Spiral ganglion cell morphology in guinea pigs after deafening and neurotrophic treatment.
It is well known that spiral ganglion cells (SGCs) degenerate in hair-cell-depleted cochleas and that treatment with exogenous neurotrophins can prevent this degeneration. Several studies reported that, in addition, SGC size decreases after deafening and increases after neurotrophic treatment. The dynamics of these cell size changes are not well known. In a first experiment we measured size, shape (circularity) and intracellular density of SGCs in guinea pigs at various moments after deafening (1, 2, 4, 6, and 8 weeks) and at various cochlear locations. In a second experiment, the effect of treatment with brain-derived neurotrophic factor (BDNF) on SGC morphology was investigated at various cochlear locations in deafened guinea pigs. We found that SGC size gradually decreased after deafening in the basal and middle cochlear turns. Already after one week a decrease in size was observed, which was well before the number of SGCs started to decrease. After BDNF treatment SGCs became noticeably larger than normal throughout the cochlea, including the middle and apical turns, whereas an effect on survival of SGCs was primarily observed in the basal turn. Thus, both after deafening and after neurotrophic treatment a change in size occurs before survival is affected. Morphological changes were not restricted to a subpopulation of SGCs. We argue that although changes in cell size and changes in survival might be manifestations of two separate mechanisms, morphological measures such as size, circularity and intracellular density are indicative for survival and degeneration.
Department of Otorhinolaryngology and Head & Neck Surgery, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, P.O. Box 85500, 3508 GA Utrecht, The Netherlands.
Maarten C
MC
van Loon
Dyan
D
Ramekers
Martijn J H
MJ
Agterberg
John C M J
JC
de Groot
Wilko
W
Grolman
Sjaak F L
SF
Klis
Huib
H
Versnel
D000818:Animals; D001309:Auditory Threshold; D019208:Brain-Derived Neurotrophic Factor / Q000494:pharmacology*; D048430:Cell Shape / Q000187:drug effects; D048429:Cell Size / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003638:Deafness / Q000139:chemically induced / Q000188:drug therapy* / Q000473:pathology; D004195:Disease Models, Animal; D005260:Female; D005665:Furosemide; D005727:Ganglia, Spinal / Q000187:drug effects* / Q000473:pathology; D006168:Guinea Pigs; D006198:Hair Cells, Auditory / Q000187:drug effects / Q000473:pathology; D007612:Kanamycin; D009410:Nerve Degeneration; D009474:Neurons / Q000187:drug effects* / Q000473:pathology; D013997:Time Factors
D019208:Brain-Derived Neurotrophic Factor; D007612:Kanamycin; D005665:Furosemide