[Pathobiochemistry of organ fibroses. Changes in the connective tissue metabolism in liver fibrosis and in chronic polyarthritis]

Many chronic inflammations of various origin are characterized by an elevated metabolic activity of connective tissue, causing an increased tissue proliferation. The authors first review the more recent methods of analyzing the connective tissue metabolism. Details of changes of this metabolism are described with reference to liver fibrosis and rheumatoid arthritis. First steps of a pathobiochemical diagnosis of activity in organ fibroses are discussed. It seems possible to judge the activity of liver fibrosis by estimating the serum activity of lysosomal glycosidases and serum levels of terminal collagen peptides. Elevated antiprotease serum levels in rheumatoid patients may indicate an inflammatory activity.

Separate amino and carboxyl procollagen peptidases in chick embryo tendon

Procollagen synthesized by freshly excised chick enbryo leg tendons is efficiently processed by proteolytic removal of first the amino propeptides and then the carboxyl propeptides. The same processes proceed in confluent short term cell cultures derived from such tendon explants; in sparse cultures cleavage of the amino propeptides predominates. Separate amino and carboxyl procollagen peptidase activities were demonstrated by specific assays in enzymes obtained from cell culture media by ammonium sulfate precipitation, ion exchange chromatography, and velocity sedimentation. Both enzymes are inhibited by EDTA and 1:10 phenanthroline but not by inhibitors of serine proteases. Evidence is provided that the proteolytic scissions are specific and similar to the physiologically occurring processes. The collagen telopeptides left after cutting by the enzymes can participate in lysyl oxidase-induced cross-linking. The enzymes can remove propeptides from cross-linked procollagens without destroying these links which occur through telopeptides. The enzymes act on the separated amino and carboxyl portions of procollagen fragmented by vertebrate collagenase and can act on procollagens which have been associated as well as on molecules in solution.

[The biochemistry of collagen and the locomotor apparatus. Hereditary diseases of connective tissue and rheumatologic diseases (part 2)]

In lathyrism, the toxic agent directly blocks the development of the transverse links in the collagen fibre, while in bovine dermatosparaxis there is a deficiency of procollagen peptidase. Of the many clinical forms of the Ehlers-Danlos syndrome, some are due to a deficiency of lysine oxidase, others to deficiency of lysine hydroxylase and still others to procollagen peptidase deficiency. The essential deficiency in Marfan's disease is still unknown, but that in homocystinuria causes blocking of the groups necessary to form the transverse links. In osteogenesis imperfecta, which is probably a heterogeneous group, there is deficient consolidation of the collagen fibrils, the cause of which is still unknown. One possibility is a quantitative imbalance between chains of different types. In scleroderma there is excessive synthesis of an apparently normal connective tissue; the cause of this is also still unknown.

[Biochemistry of collagen and the locomoter apparatus (Hereditary connective tissue diseases and rheumatic diseases. Part I]

The elementary collagen molecule consists of three chains rolled into a spiral and ending in nonhelical telopeptides. In cutaneous collagen, there are two types of chains, in cartilaginous collagen there is only one. In the synthesis, several enzymes play successive parts: proline hydroxylase, lysine hydroxylase, then pro-collagen peptidase and finally, lysine oxidase and hydroxylysine oxidase; their coordinated actions ultimately allow the chains to establish the transverse intra and intermolecular links which give the collagen fiber its cohesion. The type and number of these transverse links vary from one tissue to another. Specific collagenases make collagen degradation possible.

Connective tissue metabolism in culture fibroblasts of a patient with Ehlers-Danlos syndrome type I

Study on connective tissue metabolism was conducted with a patient with Ehlers-Danlos syndrome (E-D) of Type I who visited our institute. The conversion of procollagen into tropocollagen in the medium of cultured fibroblasts was assayed by the chase technique using 3H-proline. The conversion was inhibited in the cultured fibroblasts of the patient. The components of glycosaminoglycans in cultured medium and fibroblasts from E-D were within normal ranges, however, the ratio of glycoprotein to glycosaminoglycans of intra- and extra-cellular fractions of E-D fibroblasts was higher than the normal one. These findings suggest that the insufficient maturation of collagen fiber may be considered fundamental disorders of E-D.