Apoptosis following peripheral sensory deafferentation in the olfactory bulb of adult zebrafish

Abstract

Removal of the olfactory organ in adult zebrafish results in a significant decrease in volume of the ipsilateral olfactory bulb. The current study investigated the potential role of apoptosis in this phenomenon. It was hypothesized that cells in the adult olfactory bulb normally undergo minimal apoptosis and that apoptosis increases upon removal of sensory stimulation. By using both the terminal transferase-mediated deoxyuridine nick-end labeling method and bis-benzimide labeling, the current study showed that, in the normal adult olfactory bulb, cells exhibiting apoptotic profiles were scarce and were localized to the outer layers of the bulb. However, in deafferented animals, there was a significant increase in the number of apoptotic cells. The apoptotic response occurred in two phases and was confined to the rostral half of the bulb. The first phase of cell death peaked at 1 hour postsurgery. These apoptotic profiles appeared to be primarily nonneuronal in nature, in that they exhibited no immunohistochemical labeling to the neuron-specific protein Hu. The second phase of cell death peaked at 24 hours and declined to normal levels by 1 week. At the 24 hour time point, only a fraction of the apoptotic cells was neuronal in nature. Thus, apoptosis of nonneuronal and neuronal elements accounts for at least part of the deafferentation-induced volume decrease in the zebrafish olfactory bulb. This model of anterograde transneuronal degeneration will be useful in elucidating the afferent signals involved in survival and maintenance of mature brain neurons.

Sex differences in adult cell proliferation within the zebrafish (Danio rerio) cerebellum

“…In adult zebrafish, apoptosis has been previously studied in the olfactory bulbs following the removal of the olfactory organ (Vankirk & Byrd, 2003). In the present study, TUNEL-positive cell profiles were mainly included in the granule cell layer of Va and CCe cerebellum, while the molecular layer, the site of cell proliferation, showed low apoptotic activity, in agreement with previous studies in adult gymnotiform cerebellum (Soutschek & Zupanc, 1996).…”

“…In agreement, programmed cell death is correlated with high proliferative activity in adult gymnotiform fish cerebellum, Apteronotus leptorhynchus (Soutschek & Zupanc, 1996;Zupanc et al, 1998). The observed density of apoptotic cells in the granular layer of adult zebrafish cerebellum is higher than that reported in other regions of the adult brown trout teleost brain (Candal et al, 2005) but is similar to that of cells which have been deafferented for 1 h in the olfactory bulb (Vankirk & Byrd, 2003).…”

Peripheral sensory deafferentation affects olfactory bulb neurogenesis in zebrafish

“…It is possible that in our analysis fewer cells matured or that there were fewer divisions of cells due to apoptosis following deafferentation that killed the precursor cells. Indeed, a previous study from our lab examined apoptosis in response to the same form of deafferentation (VanKirk and Byrd, 2003). There is a significant increase in number of apoptotic cells in the olfactory bulb peaking one hour and 24 hours following removal of the olfactory organ.…”

Osteogenic response to BMP‐2 of hMSCs grown on apatite‐coated scaffolds

“…The importance of afferent input to neural integrity has been well demonstrated in many systems (Guillery,1973; Kalil,1980; Trune,1982; Clarke and Egloff,1988; Rubel and Fritzsch,2002; Vankirk and Byrd,2003). Neuronal cell death induced by afferent deprivation involves significant alterations in the overall rate of protein synthesis as well as in the expression level of certain apoptotic and antiapoptotic proteins (Steward and Rubel,1985; Garden et al,1994; Mostafapour et al,2000, 2002; Wilkinson et al,2002, 2003; Robinson et al,2003; Karnes et al,2009).…”