Further biochemical and physicochemical characterization of minor disulfide-bonded (type IX) collagen, extracted from foetal calf cartilage

Contributions of Women in Recent Research on Biopolymer Science

Nowadays, biopolymers are playing a fundamental role in our society because of the environmental issues and concerns associated with synthetic polymers. The aim of this Special Issue entitled ‘Women in Polymer Science and Technology: Biopolymers’ is highlighting the work designed and developed by women on biopolymer science and technology. In this context, this short review aims to provide an introduction to this Special Issue by highlighting some recent contributions of women around the world on the particular topic of biopolymer science and technology during the last 20 years. In the first place, it highlights a selection of important works performed on a number of well-studied natural polymers, namely, agar, chitin, chitosan, cellulose, and collagen. Secondly, it gives an insight into the discovery of new polysaccharides and enzymes that have a role in their synthesis and in their degradation. These contributions will be paving the way for the next generation of female and male scientists on this topic.

Thermally labile domains in the collagen molecule

We have proposed that the denaturation kinetics of the characteristic sharp melting point of the collagen molecules is an irreversible rate rather than an equilibrium process as previously believed. This leads to the concept of domains of variable thermal stability along the length of the molecule. We have identified the major thermally labile domains from which the denaturation process is initiated as hydroxyproline deficient sequences of 65, 65 and 59 residues near the carboxy terminus in fibrillar collagen types I, II and III, respectively. These domains differ in that there is a single hydroxyproline in the type II domain and two hydroxyprolines in the type III domain. Similar sized domains are conserved in these collagen types across species including amphibians and invertebrates. The effective size of the domain is reduced in the fibrillar aggregates to 26 residues due to the interaction with adjacent molecules and because of the precise quarter-staggered alignment of the molecules the domains are located in the gap region. This spatial confinement within the lattice of the fibre leads to the significant increase in denaturation temperature of the fibre compared to the molecule. These labile domains have also been located in molecules that form the non-fibrillar type IV basement membrane collagens and the fibril-associated aggregates such as type IX. Based on the location of the different domains in type IX we have proposed a different arrangement of the type IX on the type II fibril. The model stresses the importance of hydroxyproline in stabilising the triple helix and supports the concept of hydrogen-bonded water-bridges originally proposed from X-ray diffraction studies in contrast to other studies indicating water-bridges do not play a role in stabilising the collagen molecule.

Oral tolerization as a treatment of rheumatoid arthritis

The basic science immunology community is quite accepting of the phenomenon of oral tolerance induction in animals; however, in contradistinction, the clinical community is somewhat agnostic regarding oral tolerance. Progress in multiple sclerosis has not been definitive and outcomes in RA have been modest at best. Recent reports in animal models have suggested that oral ingestion of autoantigen can have deleterious effects on the host. Although those experiments have had a highly artificial framework, they are consistent with the possibility that oral antigen therapy in human disease may be: (1) beneficial; (2) of no consequence; or (3) detrimental. An extremely open mind will hopefully be applied to future research efforts.

Determination of collagen-proteoglycan interactions in vitro

The objective of this study was to characterize the physical interactions of the molecular networks formed by mixtures of collagen and proteoglycan in vitro. Pure proteoglycan aggrecan solutions, collagen (type II) suspensions and mixtures of these molecules in varying proportions and concentrations were subjected to viscometric flow measurements using a cone-on-plate viscometer. Linear viscoelastic and non-Newtonian flow properties of these solutions and suspensions were described using a second-order statistical network theory for polymeric fluids (Zhu et al., 1991, J. Biomechanics 24, 1007-1018). This theory provides a set of material coefficients which relate the macroscopic flow behavior of the fluid to an idealized molecular network structure. The results indicated distinct differences between the flow properties of pure collagen suspensions and those of pure proteoglycan solutions. The collagen network showed much greater shear stiffness and more effective energy storage capability than the proteoglycan network. The relative proportion of collagen to proteoglycan is the dominant factor in determining the flow behavior of the mixtures. Analysis of the statistical network theory indicated that the collagen in a collagen-proteoglycan mixture enhances molecular interactions by increasing the amount of entanglement interactions and/or the strength of interaction, while aggrecan acts to reduce the number and/or strength of molecular interactions. These results characterize the physical interactions between type II collagen and aggrecan and provide some insight into their potential roles in giving articular cartilage its mechanical behavior.

Oral type II collagen treatment in early rheumatoid arthritis. A double-blind, placebo-controlled, randomized trial

OBJECTIVE

To investigate the efficacy of oral type II collagen in the treatment of early rheumatoid arthritis (RA).

METHODS

Ninety patients with RA (disease duration < or = 3 years) were treated for 12 weeks with oral bovine type II collagen at 1 mg/day (n = 30) or 10 mg/day (n = 30) or with placebo (n = 30), in a double-blind randomized study.

RESULTS

There were no significant difference between the 3 groups in terms of response to treatment. However, we observed a higher prevalence of responders in the type II collagen-treated groups: 7 responders in the 10-mg type II collagen group and 6 in the 1-mg group, versus 4 in the placebo group. Furthermore, 3 patients in the 10-mg type II collagen group and 1 patient in the 1-mg type II group, but no patients in the placebo group, had very good response. A total of 14 patients had to be withdrawn from the study: 2 because of side effects (nausea) and 12 because of lack of efficacy.

CONCLUSION

Only a minority of patients responded to treatment with oral type II collagen. These results justify further efforts to identify which patients will have good response to such therapy.

Ultrastructural organization of type XI collagen in fetal bovine epiphyseal cartilage

Type XI collagen was localized with polyclonal antibodies specific for alpha 1 (XI) and alpha 2 (XI) chains in the resting zone of epiphyseal cartilage from calf fetuses. The immunofluorescence technique was used on sections of cartilage, and the immunogold labelling technique for electron microscopy on fibrils isolated from cartilage and, for the first time, in situ on blocks of cartilage fractured in liquid nitrogen. Immunofluorescence showed that without pepsin treatment the staining of type XI collagen was restricted to the pericellular zones; after pepsin treatment, the staining was co-distributed with that of type II collagen. Immunoelectron microscopy performed on isolated fibrils and on cartilage blocks showed that after disruption of fibrils with pepsin, type XI collagen was labelled on small filaments on the fibrils. When the fibrils were not disrupted, labelling was observed in situ only at the ends of the fibrils or on cross-sections of some fibrils. These results indicate that type XI collagen is located inside type II collagen fibrils in fetal bovine epiphyseal cartilage, as already postulated for embryonic chicken sterna.

Autoantibodies to cartilage collagens in relapsing polychondritis

Relapsing polychondritis is a systemic disease associated with a destruction of cartilage in various parts of the body. Sera from six patients with relapsing polychondritis and one patient with microscopic polyarteritis nodosa as well as from six controls were analyzed by immunoblotting and ELISA. All patients had autoantibodies against native collagens II and IX. The serum from one patient showed a strong reaction with all three collagen chains of the high molecular weight fraction of collagen IX after denaturation; sera from four patients showed autoantibodies against alpha 2 (XI) and sera from three patients showed autoantibodies against the covalently cross-linked gamma component of collagen XI. The presence of autoantibodies against collagens II, IX, and XI, which form the major fibrillar scaffold in cartilage and mediate the interaction of collagen fibrils and proteoglycan, suggests that autoantibodies against cartilaginous collagen may play a crucial role in the pathogenesis of relapsing polychondritis and microscopic polyarteritis nodosa.

Comparative analysis of collagens solubilized from human foetal, and normal and osteoarthritic adult articular cartilage, with emphasis on type VI collagen

The different collagen types were extracted sequentially, by 4 M guanidinium chloride and pepsin, from human foetal and normal and osteoarthritic adult articular cartilage. They were characterized by electrophoresis and immunoblotting. Most of the collagenous proteins present in articular cartilage from young human foetuses were solubilized: almost 40% of the total collagen was extracted in the native form with 4 M guanidinium chloride. Type VI collagen was detected in this fraction as high-molecular-mass chains (185-220 kDa) and a low-molecular-mass chain (140 kDa). Type II, IX and XI collagens were also present, but were extracted more extensively by pepsin digestion. Comparative analysis of normal and osteoarthritic cartilage from adults reveals some major differences: an increase in the solubility of the collagen and modifications of soluble collagen types in osteoarthritic cartilage. Furthermore, type VI collagen was present at a higher concentration in guanidinium chloride extracts of osteoarthritic cartilage than those of normal tissue. This finding was corroborated by electron microscopic observations of the same samples: abundant (100 nm) periodic fibrils were observed in the disorganized pericellular capsule of cloned cells in osteoarthritic cartilage. In normal tissues the pericellular zone was more compact and contained only a few such banded fibrils. The differences in the collagen types solubilized from normal and osteoarthritic cartilage, although corresponding to a minor proportion of the total collagen, demonstrate that important modifications in chondrocyte metabolism and in the collagenous network do occur in degenerated cartilage.

Arthritogenicity of minor cartilage collagens (types IX and XI) in mice

Native type II collagen, the major cartilage collagen, is immunogenic and arthritogenic in rodents. To investigate whether minor cartilage collagens are arthritogenic, we immunized DBA/1 mice with the pepsin-soluble fractions of type IX or type XI collagen emulsified in Freund's complete adjuvant. Both collagens were arthritogenic in DBA/1 mice after only 1 injection. However, the incidence of the polyarthritis was lower and the severity was lesser than with that induced by bovine type II collagen, even when a booster injection was administered. All mice developed a humoral response to the immunizing antigen, without any relationship to the arthritic status. Interestingly, competition experiments showed that antibodies raised against type XI collagen also bound with high avidity to type II collagen. In contrast, sera from type IX collagen-immunized mice did not react with either type II or type XI collagen. We conclude that types IX and XI minor cartilage collagens are both arthritogenic and immunogenic in DBA/1 mice. Whether the recognition of epitopes common to different collagens is relevant to the articular pathology remains to be elucidated.

Diastrophic dysplasia: evidence against a defect of type II collagen

A description of an abnormal segment-long-spacing crystallite (SLS) pattern has been reported for type II collagen from patients with diastrophic dysplasia (Stanescu et al., 1982 a), a disorder that is characterized by large collagen fibrils in the cartilage matrix. The abnormal SLS consisted of an altered electron density between bands 42 and 45, which was interpreted as an abnormality in the type II collagen molecule. It was suggested that the type II collagen is abnormal in diastrophic dysplasia. We have examined SLS of type II collagen from two patients with diastrophic dysplasia and found the SLS patterns to be identical with that of control type II SLS in almost all micrographs. In a few micrographs of diastrophic SLS, crystallites exhibiting the pattern reported by Stanescu et al. were seen. However, the abnormally patterned crystallites always consisted of dimers that were overlapped at the COOH ends in such a way that an electron dense band of one crystallite was positioned between bands 42 and 45 of the second crystallite, apparently creating the abnormal pattern. The abnormal SLS pattern seen in these cases of diastrophic dysplasia appears to be the result of overlapping crystallites and may not be the result of an intrinsic abnormality of type II collagen. We have constructed histograms of the collagen fibril diameters in diastrophic cartilage. While they are larger than normal collagen fibrils, this by itself does not indicate an abnormality of type II collagen. We have shown that large fibrils such as these can be obtained from normal type II collagen when the structure of the cartilage is disrupted by extraction with guanidine.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of mammalian type IX collagen fragments from limited pepsin digests of a transplantable swarm rat chondrosarcoma

Collagenous fragments from type IX molecules have been solubilized by limited pepsin proteolysis of a transplantable rat chondrosarcoma and isolated by selective salt precipitation. Chromatography of the solubilized precipitate on CM-cellulose under nondenaturing conditions yielded three fractions. When examined by polarimetry, the material in all three fractions revealed native collagen helical structure with melting points which ranged from 31-37 degrees C. When the fractions were denatured and rechromatographed on a column of agarose beads, the most acidic fraction eluted as 13-kDa polypeptides with and without prior reduction and alkylation. In contrast, the second and third fractions eluted as 100-kDa and 30-kDa polypeptides prior to reduction, but on reduction and alkylation produced reducible products of 34 kDa and 10 kDa, respectively. The general compositional features of the three fractions closely resemble comparable collagenous fragments of type IX collagen from other species. The denaturation products of the 13-kDa nonreducible, the 30-kDa reducible, and the 100-kDa reducible fractions were sequentially purified by CM-cellulose and reversed-phase chromatography to resolve the chain constituents. The isolated 10-kDa, 13-kDa, and 34-kDa chains were cleaved with CNBr, and the cleavage products identified by gel-permeation chromatography. Two 13-kDa polypeptides, 13K2 and 13K3, which did not contain any methionyl residues and were not cleaved with CNBr, were digested with trypsin, and the peptide digests were resolved by reversed-phase chromatography. Comparisons of the CNBr and tryptic cleavage products demonstrate that the three major collagenous fragments are composed of three unique polypeptides. A partial amino acid sequence of an 8-kDa CNBr peptide derived from a purified 10-kDa peptide (10K1) matches identically the amino acid sequence derived from a cDNA sequence in the rat alpha 1(IX) chain (Kimura et al., 1989). These studies, then, present convenient procedures useful in the isolation of mammalian type IX collagen fragments and describe features of the rat molecule, indicating that it is similar to the avian counterpart with respect to chain composition and general molecular structure.

The head cartilage of cephalopods. II. Ultrastructure of isolated native collagen fibrils and of polymeric aggregates obtained in vitro: comparison with the cartilage of mammals

Native collagen fibrils were isolated from cephalopod head cartilage and mammal hyaline cartilage. The analysis with TEM after positive and negative staining demonstrated that the fibrils have a periodic structure similar to that of fibrillar type I collagen of mammals. The banding pattern of polymeric forms (SLS, FLS) obtained in vitro from squid cartilage collagen was remarkably different from the analogous forms of mammal collagen types I and II.

Problems in the immunolocalization of type IX collagen in fetal calf cartilage using a monoclonal antibody

Monoclonal antibodies were prepared against the pepsin-resistant fragments (X1-X3) of bovine type IX collagen. One of the five hybridomas that gave a positive reaction in an enzyme-linked immunosorbent assay was selected (H1a) for structural analysis and immunolocalization of type IX collagen. The location of the epitope for H1a was deducted from immunoblots and electron microscopic observations after rotary shadowing. The H1a antibody binds to one end of the longest X2, X3, X4 molecules, and preferentially 40-55nm from one end of X1 molecules thus, on or near the noncollagenous domain, NC2. Different immunolocalizations of type IX collagen in the superficial, middle and deep zones of fetal calf epiphyseal cartilage were observed depending on the thickness of the section and on hyaluronidase digestion conditions. In the middle and deep zones, staining with H1a throughout the matrix was obtained only with thin sections (5 microns) and digestion for 1 h at 37 degrees C. With thick sections (15 microns) or with digestion for 1 h at 24 degrees C, staining was restricted to the pericellular regions. Staining throughout the matrix was obtained in the superficial zone under all experimental conditions. Without hyaluronidase treatment, no immunofluorescent staining was seen with either H1a or polyclonal antibody to type II collagen, indicating that type IX collagen is present throughout the matrix in the different zones of fetal calf cartilage. This result is in good accordance with the recent demonstration of common cross-links between type II and type IX collagen in chicken and bovine cartilage. However, the preferential unmasking of type IX collagen antigenic sites in the pericellular regions of middle and deep zones of fetal calf cartilage does not preclude the presence in that region of a special pericellular organization of the collagenous network.

Antibodies to types I, II, IX, and XI collagen in the serum of patients with rheumatic diseases

Antibodies to native types I, II, IX, and XI collagen were measured, using a 125I-solid-phase radioimmunoassay, in serum from 104 patients with rheumatic diseases (rheumatoid arthritis, osteoporosis, Paget's disease, or osteoarthritis). In all disease groups, antibodies to type II collagen occurred with greater frequency than antibodies to type I collagen (11-35% versus 5-23%). Antibodies to type XI collagen were the most frequent: They were present in approximately 50% of the patients in the rheumatoid arthritis, Paget's disease, and osteoporosis groups. Antibodies to type IX collagen were found at a high frequency in the rheumatoid arthritis group only (44%). Analysis of the clinical data suggested that the presence of antibodies to collagen was associated with disease that was less severe or of shorter duration.

Type IX collagen is a potent inducer of PGE2 and interleukin 1 production by human monocyte macrophages

Type IX collagen and its collagenous fragments are potent stimulatory agents on human blood mononuclear cells for the production of prostaglandin E2 and interleukin 1/mononuclear cell factor. Type IX collagen is 2-4-fold more potent that type I and II and 1 alpha-, 2 alpha- and 3 alpha-collagens. This property may be important in the destructive process of cartilage in inflammatory diseases.

Change in collagen synthesis of human chondrocyte culture. I. Development of a human model, demonstration of collagen type conversion by immunofluorescence

A research system constituted entirely of components of human origin was developed to study conversion of collagen synthesis by human chondrocytes. Type specificity of affinity chromatography-purified antibodies to human type II or type I collagen was proven by ELISA inhibition and immunofluorescence analysis. Human chondrocytes were isolated from articular cartilage and kept in monolayer cultures for eight subpassages. Conversion of type II to type I synthesis by chondrocytes was investigated by immunofluorescence. Staining with anti-type II collagen antibodies could be detected during primary cultures and in the first subpassage, whereas staining with anti-type I collagen antibodies occurred beginning from the end of primary cultures and was present up to the eighth subpassage. Results are compared to observations obtained in animal systems and their relevance to conditions in osteoarthritis is discussed.