FIGURE 5.

Histological analysis of meibomian glands in Fatp4^−/−;Tg(IVL-Fatp4) mice reveals underdevelopment and progressive atrophy. Sagittal eyelid sections from Fatp4^−/−;Tg(IVL-Fatp4) mice and control littermates were subjected to Oil Red O staining and immunostaining with antibodies as indicated (higher magnification of boxed areas in K6 signals shown in E, F, O, and P). At P10.5, meibocytes of Fatp4^−/−;Tg(IVL-Fatp4) mice (arrowheads in B, D, F, and H) were dystrophic and mixed with many K6- and transgenic FATP4-positive epithelial cells, in contrast to controls (black arrowheads in A, C, E, and G). Those meibocytes also expressed low levels of transgenic FATP4 (compare insets of high magnification in G and H). By P53, residual meibocytes (arrowheads in L, P, and R) were enwrapped by thick layers of epithelial cells positive for K6- and transgene-derived FATP4, in contrast to controls (K, O, and Q). In controls, both K6 and FATP4 were detected in the surface layer of the luminal epithelium lining the main excretory ducts (white arrowheads in E and G) and the intralobular ducts (white arrowheads in O and Q). FATP4 levels in meibocytes declined when they matured centripetally (compare arrow and black arrowhead in Q). Fatp4^−/−;Tg(IVL-Fatp4) mice showed a normal level of SCD1 in residual meibocytes (green; arrowheads in J and T) and normal basement membranes by nidogen counterstain (red). Brackets and arrows in the top panels demarcate the meibomian glands and sebaceous glands of eyelash follicles, respectively. Asterisks mark the conjunctival side. Panels in the same column are from adjacent sections, except for K and S. Bars are 100, 100, and 50 μm for panels of low, medium, and high magnification, respectively.