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1.  Nestin expressing progenitor cells during establishment of the neural retina and its vasculature 
Anatomy & Cell Biology  2012;45(1):38-46.
In order to test if nestin is a useful marker for various types of progenitor cells, we explored nestin expression in the retina during development. Nestin expression was co-evaluated with bromodeoxyuridine (BrdU) labeling and Griffonia simplicifolia isolectin B4 (GSIB4) histochemistry. Nestin immunoreactivity appears in cell soma of dividing neural progenitor cells and their leading processes in retinas from embryonic day (E) 13 to E20, in accordance with a BrdU-labeled pattern. At postnatal day (P) 5, it is restricted to the end feet of Müller cells. BrdU-labeled nuclei were mainly in the inner part of the inner nuclear layer in postnatal neonates. The retinal vessels demarcated with GSIB4-positive endothelial cells were first distributed in the nerve fiber layer from P3. Afterward the vascular branches sprouted and penetrated deeply into the retina. The endothelial cells positive for GSIB4 and the pericytes in the microvessels were additionally immunoreactive for nestin. Interestingly, the presumed migrating microglial cells showing only GSIB4 reactivity preceded the microvessels throughout the neuroblast layer during vascular sprouting and extension. These findings may suggest that nestin expression represents the proliferation and movement potential of the neural progenitor cells as well as the progenitor cells of the endothelial cell and the pericyte during retinal development. Thus, Müller glial cells might be potential neural progenitor cells of the retina, and the retinal microvasculature established by both the endothelial and the pericyte progenitor cells via vasculogenesis along microglia migrating routes sustains its angiogenic potential.
PMCID: PMC3328739  PMID: 22536550
Neurogenesis; Vasculogenesis; Retina; Nestin; Proliferation; Migration
2.  Morphological and functional evaluation of an animal model for the retinal degeneration induced by N-methyl-N-nitrosourea 
Anatomy & Cell Biology  2011;44(4):314-323.
The retinal degeneration (RD) is a general cause of blindness. To study its pathophysiology and evaluate the effects of new therapeutic agents before clinical trials, it is essential to establish reliable and stable animal models. This study evaluated a RD animal model in which blindness was induced by N-methyl-N-nitrosourea (MNU), a potent retinotoxin leading to apoptosis of photoreceptors. MNU was applied to the Sprague-Dawley rats by a single intraperitoneal injection in different doses (40, 50, and 60 mg/kg). The retinal functions were examined at 1 week after MNU injection by electroretinogram (ERG). Afterwards, each retina was examined by hematoxylin and eosin stain and immunohistochemistry with anti-glial fibrillary acidic protein antibody. Upon MNU injection of 40, 50 and 60 mg/kg, the ERG amplitude of a-waves showed significant reductions of 7, 26, and 44%, respectively, when compared to that of normal a-waves. The b-wave amplitudes were about 89, 65, and 58% of normal b-waves in the response to scotopic light stimulus. At 1 week, 2 weeks, and 4 weeks after MNU injection (50 mg/kg), all scotopic ERG components decreased progressively. In addition, degeneration of retinal neurons was observed in a time- and dose-dependent manner after MNU injection. Taken together, functional reduction following RD induced by MNU correlates with morphological changes. Thus, this RD rat model may be a useful model to study its pathophysiology and to evaluate the effects of new therapeutic agents before clinical trials.
PMCID: PMC3254885  PMID: 22254160
Animal models; Electroretinography; N-methyl-N-nitrosourea; Retinal degeneration
3.  Immunochemical changes of calbindin, calretinin and SMI32 in ischemic retinas induced by increase of intraocular pressure and by middle cerebral artery occlusion 
Anatomy & Cell Biology  2011;44(1):25-34.
The reaction of neuroactive substances to ischemic conditions in the rat retina evoked by different methods was immunochemically evaluated in adult Sprague-Dawley rats. Ocular ischemic conditions were unilaterally produced by elevating intraocular pressure (EIOP) or by middle cerebral artery occlusion (MCAO). Two EF-hand calcium binding proteins, calbindin D28K (CB) and calretinin (CR), in the normal retina showed similar immunolocalization, such as the amacrine and displaced amacrine cells, the ganglion cells, and their processes, particularly CB in horizontal cells. CB immunoreactive neurons in the ganglion cell layer in both types of ischemic retinas were more reduced in number than CR neurons compared to those in a normal retina. The CB protein level in both ischemic retinas was reduced to 60-80% of normal. The CR protein level in MCAO retinas was reduced to about 80% of normal but increased gradually to the normal value, whereas that in the EIOP showed a gradual reduction and a slight recovery. SMI32 immunoreactivity, which detects a dephosphorylated epitope of neurofilaments-M and -H, appeared in the axon bundles of ganglion cells in the innermost nerve fiber layer of normal retinas. The reactivity in the nerve fiber bundles appeared to only increase slightly in EIOP retinas, whereas a moderate increase occurred in MCAO retinas. The SMI32 protein level in MCAO retinas showed a gradual increasing tendency, whereas that in the EIOP showed a slight fluctuation. Interestingly, the MCAO retinas showed additional SMI32 immunoreactivity in the cell soma of presumed ganglion cells, whereas that of EIOP appeared in the Müller proximal radial fibers. Glial fibrillary acidic protein (GFAP) immunoreactivity appeared in the astrocytes located in the nerve fiber layer of normal retinas. Additional GFAP immunoreactivity appeared in the Müller glial fibers deep in EIOP retinas and at the proximal end in MCAO retinas. These findings suggest that the neurons in the ganglion cell layer undergo degenerative changes in response to ischemia, although EIOP retinas represented a remarkable Müller glial reaction, whereas MCAO retinas had only a small-scaled axonal transport disturbance.
PMCID: PMC3080005  PMID: 21519546
Elevation of intraocular pressure; Middle cerebral artery occlusion; Calcium-binding protein; SMI32; Retina
4.  Changes in transcript and protein levels of calbindin D28k, calretinin and parvalbumin, and numbers of neuronal populations expressing these proteins in an ischemia model of rat retina 
Anatomy & Cell Biology  2010;43(3):218-229.
Excessive calcium is thought to be a critical step in various neurodegenerative processes including ischemia. Calbindin D28k (CB), calretinin (CR), and parvalbumin (PV), members of the EF-hand calcium-binding protein family, are thought to play a neuroprotective role in various pathologic conditions by serving as a buffer against excessive calcium. The expression of CB, PV and CR in the ischemic rat retina induced by increasing intraocular pressure was investigated at the transcript and protein levels, by means of the quantitative real-time reverse transcription-polymerase chain reaction, western blot and immunohistochemistry. The transcript and protein levels of CB, which is strongly expressed in the horizontal cells in both normal and affected retinas, were not changed significantly and the number of CB-expressing horizontal cells remained unchanged throughout the experimental period 8 weeks after ischemia/reperfusion injury. At both the transcript and protein levels, however, CR, which is strongly expressed in several types of amacrine, ganglion, and displaced amacrine cells in both normal and affected retinas, was decreased. CR-expressing ganglion cell number was particularly decreased in ischemic retinas. Similar to the CR, PV transcript and protein levels, and PV-expressing AII amacrine cell number were decreased. Interestingly, in ischemic retinas PV was transiently expressed in putative cone bipolar cell types possibly those that connect with AII amacrine cells via gap junctions. These results suggest that these three calcium binding proteins may play different neuroprotective roles in ischemic insult by their ability to buffer calcium in the rat retina.
PMCID: PMC3015040  PMID: 21212862
Calbindin; calretinin; ischemia; parvalbumin; rat retina

Results 1-4 (4)