Mouse strains and sexual divergence in corneal innervation and nerve regeneration

Abstract

A variety of mouse strains and sexes are used in studies of corneal wound healing and nerve regeneration. However, there is a gap of knowledge about corneal nerve density and its function in different mouse strains and sexes. In this study, we report a strain divergence of total and substance P (SP) sensory corneal nerves in uninjured mice. The BALB/c mouse showed the highest nerve density, corneal sensitivity, and tear volume followed by CFW and then C57BL/6. No differences were found in total nerves and SP-positive nerves between sexes. After injury damaged the corneal nerves, an important role for mouse strains, biologic sex, and their association to corneal nerve regeneration was identified. All female mice have a faster nerve regeneration rate than males. The molecular mechanism of this sexual divergence involves higher secretion neurotrophic factors in tears, which in turn modulate gene expression in trigeminal ganglion neurons. An important upstream signaling regulator was β-estradiol, and topical treatment with β-estradiol confirmed its function in corneal nerve regeneration. In conclusion, our study shows that the strain and sex of laboratory mice significantly affect the different indicators of corneal innervation and nerve regeneration. Researchers investigating corneal diseases should carefully consider these factors.—Pham, T. L., Kakazu, A., He, J., Bazan, H. E. P. Mouse strains and sexual divergence in corneal innervation and nerve regeneration.

Novel RvD6 stereoisomer induces corneal nerve regeneration and wound healing post-injury by modulating trigeminal transcriptomic signature

“…Substance P is a main neuropeptide in mammalian corneas [26][27][28] . Moreover, a previous study from our group has demonstrated that there is a correlation between corneal sensitivity and SP-positive nerves 29 . RvD6si-treated mice have significantly higher sensitivity at day 3, 6, and 9, while PEDF + DHA-and RvD6treated groups showed higher cornea sensation only at day 9.…”

“…Mice were anesthetized with a mix of ketamine (200 mg/kg) and xylazine (10 mg/kg) that was injected intraperitoneally, and one drop of proparacaine hydrochloride solution (0.5%) was applied to the right eye subjected to injury. As previously described 19,29 , the center of the cornea was demarcated with a 2 mm trephine, and the epithelium and the anterior stroma were gently removed under a surgical microscope using a corneal rust ring remover (Algerbrush II; Alger Equipment Co., Lago Vista, TX, USA). One drop of 0.3% of tobramycin ophthalmic solution (Henry Schein, Melville, NY, USA) was applied to the eye to prevent postoperative infection.…”

“…Corneal wound healing. As previously described 29 , mice were euthanized 20 h after injury and treatment, and corneas were stained with 0.5% methylene blue for 20sec and then washed with PBS for 2 min. Photographs were taken with a dissecting microscope (SMZ 1500; Nikon, Tokyo, Japan) through an attached digital camera (DXM 1200; Nikon).…”

“…Twelve days after injury and treatment, mice were euthanized, and the eyes enucleated and fixed with Zamboni's fixative (American Master Tech Scientific, Lodi, CA, USA) for 45 min at room temperature. As previously described 19,24,29 , the corneas were then excised and fixed for an additional 15 min, followed by 3 washes with PBS. To block nonspecific binding, corneas were incubated with 10% normal goat serum plus 0.5% Triton X-100 in PBS for 1 h at room temperature.…”

Amelioration of Both Central and Peripheral Neuropathy in Mouse Models of Type 1 and Type 2 Diabetes by the Neurogenic Molecule NSI-189

“…Dose-efficacy studies are warranted to establish whether this is a dose-or modelrelated phenomenon. Corneal nerve density was lower in control C57BLKS mice than in control Swiss Webster mice, reflecting known between-strain differences (43,44). It is notable that db/db mice did not show loss of sensory nerves in the corneal subbasal nerve plexus.…”