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Lubica Dudakova, Sarka Kalasova, Katerina Jirsova; Presence of lysyl oxidase-like enzymes in human control and keratoconic corneas. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5293.
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© ARVO (1962-2015); The Authors (2016-present)
Lysyl oxidases, a family comprising lysyl oxidase (LOX) and four LOX-like enzymes, catalyze the crosslinking of elastin and collagen fibrils. LOX and LOX-like proteins differ mainly in their N-terminal sequence, which may confer individual functions. Recently, we have demostrated lower activity and an irregular pattern of LOX in keratoconic (KC) corneas compared healthy controls. To extend our knowledge about enzymes those crosslink collagens in the human cornea, we have focused on the detection of other members of this enzyme family in normal and KC corneas.
Cryosections of human control and KC corneas were used. The presence of LOX-like enzymes was examined using mouse anti-LOX-like 1 (sc-166632, Santa Cruz), mouse anti-LOX-like 2 (ab60753, Abcam) and rabbit anti-LOX-like 3 (sc-68939, Santa Cruz) and 4 (ab88186, Abcam) antibodies and indirect fluorescent immunohistochemistry. The staining intensity was assessed using fluorescent microscopy, and the intensity of cell staining was graded using a scale: 0: no staining, 1: weak, 2: moderate, 3: intense staining.
Weak immunostaining for LOX-like 1, represented by a punctate-like pattern throughout all parts of the cornea was observed in the control as well as in the KC samples. Using LOX-like 2 antibody, moderate to intense staining was observed in the epithelium, stroma and endothelium of control corneas. Irregular staining in the epithelium and a gradual weakening of the signal from moderate to weak was observed in the stroma. LOX-like 3 antibody yielded moderate to intense staining in the epithelium and endothelium of both control and KC samples. The staining in the stroma of control corneas was weak and almost absent in most of the KC specimens. Using LOX-like 4 antibody, the epithelium and endothelium of both control and KC samples showed a moderate to intense signal, while a moderate signal with a punctate-like pattern was observed in the stroma.
LOX-like enzymes were first described in normal human corneas as well as in keratoconic corneas. Almost no difference between control and pathological specimens were found in the staining for LOX-like 1 and 4. The decrease of LOX-like 2 and 3 staining in the keratoconic samples may indicate that other members of this enzyme family may participate in the pathogenesis of keratoconus.
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