Retrograde degeneration of spiral ganglion cells in the cochlea following hair cell loss is similar to dying back in pathology. The EFR3A gene has recently been discovered to be involved in the pathogenesis of dying back. The relationship of EFR3A and spiral ganglion degeneration, however, was rarely investigated. In this study, we destroyed the hair cells of the mouse cochlea by co-administration of kanamycin and furosemide and then investigated the EFR3A expression during the induced spiral ganglion cell degeneration. Our results revealed that co-administration of kanamycin and furosemide quickly induced hair cell loss in the C57BL/6J mice and then resulted in progressive degeneration of the spiral ganglion beginning at day 5 following drug administration. The number of the spiral ganglion cells began to decrease at day 15. The expression of EFR3A increased remarkably in the spiral ganglion at day 5 and then decreased to near normal level within the next 10 days. Our study suggested that the change of EFR3A expression in the spiral ganglion was coincident with the time of the spiral ganglion degeneration, which implied that high expression of EFR3A may be important to prompt initiation of spiral ganglion degeneration following hair cell loss.

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Some (21.1 ± 1.56)% of the hypopharyngeal cancer cell line FaDu cells expressed CD44. The CD44(+) population was efficiently sorted by MACS, and after separation, the purity of the CD44(+) cells was (99.4 ± 0.29)%. The MTT assay indicated that the sorted CD44(+) cells had a stronger proliferative capacity than the CD44(-) cells. The tumorigenicity study showed that all the mice injected with 1 × 10(6) CD44(+) cells developed tumors (8/8), half the mice injected with 1 × 10(6) CD44(-) cells developed tumors (4/8), 1 of the 8 mice injected with 1 × 10(5) CD44(+) cells developed tumors (12.5%), but none of the mice injected with 1 × 10(5) CD44(-) cells developed any tumors (0/8). At the same concentration, the difference in tumorigenic rates between the CD44(+) and CD44(-) groups was statistically significant (Fisher's exact test, p < 0.05). Furthermore, the CD44(+) group had a shorter incubation period than the CD44(-) group. In addition, the average tumor volume of the CD44(+) group was (2017.81 ± 538.50) mm(3); however, the average tumor volume of the CD44(-) group was (1153.25 ± 503.18) mm(3). The difference was statistically significant (t = 2.67, p < 0.05).