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Mature retinal pigment epithelium cells are retained in the cell cycle and proliferate in vivo.

Al-Hussaini H, Kam JH, Vugler A, Semo M, Jeffery G - Mol. Vis. (2008)

Bottom Line: These cells were negative for Caspase 3, hence were not apoptotic.Ki67-positive cells were also seen in human RPE.Further, many cells positive for BrdU were identified in similar retinal regions, confirming that RPE cells not only enter the cell cycle but also divide, albeit at a slow cell cycle rate.

View Article: PubMed Central - PubMed

Affiliation: Institute of Ophthalmology, University College London, London, United Kingdom.

ABSTRACT

Purpose: To investigate the capacity of mature retinal pigment epithelium (RPE) cells to enter the cell cycle in vivo using a range of RPE-specific and proliferative specific markers in both pigmented and albino rats.

Methods: Whole-mounted retinas of both Dark Agouti and albino rats were immunolabeled with cell cycle markers Ki67 or PCNA and double labeled with RPE cell marker RPE65 or CRALBP. The number and distribution of these cells was mapped. An additional group of Dark Agouti rats were given repeated intraperitoneal injections of Bromodeoxyuridine (BrdU )for 20 days and then sacrificed 30 days later. The retinas were then processed for BrdU detection and Otx, a RPE cell-specific marker. For comparison, human RPE tissue from a postmortem donor was also labeled for Ki67.

Results: In both pigmentation phenotypes, a subpopulation of mature RPE cells in the periphery were positive for both cell cycle markers. These cells were negative for Caspase 3, hence were not apoptotic. Ki67-positive cells were also seen in human RPE. Further, many cells positive for BrdU were identified in similar retinal regions, confirming that RPE cells not only enter the cell cycle but also divide, albeit at a slow cell cycle rate. There was a ten fold increase in the number of RPE cells positive for cell cycle markers in albino (approximately 200 cells) compared to pigmented rats (approximately 20 cells).

Conclusions: Peripheral RPE cells in rats have the capacity to enter the cell cycle and complete cellular division.

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Related in: MedlinePlus

The number of Ki67-positive cells found in the RPE flat mounts of pigmented animals sampled from embryonic day 18 (E18) through to postnatal day 150. Relatively few cells were in the cell cycle at E18, which is when the normal patterns of cell division in developing tissue end. However there was a marked increase (ANOVA, p<0.0001) in the number of these cells on the day of birth (0), which was statistically significant compared to E18 (Newman-Keuls, p<0.001). From P0 on, cell number gradually declined with age.
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f8: The number of Ki67-positive cells found in the RPE flat mounts of pigmented animals sampled from embryonic day 18 (E18) through to postnatal day 150. Relatively few cells were in the cell cycle at E18, which is when the normal patterns of cell division in developing tissue end. However there was a marked increase (ANOVA, p<0.0001) in the number of these cells on the day of birth (0), which was statistically significant compared to E18 (Newman-Keuls, p<0.001). From P0 on, cell number gradually declined with age.

Mentions: As the retina develops with a center to periphery gradient, such that late cell division occurs in the peripheral retina [19], it is natural to ask whether the relatively peripheral patterns of Ki67 labeling found in the mature RPE are not simply a reflection of those patterns present during late development, or whether they represent a distinct and separate event. We labeled RPE flat mounts from pigmented animals at progressive stages from E18 through the postnatal period and into maturity with Ki67. Unfortunately, it was not possible to generate retinal whole-mounts of sufficient quality before E18 without inducing some damage to the periphery that resulted in loss of labeled cells. At E18, approximately 50 Ki67-positive cells could be identified in the RPE sheet. However, three days later on the day of birth, there was a large increase in the number of positive cells found, from around 50 to approximately 260, which is statistically significant compared to the earlier time point (Newman-Keuls, p<0.001; Figure 8). From this point onward the number of positive cells declined gradually until around p20–P25 when their number reached comparable levels to those found in older animals. At all of these stages of development, few if any Ki67-positive cells were identified in central regions, rather they were confined to equatorial and peripheral retinal regions similar to that shown in Figure 2 for the adult. These patterns of Ki67 labeling through postnatal development were similar in albinos, although the absolute number of positive cells found was markedly elevated (data not shown). These data are consistent with the notion that the increase in cell labeling found in the RPE around the time of birth may represent a distinct and separate event from earlier patterns that start centrally and end in the periphery.


Mature retinal pigment epithelium cells are retained in the cell cycle and proliferate in vivo.

Al-Hussaini H, Kam JH, Vugler A, Semo M, Jeffery G - Mol. Vis. (2008)

The number of Ki67-positive cells found in the RPE flat mounts of pigmented animals sampled from embryonic day 18 (E18) through to postnatal day 150. Relatively few cells were in the cell cycle at E18, which is when the normal patterns of cell division in developing tissue end. However there was a marked increase (ANOVA, p<0.0001) in the number of these cells on the day of birth (0), which was statistically significant compared to E18 (Newman-Keuls, p<0.001). From P0 on, cell number gradually declined with age.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2562424&req=5

f8: The number of Ki67-positive cells found in the RPE flat mounts of pigmented animals sampled from embryonic day 18 (E18) through to postnatal day 150. Relatively few cells were in the cell cycle at E18, which is when the normal patterns of cell division in developing tissue end. However there was a marked increase (ANOVA, p<0.0001) in the number of these cells on the day of birth (0), which was statistically significant compared to E18 (Newman-Keuls, p<0.001). From P0 on, cell number gradually declined with age.
Mentions: As the retina develops with a center to periphery gradient, such that late cell division occurs in the peripheral retina [19], it is natural to ask whether the relatively peripheral patterns of Ki67 labeling found in the mature RPE are not simply a reflection of those patterns present during late development, or whether they represent a distinct and separate event. We labeled RPE flat mounts from pigmented animals at progressive stages from E18 through the postnatal period and into maturity with Ki67. Unfortunately, it was not possible to generate retinal whole-mounts of sufficient quality before E18 without inducing some damage to the periphery that resulted in loss of labeled cells. At E18, approximately 50 Ki67-positive cells could be identified in the RPE sheet. However, three days later on the day of birth, there was a large increase in the number of positive cells found, from around 50 to approximately 260, which is statistically significant compared to the earlier time point (Newman-Keuls, p<0.001; Figure 8). From this point onward the number of positive cells declined gradually until around p20–P25 when their number reached comparable levels to those found in older animals. At all of these stages of development, few if any Ki67-positive cells were identified in central regions, rather they were confined to equatorial and peripheral retinal regions similar to that shown in Figure 2 for the adult. These patterns of Ki67 labeling through postnatal development were similar in albinos, although the absolute number of positive cells found was markedly elevated (data not shown). These data are consistent with the notion that the increase in cell labeling found in the RPE around the time of birth may represent a distinct and separate event from earlier patterns that start centrally and end in the periphery.

Bottom Line: These cells were negative for Caspase 3, hence were not apoptotic.Ki67-positive cells were also seen in human RPE.Further, many cells positive for BrdU were identified in similar retinal regions, confirming that RPE cells not only enter the cell cycle but also divide, albeit at a slow cell cycle rate.

View Article: PubMed Central - PubMed

Affiliation: Institute of Ophthalmology, University College London, London, United Kingdom.

ABSTRACT

Purpose: To investigate the capacity of mature retinal pigment epithelium (RPE) cells to enter the cell cycle in vivo using a range of RPE-specific and proliferative specific markers in both pigmented and albino rats.

Methods: Whole-mounted retinas of both Dark Agouti and albino rats were immunolabeled with cell cycle markers Ki67 or PCNA and double labeled with RPE cell marker RPE65 or CRALBP. The number and distribution of these cells was mapped. An additional group of Dark Agouti rats were given repeated intraperitoneal injections of Bromodeoxyuridine (BrdU )for 20 days and then sacrificed 30 days later. The retinas were then processed for BrdU detection and Otx, a RPE cell-specific marker. For comparison, human RPE tissue from a postmortem donor was also labeled for Ki67.

Results: In both pigmentation phenotypes, a subpopulation of mature RPE cells in the periphery were positive for both cell cycle markers. These cells were negative for Caspase 3, hence were not apoptotic. Ki67-positive cells were also seen in human RPE. Further, many cells positive for BrdU were identified in similar retinal regions, confirming that RPE cells not only enter the cell cycle but also divide, albeit at a slow cell cycle rate. There was a ten fold increase in the number of RPE cells positive for cell cycle markers in albino (approximately 200 cells) compared to pigmented rats (approximately 20 cells).

Conclusions: Peripheral RPE cells in rats have the capacity to enter the cell cycle and complete cellular division.

Show MeSH
Related in: MedlinePlus