in Hair Cell-like Cells Derived from Bone Marrow Mesenchymal Stem Cells

Oxidative stress plays an important role in auditory dysfunction. Exogenous cell therapy has brought new hopes for repairing mammalian inner ear hair cells. However, poor cell viability of transplanted cells under oxidative stress conditions has limited their therapeutic potential. The adipocytokine apelin-13 was isolated from a bovine stomach. Apelin-13 might protect oxidative stress-induced hair cell damage was raised considering other oxidative stress-induced injury, including brain ischemia-induced cell death. Therefore, we evaluated the protective effects of apelin- 13 on the damage induced by hydrogen peroxide (H2O2) to the hair cells-derived from bone marrow mesenchymal stem cells (BMSCs) in vitro. Stem cells were differentiated into hair cell- like cells with B27, FGF, EGF and IGF-1. Expression of neuron specific markers including β tubulin III, Nestin, MAP2, Neurofilament 68 and GFAP was tested by flow cytometry. As well, inner ear hair cell markers such as Myosin VIIA, Sox2 and TrkB expression were assayed by immunocytochemistry (ICC) method. We designed an in vitro model of oxidative stress by exposing hair cell- like cells to H2O2. Protein expression levels of caspase-3, Bax and Bcl-2 were detected by western blot. Apoptotic cells were also detected by acridin-orange staining and TUNEL assay. Protein expression of caspase-3 and Bax/Bcl-2 ratio was significantly lower in the apelin-13-pretreated group than only H2O2 treated group. In addition, apoptotic cells were significantly decreased in the apelin-13+H2O2 co-treated cells compared to the H2O2-treated group. Treating hair cells-like cells with apelin13 increases their survival against oxidative stress damage by inhibition of apoptosis signaling pathway.