Abstract
Purpose :
Previously, Soat1-/- mice were shown to have abnormal meibum that lacked one of its major lipid components – cholesteryl esters (CE). The mutation disrupted ocular homeostasis and led to an abnormal ocular phenotype such as slit eyes, abnormal cornea, increased tearing, and thick meibum. The purpose of this study was to investigate in depth the changes to the ocular tissues, such as cornea and tarsal plates (TP), due to the loss of Soat1.
Methods :
3 to 6 month old male and female Soat1-/- mice and their wild type (WT) littermates were studied. Eyes were enucleated, weighed, and cornea buttons (CB) and TP were harvested and processed for further examination. The corneal basement membrane (BM) was stained using periodic acid Schiff (PAS) staining kit. Upper and lower conjunctival flat mounts were stained with PAS to visualize and count the goblet cells in the conjunctival fornix. CB and TP transcriptomes were analyzed using mRNA microarrays. Lipid analysis of the TP was conducted using ultra high performance liquid chromatography and high resolution mass spectrometry (LC—MS).
Results :
The weights of WT and Soat1-/- eyeballs did not differ (P=0.378) indicating that the slit eye phenotype is not a result of a smaller eye in Soat1-/- mice. Soat1-/- corneas displayed alterations to the BM with patchy or absent PAS staining in the central cornea, while WT corneas retained uniform BM staining. Conjunctival flat mount staining revealed an increase of goblet cells (P<0.001) in the conjunctival fornix of Soat1-/- mice compared to WT mice. CB transcriptomes demonstrated a multifold increase in genes responsible for keratinization, keratinocyte differentiation, inflammation and MAPK1/ERKK2 cascade (e.g. Sprr1a, Sprr1b, Ptgs2, Cdsn, and Dusp1), among other changes. TP of Soat1-/- mice demonstrated a multifold decline in expression of genes of the wax esters (WE) and CE cascades, which correlated positively with a multifold decline of major meibomian WE and CE.
Conclusions :
These findings, together with our earlier results, suggest the existence of compensatory mechanisms in the cornea in response to Soat1 inactivation, and its broader impact on the lipid homeostasis in TP. Soat1-/- mouse model may be useful to improve our understanding of the underlying mechanisms that are involved in abnormal corneal and ocular phenotypes due to the altered lipid production in TP.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.