Integration of donor bone marrow cells into the cochlea at one year

C57Bl/6 mice were subjected to 900 cGy from a γ‐emitting source, followed by transplantation of bone marrow derived cells (BMDCs) from mice expressing green fluorescent protein (GFP). The mice were euthanized at 13 months. The population of cochlear cells labeled by GFP + /BMDCs in the areas of the organ of Corti and cochlear lateral wall were determined. We found BMDCs to exclusively differentiate into vascular cells and fibrocytes. At one year, the majority of vascular cells and resident macrophages in the stria vascularis, as well as many fibrocytes in the spiral ligament, were of donor origin. No trans‐differentiation to other cochlea cell types, such as hair cells, spiral ganglion cells, and supporting cells, was detected. In addition, all mice showed graying hair and hearing loss as expected from the C57 BL/6 strain, which is known to have early onset hearing loss. The data indicate that some adult vascular cells and resident macrophages in the cochlea of aging animals are derived from a migratory population of bone marrow precursors. This study also provides useful information on the timeframe of reconstitution after transplantation with donor bone marrow cells. This work was supported by NIH NIDCD grants R03‐DC008888 (XS), R01‐DC008888S1 (XS), R01‐DC010844 (XS), R01‐DC000105 (ALN), and P30‐DC005983.