Collagen type I and type V are present in the same fibril in the avian corneal stroma.
The distribution, supramolecular form, and arrangement of collagen types I and V in the chicken embryo corneal stroma were studied using electron microscopy, collagen type-specific monoclonal antibodies, and a preembedding immunogold method. Double-label immunoelectron microscopy with colloidal gold-tagged monoclonal antibodies was used to simultaneously localize collagen type I and type V within the chick corneal stroma. The results definitively demonstrate, for the first time, that both collagens are codistributed within the same fibril. Type I collagen was localized to striated fibrils throughout the corneal stroma homogeneously. Type V collagen could be localized only after pretreatment of the tissue to partially disrupt collagen fibril structure. After such pretreatments the type V collagen was found in regions where fibrils were partially dissociated and not in regions where fibril structure was intact. When pretreated tissues were double labeled with antibodies against types I and V collagen coupled to different size gold particles, the two collagens colocalized in areas where fibril structure was partially disrupted. Antibodies against type IV collagen were used as a control and were nonreactive with fibrils. These results indicate that collagen types I and V are assembled together within single fibrils in the corneal stroma such that the interaction of these collagen types within heterotypic fibrils masks the epitopes on the type V collagen molecule. One consequence of the formation of such heterotypic fibrils may be the regulation of corneal fibril diameter, a condition essential for corneal transparency.
Birk
D E
DE
Department of Pathology, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway 08854.
Fitch
J M
JM
Babiarz
J P
JP
Linsenmayer
T F
TF
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002642:Chick Embryo; D003094:Collagen / Q000032:analysis* / Q000276:immunology; D003315:Cornea / Q000032:analysis* / Q000648:ultrastructure; D007150:Immunohistochemistry
D000911:Antibodies, Monoclonal; D003094:Collagen