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Retinal ganglion cell degeneration is topological but not cell type specific in DBA/2J mice.

Jakobs TC, Libby RT, Ben Y, John SW, Masland RH - J. Cell Biol. (2005)

Bottom Line: Regions of cell death or survival radiated from the optic nerve head in fan-shaped sectors.Collectively, the data suggest axon damage at the optic nerve head as an early lesion, and damage to axon bundles would cause this pattern of degeneration.However, the architecture of the mouse eye seems to preclude a commonly postulated source of mechanical damage within the nerve head.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02114.

ABSTRACT
Using a variety of double and triple labeling techniques, we have reevaluated the death of retinal neurons in a mouse model of hereditary glaucoma. Cell-specific markers and total neuron counts revealed no cell loss in any retinal neurons other than the ganglion cells. Within the limits of our ability to define cell types, no group of ganglion cells was especially vulnerable or resistant to degeneration. Retrograde labeling and neurofilament staining showed that axonal atrophy, dendritic remodeling, and somal shrinkage (at least of the largest cell types) precedes ganglion cell death in this glaucoma model. Regions of cell death or survival radiated from the optic nerve head in fan-shaped sectors. Collectively, the data suggest axon damage at the optic nerve head as an early lesion, and damage to axon bundles would cause this pattern of degeneration. However, the architecture of the mouse eye seems to preclude a commonly postulated source of mechanical damage within the nerve head.

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Neuronal cell counts in the GCL. (A–D) Total cells in the GCL, excluding endothelial cells and microglia, were counted and graphed as density maps. For easier comparison, all retinas are shown with a temporal to nasal orientation (as if they were all right eyes). The deep cut in the superior pole of the retina (arrowhead) was used for orientation during the preparation. Dark red corresponds to a cell density of 10,000 cells/mm2, as indicated in the color bar; areas shown in gray could not be counted because of technical reasons. The retina in A (DBA/2J, unaffected optic nerve) shows no sign of degeneration. The retina in B showed moderate glaucoma by optic nerve grading; in this particular case, cell numbers in the nasal half of the retina were severely reduced, whereas the temporal half appears normal. C and D show severe glaucoma by nerve grading. Note that in the retina shown in C, even though the overall cell loss is severe, a region remains with fairly normal cell numbers. (E) Neurons in the GCL were counted along the nasotemporal axis and graphed as cells per millimeter squared. Open circles, C57BL/6J (one retina); black circles, 3-mo-old (predisease) DBA/2J (mean of three retinas ± SEM); green squares, DBA/2J nerve grade unaffected (mean of three retinas); blue diamonds, DBA/2J nerve grade moderate (one retina); red triangles, DBA/2J nerve grade severe (mean of four retinas). (F) GCL neurons along the dorsoventral axis (symbols are the same as in E).
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fig1: Neuronal cell counts in the GCL. (A–D) Total cells in the GCL, excluding endothelial cells and microglia, were counted and graphed as density maps. For easier comparison, all retinas are shown with a temporal to nasal orientation (as if they were all right eyes). The deep cut in the superior pole of the retina (arrowhead) was used for orientation during the preparation. Dark red corresponds to a cell density of 10,000 cells/mm2, as indicated in the color bar; areas shown in gray could not be counted because of technical reasons. The retina in A (DBA/2J, unaffected optic nerve) shows no sign of degeneration. The retina in B showed moderate glaucoma by optic nerve grading; in this particular case, cell numbers in the nasal half of the retina were severely reduced, whereas the temporal half appears normal. C and D show severe glaucoma by nerve grading. Note that in the retina shown in C, even though the overall cell loss is severe, a region remains with fairly normal cell numbers. (E) Neurons in the GCL were counted along the nasotemporal axis and graphed as cells per millimeter squared. Open circles, C57BL/6J (one retina); black circles, 3-mo-old (predisease) DBA/2J (mean of three retinas ± SEM); green squares, DBA/2J nerve grade unaffected (mean of three retinas); blue diamonds, DBA/2J nerve grade moderate (one retina); red triangles, DBA/2J nerve grade severe (mean of four retinas). (F) GCL neurons along the dorsoventral axis (symbols are the same as in E).

Mentions: For every retina, the severity of the glaucomatous damage was assessed by grading the optic nerve on a previously reported three-point scale (mild, moderate, and severe; Anderson et al., 2005; Libby et al., 2005a). Mild-stage nerves can have the minor degree of axon damage that occurs in normal mouse eyes at the studied ages, but they show no evidence of glaucomatous damage and are regarded as unaffected (Anderson et al., 2005; Libby et al., 2005c). By the age of 1 yr, a substantial percentage of DBA/2J mice have developed moderate or severe glaucoma as determined from optic nerve grading. Out of 67 optic nerves that were examined in this study, 19 (28%) showed no indication of glaucomatous damage, 3 (4%) were affected moderately, and 44 (66%) showed signs of severe disease (1 nerve was ungradeable). The progression of the disease in the left and right eyes of any one mouse was not highly correlated. We determined total cell numbers in the ganglion cell layer (GCL) in 29 retinas (4 of which were from 3-mo-old DBA/2J controls) by taking 16× or 25× surveys of the whole-mounted retina and counting the cell nuclei. As expected, the total cell counts corresponded well to the optic nerve grading. In the unaffected retinas, as in the 3-mo-old DBA/2J animals, the total cell density in the central parts of the retina exceeded 9,000 cells/mm2, which is conforms well with the figure determined previously in normal mice (∼8,000 cells/mm2), tapering off to ∼3,000–4,000 cells/mm2 in the periphery (Jeon et al., 1998). In the most severely affected retinas, we found maximal local cell densities of 6,000 cells/mm2 (Fig. 1). Interestingly, however, the cell loss was not uniform over the whole area of the retina. In some cases, one or two quadrants were spared from the disease (Fig. 1 B). It was not uncommon, even in retinas with strongly reduced overall ganglion cell counts, to find small sectors of the retina (Fig. 1 C), or at least small islands, that were almost normal. In the most severe cases, the total cell count in the GCL was reduced to a degree such that probably all the remaining cells are amacrine cells (Fig. 1 D). The implications of the spatial anisotropy will be discussed later. To begin, we will describe the neuronal changes that occur during the degeneration.


Retinal ganglion cell degeneration is topological but not cell type specific in DBA/2J mice.

Jakobs TC, Libby RT, Ben Y, John SW, Masland RH - J. Cell Biol. (2005)

Neuronal cell counts in the GCL. (A–D) Total cells in the GCL, excluding endothelial cells and microglia, were counted and graphed as density maps. For easier comparison, all retinas are shown with a temporal to nasal orientation (as if they were all right eyes). The deep cut in the superior pole of the retina (arrowhead) was used for orientation during the preparation. Dark red corresponds to a cell density of 10,000 cells/mm2, as indicated in the color bar; areas shown in gray could not be counted because of technical reasons. The retina in A (DBA/2J, unaffected optic nerve) shows no sign of degeneration. The retina in B showed moderate glaucoma by optic nerve grading; in this particular case, cell numbers in the nasal half of the retina were severely reduced, whereas the temporal half appears normal. C and D show severe glaucoma by nerve grading. Note that in the retina shown in C, even though the overall cell loss is severe, a region remains with fairly normal cell numbers. (E) Neurons in the GCL were counted along the nasotemporal axis and graphed as cells per millimeter squared. Open circles, C57BL/6J (one retina); black circles, 3-mo-old (predisease) DBA/2J (mean of three retinas ± SEM); green squares, DBA/2J nerve grade unaffected (mean of three retinas); blue diamonds, DBA/2J nerve grade moderate (one retina); red triangles, DBA/2J nerve grade severe (mean of four retinas). (F) GCL neurons along the dorsoventral axis (symbols are the same as in E).
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fig1: Neuronal cell counts in the GCL. (A–D) Total cells in the GCL, excluding endothelial cells and microglia, were counted and graphed as density maps. For easier comparison, all retinas are shown with a temporal to nasal orientation (as if they were all right eyes). The deep cut in the superior pole of the retina (arrowhead) was used for orientation during the preparation. Dark red corresponds to a cell density of 10,000 cells/mm2, as indicated in the color bar; areas shown in gray could not be counted because of technical reasons. The retina in A (DBA/2J, unaffected optic nerve) shows no sign of degeneration. The retina in B showed moderate glaucoma by optic nerve grading; in this particular case, cell numbers in the nasal half of the retina were severely reduced, whereas the temporal half appears normal. C and D show severe glaucoma by nerve grading. Note that in the retina shown in C, even though the overall cell loss is severe, a region remains with fairly normal cell numbers. (E) Neurons in the GCL were counted along the nasotemporal axis and graphed as cells per millimeter squared. Open circles, C57BL/6J (one retina); black circles, 3-mo-old (predisease) DBA/2J (mean of three retinas ± SEM); green squares, DBA/2J nerve grade unaffected (mean of three retinas); blue diamonds, DBA/2J nerve grade moderate (one retina); red triangles, DBA/2J nerve grade severe (mean of four retinas). (F) GCL neurons along the dorsoventral axis (symbols are the same as in E).
Mentions: For every retina, the severity of the glaucomatous damage was assessed by grading the optic nerve on a previously reported three-point scale (mild, moderate, and severe; Anderson et al., 2005; Libby et al., 2005a). Mild-stage nerves can have the minor degree of axon damage that occurs in normal mouse eyes at the studied ages, but they show no evidence of glaucomatous damage and are regarded as unaffected (Anderson et al., 2005; Libby et al., 2005c). By the age of 1 yr, a substantial percentage of DBA/2J mice have developed moderate or severe glaucoma as determined from optic nerve grading. Out of 67 optic nerves that were examined in this study, 19 (28%) showed no indication of glaucomatous damage, 3 (4%) were affected moderately, and 44 (66%) showed signs of severe disease (1 nerve was ungradeable). The progression of the disease in the left and right eyes of any one mouse was not highly correlated. We determined total cell numbers in the ganglion cell layer (GCL) in 29 retinas (4 of which were from 3-mo-old DBA/2J controls) by taking 16× or 25× surveys of the whole-mounted retina and counting the cell nuclei. As expected, the total cell counts corresponded well to the optic nerve grading. In the unaffected retinas, as in the 3-mo-old DBA/2J animals, the total cell density in the central parts of the retina exceeded 9,000 cells/mm2, which is conforms well with the figure determined previously in normal mice (∼8,000 cells/mm2), tapering off to ∼3,000–4,000 cells/mm2 in the periphery (Jeon et al., 1998). In the most severely affected retinas, we found maximal local cell densities of 6,000 cells/mm2 (Fig. 1). Interestingly, however, the cell loss was not uniform over the whole area of the retina. In some cases, one or two quadrants were spared from the disease (Fig. 1 B). It was not uncommon, even in retinas with strongly reduced overall ganglion cell counts, to find small sectors of the retina (Fig. 1 C), or at least small islands, that were almost normal. In the most severe cases, the total cell count in the GCL was reduced to a degree such that probably all the remaining cells are amacrine cells (Fig. 1 D). The implications of the spatial anisotropy will be discussed later. To begin, we will describe the neuronal changes that occur during the degeneration.

Bottom Line: Regions of cell death or survival radiated from the optic nerve head in fan-shaped sectors.Collectively, the data suggest axon damage at the optic nerve head as an early lesion, and damage to axon bundles would cause this pattern of degeneration.However, the architecture of the mouse eye seems to preclude a commonly postulated source of mechanical damage within the nerve head.

View Article: PubMed Central - PubMed

Affiliation: Howard Hughes Medical Institute, Harvard Medical School, Boston, MA 02114.

ABSTRACT
Using a variety of double and triple labeling techniques, we have reevaluated the death of retinal neurons in a mouse model of hereditary glaucoma. Cell-specific markers and total neuron counts revealed no cell loss in any retinal neurons other than the ganglion cells. Within the limits of our ability to define cell types, no group of ganglion cells was especially vulnerable or resistant to degeneration. Retrograde labeling and neurofilament staining showed that axonal atrophy, dendritic remodeling, and somal shrinkage (at least of the largest cell types) precedes ganglion cell death in this glaucoma model. Regions of cell death or survival radiated from the optic nerve head in fan-shaped sectors. Collectively, the data suggest axon damage at the optic nerve head as an early lesion, and damage to axon bundles would cause this pattern of degeneration. However, the architecture of the mouse eye seems to preclude a commonly postulated source of mechanical damage within the nerve head.

Show MeSH
Related in: MedlinePlus