Cornea is a highly differentiated tissue rich in extracellular matrix (ECM)
specifically distributed in space in order to insure its dual role - trans
parency and protection of inner eye-tissues. Corneal ECM is especially rich
in collagens. Since the characterisation of a number of distinct collagen
types it appeared that most of them are present in the cornea. Their synthe
sis follows a specific program of sequential expression of the different co
llagen types to be synthesised during the development and maturation of the
cornea. The precise regulation of the diameter and orientation of fibers,
and of the interfibrillar spaces is partially at least attributed to intera
ctions between glycosaminoglycans and collagens. This 'program' of vectoria
l collagen synthesis and GAG-collagen interactions changes also with age an
d in several pathological conditions as corneal dystrophies and wound heali
ng. The Maillard reaction, especially in diabetes, is one of these importan
t factors involved in age-dependent modifications of corneal structure and
function. Far from being inert, corneal collagens were shown to have relati
vely short half-lives. The biosynthesis of corneal collagens was studied al
so during wound healing. The refibrillation of wounded corneas does not fol
low the original 'program' of ECM-synthesis as shown by the comparative stu
dy of wound healing using biochemical and morphometric methods. This review
recapitulates briefly previous and recent studies on corneal collagens in
order to present to clinicians and scientists an overview of the state of t
he art of this important field at the intersection of eye research and matr
ix biology. (C) 2001 Editions scientifiques et medicales Elsevier SAS.