Purpose

The purpose of this study was to assess the ability of quantitative in vivo confocal microscopy (CM) to detect changes in cystine crystal volume in the cystinosisn (Ctns^−/−)mouse cornea following topical cysteamine therapy.

Methods

Fifteen Ctns^−/− mice were sequentially followed using in vivo CM from 3 to 10 months of age. In a second experiment, five mice receiving topical cysteamine eyedrops (0.55%) for 4 weeks were compared to five untreated mice. The volume of corneal cystine crystals was determined by thresholding and counting high intensity pixels in the in vivo CM scans and dividing by the stromal volume to calculate a crystal volume index (CVI).

Results

Corneal crystals progressively increased in density with age, reaching a peak density at 6–8 months and showing a 70 fold increase in CVI. Eyes treated with cysteamine drops showed significantly less crystal accumulation compared to control eyes (p<0.001) with only a 15% increase in treated eyes (p=ns) compared to 173% increase (p<0.04) for untreated eyes.

Conclusions

Measurement of CVI shows that there is a progressive increase in cystine crystal volume up to 8 months of age and that cysteamine eyedrops significantly inhibits progression in the Ctns^−/− mouse. These findings are similar to those seen clinically in patients with cystinosis, and suggest that measurement of CVI in the Ctns^−/− mouse may be used as a model to develop novel therapeutic strategies for treating corneal cystinosis.

Purpose

Blinding ocular herpetic disease in humans is due to spontaneous reactivation of herpes simplex virus type 1 (HSV-1) from latency, rather than to primary acute infection. Mice latently infected with HSV-1 undergo little or no in vivo spontaneous reactivation with accompanying virus shedding in tears. HSV-1 reactivation can be induced in latently infected mice by several in vivo procedures, with UV-B-induced reactivation being one commonly used method. In the UV-B model, corneas are scarified (lightly scratched) just prior to ocular infection to increase efficiency of the primary infection and immune serum containing HSV-1 neutralizing antibodies is injected intraperitoneally (i.p.) to increase survival and decrease acute corneal damage. Since scarification can significantly alter host gene transcription in the cornea and in the trigeminal ganglia (TG; the site of HSV-1 latency) and since injection of immune serum likely modulates innate and adaptive herpes immunity, we investigated eliminating both treatments.

Material and methods

Mice were infected with HSV-1 with or without corneal scarification and immune serum. HSV-1 reactivation and recurrent disease were induced by UV-B irradiation.

Results

When corneal scarification and immune serum were both eliminated, UV-B irradiation still induced both HSV-1 reactivation, as measured by shedding of reactivated virus in tears and herpetic eye disease, albeit at reduced levels compared to the original procedure.

Conclusion

Despite the reduced reactivation and disease, avoidance of both corneal scarification and immune serum should improve the clinical relevance of the UV-B mouse model.