Limits...
Abnormal fiber end migration in Royal College of Surgeons rats during posterior subcapsular cataract formation.

Joy A, Mohammed TA, Al-Ghoul KJ - Mol. Vis. (2010)

Bottom Line: At all time points thereafter, F-actin was rearranged into a 'rosette' pattern of prominent foci at cell vertices.The data are consistent with the hypothesis that migration of basal fiber ends is altered in a two stage process wherein initially, migration patterns undergo a rapid shift resulting in abnormal suture sub-branch formation.Subsequent cytological alterations are consistent with an eventual cessation of migration, precluding proper targeting of basal ends to their sutural destinations and leading to cataract plaque formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, Rush University Medical Center, 600 S. Paulina St., Chicago, IL 60612, USA.

ABSTRACT

Purpose: Prior structural studies of posterior subcapsular cataract (PSC) development in Royal College of Surgeons (RCS) rats suggest that migration of basal fiber ends was disrupted, ultimately resulting in a PSC. Therefore the goal of this study was to assess the overall migration patterns as well as changes to the structure and cytoskeleton of basal fiber ends during PSC development.

Methods: Lenses from 48 RCS dystrophic rats (RCS/Lav) and 24 genetically matched control animals (RCS-rdy(+)/Lav) from 2 to 8 weeks old were examined. Equatorial diameters were measured and suture patterns were photographed immediately following enucleation/dissection. Right eye lenses were fixed and processed to visualize the actin cytoskeleton via laser scanning confocal microscopy (LSCM), left eye lenses were decapsulated, fixed and processed for scanning electron microscopy (SEM). Scaled 3D-computer assisted drawings (CADs) and animations were constructed from the data to depict the changes in suture patterns and fiber end architecture.

Results: At 2 weeks, dystrophic lenses displayed an inverted Y suture on the posterior, and by 3 weeks most lenses had at least one sub-branch. Additional sub-branches were observed with time, opacities being visible as early as 4 weeks and progressing into PSC plaques by 6 weeks. Control lenses displayed inverted Y sutures at all ages and were transparent. SEM of dystrophic lenses revealed fiber ends with normal size, shape, arrangement, and filopodia at 2 weeks; scattered areas of dome-shaped fiber ends and small filopodia were present at 3 weeks. At 4 weeks the irregularly arranged domed fiber ends had extremely long filopodia with 'boutons' at their tips. By 6 weeks all fiber ends within plaques displayed rounded or domed basal membranes and lacked filopodial extensions. Control lenses at all time points had comparable ultrastructure to the 2 week old dystrophic lenses. F-actin arrangement within the basal membrane complex (BMC) of control lenses showed the expected peripheral pattern of labeling at all ages. Dystrophic RCS lenses at 2 weeks were comparable to controls, however by 3-4 weeks they displayed scattered foci of F-actin within the BMC. At all time points thereafter, F-actin was rearranged into a 'rosette' pattern of prominent foci at cell vertices.

Conclusions: The data are consistent with the hypothesis that migration of basal fiber ends is altered in a two stage process wherein initially, migration patterns undergo a rapid shift resulting in abnormal suture sub-branch formation. Subsequent cytological alterations are consistent with an eventual cessation of migration, precluding proper targeting of basal ends to their sutural destinations and leading to cataract plaque formation.

Show MeSH

Related in: MedlinePlus

Scaled 3D-CAD animation summarizing the growth, changes in suture pattern and opacity formation in the RCS/Lav rat lenses. The animation begins with the normal posterior Y suture pattern at 2 weeks postnatal and follows the changes through 7–8 weeks postnatal, when the PSC completely obscures the suture. The changes in suture pattern begin as early as 3 weeks postnatal and continue to be altered with age. The loss of transparency is first seen as a sutural opacity at around 5 weeks of age, progressing to a large PSC by 7–8 weeks postnatal. Note that the slide bar at the bottom of the quicktime movie can be used to manually control the flow of the movie. If you are unable to view the movie, a representative frame for each movie is included below.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC2925909&req=5

f3: Scaled 3D-CAD animation summarizing the growth, changes in suture pattern and opacity formation in the RCS/Lav rat lenses. The animation begins with the normal posterior Y suture pattern at 2 weeks postnatal and follows the changes through 7–8 weeks postnatal, when the PSC completely obscures the suture. The changes in suture pattern begin as early as 3 weeks postnatal and continue to be altered with age. The loss of transparency is first seen as a sutural opacity at around 5 weeks of age, progressing to a large PSC by 7–8 weeks postnatal. Note that the slide bar at the bottom of the quicktime movie can be used to manually control the flow of the movie. If you are unable to view the movie, a representative frame for each movie is included below.

Mentions: Changes in posterior suture patterns and transparency were assessed using photographs of the posterior surface of unfixed RCS rat lenses immediately following sacrifice. The observations reveal that RCS rat lenses demonstrated rapid, abnormal changes from the expected suture pattern. At 2 weeks post natal, all lenses presented with the normal ‘inverted Y’ suture on the posterior surface (Figure 2A), however this pattern began to show changes in some lenses as early as 3 weeks postnatal, with the earliest change being the formation of one or more small sub-branches. Suture pattern alterations were more evident by 4 weeks postnatal with the formation of multiple abnormal suture sub-branches (Figure 2B, arrows). By 5 weeks, a sutural opacity was evident in most lenses (Figure 2C, arrowhead) and the opacity completely circumscribed the extent of the posterior suture branches (Figure 2D, arrows). The sutural opacity continued to expand between 5 and 6 weeks post natal (Figure 2E) and completely obscured the posterior suture by about 7–8 weeks post natal (Figure 2F). The genetically matched control lenses (RCS-rdy+/Lav) showed the expected inverted Y suture pattern at all age groups (Figure 2G-I). A scaled 3D-CAD animation (Figure 3) summarizes the changes (detailed above) in lens posterior suture pattern and transparency that occur in the dystrophic RCS rat lens between 2 and 8 weeks of age. The animation shows the alterations that begin as early 3 weeks of age and progresses gradually through the concomitant changes in suture pattern and the loss of transparency, with eventual PSC formation in the RCS rat lens. The growth of the lens is also depicted with phases of slower or paused growth that is seen by 7–8 weeks postnatal. By this age, the opacity continued to expand in size, but the lens by itself did not show a significant change in the equatorial diameter.


Abnormal fiber end migration in Royal College of Surgeons rats during posterior subcapsular cataract formation.

Joy A, Mohammed TA, Al-Ghoul KJ - Mol. Vis. (2010)

Scaled 3D-CAD animation summarizing the growth, changes in suture pattern and opacity formation in the RCS/Lav rat lenses. The animation begins with the normal posterior Y suture pattern at 2 weeks postnatal and follows the changes through 7–8 weeks postnatal, when the PSC completely obscures the suture. The changes in suture pattern begin as early as 3 weeks postnatal and continue to be altered with age. The loss of transparency is first seen as a sutural opacity at around 5 weeks of age, progressing to a large PSC by 7–8 weeks postnatal. Note that the slide bar at the bottom of the quicktime movie can be used to manually control the flow of the movie. If you are unable to view the movie, a representative frame for each movie is included below.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2925909&req=5

f3: Scaled 3D-CAD animation summarizing the growth, changes in suture pattern and opacity formation in the RCS/Lav rat lenses. The animation begins with the normal posterior Y suture pattern at 2 weeks postnatal and follows the changes through 7–8 weeks postnatal, when the PSC completely obscures the suture. The changes in suture pattern begin as early as 3 weeks postnatal and continue to be altered with age. The loss of transparency is first seen as a sutural opacity at around 5 weeks of age, progressing to a large PSC by 7–8 weeks postnatal. Note that the slide bar at the bottom of the quicktime movie can be used to manually control the flow of the movie. If you are unable to view the movie, a representative frame for each movie is included below.
Mentions: Changes in posterior suture patterns and transparency were assessed using photographs of the posterior surface of unfixed RCS rat lenses immediately following sacrifice. The observations reveal that RCS rat lenses demonstrated rapid, abnormal changes from the expected suture pattern. At 2 weeks post natal, all lenses presented with the normal ‘inverted Y’ suture on the posterior surface (Figure 2A), however this pattern began to show changes in some lenses as early as 3 weeks postnatal, with the earliest change being the formation of one or more small sub-branches. Suture pattern alterations were more evident by 4 weeks postnatal with the formation of multiple abnormal suture sub-branches (Figure 2B, arrows). By 5 weeks, a sutural opacity was evident in most lenses (Figure 2C, arrowhead) and the opacity completely circumscribed the extent of the posterior suture branches (Figure 2D, arrows). The sutural opacity continued to expand between 5 and 6 weeks post natal (Figure 2E) and completely obscured the posterior suture by about 7–8 weeks post natal (Figure 2F). The genetically matched control lenses (RCS-rdy+/Lav) showed the expected inverted Y suture pattern at all age groups (Figure 2G-I). A scaled 3D-CAD animation (Figure 3) summarizes the changes (detailed above) in lens posterior suture pattern and transparency that occur in the dystrophic RCS rat lens between 2 and 8 weeks of age. The animation shows the alterations that begin as early 3 weeks of age and progresses gradually through the concomitant changes in suture pattern and the loss of transparency, with eventual PSC formation in the RCS rat lens. The growth of the lens is also depicted with phases of slower or paused growth that is seen by 7–8 weeks postnatal. By this age, the opacity continued to expand in size, but the lens by itself did not show a significant change in the equatorial diameter.

Bottom Line: At all time points thereafter, F-actin was rearranged into a 'rosette' pattern of prominent foci at cell vertices.The data are consistent with the hypothesis that migration of basal fiber ends is altered in a two stage process wherein initially, migration patterns undergo a rapid shift resulting in abnormal suture sub-branch formation.Subsequent cytological alterations are consistent with an eventual cessation of migration, precluding proper targeting of basal ends to their sutural destinations and leading to cataract plaque formation.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Cell Biology, Rush University Medical Center, 600 S. Paulina St., Chicago, IL 60612, USA.

ABSTRACT

Purpose: Prior structural studies of posterior subcapsular cataract (PSC) development in Royal College of Surgeons (RCS) rats suggest that migration of basal fiber ends was disrupted, ultimately resulting in a PSC. Therefore the goal of this study was to assess the overall migration patterns as well as changes to the structure and cytoskeleton of basal fiber ends during PSC development.

Methods: Lenses from 48 RCS dystrophic rats (RCS/Lav) and 24 genetically matched control animals (RCS-rdy(+)/Lav) from 2 to 8 weeks old were examined. Equatorial diameters were measured and suture patterns were photographed immediately following enucleation/dissection. Right eye lenses were fixed and processed to visualize the actin cytoskeleton via laser scanning confocal microscopy (LSCM), left eye lenses were decapsulated, fixed and processed for scanning electron microscopy (SEM). Scaled 3D-computer assisted drawings (CADs) and animations were constructed from the data to depict the changes in suture patterns and fiber end architecture.

Results: At 2 weeks, dystrophic lenses displayed an inverted Y suture on the posterior, and by 3 weeks most lenses had at least one sub-branch. Additional sub-branches were observed with time, opacities being visible as early as 4 weeks and progressing into PSC plaques by 6 weeks. Control lenses displayed inverted Y sutures at all ages and were transparent. SEM of dystrophic lenses revealed fiber ends with normal size, shape, arrangement, and filopodia at 2 weeks; scattered areas of dome-shaped fiber ends and small filopodia were present at 3 weeks. At 4 weeks the irregularly arranged domed fiber ends had extremely long filopodia with 'boutons' at their tips. By 6 weeks all fiber ends within plaques displayed rounded or domed basal membranes and lacked filopodial extensions. Control lenses at all time points had comparable ultrastructure to the 2 week old dystrophic lenses. F-actin arrangement within the basal membrane complex (BMC) of control lenses showed the expected peripheral pattern of labeling at all ages. Dystrophic RCS lenses at 2 weeks were comparable to controls, however by 3-4 weeks they displayed scattered foci of F-actin within the BMC. At all time points thereafter, F-actin was rearranged into a 'rosette' pattern of prominent foci at cell vertices.

Conclusions: The data are consistent with the hypothesis that migration of basal fiber ends is altered in a two stage process wherein initially, migration patterns undergo a rapid shift resulting in abnormal suture sub-branch formation. Subsequent cytological alterations are consistent with an eventual cessation of migration, precluding proper targeting of basal ends to their sutural destinations and leading to cataract plaque formation.

Show MeSH
Related in: MedlinePlus