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Azucena H Kakazu, Thang L Pham, Scott Sullivan, Kenneth Terry II, Jiucheng He, Haydee E P Bazan; Mice gender and strain affect neurotrophin secretion and corneal nerve regeneration after injury. Invest. Ophthalmol. Vis. Sci. 2017;58(8):154.
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A variety of mouse strains and genders are used in studies of corneal wound healing and nerve regeneration. Previous studies have shown that C57BL/6 mice heal corneal epithelial wounds faster than BALB/c (S. Pal-Ghosh, et al. Exp. Eye Res. 2008;87:478-486) and that female mice have slower re-epithelialization compared with males (T. Krishnan, et al. Br J Ophthalmol.2012;96:137-8). The purpose of this study is to compare different mouse strains and genders on corneal wound healing, neurotrophin secretion in tears, corneal sensitivity, and nerve regeneration after corneal injury.
Eight week-old male and female BALB/c, C57BL/6, and CFW mouse strains were used for this study. The epithelium from the right eye was wounded using an Algerbrush II inside a 2mm diameter surface demarked with a trephine. Corneal sensitivity was measured and the Schirmer test performed every 3 days for two weeks. Tears were collected at days 4, 7, 10, and 13 and analyzed by Western blot for the secretion of BDNF (brain derived neurotrophic factor) and NGF (nerve growth factor). At 24h post-injury, mice from each group were euthanized and the corneas stained with methylene blue to quantify the wounded area. At days 7 and 14, corneas from each strain and gender were collected and stained with the monoclonal antibody anti-PGP 9.5 (protein gene product 9.5) to quantify the total corneal nerves.
Twenty-four hours after injury, corneal wound healing in BALB/c and C57BL/6 mice was 1.24 and 1.84 time faster compared with CFW mice. Gender also affected the healing rate in each strain with higher healing in males than females. BALB/c and C57BL/6 strains were shown to have faster recovery of corneal sensitivity compared to the CFW strain, returning to the baseline at day 6 for BALB/c and at day 9 for C57BL/6. Significant changes in sensitivity between genders was found only in the C57BL/6 strain. There were significant differences in the secretion of BDNF but not of NGF in tears for all three strains. BALB/c mice showed higher corneal nerve densities (12.25±0.58 %) at 14 days after injury compared to C57BL/6 (9.45±0.57 %) and CFW (10.41±0.67 %) mice.
Our study shows that strain as well as gender of laboratory mice may significantly impact the different indicators of corneal nerve regeneration and wound healing. These factors should be carefully considered by researchers investigating the mouse cornea.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
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