Dysfunction of tear film and ultrastructural changes of corneal epithelial cells in castrated male mice

Background

Studies indicate that the decline of androgen level affects the secretion function of epithelial cells of meibomian glands and lacrimal glands, which results in the abnormality of tear quality and quantity. However, whether androgen level regulates the mucin adhesion to ocular surface is still not elucidated.

Objective

This study was to investigate the tear functional changes and corneal ultrastructural changes in castrated male mice.

Methods

Fifty-six SPF male BALB/c mice were devided into normal control group, sham group, and orchectomy 1-week group, orchectomy 2-week group, orchectomy 4-week group, orchectomy 6-week group, orchectomy 8-week group according to random number table. Orchectomy was performed in the mice of the orchectomy 1-, 2-, 4-, 6-and 8-week group, and only incision rather than enucleation of testis was carried out in the mice of the sham group. Peripheral venous blood samples were collected during eyeball enucleation in all the mice and serum androgen concentration was detected by radioimmunoassay. Tear secretion level was measured with phenol red thread. Break-up time of tear film (BUT) was tested, and corneal inflorescence staining was scored based on the criterion of Toshida. The corneas of all the mice were collected for ultrastructural examination under the transmission electron microscope. The study complied with the Regulations for the Administration of Affairs Concerning Experimental Animals by State Science and Technology Commission.

Results

Mouse serum androgen concentration was (573.87±6.74)ng/μl in the normal control group and (579.74±8.24)ng/μl in the sham group, and there was no significant difference between these two groups (t=1.432, P=0.251), however, the serum androgen concentration was 0 ng/μl in all castrated mice after orchectomy. The tear secretion levels were (5.26±0.99), (4.89±0.56), (4.62±0.83), (4.28±0.63), (3.36±0.56), (2.60±0.27) and (2.08±0.35)mm/5 minutes in the normal control group, sham group and orchectomy 1-, 2-, 4-, 6-and 8-week groups, respectively, and the tear secretion levels were significantly lower in the orchectomy 2-, 4-, 6-and 8-week groups than those in the normal control group (all at P<0.05). The BUT were (68.33±12.86), (62.47±3.75), (58.67±10.03), (47.17±7.64), (39.51±3.39), (32.67±3.88) and (31.00±2.36) seconds in the normal control group, sham group and orchectomy 1-, 2-, 4-, 6-and 8-week groups, respectively, and the BUTs were significantly shorter in the orchectomy 2-, 4-, 6-and 8-week groups than those in the normal control group (all at P<0.05). The fluorescein stain score of corneal epithelium was gradually increased with the lapse of castrated time. The decrease of number, shortening and edema of microvilli as well as separation of desmosomes of corneal epithelial cells were found under the transmission electron microscope in castrated mice.

Conclusions

Decreasing of serum androgen level, declining of aqueous tears, instability of tear film and damage of corneal epithelial cell ultrastructures occur in castrated male mice, and these manifestations are similar to dry eyes.

[Key words] Androgen; Epithelial cells, corneal; Dry eye; Tear; Ultrastructure; Orchectomy; Disease models, animal; Mice, BALB/c