Development and Long-Term Evaluation of Ocular Surface Conditions Using Ovariectomized Cynomolgus Monkey.

OBJECTIVES: We aim to use the ovariectomized cynomolgus monkey to observe the effect of long-term changes of sex hormone levels on ocular surface.

METHODS: Six healthy adolescent cynomolgus monkeys were randomly assigned to control and experimental groups (n=3/group). Bilateral ovariectomy was performed in experimental group, and sham operation was performed on control animals with their ovaries reserved. The concentrations of serum estradiol and testosterone in cynomolgus monkeys' lower-limb venous were detected by radioimmunoassay before surgery, and at 6, 12, 18, and 24 months after the surgery. Phenol red cotton thread test, tear osmolarity, corneal fluorescein staining, and conjunctival impression cytology were performed to evaluate the ocular surface conditions before surgery, and at 6, 12, 18, and 24 months after the surgery. The histological examinations of the bulbar conjunctiva and labial glands tissues were performed at 12 and 24 months after the surgery.

RESULTS: There were no significant differences in the serum level of estradiol and testosterone between the experimental and control groups before surgery, at 6, and 12 months after surgery (P>0.05). Serum level of estradiol and testosterone were significantly less in experimental versus control group at 18 and 24 months after surgery (P<0.05). There was no significant differences in phenol red cotton between the experimental and control groups before surgery, at 6, 12, 18, and 24 months after surgery (P>0.05). Tear osmolarity had no significant differences between experimental and control group before surgery (P>0.05), and it was significantly higher in experimental versus control group at all four time-points after surgery (P<0.05). The number of conjunctival goblet cells had no significant differences between experimental and control group before surgery, at 6 months after surgery (P>0.05), and it was significantly lower in experimental versus control group at 12, 18, and 24 months after surgery (P<0.05). There were no significant differences in the corneal fluorescein staining score between the experimental and control groups before surgery, at 6, 12, and 18 months after surgery (P>0.05), and it was higher in experimental than control group at 24 months after surgery (P<0.05). In addition, inflammatory cell infiltration in bulbar conjunctiva and labial glands tissues was observed in experimental group and was unobserved in control group at 24 months after surgery.

CONCLUSIONS: Ovariectomy led to decreased sex hormone levels in cynomolgus monkey. In turn, tear osmolarity was increased, the number of conjunctival goblet cells were decreased, the corneal fluorescence staining was increased, and the pathological examination of the bulbar conjunctiva and labial glands tissues were abnormal, phenol red cotton thread test did not change significantly.