| Background：Stem cells are the kind of cells that have the capabilities of self-renewal andmultipotential differentiation. These cells can reconstruct a certain tissue or an organ undersome specific environments. To date, many kinds of stem cells have been found indifferent tissues and organs, for example, hematopoietic stem cells and bone marrow stemcells. There are also many stem cells in the eye, for instance, corneal limbal stem cells andretinal stem cells. Some evidences have indicated that stem cells exist in the lenses, thelocation and characteristics of them are not clear. In our study, we will try to detect thelens stem cells by characteristics of stem cell, such as slow metabolism, expressingspecific stem cell markers and proliferation after stimulating of injury.Objectives：To detect the possible stem cells in the lens epithelium and investigate their location.To observe the proliferation of lens epithelial cells after stimulating of injury. Methods：Sixty3-week-old Balb/c mice were randomly divided into BrdU-labeling group(n=30) and0.9%saline control group (n=30). In BrdU-labeling group, mice were injectedintraperitoneally with bromodeoxyuridine (BrdU) twice daily at the dose of150mg/Kg for10days. In0.9%saline control group, mice were injected intraperitoneally with0.9%saline at the dose of15ml/Kg twice daily for10days. Three mice (n=3) were killed at0w,1w,2w,3w,4w,6w,8w,10w,12w and14w after BrdU or normal saline injection,respectively. The cryosections of the eyes were prepared. By immunofluorescent stainingof BrdU, the BrdU label-retaining cells (LRCs) which represent the slow-cycling cells inlens epithelium were detected. By immunofluorescent staining of SOX2, one of themarkers of stem cells, SOX2positive cells were detected at0w,4w,8w,12w and14w. Inaddition, twelve3-week-old mice were operated on to make the model of lens anteriorcapsular injury. The right eye of each mouse was injured for experiment，and the left eyewas not injured for control. Then, every three mice were injected intraperitoneally withBrdU at the dose of150mg/kg once at0h,12h,24h and36h after capsular injury.1h afterinjection, whole mounts of the lens capsules were prepared, BrdU positive cells weredetected by immunofluorescent staining.Results：After BrdU labeling, about100%of the lens epithelial cells were incorporated BrdU,while the percentage of BrdU positive cells declined with time. At week12, thepercentage of BrdU positive cells at the central and equatorial zone reached the lowestlevel, which were14.23%and5.86%, respectively (t=-20.123, P=0.000). SOX2positivecells mainly located at the central zone of lens epithelium and the percentage of positivecells was stable，3.74%at week0and3.70%at week14(t=0.027, P=0.979). In someBrdU-labeling cells, SOX2expressed at the central zone of lens epithelium.At the central zone of the lens epithelium in control groups, BrdU positive cells perfield (×400) under the microscope were stable. In anterior capsular injured groups, the numbers of BrdU positive cells per field at central zone are different. It was44.9±10.9（vs.28.5±8.0）at0h, reached the highest level111.8±17.2（vs.26.4±6.0）at12h, and thendeclined to the lowest level,27.5±9.7(vs.26.1±8.1) at36h. For BrdU positive cells perfield at equatorial zone, there are no significant differences between two groups andamong different time points.Conclusions：Both BrdU-label retaining and SOX2positive cells are mainly located at the centralzone of the lens epithelium. Some of the cells at this zone start to proliferate afterstimulating of injury. This suggests that the lens stem cells may exist at the central zone oflens epithelium. |
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