Mouse strains and sexual divergence in corneal innervation and nerve regeneration

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.