Abstract
Purpose:
sPLA2-IIa has been demonstrated as a modulator of ocular surface (OS) inflammation and a biomarker of DED. Previous results on DED mice indicate that sPLA2-IIa is normally expressed in the fornix fold by the goblet (GC) and conjunctival (CNJ) epithelial cells but greatly induced by desiccation. However, the distribution of GCs is beyond the fornix of CNJ and does not fully overlap with that of sPLA2-IIa, and its role on cornea (CN) epithelia has not been clarified yet. The purpose of this study is to characterize the sPLA2-IIa+- cells in OS of DED mice.
Methods:
DED was induced on BALB/C mice as previously reported. Tear volumes were measured and ocular surface fluorescence staining were performed by masked ophthalmologists on Days 0, 4 and 7. Immunofluorescence assays (IFAs) were conducted on whole-mounted fresh eye samples or on frozen sections of inside-out or right-side-out eye samples.
Results:
Single or double staining with primary antibodies against sPLA-IIa and/or biomarkers of goblet cells (Muc5AC), epithelial cells (CK-7) and infiltrated inflammatory cells (CD11b, CD45 or Gr-1) were performed. (1) sPLA2-IIa+-signals are mainly found lining the surface of or within CNJ epithelial layer at fornix fold as previous reported; but heavy sPLA2-IIa+-staining can also be found on wounded CN epithelial spots, some even penetrating Stroma to reach to endothelial layer--- this has never been reported before; (2) most heavy staining signals of sPLA2-IIa co-localize with that of Muc5AC lining the CNJ epithelia at the fornix fold, some do not overlap with each other; (3) sPLA2-IIa+-signals weakly overlap with CK7+-signals; (4) sPLA2-IIa+-signals barely overlap with the CD11b+, CD45+ or Gr-1+-signals, these infiltrated inflamed cells are restrained by CNJ epithelia barrier.
Conclusions:
The heavy staining sPLA2-IIa+-cells separate from the infiltrated inflammatory responding cells may indicate a novel mechanism of sPLA2-IIa enzymes that pre-exist in the tear-film and OS to modulate immunity both in normal conditions and under stress. The finding of sPLA2-IIa accumulating at wounded corneal epithelial-defects may imply a possible new role of sPLA2-IIa in corneal wound healing and remodeling.
Keywords: 486 cornea: tears/tear film/dry eye •
514 enzymes/enzyme inhibitors •
637 pathology: experimental