OLFACTORY BULB ASTROGLIAL RESPONSE TO OLFACORY ORGAN DAMAGE IN ADULT ZEBRAFISH
Reactive glial cells are present in multiple neurological conditions including Alzheimer’s disease, ALS, and traumatic brain injury. In the mammalian CNS, astrocytes proliferate in response to CNS insults, and in severe cases will form a permanent glial scar. This is due to two distinct subclasses of astrocytes: scar-forming, and hypertrophic astrocytes. Zebrafish do not have mammalian-type astrocytes but instead have astroglia that have been shown to have processes and roles similar to mammalian astrocytes but also serve as a neural progenerators. Zebrafish have been shown to be a reliable model of neuroplasticity. Studying these astroglia in a regenerative model may lead to novel treatment methods of neurological disorders where reactive astrocytes are present.
In this study, we used the zebrafish olfactory system to study reactive astroglia in response to peripheral damage. Our hypothesis is that insults to the zebrafish olfactory organ will cause astroglia to react similar to mammalian astrocytes. The olfactory organ was damaged using a wax plug inserted into the right nasal cavity every twelve hours for varying time points, while the left organ was kept as an internal control. Astroglial processes in the olfactory bulb were observed and identified using antibodies for glial fibrillary acidic protein. Preliminary data suggests that astroglial processes proliferate in the olfactory bulb bilaterally up to and including seven days of olfactory organ damage, and return to control levels after the cessation of treatment. Our data also suggests that antibodies for a known astrocyte glutamate receptor, mGluR 2/3, increase in expression within the olfactory bulb after olfactory organ insult. Our data suggests there is no detectable scar found in the olfactory bulb after three weeks of recovery. These finding are similar to both hypertrophic and scar-forming astrocytes in the mammalian CNS. However, the non-local hypertrophy of astroglial processes and the lack of scar formation are not indicative of mammalian astrocytes. These unique glial populations might be the key to understanding the dynamic neuroplasticity of zebrafish. Further study of reactive glia in zebrafish may eventually lead to novel medical practices for a wide variety of neurological disorders.