Abstract
Purpose:
To map and quantify lens epithelial cell proliferation in a rodent model of lens regeneration.
Methods:
An extracapsular crystalline lens extraction that preserved the lens capsular bag and the anterior lens epithelium, was undertaken on the right eye of 30 male Sprague-Dawley rats. Contralateral, unoperated eyes, served as controls. An intraperitoneal injection of 1.5 ml of EdU (5-ethynyl-2’-deoxyuridine, 15 mg/ml) was performed prior to the sacrifice at times 0, 1, 2, 3 and 7 days postoperatively. Proliferating cells and nuclei were detected using Click-iT chemistry and DAPI, respectively. Four images per eye from the original germinative zone (GZ), central zone (CZ) and the incision wound area (WA) were randomly taken. Proliferating and total cell numbers in each picture were counted by ImageJ and delineator, a software specially developed by ourselves to count lens epithelial cells. The percentage of proliferating cells was obtained by dividing the number of EdU-positive cells by the total cell number for each region.
Results:
Regenerated lenses were optically clear and became thicker post-operatively. In all regenerated lenses, a relatively small linear scar was observed at the site of the surgical incision in the anterior capsule (site of opening of the lens capsular bag). Most cells in the original GZ and CZ retained a two layer distribution corresponding to the anterior and posterior capsule surfaces, which remained throughout the 7 days, whilst the cells in the WA proliferated and elongated to form multiple cell layers. The proportion of proliferating cells in the GZ and CZ of the control lenses was 3.37% and 0.62%. On day 1 postoperatively, a burst of cell proliferation occurred throughout the entire lens with a proportion of proliferating cells over 10 times higher than that in the GZ of control lenses. This elevated cell proliferation decreased on day 2 and came to a level similar to the GZ of control lenses on day 3 and day 7.
Conclusions:
The distribution and onset of lens epithelial cell proliferation following fibre cell extraction and preservation of the integrity of the lens capsular bag is similar to that observed in the early stages of lens development with cell proliferation occurring throughout. Nevertheless there are both temporal and radial influences on this proliferation rate.
Keywords: 687 regeneration