Immunohistochemical study of collagens of the extracellular matrix in cartilage of Sepia officinalis

We used various anti-collagen antibodies to perform indirect immunofluoresc ent staining of cartilage sections from cuttlefish (S. officinalis). On ult rathin sections and collagen fibril preparations from the same tissue, we p erformed immunostaining with colloidal gold. The extracellular matrix (ECM) of S. officinalis cartilage reacted intensely and homogeneously with an an tibody directed against type I-like collagen isolated from the cartilage of cuttlefish and with anti-rat type-V collagen antibody. A weak reaction was observed with anti-fish and anti-chicken type I collagen antibodies, while no reaction was observed with anti-rat type I and anti calf type II collag en antibodies. Anti-chicken type II, anti calf type IX and type XI collagen antibodies reacted weakly with ECM, while stained cell bodies and cell pro cesses reacted more intensely. A similar pattern of reaction was observed o n cartilage section and isolated collagen fibrils prepared for electron mic roscopy. These findings suggest that ECM of cuttlefish cartilage may be com posed of molecules similar to the type I, type V, type IX and type XI colla gen molecules of vertebrates. Cephalopods have evolved a cartilage of struc ture and macromolecular organisation similar to that of vertebrate cartilag e. However, the main molecular components of S. officinalis cartilage -type I-like and type V collagens- differ from those of vertebrate cartilage. We suggest that this type I-like collagen can be considered an initial step t oward the evolution of type II collagen typical of vertebrates.