Human cartilage collagens. Comparison of cartilage collagens with human type V collagen

Evaluation of IR and Raman spectroscopic markers of human collagens: Insides for indicating colorectal carcinogenesis

Vibrational spectroscopic methods are widely used in the molecular diagnostics of carcinogenesis. Collagen, a component of connective tissue, plays a special role as a biochemical marker of pathological changes in tissues. The vibrational bands of collagens are very promising to distinguish between normal colon tissue, benign and malignant colon polyps. Differences in these bands indicate changes in the amount, structure, conformation and the ratio between the individual structural forms (subtypes) of this protein. The screening of specific collagen markers of colorectal carcinogenesis was carried out based on the FTIR and Raman (λ_ex 785 nm) spectra of colon tissue samples and purified human collagens. It was found that individual types of human collagens showed significant differences in their vibrational spectra, and specific spectral markers were found for them. These collagen bands were assigned to specific vibrations in the polypeptide backbone, amino acid side chains and carbohydrate moieties. The corresponding spectral regions for colon tissues and colon polyps were investigated for the contribution of collagen vibrations. Mentioned spectral differences in collagen spectroscopic markers could be of interest for early ex vivo diagnosis of colorectal carcinoma if combine vibrational spectroscopy and colonoscopy.

Isolation and Characterisation of Major and Minor Collagens from Hyaline Cartilage of Hoki (Macruronus novaezelandiae)

The composition and properties of collagen in teleost (bony fish) cartilage have never been studied. In this study, we aimed to identify and characterise all collagen species in the nasal cartilage of hoki (Macruronus novaezelandiae). Four native collagen species were extracted using two techniques, and isolated with differential salt precipitation. We were able to assign the identity of three of these collagen species on the basis of solubility, SDS-PAGE and amino acid analyses. We found that hoki cartilage contains the major collagen, type II, and the minor collagens, type IX and type XI, which are homologous to those found in mammal and chicken cartilage. Using these extraction protocols, we also isolated a full-length type IX collagen from cartilage for the first time. In addition, we detected a 90 kDa, highly glycosylated collagen that has not been identified in any other species. For each isolate, structural and biochemical characterisations were performed using circular dichroism and Fourier transform infrared spectroscopy analyses, and the thermal denaturation properties were determined. Our results showed that the properties of hoki cartilage-derived collagens are similar to those of collagens in mammalian cartilage, indicating that teleost cartilage could provide biological ingredients for the development of biomaterials to treat cartilage-related illnesses.

Association of COL11A1 4603C/T polymorphism with cervical disc degeneration in collegiate wrestlers

BACKGROUND

The authors previously identified that COL11A1 gene polymorphism is not a susceptibility factor for lumbar disc degeneration (LDD) in athletes. However, the relationship between COL11A1 gene polymorphism and cervical disc degeneration (CDD) remains unclear. We hypothesized that significant associations between COL11A1 4603C/T gene polymorphism and CDD, but not LDD, in collegiate wrestlers exist. This study aims to examine the relationship between CDD, LDD, and COL11A1 4603C/T gene polymorphism in collegiate wrestlers.

METHODS

The subjects enrolled in this study were 92 (Study-1) and 123 (Study-2) Japanese collegiate male wrestlers. Study-1 and Study-2 were conducted in 2010-2012 and 2012-2015, respectively.

RESULTS

CDD and LDD prevalence among the wrestlers was 51.1% (47/92) and 43.9% (54/123), respectively. We found that COL11A1 4603C/T was significantly associated with CDD, but not with LDD. Using logistic regression analysis with concomitant confounding factors, we further confirmed that COL11A1 4603C/T was a significant risk factor for CDD (co-dominant genetic model [CC vs. CT+TT]: adjusted odds ratio [OR] 2.28; 95% CI: 1.13-4.59; dominant genetic model [CC+CT vs. TT]: adjusted OR 11.71; 95% CI: 1.36-101.06).

CONCLUSIONS

Results suggest that COL11A1 4603C/T gene polymorphism is associated with an increased risk of CDD, but not LDD, in Japanese collegiate wrestlers.

MicroRNAs play a role in chondrogenesis and osteoarthritis (review)

Osteoarthritis (OA) is one of the most widespread degenerative joint diseases affecting the elderly. Research into the regulatory mechanisms underlying the pathogenesis of OA is therefore warranted, and over the past decade, there has been an increased focus on the functional role of microRNAs (miRNAs or miRs). In this systematic review, we aimed to review the evidence implicating miRNAs in the pathogenesis of chondrogenesis and OA. Systematic reviews of PubMed and Embase were performed to search for studies using strings of miRNAs, non-coding RNAs, cartilage, chondrocytes, chondrogenesis, chondrocytogenesis and OA. The identified studies were retrieved, and the references provided were searched. The selected studies were required to focus on the role of miRNAs in chondrogenesis and OA. The results of this review indicated that more than 25 miRNAs have been implicated in chondrogenesis and OA. In particular, chondrocytogenesis, chondrogenic differentiation, chondrocyte proliferation, chondrocyte hypertrophy, endochondral ossification, and proteolytic enzyme regulation are targeted or facilitated by more than 1 miRNA. To date, limited efforts have been performed to evaluate translational applications for this knowledge. Novel therapeutic strategies have been developed and are under investigation to selectively modulate miRNAs, which could potentially enable personalized OA therapy. miRNAs appear to be important modulators of chondrogenesis and OA. Their expression is frequently altered in OA, and many are functionally implicated in the pathogenesis of the disease. The translational roles and therapeutic potential of miRNAs remains to be evaluated.

Cartilage biology, pathology, and repair

Osteoarthritis is one of the most common forms of musculoskeletal disease and the most prominent type of arthritis encountered in all countries. Although great efforts have been made to investigate cartilage biology and osteoarthritis pathology, the treatment has lagged behind that of other arthritides, as there is a lack of effective disease-modifying therapies. Numerous approaches for dealing with cartilage degradation have been tried, but enjoyed very little success to develop approved OA treatments with not only symptomatic improvement but also structure-modifying effect. In this review we discuss the most recent findings regarding the regulation of cartilage biology and pathology and highlight their potential therapeutic values.

Sp1 family of transcription factors regulates the human alpha2 (XI) collagen gene (COL11A2) in Saos-2 osteoblastic cells

Genes encoding type XI collagen, normally associated with chondrogenesis, are also expressed by osteoblasts. By studying Saos-2 cells, we showed that the transcription factors, Sp1, Sp3, and Sp7 (Osterix), regulate COL11A2 expression through its proximal promoter. The findings indicate both ubiquitous and osteoblast-specific mechanisms of collagen gene regulation.

INTRODUCTION

Type XI collagen is essential for skeletal morphogenesis. Collagen XI gene regulation has been studied in chondrocytes but not in osteoblasts.

MATERIALS AND METHODS

We cultured Saos-2 cells, a human osteosarcoma-derived line of osteoblasts, and analyzed them for alpha2(XI) protein and COL11A2 regulatory mechanisms.

RESULTS AND CONCLUSIONS

Although types I and V were the dominant collagens deposited by Saos-2 cells, they expressed COL11A2 mRNA, and alpha2(XI) chains were present in the extracellular matrix. The COL11A2 promoter region (from -149 to -40) containing three Sp1 binding sites was required for promoter activity in transient transfection assays. All three Sp1 sites were critical for binding by nuclear proteins in electrophoretic mobility shift assays. Further analysis using consensus oligonucleotides and specific antibodies as well as chromatin immunoprecipitation assay implicated Sp1 and Sp3 in binding to this promoter region. Overexpressing Sp1 or Sp3 significantly increased COL11A2 promoter activity and endogenous COL11A2 gene expression, an effect that was suppressed by the Sp1-binding inhibitor mithramycin A. Further experiments showed that Sp1, Sp3, CREB-binding protein (CBP), p300, and histone deacetylase (HDAC) were physically associated and HDAC inhibitors (trichostatin A or NaB) upregulated COL11A2 promoter activity and endogenous gene expression. Another Sp1 family member, Sp7 (Osterix), was expressed in Saos-2 cells, but not in chondrocytes, and was shown by chromatin immunoprecipitation to occupy the COL11A2 promoter. Overexpressing Sp7 increased COL11A2 promoter activity and endogenous gene expression, an effect also blocked by mithramycin A. Using siRNA to knockdown Sp1, Sp3, or Sp7, it was shown that depression of any of them decreased COL11A2 promoter activity and endogenous gene expression. Finally, primary cultures of osteoblasts expressed COL11A2 and Sp7, upregulated COL11A2 promoter activity and endogenous gene expression when Sp1, Sp3, or Sp7 were overexpressed, and downregulated them when Sp1, Sp3, or Sp7 were selectively depressed. The results establish that Sp1 proteins regulate COL11A2 transcription by binding to its proximal promoter and directly interacting with CBP, p300, and HDAC.

Tissue engineering of autologous cartilage grafts in three-dimensional in vitro macroaggregate culture system

In the field of tissue engineering, techniques have been described to generate cartilage tissue with isolated chondrocytes and bioresorbable or nonbioresorbable biomaterials serving as three-dimensional cell carriers. In spite of successful cartilage engineering, problems of uneven degradation of biomaterial, and unforeseeable cell-biomaterial interactions remain. This study represents a novel technique to engineer cartilage by an in vitro macroaggregate culture system without the use of biomaterials. Human nasoseptal or auricular chondrocytes were enzymatically isolated and amplified in conventional monolayer culture before the cells were seeded into a cell culture insert with a track-etched membrane and cultured in vitro for 3 weeks. The new cartilage formed within the in vitro macroaggregates was analyzed by histology (toluidine blue, von Kossa-safranin O staining), and immunohistochemistry (collagen types I, II, V, VI, and X and elastin). The total glycosaminoglycan (GAG) content of native and engineered auricular as well as nasal cartilage was assayed colorimetrically in a safranin O assay. The biomechanical properties of engineered cartilage were determined by biphasic indentation assay. After 3 weeks of in vitro culture, nasoseptal and auricular chondrocytes synthesized new cartilage with the typical appearance of hyaline nasal cartilage and elastic auricular cartilage. Immunohistochemical staining of cartilage samples showed a characteristic pattern of staining for collagen antibodies that varied in location and intensity. In all samples, intense staining for cartilage-specific collagen types I, II, and X was observed. By the use of von Kossa-safranin O staining a few positive patches-a possible sign of beginning mineralization within the engineered cartilages-were detected. The unique pattern for nasoseptal cartilage is intense staining for type V collagen, whereas auricular cartilage is only weakly positive for collagen types V and VI. Engineered nasal and auricular macroaggregates were negative for anti-elastin antibody (interterritorially). The measurement of total GAG content demonstrated higher GAG content for reformed nasoseptal cartilage compared with elastic auricular cartilage. However, the total GAG content of engineered macroaggregates was lower than that of native cartilage. In spite of the mechanical stability of the auricular macroaggregates, there was no equilibrium of indentation. The histomorphological and immunohistochemical results demonstrate successful cartilage engineering without the use of biomaterials, and identify characteristics unique to hyaline as well as elastic cartilage. The GAG content of engineered cartilage was lower than in native cartilage and the biomechanical properties were not determinable by indentation assay. This study illustrates a novel in vitro macroaggregate culture system as a promising technique for tissue engineering of cartilage grafts. Further long-term in vitro and in vivo studies must be done before this method can be applied to reconstructive surgery of the nose or auricle.

Expression profiles of two types of human knee-joint cartilage

We have performed a comprehensive analysis of gene-expression profiles in human articular cartilage (hyaline cartilage) and meniscus (fibrocartilage) by means of a cDNA microarray consisting of 23,040 human genes. Comparing the profiles of the two types of cartilage with those of 29 other normal human tissues identified 24 genes that were specifically expressed in both cartilaginous tissues; these genes might be involved in maintaining phenotypes common to cartilage. We also compared the cartilage profiles with gene expression in human mesenchymal stem cells (hMSC), and detected 22 genes that were differentially expressed in cells representing the two cartilaginous lineages, 11 specific to each type, which could serve as markers for predicting the direction of chondrocyte differentiation. Our data should also provide useful information about regeneration of cartilage, especially in support of efforts to identify cartilage-specific molecules as potential agents for therapeutic approaches to joint repair.

The transcription factor CCAAT-binding factor CBF/NF-Y regulates the proximal promoter activity in the human alpha 1(XI) collagen gene (COL11A1)

We have characterized the proximal promoter region of the human COL11A1 gene. Transient transfection assays indicate that the segment from -199 to +1 is necessary for the activation of basal transcription. Electrophoretic mobility shift assays (EMSAs) demonstrated that the ATTGG sequence, within the -147 to -121 fragment, is critical to bind nuclear proteins in the proximal COL11A1 promoter. We demonstrated that the CCAAT binding factor (CBF/NF-Y) bound to this region using an interference assay with consensus oligonucleotides and a supershift assay with specific antibodies in an EMSA. In a chromatin immunoprecipitation assay and EMSA using DNA-affinity-purified proteins, CBF/NF-Y proteins directly bound this region in vitro and in vivo. We also showed that four tandem copies of the CBF/NF-Y-binding fragment produced higher transcriptional activity than one or two copies, whereas the absence of a CBF/NF-Y-binding fragment suppressed the COL11A1 promoter activity. Furthermore, overexpression of a dominant-negative CBF-B/NF-YA subunit significantly inhibited promoter activity in both transient and stable cells. These results indicate that the CBF/NF-Y proteins regulate the transcription of COL11A1 by directly binding to the ATTGG sequence in the proximal promoter region.

Similarity between the major collagens of cuttlefish cranial cartilage and cornea

Invertebrates possess unique collagen-containing connective tissue elements, the biochemistry of which is not clearly understood. We previously reported the occurrence of a novel heterotrimeric type V/XI like collagen in the cranial cartilage of the cuttlefish Sepia officinalis. We report here the purification of the three chains by ion exchange chromatography and the physicochemical characteristics of this collagen. This collagen shared substantial similarity to the collagen purified from the cornea of S. officinalis, with respect to chain composition, cyanogen bromide peptide profile and amino acid composition. The mobility of the C3 chain was retarded in the corneal collagen, which also had an increased glycine content and a smaller ratio of hydroxylysine to lysine, together with a reduction in bound carbohydrates. The cartilage collagen had a higher denaturation temperature than corneal collagen. As observed by transmission electron microscopy of reconstituted fibrils, the heterotrimeric invertebrate collagen formed fibrils of no apparent periodicities as opposed to the regular 64-nm banding pattern of milk shark (Rhizoprionodon acutus) cartilage collagen. This is also the first report on the molecular species of collagen in an invertebrate cornea. Our results strongly support the functioning of minor vertebrate collagens as major collagens in some invertebrates, close similarity of collagens in two tissues with different functions and would hold significance to our understanding of collagen polymorphism and the evolution of the extracellular matrix.

Electrophoretic and immunochemical study of collagens from Sepia officinalis cartilage

Electrophoretic and Western blot studies were conducted on collagen fractions extracted from Sepia officinalis (cuttlefish) cartilage using a modified salt precipitation method developed for the isolation of vertebrate collagens. The antibodies used had been raised in rabbit against the following types of collagen: Sepia I-like; fish I; human I; chicken I, II, and IX; rat V; and calf IX and XI. The main finding was that various types of collagen are present in Sepia cartilage, as they are in vertebrate hyaline cartilage. However, the main component of Sepia cartilage is a heterochain collagen similar to vertebrate type I, and this is associated with minor forms similar to type V/XI and type IX. The cephalopod type I-like heterochain collagen can be considered a first step toward the evolutionary development of a collagen analogous to the typical collagen of vertebrate cartilage (type II homochain). The type V/XI collagen present in molluscs, and indeed all phyla from the Porifera upwards, may represent an ancestral collagen molecule conserved relatively unchanged throughout evolution. Type IX-like collagen seems to be essential for the formation of cartilaginous tissue.

Immunochemical and mechanical characterization of cartilage subtypes in rabbit

Cartilage is categorized into three general subgroups, hyaline, elastic, and fibrocartilage, based primarily on morphologic criteria and secondarily on collagen (Types I and II) and elastin content. To more precisely define the different cartilage subtypes, rabbit cartilage isolated from joint, nose, auricle, epiglottis, and meniscus was characterized by immunohistochemical (IHC) localization of elastin and of collagen Types I, II, V, VI, and X, by biochemical analysis of total glycosaminoglycan (GAG) content, and by biomechanical indentation assay. Toluidine blue staining and safranin-O staining were used for morphological assessment of the cartilage subtypes. IHC staining of the cartilage samples showed a characteristic pattern of staining for the collagen antibodies that varied in both location and intensity. Auricular cartilage is discriminated from other subtypes by interterritorial elastin staining and no staining for Type VI collagen. Epiglottal cartilage is characterized by positive elastin staining and intense staining for Type VI collagen. The unique pattern for nasal cartilage is intense staining for Type V collagen and collagen X, whereas articular cartilage is negative for elastin (interterritorially) and only weakly positive for collagen Types V and VI. Meniscal cartilage shows the greatest intensity of staining for Type I collagen, weak staining for collagens V and VI, and no staining with antibody to collagen Type X. Matching cartilage samples were categorized by total GAG content, which showed increasing total GAG content from elastic cartilage (auricle, epiglottis) to fibrocartilage (meniscus) to hyaline cartilage (nose, knee joint). Analysis of aggregate modulus showed nasal and auricular cartilage to have the greatest stiffness, epiglottal and meniscal tissue the lowest, and articular cartilage intermediate. This study illustrates the differences and identifies unique characteristics of the different cartilage subtypes in rabbits. The results provide a baseline of data for generating and evaluating engineered repair cartilage tissue synthesized in vitro or for post-implantation analysis.

Targeted disruption of Col11a2 produces a mild cartilage phenotype in transgenic mice: comparison with the human disorder otospondylomegaepiphyseal dysplasia (OSMED)

Transgenic mice were prepared by homologous recombination with a Col11a2 targeting gene in which an inverted neomycin-resistant gene was inserted between restriction sites in exons 27 and 28. The targeted allele was transcribed in shortened mRNAs, which could be detected by Northern blotting. However, translation of the full-length Col11a2 chain was unable to occur because of the presence of premature termination codons within the inverted neomycin-resistant gene. Analysis of pepsin-resistant collagen chains from rib cartilage of homozygous mice demonstrated the lack of synthesis of intact alpha2(XI) chains. However, pepsin-resistant collagen chains of either alpha1(XI) or alpha1(V) were still detected on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Therefore, alpha2(XI) chains are not essential for the assembly of some molecular forms of triple-helical type V/XI collagen. The phenotype was milder than in the cho/cho mouse in which, as the result of mutation, translation of the full-length alpha1(XI) chain fails to occur and the mice die at birth (Li et al., 1995). Homozygous mice without expression of an alpha2(XI) chain had a smaller body size, receding snouts, and deafness. Nasal bones in the homozygous transgenic mice were specifically shorter and dimpled on their external surfaces. Chondrocytes in growth plates of all long bones were markedly disorganized and failed to align in columns. Analysis of growth plates from transgenic mice by in situ hybridization showed expression of alpha1(II) and alpha1(XI) but not of alpha1(I) or alpha1(V) which, in contrast, were expressed in the developing bone and in the bone collar. Expression of alpha1(X) specifically in the hypertrophic cartilage was observed in normal and transgenic mice. No obvious osteoarthritis was observed throughout the life of homozygous mice up to 1 year of age, although minor morphologic anomalies in the articular cartilages were discernible. The mild phenotype is consistent with similar mutations in the COL11A2 gene seen in patients with nonocular Stickler syndrome and some patients with otospondylomegaepiphyseal dysplasia (OSMED), as well as in patients with a nonsyndromic form of deafness called DFNA13.

Occurrence of a novel collagen with three distinct chains in the cranial cartilage of the squid Sepia officinalis: comparison with shark cartilage collagen

A unique collagen with three distinct chains, was purified from the cranial cartilage of the squid Sepia officinalis, by pepsinisation and salt precipitation and compared with shark cartilage collagen. These chains, which were different from the known cartilage collagen chains, were referred as C1, C2 and C3, had approximate molecular weights of 105 kDa, 115 kDa and 130 kDa, respectively, and were present in a ratio of 3:2:1, suggestive of two molecules of composition, [(C1)2C2] and [C1C2C3]. These collagens were purified by fractionation at acid and neutral pH, and by ammonium sulfate precipitation. Solubility data indicated that this collagen was more crosslinked than the type I collagen isolated from cartilage of shark, Carcharius acutus. In vitro fibrillogenesis revealed that the sepia collagen formed denser aggregates, as compared to shark collagen, and was stabilised by a higher degree of carbohydrate association. Polyclonal antisera raised against shark collagen was also reactive against the sepia collagens, while the converse was not true, indicating the high immunospecificity of the latter. These results demonstrate collagen polymorphism in an invertebrate cartilage and may hold significance in understanding tissue calcification and molecular evolution. Further, these collagens may represent ancestral forms of vertebrate minor collagens like typeV/XI.

A 1,064 bp fragment from the promoter region of the Col11a2 gene drives lacZ expression not only in cartilage but also in osteoblasts adjacent to regions undergoing both endochondral and intramembranous ossification in mouse embryos

We isolated a 1,064 bp promoter fragment that extended from the 3'-end of the adjacent gene for retinoic X receptor-beta to beyond the most clearly defined start site of the mouse Col11a2 gene. The fragment was then joined to a beta-galactosidase gene and used to prepare transgenic mice. Three independent lines of transgenic mice were generated. The reporter beta-galactosidase gene was expressed in essentially all cartilaginous tissues in 15.5-day-old mouse embryos. In addition, the construct was expressed in osteoprogenitors within developing periosteum and in osteoblasts within mineralized bone. This pattern of expression was evident during both endochondral and intramembranous bone formation. Therefore, the results suggest that 1,064 bp promoter fragment can drive tissue-specific expression of the Col11a2 gene.

The mouse col11a2 gene. Some transcripts from the adjacent rxr-beta gene extend into the col11a2 gene

Type XI collagen is present in small amounts in cartilage, together with small amounts of type IX and type V collagens and large amounts of type II collagen. Here, primers based on the nucleotide sequences of partial human cDNAs and mouse genomic DNAs that were analyzed by other investigators were used to isolate a cDNA for the mouse col11a2 gene. Cosmid clones for the mouse col11a2 gene were isolated, and 12.4 kb of the nucleotide sequences were defined. Analysis of the genomic sequences identified three exons in the mouse gene that were recently shown to undergo alternative splicing (Tsumaki and Kimura, J. Biol. Chem. 270, 2372-2378, 1995; Zhidkova et al., J. Biol. Chem. 270, 94886-9493, 1995). In addition, analysis of the cosmid clones revealed that the 5' end of the mouse col11a2 gene was located head-to-tail with the mouse retinoic X receptor beta gene. RT-PCR assays demonstrated that some transcripts from the retinoic X receptor beta gene extend into the col11a2 gene. Therefore, there may be coordinate expression of the two genes.

Processing of type XI collagen. Determination of the matrix forms of the alpha1(XI) chain

Type XI collagen is mainly found as a minor constituent in type II-containing fibrils and presents a alpha1(XI)alpha2(XI)alpha3(XI) stoichiometry. This molecule was shown to be partially processed in its intact tissue form. Moreover, alternative splicing has been demonstrated in the variable region of the N-terminal domain of alpha1(XI) and alpha2(XI) chains. In this work, the processing of a major intact form of alpha1(XI) from matrix laid down by chick chondrocytes in culture was identified using N-terminal sequencing and antibodies to synthetic peptides corresponding to the N-terminal propeptide cDNA-derived sequence. The results show that the fully processed form of alpha1(XI) begins at Gln254 of the N-terminal propeptide, seven residues before the end of the proline/arginine-rich protein region encoded by exon I (Zhidkova, N. I., Justice, S. K., and Mayne, R. (1995) J. Biol. Chem. 270, 9486-9493). This sequence is immediately followed by a sequence encoded by exon III. The processing takes place at an Ala-Gln sequence that corresponds to a consensus sequence for procollagen N-proteinase. The antibody raised against a sequence located within the region corresponding to exon IV (anti-P8) fails to recognize this fully processed form of the alpha1(XI) chain. It recognizes, however, two minor bands of high molecular mass. These results suggest that a major cartilage form of alpha1(XI) is the product of alternative splicing in which sequences encoded by both exons II and IV are skipped. The presence of a highly acidic subdomain encoded by exon III at the N terminus of the major form of the alpha1(XI) chain, as predicted by these data, provides potential sites for interaction of collagen XI with other molecules.

The human COL11A2 gene structure indicates that the gene has not evolved with the genes for the major fibrillar collagens

The human COL11A2 gene was analyzed from two overlapping cosmid clones that were previously isolated in the course of searching the human major histocompatibility region (Janatipour, M., Naumov, Y., Ando, A., Sugimura, K., Okamoto, N., Tsuji, K., Abe, K., and Inoko, H. (1992) Immunogenetics 35, 272-278). Nucleotide sequencing defined over 28,000 base pairs of the gene. It was shown to contain 66 exons. As with most genes for fibrillar collagens, the first intron was among the largest, and the introns at the 5'-end of the gene were in general larger than the introns at the 3'-end. Analysis of the exons coding for the major triple helical domain indicated that the gene structure had not evolved with the genes for the major fibrillar collagens in that there were marked differences in the number of exons, the exon sizes, and codon usage. The gene was located close to the gene for the retinoic X receptor beta in a head-to-tail arrangement similar to that previously seen with the two mouse genes (P. Vandenberg and D. J. Prockop, submitted for publication). Also, there was marked interspecies homology in the intergenic sequences. The amino acid sequences and the pattern of charged amino acids in the major triple helix of the alpha 2(XI) chain suggested that the chain can be incorporated into the same molecule as alpha 1(XI) and alpha 1(V) chains but not into the same molecule as the alpha 3(XI)/alpha 1(II) chain. The structure of the carboxyl-terminal propeptide was similar to the carboxyl-terminal propeptides of the pro alpha 1(XI) chain and pro alpha chains of other fibrillar collagens, but it was shorter because of internal deletions of about 30 amino acids.

Another look at collagen V and XI molecules

The fibrillar collagens are the most abundant proteins of extracellular matrices. Among them, collagens V and XI are quantitatively minor components which participate in the formation of the fibrillar collagen network. Since these collagens were discovered, studies have demonstrated that they may play a fundamental role in the control of fibrillogenesis, probably by forming a core within the fibrils. Another characteristic of these collagens is the partial retention of their N-propeptide extensions in tissue forms, an unusual observation in comparison to the other known fibrillar collagens. The tissue locations of collagens V and XI are different, but their structural and biological properties seem to be closely related. It has been shown that their primary structures are highly conserved at both the gene and protein levels, and that these conserved features are the bases of their similar biological properties. In particular, they are both resistant to mammalian collagenases, and surprisingly sensitive to trypsin treatment. Collagens V and XI are usually buried within the major collagen fibrils, although they have both cell adhesion and heparin binding sites which could be of crucial importance in physiological processes such as development and wound healing. It has became evident that several molecules are in fact heterotypic associations of chains from both collagens V and XI, demonstrating that these two collagens are not distinct types but a single type which can be called collagen V/XI.

Type XI and II collagen-induced arthritis in rats: characterization of inbred strains of rats for arthritis-susceptibility and immune-responsiveness to type XI and II collagen

To determine the relationship between susceptibility to bovine type XI and II (BXI and BII) collagen-induced arthritis, we immunized 14 inbred and one outbred strains of rats with BXI and BII. Susceptibility to BXI-arthritis corresponded largely with susceptibility, or resistance, to BII-arthritis. LEW, BB, WF, DA, and WKY were readily susceptible to BXI- and BII-arthritis. Likewise, BII-resistant F344 and BN rats were BXI-resistant. Some strains responded differently to BXI and BII. BUF and COP, which are moderately susceptible to BII, were BXI-resistant, whereas the BII-resistant rats, DA.1N and WF.1N, were partially susceptible to BXI. (F344 x BN) F1 hybrids responded to both collagens suggesting gene complementation. Arthritis occurred in all strains producing the highest titer antisera (LEW, WF and BB). Antibody responses to BXI and BII were generally commensurate within individual strains. DA were susceptible to arthritis but produced low levels of antibody comparable to BN rats which were arthritis-resistant. BXI and BII-susceptibility was variable in rats producing intermediate antibody responses. Antibodies to RXI were detected in all BXI-immunized rats, whereas antibodies to RV and RII were uniformly weaker. DTH to RXI and RII was strong in both groups of rats, correlating poorly with arthritis and antibody responses. These studies show that phenotypic susceptibility to BXI- and BII-arthritis are largely concordant among inbred rat strains but clear differences exist in certain strains; multiple genes are likely involved.

Monoclonal antibody to the aminotelopeptide of type II collagen: loss of the epitope after stromelysin digestion

A monoclonal antibody was prepared to the aminotelopeptide of type II collagen after immunization of DBA/1 mice with lathyritic type II collagen and subsequent screening for antibodies that recognize lathyritic but not pepsin-digested type II collagen. One antibody (called 5B2) was identified that recognized a short peptide sequence in the aminotelopeptide of chicken type II collagen but did not recognize other collagen types. Further characterization of the epitope was achieved using a Multipin system and the epitope was localized to a short linear sequence of six amino acids. The antibody recognized type II collagen from a variety of species including man and mouse. The epitope for 5B2 was found to be susceptible to cleavage with recombinant stromelysin without cleavage of the major collagen triple helix. Comparison was made between MAb 5B2 and two other antibodies (called MAb 2B1 and MAb 6B3) that recognize separate epitopes located along the triple helix of the type II collagen molecule.

Evidence for the degradation of type XI collagen by bovine intervertebral disc- and articular cartilage extracts

Bovine intervertebral disc- and articular cartilage extracts contain a metalloproteinase system capable of degrading type XI collagen. The collagen-degrading activity is rather low in unmodified extracts but increases considerably on metalloproteinase activation. The similarity between intervertebral disc and articular cartilage in their patterns of (casein-degrading) metalloproteinases and type XI and type II collagen degradation is believed to suggest a similarity in the events underlying the degradative disorders of articular cartilage and intervertebral disc.

Characterization of heterotrimeric collagen molecules in a sea-pen (Cnidaria, Octocorallia)

The collagen of a primitive invertebrate, the sea-pen Veretillum Cnidaria, Octocorallia), was studied with respect to its molecular-chain composition. The soft extracellular tissues (mesoglea) were solubilized by limited pepsin proteolysis and the collagen was isolated by selective precipitation at 0.7 M NaCl under acidic conditions. The pepsinized molecules were 260 nm in length, as demonstrated by electron microscope studies of rotary-shadowed molecules and of the segment-long-spacing crystallites obtained by dialysis against ATP. SDS/PAGE of the extract produced two main bands susceptible to bacterial collagenase, designated as the alpha 1 and alpha 2 chain, which were differentiated clearly by their CNBr cleavage products and the higher glycosylation rate of the alpha 2 chain. The latter finding corresponds with the high hydroxylysine content of the alpha 2 chain. The alpha 1/alpha 2 chain ratio observed in SDS/PAGE and the fact that only one peak was obtained by concanavalin-A affinity chromatography of a non-denatured 0.7 M NaCl extract demonstrate the alpha 1 [alpha 2]2 molecular structure of this collagen. These results contrast with data on the structure of other coelenterates (i.e. [alpha]3 for sea anemone collagen molecules and alpha 1 alpha 2 alpha 3 for jellyfish collagen molecules). They are discussed in relation to the evolution of collagen.

Immunolocalization of types V and XI collagen in cartilage using monoclonal antibodies

Monoclonal antibodies produced against pepsin-solubilized newborn rat skin type V collagen [alpha 1(V)]2 alpha 2(V), and chondrosarcoma type XI collagen [alpha 1(XI) alpha 2(XI) alpha 3(XI)] are used to localize the collagens in sections of the chondrosarcoma as well as the normal rat knee joint by indirect immunofluorescence. Immunostaining for type V collagen shows strong cellular staining of chondrocytes; while the interstitial matrix as well as the lacunae are not stained. In contrast, antitype XI stains not only chondrocytes, but the extracellular compartments as well. In ELISA, rat anti-type XI collagen reacts with its native antigen, but does not cross-react with native types I, II, III, or V collagen from rat. The distinct locations of type V and XI collagens in cartilaginous tissue suggest varied functional roles for these constituents in the tissue.

Type XI collagen-degrading activity in human osteoarthritic cartilage

Homogenates of 6 samples of human osteoarthritic cartilage were shown to degrade exogenous type XI collagen. On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the cleavage products generated by each homogenate were similar, and they were identical to those obtained by cleavage of the substrate with purified gelatinase. Enzyme activity, which was inhibited by EDTA, was greater in extracts of fibrillated osteoarthritic cartilage than in extracts of grossly normal cartilage from the same joint or in extracts of cartilage from joints with osteonecrosis. Activation with APMA enhanced digestion, but breakdown was apparent in extracts of fibrillated osteoarthritic cartilage even without APMA. Enzymatic degradation of type XI collagen could play a significant role in the turnover of articular cartilage in health and disease states.

Covalent structure of collagen: amino acid sequence of three cyanogen bromide-derived peptides from human alpha 1(V) collagen chain

Type V collagen was prepared from human amnionic/chorionic membranes and separated into alpha 1(V) and alpha 2(V) polypeptide chains. The alpha 1(V) chain was digested with cyanogen bromide and nine peptides were obtained and purified. Three of the peptides, alpha 1(V)CB1, CB4, and CB7 having molecular weights of 5000, 8000, and 6000, respectively, were further analyzed by amino acid sequence analysis and thermolytic or tryptic digestions. CB1 contained 54 amino acids and identification of its complete sequence was aided by thermolysin digestion and isolation of two peptides, Th1 and Th2. CB4 contained 81 amino acids and sequence analysis of intact CB4 and five tryptic peptides provided us with its complete amino acid sequence. The peptide CB7 contained 67 amino acids and was cleaved into four tryptic peptides that were used for complete sequence analysis. The above results represent the first available covalent structure information on the alpha 1(V) collagen chain. These data enabled us to establish the location of these peptides within the helical structure of other collagen chains. CB4 was homologous to residues 66-145 in the collagen chain while CB1 represented residues 146-200 and CB7 was homologous with residues 201-269. This alignment was facilitated by identification of a helical collagen crossing site consisting of Hyl-Gly-His-Arg located at positions 87-90 in all collagen chains of this size thus far identified. Seventy-one percent homology (excluding Gly residues) was found between amino acids in this region of the alpha 1(XI) and of alpha 1(V) collagen chains while only 21 and 19% identity was calculated for the same region of alpha 2(V) and alpha 1(I) collagen chains, respectively.

Bone type V collagen: chain composition and location of a trypsin cleavage site

The component alpha-chains of type V collagen from bovine bone were isolated and structurally characterized by gel electrophoresis, high performance liquid chromatography (HPLC) and amino acid sequence analysis. Three distinct alpha-chains were identified. Two of these were the well described alpha 1 (V) and alpha 2 (V) chains; the third proved to be identical to the cartilage alpha 1 (XI) chain. In adult bone the ratio between the three chains was about 1:1:1. Native type V collagen was cleaved by trypsin at 33 degrees C or 37 degrees C into 3/5 fragments. Aminoterminal sequence analysis of the alpha 1 (V) and alpha 1 (XI) fragments showed they both resulted from trypsin cleavage between residue 434 and 435. Trypsin apparently cleaves the type V molecule within a relatively unstable domain of the triple helix which presumably may also be a natural site of initial cleavage by a protease in vivo.

Antibodies to type II and XI collagens: evidence for the formation of antigen specific as well as cross reacting antibodies in patients with rheumatoid arthritis

Antigen specific and cross reacting antibodies to native and denatured types II and XI collagen were detected in the sera of rats immunised with either of these antigens. The antibodies from rats immunised with type XI collagen initially showed the strongest binding to the alpha 2(XI) chain of type XI collagen but later binding to the alpha 3(XI) chain was seen. Sera from patients with rheumatoid arthritis had antibodies that bound to both type II and XI collagens. Immunoblotting studies showed that most patients had antibodies which bound to the alpha 1(II) chain of type II collagen and to the alpha 3(XI) chain of type XI collagen. Some patients also had antibodies which bound to the alpha 1(XI) and to the alpha 2(XI) chains of type XI collagen. Thus antibodies to unique as well as to common epitopes on each of the two types of collagen molecule occur in some patients with rheumatoid arthritis.

Effect of relaxin on the phenotype of collagens synthesized by cultured rabbit chondrocytes

The effect of porcine relaxin on rabbit articular and growth plate chondrocytes in primary culture was investigated by measurement of total collagen production and analysis of the phenotypes of newly synthesized collagen chains. A 24-h treatment of monolayer articular and multilayer growth plate chondrocytes with 2 micrograms per ml relaxin had no effect on total DNA and did not significantly modify the amount of [3H]proline-labelled collagen chains secreted by the cells. However, polyacrylamide gel electrophoresis demonstrated relevant modifications in relaxin treated chondrocytes. A significant increase was observed in the proportion of type III collagen and in the intensity of the band corresponding to alpha 2I chains. Two-dimensional peptide mapping of CNBr-cleaved molecules indicated that the band that was identified as alpha 1II on monodimensional gels contained a significant proportion of alpha 1I collagen chains, as demonstrated by the presence of alpha 1I cyanogen bromide-digested peptides. The intensity of this band was increased by relaxin treatment. Furthermore, total RNA analysis by slot blot and Northern blot techniques showed a dose-dependent stimulation of alpha 1I and alpha 1III mRNA levels after incubation with increased relaxin concentrations, but no change in the amount of alpha 1II mRNA. These results suggested that when added to cartilage cells in vitro, relaxin modulated the expression of type I, type II and type III collagen genes by amplifying the dedifferentiation process.

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.

Bovine achondrogenesis: evidence for defective chondrocyte differentiation

A survey study of growth cartilage abnormalities in bovine bone dysplasias revealed that a disorder in Holstein cattle called bulldog calf closely resembles human achondrogenesis Type II. Substantial amounts of Type I collagen and other non Type II collagens were detected in the bulldog cartilage which was comprised primarily of extensive vascular canals and cells having the characteristics of hypertrophic and degenerative chondrocytes normally found in the growth plate. It is proposed that chondrocytes throughout the bulldog growth cartilage prematurely differentiate into hypertrophic cells that degenerate and predispose the cartilage to vascular invasion and the formation of cartilage canals. The presence of these canals probably accounts for most of the observed collagen abnormalities.

Polypeptide composition of the mammalian tectorial membrane

The effects of the enzymes collagenase, pepsin, chondroitinase ABC and keratanase on the polypeptide composition of the mammalian tectorial membrane have been analysed using one dimensional SDS-polyacrylamide gel electrophoresis (SDS-PAGE). After reduction at least ten polypeptides can be consistently and clearly recognized in SDS gels with molecular weights relative to globular protein standards of 245, 235, 190, 165, 155, 145, 100, 93, 60-73 and 35-49 kDa. With the exception of the 60-73 and 35-49 kDa bands all these polypeptides are sensitive to digestion with bacterial collagenase. The 235, 165, 155, 145 and 93 kDa bands also resist degradation by cold, acidic pepsin. Amino acid analysis of whole tectorial membranes demonstrates that glycine accounts for nearly 25% of the total amino acid content, that proline, hydroxyproline and hydroxylysine are present and that amine sugars can be detected in fairly high concentrations. Estimates based on hydroxyproline content suggest that collagens account for 25-50% of the total tectorial membrane protein. Immunoblotting techniques demonstrate the presence of polypeptides cross reacting with antisera to Type II collagen, Type IX collagen and Type V collagen. Results from immunohistochemical studies confirm that these polypeptides are present in the tectorial membrane and are not contaminants of the isolation procedure. Collagenase treatment of tectorial membranes reveals the presence of an additional non-collagenous polypeptide with an apparent molecular weight of 173 kDa on 7.5% polyacrylamide gels, and polydisperse high molecular weight material spreading over a broad range at the top of the gels. This high molecular weight material and the 173, 60-73 and 35-49 kDa non-collagenous polypeptides are pepsin sensitive and all bind wheat germ agglutinin (WGA) suggesting that they contain N-acetyl glucosamine. The 173 kDa band also binds soybean agglutinin (SBA) suggesting the presence of N-acetyl galactosamine. In the absence of reducing agent the 173 and 60-73 kDa bands are no longer observed and high molecular weight material forming a broad band at the top of the separating gel is seen. The electrophoretic behaviour of this non-collagenous, glycosylated, disulphide bonded, high molecular weight material is altered by treatment with keratanase but not by chondroitinase ABC. The results of this study indicate the tectorial membrane contains at least three different collagen types and, in addition to these collagenous proteins, several non-collagenous, glycosylated polypeptides that may account for as much as 50% of the total tectorial membrane protein.