MUC4 and dry eye syndrome: The evolution of the dry eye condition was assessed by histology, immunohistochemistry staining, scanning electron microscopy, and gene expression by using TaqMan gene assay technology (mucin-4 [MUC4], matrix metallopeptidase-9 [MMP9], tumor necrosis factor-α [TNF-α], and defensin β-2 [DEFB2).