The Alteration of Avian Retinal Microglia Induced by Optic Nerve Transection / 대한해부학회지

Retina, a part of CNS, has served valuable and accessible tissue for elucidating the cellular properties of neurons and glia due to its similarity to brain. Unlike mammalian counterpart, avian retina is devoid of vessels and astrocytes. However little is known about glial reaction to neuronal injuries in this species. Therefore, this study was performed to investigate the microglial responses in the quail retina following neuronal injuries. The retinae from normal and optic nerve transected adult quails were studied immunohistochemically with anti-QH1, a marker known to be specific for microglia. In the normal retina, QH1-labeled microglial cells displayed typical feature of ramified (resting) form and were localized mainly in the inner plexiform layer. After optic nerve transection (ONT) morphology of microglial cells changed from the ramified to the amoeboid form. This feature of microglial cells maintained throughout the post operational periods until 28 days after ONT. Particularly, at 14 and 21 days after ONT amoeboid microglia displayed cell bodies with stout and bushy processes, suggesting active phagocytosis. The distribution pattern of microglia also changed in accord to ganglion cell degeneration: they gradually moved to layers of ganglion cells and optic nerve fibers where ganglion cell bodies and axons were under degeneration. This change of microglial distribution was most prominent at 14 days of ONT. The result of this study is generally consistent with that reported in mammalian counterpart and this similarity between the avascular avian retina and the vascularized mammalian counterpart suggests that processes of microglial activation, such as migration and phagocytosis, can occur in the vessel-free CNS tissue.

TRANSECTION OF THE OPTIC NERVE INDUCES EXPRESSION OF THE SMALL HEAT SHOCK PROTEIN HSP27 IN THE OPTIC PATHWAY OF GOLDEN HAMSTER / 解剖学报

Objective To observe the expression of the small heat shock protein (HSP27) in the optic chiasma (OC), optic tract (OT), dorsal lateral geniculate body(LG) and superior colliculus (SC) of the adult golden hamster after intraorbital transection of the left optic nerve (ON). Methods The experimental animals were left to survive for l, 2, 3, 4, 5, 6, 8 weeks following ON transection. The animals were perfused with formol-saline and brains were excised, sectioned and stained with the immunohistochemistry. The sections were observed under the light microscope, the optical density (A) was measured and the data were analysed statistically. Results Immunohistochemical results indicated that the HSP27-expressions were not different between the right and left side of the OC, OT, LG and SC in normal or sham-operation controls. However, following transection of the left ON, HSP27 immunohistochemical stainings in the right site of OC, OT,LG and SC were increased, comparing with the left side. The maximum difference of HSP27 immunostaining between the right and left side appeared in the lst week following left ON axotomy. The sharply decrease of the A difference occurred at the 2nd week after axotomy with insignificant changes in the subsequent several weeks. And the significant A difference was observed in most time except 6th week. Most of HSP27-positive cells had morphological appearances similar to astrocytes with smaller cell body and numerous processes. Conclusion After the transection of monolateral ON, HSP27 expressions in the contralateral optic pathway of brain increased and persisted up to 8 weeks. This result suggested that the increase of HSP27 expression had something to do with the injury of the optic pathway, but the mechanism and biological significance of the increase in HSP27 expression level required to be studied further.;