Comparison of different doses streptozotocin-induced mouse models for the research of type 1 diabetic keratopathy

Objective

To compare the rates and pathological features of diabetic keratopathy in mice induced by single high dose or multiple low dose streptozotocin (STZ) injections.

Methods

Eighty male C57BL/6 mice (6-8 weeks old) were randomly divided into 4 groups with each group contain 20 mice: normal control group, multiple low dose 1 month group and multiple low dose 3 months group (injected with 60 mg/kg STZ for 5 consecutive times), single high dose 1 month group (injected with 150 mg/kg STZ). The survival rate, model success rate, body weight, glycosylated hemoglobin (HbA1c) content were compared among different modeling group.The percentages of residual epithelial defect area were examined by fluorescein sodium staining after removal of central corneal epithelium.The expression of p-Akt, Sirt1 and Ki67 were evaluated by immunofluorescent staining.The corneal sensitivity were compared among different groups before corneal epithelial curettage, 3, 7, 10 and 14 days after corneal epithelial curettage.The corneal subbasal nerve density at 14 days after corneal epithelial curettage were compared among different groups.This study complied with the declaration of ARVO

Results

The success rate of diabetic modeling in multiple low dose 1 month group, multiple low dose 3 months group and single high dose 1 month group was 90%, 80% and 70%, respectively.The HbA1c levels in the diabetic modeling groups were significantly higher than that in the normal control group (all at P<0.05). The percentage of residual epithelial defect area 24 and 48 hours after corneal epithelial curettage in the multiple low dose 3 months group and single high dose 1 month group were significantly higher than those in the normal control group (all at P<0.05). The fluorescence intensity of p-Akt, Sirt1 and Ki67 in the multiple low dose 3 months group and single high dose 1 month group were stronger than those in the normal control group.There were no significant differences on corneal sensitivity and corneal nerve density between normal control and multiple low dose 3 months group before and 14 days after the corneal epithelial removal (all at P>0.05). However, the corneal sensitivity and corneal nerve density were dramatically decreased in the multiple low dose 3 months group and single high dose 1 month group before and 14 days after the corneal epithelial removal, and there were significant differences compared with normal control group (all at P<0.05).

Conclusions

The injection of 60 mg/kg STZ can not induce the features of diabetic keratopathy in mice within 1 month.However, the mice of both 1 month after 150 mg/kg STZ injection and 3 months after 60 mg/kg STZ injection appear the typical epithelial and nerve features of diabetic keratopathy, therefore can be the ideal animal models for research.