Intravenous administration of human mesenchymal stem cells after noise- or drug-induced hearing loss in rats

Conclusion: Systemic application of human mesenchymal stem cells (hMSCs) may be another effective tool for stem cell supply to the inner ear. Objectives: Most researchers have used local application to provide the inner ear with stem cells. In spite of their efficacy, these methods can potentially cause irreversible damage to the inner ear. A homing phenomenon of systemically administered MSCs to the ischemic myocardium and brain was recently reported. Moreover, hMSCs have several advantages over conventional neural or embryonic stem cells. Thus we hypothesized that intense noise or ototoxic injury to the cochlea could induce the homing of hMSCs. Methods: We harvested hMSCs from bone marrow of the iliac crest of five normal individuals. Then hMSCs at a dose of 4 x 106 cells were given via intravenous injection of cell suspension into rats with cochleae damaged by noise or ototoxic drugs. Histological analysis was undertaken 30 days later. Results: Systemically delivered hMSCs were usually largely entrapped in the lungs. However, we documented the homing of some hMSCs to the cochlea with degenerated inner hair cells. The recruitment of hMSCs was limited to the spiral ganglion area only. The migration of donor cells into the cochlea was accompanied by the expression of brain-derived neurotrophic factor (BDNF).