Evidence for supporting cell proliferation and hair cell differentiation in the basilar papilla of adult Belgian Waterslager canaries (Serinus canarius)

Abstract

We used the bromodeoxyuridine technique to study the proliferative activity in the basilar papilla of normal and Belgian Waterslager canaries with and without preceding sound trauma. Without sound trauma, there were, on average, six supporting cell divisions per day in the basilar papilla of Waterslager canaries. This rate of supporting cell proliferation corresponds well with estimates of the rate of hair cell differentiation derived from counts of immature-appearing hair cells obtained by using scanning electron microscopy of the Waterslager basilar papilla. Thus, supporting cell division appeared correlated with hair cell differentiation in Waterslager canaries. Bromodeoxyuridine labeling of cells in undamaged non-Waterslager canaries also indicated a very low rate of supporting cell division. In contrast with Waterslager canaries, this low rate of proliferation was not associated with a measurable rate of hair cell differentiation. In both normal and Waterslager canaries, exposure to traumatizing sound induced a dramatic increase in the rate of cell proliferation. These data show that a very low rate of supporting cell proliferation is normally present in birds, but it is not associated with a corresponding rate differentiation of hair cells. Only an increase above this low ambient rate of supporting cell proliferation, such as that following loss of hair cells, induces the differentiation of new hair cells in birds. The reason why Waterslager canaries do not completely compensate for their inherited hair cell deficit of 30% is not clear, when they can clearly respond to additional cochlear trauma from noise exposure with an increase in proliferation rate.

New studies on hair cell regeneration in birds

“…Kanamycin causes a decrease in the precision of vocal production in both birds but this precision recovers within 5-15 days following the cessation of injections and well before the return of auditory function as defined by absolute thresholds, difference limens, call discrimination, and call recognition. Using markers for cellular proliferative activity bromodeoxyuridine (BrdU) and radioactive thymidine, an average of six supporting cell divisions per day were found to occur continuously in the basilar papilla of Belgian Waterslager canaries [32]. This rate of supporting cell proliferation corresponds well with estimates of the rate of hair cell differentiation derived from counts of immature-appearing hair cells, obtained by using scanning electron microscopy of the Belgian Waterslager basilar papilla.…”

Gentamicin ototoxicity in the saccule of the lizard Podarcis Sicula induces hair cell recovery and regeneration

“…Studies on birds, amphibians and fish have led to the suggestion that new hair cells result from proliferation of supporting cells in these species (Corwin and Cotanche, 1988;Girod et al, 1989;Balak et al, 1990;Raphael, 1992;Hashino and Salvi, 1993;Stone and Cotanche, 1994;Tsue et al, 1994;Presson et al, 1996;Gleich et al, 1997).…”

WDR1 presence in the songbird basilar papilla

“…Recent physiological studies using the auditory brainstem response show that the BW canary has nearly normal hearing sensitivity during the first week post-hatch, but this sensitivity starts to deteriorate during the second week and shows the functional deficit, similar to that of adult canaries, by one month of age (Brittan-Powell et al, 2002;Wright et al, 2004). The causes of such a functional deficit in BW canaries have been attributed to structural defects in the inner ear (Gleich et al, 1994(Gleich et al, , 1995(Gleich et al, , 1997(Gleich et al, , 2001Ryals and Dooling, 2002). For example, the BW canary ear displays approximately 30% hair cell loss along its sensory epithelium (Gleich et al, 1994) and a 12% reduction in afferent nerve fibers (Gleich et al, 2001).…”

“…For example, the BW canary ear displays approximately 30% hair cell loss along its sensory epithelium (Gleich et al, 1994) and a 12% reduction in afferent nerve fibers (Gleich et al, 2001). Hair cell regeneration is observed in the BW canary basilar papilla, but the rate of hair cell replacement is lower than that for hair cell loss (Gleich et al, 1997). Interestingly, exposure to intense sound induces a greater rate of hair cell regeneration in the BW canary, but the question as to how this positive change affects hearing loss in the BW canary remains to be resolved (Gleich et al, 1997).…”