Epidermal growth factor-like, corneal wound healing substance in mouse tears

We have identified the presence of a putative corneal wound healing substance in mouse tears, which has a molecular size and immunological properties similar to those of epidermal growth factor (EGF). The substance was capable of binding to EGF receptors in mouse parenchymal cells and this binding was inhibited by anti-EGF serum. The concentration of the EGF-like substance in the tears of male and female mice was estimated to be 79.3 +/- 7.0 (SD) ng/ml and 76.5 +/- 8.1 (SD) ng/ml, respectively, by EGF radioimmunoassay. Removal of the submandibular glands, which produce large amounts of EGF, reduced plasma EGF to an undetectable level and also decreased the concentration of the EGF-like substance in tears to 27.3 +/- 3.9 (SD) ng/ml in male mice and 25.8 +/- 3.7 (SD) ng/ml in female mice. Approximately 50% of sialoadenectomized (submandibular glands removed) male mice with deep corneal wounds developed severe ocular lesions or loss of sight whereas none of normal male mice with similar wounds did. Topical application of EGF to deeply wounded eyes of sialoadenectomized mice eliminated the various complications and restored the healing rate and incidence of recovery to virtually normal levels.