■ OBJECTIVES: Potential treatment strategies of hearing loss with stem cells derived from non-embryonic tissues are much less objected to ethical criticism than embryonic stem cell-based approaches. This pilot study in mice was performed to assess viability and features of inner ear stem cells derived from postmortem temporal bones. The data obtained will be used to determine reasonable time limits for harvesting human inner ear tissues from autopsy cases.

■ METHODS: Newborn and young adult (postnatal day 21) mice were killed using CO2 asphyxiation and kept at room temperature for six hours followed by storage at 4° to simulate conditions found in  autopsy cases. At several time points ranging from 0 hours to 15 days postmortem, temporal bones were removed. The utricles, organs of Corti and spiral ganglia were isolated and dissociated to obtain single cell suspensions. After adding growth factors, the suspensions were incubated for 7 days and inspected for the presence of free-floating spheres as a direct sign of stem cells. Spheres were then subjected to self-renewal and differentiation assays.

■ RESULTS: Murine inner ear tissues, including sensory epithelia and spiral ganglion neurons, displayed remarkably robust cellular survival, even after 10 days postmortem. Similarly, isolation of sphereforming stem cells was possible up to 10 days postmortem. We  detected no difference in the proliferation and differentiation potential between stem cells isolated directly after death and up to 5 days postmortem. At longer postmortem intervals, we observed that the potency of stem cells to differentiate into mature cell types, such as hair cell-like cells and spiral ganglion-like cells, diminishes earlier than their potential for self-renewal.

■ CONCLUSIONS: Stem cells in the inner ear of mice are present, alive and functional up to 10 days after death. Human autopsy temporal bones should therefore be suitable for harvesting stem cells, at least in the first few days postmortem.