Sphingolipid Expression During Corneal Wound Healing in a Sphingosine Kinase 1 Knockout Model

Corneal scarring is a result of unregulated fibrotic processes in wound healing, which causes visual impairment. Bioactive sphingolipids (SPLs) are known to modulate physiological processes that are central to wound healing. Of these bioactive SPLs, sphingosine-1-phosphate (S1P) is perhaps the most studied. Previous research has shown that knocking out sphingosine kinase 1 (Sphk1), which produces S1P, alters SPL species metabolism and improves wound healing in mice corneas. However, it is unknown how SphK1 knockout (SphK1^-/-) affects SPL metabolism during stages of corneal wound healing. Following an alkali burn procedure on wild-type (WT) and SphK1^-/- mice, corneal lipidomic profiles in unburned corneas at 1, 7, 14, and 28 days post-injury (DPI) were measured. Significant differences in SPL species between genotypes, both in uninjured mouse corneas and during distinct stages of corneal burn healing, were observed. WT mice expressed burn healing stage-dependent modulation of SPL species, with decreased expression of most SPL species observed at 1 and 14 DPI. Interestingly, this wild-type SPL modulation was absent in most measured SPL species in the SphK1^-/- corneas. These findings provide evidence for a previously unknown modulatory role of SphK1 and S1P on the expression of SPLs during corneal wound healing.