Abstract
Purpose: :
To investigate how aging impacts morphology of the mouse palpebral conjunctival epithelium.
Methods: :
Male and female C57BL/6 mice, young adults (8 weeks), retired breeder (9-12 months, RB) and 24 months (24M) of age were utilized. One eye was fixed in 2% glutaraldehyde and processed for histology using an established protocol. The fellow eye was frozen or embedded in paraffin and utilized for immunostaining [PAS, Ki-67, MUC5AC or cytokeratin7 (K7)]. Counts and conjunctival thickness measurements were obtained from the semi-thin sections utilizing anatomical reference points and NIS elements software.
Results: :
The goblet cell populated region of the young adult mouse epithelium measured 23.5 ± 3.5 µm and was significantly thicker than the RB (19.4 ± 2.8 µm) and the 24M (20.3 ± 3.0 µm) (P < 0.05). This thickness difference was more prominent in the central portion of this area (26.1 ± 3.5 µm) young adult, (19.9 ± 3.3 µm) RB and 20.4 ± 2.7 µm) (P < 0.05). The number of Ki-67 positive cells increased with age both in the lid margin region and in the in the goblet cell rich region of the palpebral conjunctiva. A decreased number of PAS positive (+), K7+ MUC5AC double+ goblet cells was found with age. Increased epithelial coverage of goblet cells was another feature noted in the 24M old mice compared to the younger groups.
Conclusions: :
This study illustrated that the morphology of the stratified palpebral conjunctival epithelium changes with age. The palpebral conjunctival epithelium becomes significantly thinner, potentially due to increased desquamation that stimulates proliferation of basal epithelial cells in the aging mouse. A decrease in number of goblet cells and an increased epithelial coverage of the existing goblet cells are two other age induced changes. This information provides valuable clues regarding the effects of age on conjunctival epithelial and goblet cell differentiation and proliferation.