Analysis of protein distribution in cartilage using immunofluorescence and laser confocal scanning microscopy

Protein localization in cartilage sections by antibodies that specifically bind to epitopes of a protein is one of the most powerful technologies in modern cartilage research. Studies using two or more primary antibodies that recognize different protein epitopes allow the colocalization of different gene products in one cartilage section. In addition, specific histochemical stains help to visualize nuclear DNA, mitochondria, and other subcellular compartments. By these immunohistological methods, the distribution of proteins can be analyzed throughout different zones of articular cartilage. In particular, with the use of laser scanning confocal microscopy, subcellular localization of proteins can also be determined (i.e, nuclear, cytoplasmic, membrane-associated, and extracellular). Overall, immunohistochemical methods are fairly simple to handle, and the reagents required are inexpensive, with the exception of basic technical equipment (fluorescence microscope or confocal microscope). However, as with many methodologies, technical knowledge and experience is important to avoid and/or interpret either false-positive or false-negative results.

Structural Determination of Five Novel Tetrasaccharides Containing 3-O-Sulfated d-Glucuronic Acid and Two Rare Oligosaccharides Containing a β-d-Glucose Branch Isolated from Squid Cartilage Chondroitin Sulfate E

Oversulfated chondroitin sulfate E (CS-E) derived from squid cartilage exhibits intriguing biological activities, which appear to reflect the biological activities of mammalian CS chains containing the so-called E disaccharide unit [GlcAbeta1-3GalNAc(4,6-O-disulfate)]. Previously, we isolated novel tetra- and hexasaccharides containing a rare GlcA(3-O-sulfate) at the nonreducing end after digestion of squid cartilage CS-E with testicular hyaluronidase. In this study, squid cartilage CS-E was extensively digested with chondroitinase AC-II, which yielded five highly sulfated novel tetrasaccharides and two odd-numbered oligosaccharides (tri- and pentasaccharides) containing D-Glc. Their structures were determined by fast atom bombardment mass spectrometry and (1)H NMR spectroscopy. The results revealed an internal GlcA(3-O-sulfate) residue for all the novel tetrasaccharide sequences, which rendered the oligosaccharides resistant to the enzyme. The results suggest that GlcA(3-O-sulfate) units are not clustered but rather interspersed in the CS-E polysaccahride chains, being preferentially located in the highly sulfated sequences. The predominant structure on the nearest nonreducing side of a GlcA(3-O-sulfate) residue was GalNAc(4-O-sulfate) (80%), whereas that on the reducing side was GalNAc(4,6-O-disulfate) (59%). The structural variety in the vicinity of the GlcA(3-O-sulfate) residue might represent the substrate specificity of the unidentified chondroitin GlcA 3-O-sulfotransferase. The results also revealed a trisaccharide and a pentasaccahride sequence, both of which contained a beta-d-Glc branch at the C6 position of the constituent GalNAc residue. Approximately 5 mol % of all disaccharide units were substituted by Glc in the CS-E preparation used.

Gene expression analysis in cartilage by in situ hybridization

In situ hybridization allows detection and localization of specific nucleic acid sequences directly within a cell or tissue. We present an in situ hybridization protocol using double-stranded DNA or single-stranded RNA probes labeled with [32P] to localize and visualize the temporal and spatial distribution of cartilage-characteristic mRNAs. Probes labeled with this high-energy isotope provide good resolution at the tissue level with relatively low background; as a result of the probes that can be obtained that have a higher specificity to emulsion activity, very short exposure times are required.

A simple and reliable assay of proteoglycan synthesis by cultured chondrocytes

A simple and reliable method to measure proteoglycan synthesis by chondrocytes in culture is described. Confluent chondrocytes in 24-well plates are labeled for 24-72 h with (35)SO4(2-) in the presence of stimulating agents. At the end of treatment, the secretion medium containing radiolabeled neosynthesized secreted proteoglycans (SP) is harvested, and cell-associated proteoglycans (CAP) are extracted with guanidine hydrochloride for 48 h. Aliquots of medium and cell extracts are distributed on Whatman paper and left to dry. SP and CAP are trapped by precipitation with the cationic detergent cetyl pyridinium chloride (CPC), whereas nonincorporated (35)SO4(2-) remains in solution. After drying, each spot corresponding to one well in the plate is cut, and its radioactivity is measured. Counts are proportional to the amount of neosynthesized proteoglycans. In a representative experiment using rabbit chondrocytes, total proteoglycan synthesis (SP plus CAP) was increased 3.5-fold after the addition of 1.34 nM insulin-like growth factor-1 (IGF-1) compared with nonstimulated cells. Further addition of a fourfold molar ratio of IGF binding protein-3 completely abolished this effect. This method can be used to measure proteoglycan synthesis by chondrocytes from many species, including human osteoarthritic chondrocytes, as well as guinea pig, rabbit, and rat chondrocytes.

The fate of mesenchymal stem cells transplanted into immunocompetent neonatal mice: implications for skeletal gene therapy via stem cells

To explore the feasibility of skeletal gene and cell therapies, we transduced murine bone marrow-derived mesenchymal stem cells (MSCs) with a retrovirus carrying the enhanced green fluorescent protein and zeocin-resistance genes prior to transplantation into 2-day-old immunocompetent neonatal mice. Whole-body imaging of the recipient mice at 7 days post-systemic cell injection demonstrated a wide distribution of the cells in vivo. Twenty-five days posttransplantation, most of the infused cells were present in the lung as assessed by examination of the cells cultured from the lungs of the recipient mice. The cells persisted in lung and maintained a high level of gene expression and could be recovered from the recipient mice at 150 days after cell transplantation. A significant number of GFP-positive cells were also present in the bones of the recipient mice at 35 days post-cell transplantation. Recycling of the cells recovered from femurs of the recipient mice at 25 days posttransplantation by repeated injections into different neonatal mice resulted in the isolation of a clone of cells that was detected in bone and cartilage, but not in lung and liver after systemic injection. These data demonstrate that MSCs persist in immunocompetent neonatal mice, maintain a high level of gene expression, and may participate in skeletal growth and development of the recipient animals.

Mechanical Compression of Cartilage Explants Induces Multiple Time-dependent Gene Expression Patterns and Involves Intracellular Calcium and Cyclic AMP

Chondrocytes are influenced by mechanical forces to remodel cartilage extracellular matrix. Previous studies have demonstrated the effects of mechanical forces on changes in biosynthesis and mRNA levels of particular extracellular matrix molecules, and have identified certain signaling pathways that may be involved. However, the broad extent and kinetics of mechano-regulation of gene transcription has not been studied in depth. We applied static compressive strains to bovine cartilage explants for periods between 1 and 24 h and measured the response of 28 genes using real time PCR. Compression time courses were also performed in the presence of an intracellular calcium chelator or an inhibitor of cyclic AMP-activated protein kinase A. Cluster analysis of the data revealed four main expression patterns: two groups containing either transiently up-regulated or duration-enhanced expression profiles could each be subdivided into genes that did or did not require intracellular calcium release and cyclic AMP-activated protein kinase A for their mechano-regulation. Transcription levels for aggrecan, type II collagen, and link protein were up-regulated approximately 2-3-fold during the first 8 h of 50% compression and subsequently down-regulated to levels below that of free-swelling controls by 24 h. Transcription levels of matrix metalloproteinases-3, -9, and -13, aggrecanase-1, and the matrix protease regulator cyclooxygenase-2 increased with the duration of 50% compression 2-16-fold by 24 h. Thus, transcription of proteins involved in matrix remodeling and catabolism dominated over anabolic matrix proteins as the duration of static compression increased. Immediate early genes c-fos and c-jun were dramatically up-regulated 6-30-fold, respectively, during the first 8 h of 50% compression and remained up-regulated after 24 h.

A solid phase assay for the determination of heparan sulfate and its application to normal and cancerous human cartilage samples

A sensitive and accurate quantitative assay for the measurement of minor amounts of chondroitin/dermatan sulfate and heparan sulfate that does not require specific apparatus or reagents is described. The assay involves labeling of chondroitin sulfate A following reaction of carboxyl groups with biotin hydrazide in the presence of carbodiimide. ELISA plate wells were coated with glutaraldehyde and then spermine was coupled to it via a Schiff's base bond. In such activated wells, the biotinylated molecules were readily bound and detected after the interaction with avidin-peroxidase conjugates and the subsequent enzymic assay. Chondroitin/dermatan sulfate and heparan sulfate competed this interaction in a linear manner. Disaccharides derived from chondroitin sulfate A did not act as competitors, while heparan sulfate disaccharides showed significant competition. From the competition, before and after digestion with either chondroitinase ABC or heparitinases, the amounts of chondroitin sulfate and heparan sulfate in a sample could be calculated. The assay was applied for the determination of sulfated glycosaminoglycans in normal and cancerous human laryngeal cartilage samples. By using this procedure, the accurate determination, especially, of heparan sulfate in a mixture of glycosaminoglycans was achieved, which otherwise would require the use of very expensive technology.

A rapid method for fractionation and purification of a 92 kDa cartilage glycoprotein

Matrix glycoproteins are among the main components that contribute to the properties of cartilage. In this article we report on the development of a rapid method for the fractionation and purification of a 92 kDa glycoprotein from chick sternal cartilage. The developed procedure involves ion-exchange chromatography on DEAE-Sephacel, gel permeation chromatography on Sepharose CL-6B and semi-preparative SDS-polyacrylamide gel electrophoresis. Identification of protein was performed by western blotting using specific antibodies and purity by capillary electrophoresis. The proposed method is superior to those previously published since it eliminates the step of density gradient centrifugation.

Ultrastructural and immunohistochemical analysis of proteoglycans in mouse pubic symphysis

Proteoglycans were accurately localized in mouse pubic symphyseal tissues using the cuprolinic blue method. Specific glycosaminoglycans degradative enzymes, together with chondroitin sulfate and decorin antibodies, allowed the identification of glycosaminoglycans. Chondroitin sulfate proteoglycans were the main proteoglycans observed in hyaline cartilage, fibrocartilage, and dense connective tissue. Ultrastructurally, they were seen as electron-dense granules and filaments. The granules, rich in chondroitin sulfate chains, were exclusively found in hyaline cartilage, whereas filaments were present in cartilage, fibrocartilage, and dense connective tissue. The latter were classified by size and susceptibility to enzyme digestion into F1, F2 and F3 filaments: F1 filaments were small, thin, and collagen fibril-associated; F2 filaments were thick, heavily stained, and localized around individual collagen fibrils and between bundles of collagen fibrils; and F3 filaments were scattered throughout elastic fiber surfaces. Considering their localization, susceptibility to chondroitinase AC and immunohistochemical detection, the symphysial F1 filaments were found to be preferentially decorin substituted with chondroitin sulfate side chains. The F2 filaments were also susceptible to chondroitinase AC treatment, whereas F3 filaments could be digested by heparitinase. The data thus obtained on the localization and identification of pubic symphyseal proteoglycans in virgin mice may be useful in the study of structural modifications that occur throughout pregnancy.

[Changes of nitric oxide content and nitric oxide synthase activity during rabbit cartilage endplate degeneration]

OBJECTIVE

To study the role of nitric oxide (NO) and nitric oxide synthase (NOS) in the degeneration of rabbit cartilage endplate (CEP).

METHODS

Twenty-four New Zealand rabbits were divided into experiment (n=12) and control (n=12) groups, and in the former group rabbit models of lumbar CEP degeneration was established by resection of all the lumbar supraspinous and interspinous ligaments and excision of part of the zygapophyseal joints followed by detachment of the posterior paravertebral muscles from the lumbar vertebrae. Lumbar X-ray was performed in both groups 12, 24 and 36 weeks after operation, respectively. The content of NO and NOS activity in the CEP were also measured.

RESULTS

X-ray of the CEP reveal gradual calcification of the cartilage endplate with the elapse of time, which was more obvious in the experiment group. The content of NO and NOS activity was significantly increased in the experiment group after the operation (P<0.05), but their difference between the measurements at 24 and 36 weeks postoperatively was not obvious (P>0.05).

CONCLUSION

NO may play an important role in the development and progression of rabbit cartilage endplate degeneration.

Immunohistochemical distribution patterns of collagen type II, chondroitin 4-sulfate, laminin and fibronectin in human nasal septal cartilage

Collagen type II, chondroitin 4-sulfate, laminin and fibronectin are major components of cartilage matrix. It is important to know their distribution patterns to evaluate relationships between cartilage cells and surrounding cartilage matrix. In the present study, we investigated localization patterns of these macromolecules in human nasal septal cartilage by immunohistochemical methods. Samples of human nasal septal cartilage were obtained from patients with nasal septum deviations who underwent septoplastic operation and were prepared for immunohistochemical examination. Distribution patterns of cartilage matrix macromolecules correlated with those found in other cartilage tissues. Diffuse staining of collagen type II was found in the cartilage matrix, chondroitin 4-sulfate immunostaining was present in the cytoplasm and like a pericellular ring around chondrocytes. Laminin immunostaining was found in the cytoplasm of chondrocytes, and fibronectin was localized in the pericellular matrix and in capsules of human nasal septal cartilage. Moreover, fibronectin was also detected at high levels in the interconnecting segments between adjacent chondrons. In conclusion, similar localisation patterns of the components investigated in human septal cartilage as in other tissues indicate that these macromolecules may play a role in both cell-matrix adhesion and matrix-matrix cohesion in the pericellular microenvironment surrounding nasal septal cartilage chondrocytes as in other cartilage tissues.

[Interrelation of matrix vesicles with spatial distribution of mineral component in fibrous and hyaline cartilages]

Mineral components of the human fibrous and hyaline cartilages were studied by the methods of light, scanning, transmission electron microscopy and cryofractography. The interterritorial matrix of the fibrous cartilage was found to contain not only the local deposits of mineral in matrix vesicles, but also the calcified collagen fibrils and interfibrillar spaces forming the collagen fibers and occupying its major part. In the hyaline cartilage and in the territorial matrix of fibrous cartilage, mineral deposits were located in mineralized conglomerates, the basis of which was formed by matrix vesicles, surrounded by collagen fibrils and interfibrillar space substance. Such conglomerates participate in the formation of calcospherites.

Suppression of T cell responses by chondromodulin I, a cartilage-derived angiogenesis inhibitory factor: Therapeutic potential in rheumatoid arthritis

OBJECTIVE

Chondromodulin I (ChM-I), a cartilage matrix protein, promotes the growth and proteoglycan synthesis of chondrocytes. However, it also inhibits angiogenesis. Since ChM-I is expressed not only in cartilage, but also in the thymus, we investigated the modulation of T cell function by ChM-I to assess its therapeutic potential in rheumatoid arthritis (RA).

METHODS

The localization of ChM-I expression in mouse thymus tissue was examined by in situ hybridization. The proliferative response of peripheral blood T cells and synovial cells obtained from patients with RA was evaluated by (3)H-thymidine incorporation assay. The effects of ChM-I were examined using recombinant human ChM-I (rHuChM-I). Modulation of the antigen-specific immune response was evaluated by the recall response of splenic T cells and the delayed-type hypersensitivity response induced in the ear of mice primed with ovalbumin (OVA). Antigen-induced arthritis (AIA) was induced in mice by injecting methylated bovine serum albumin into the ankle joints 2 weeks after the priming.

RESULTS

ChM-I was expressed in the cortex of the thymus. Recombinant human ChM-I suppressed the proliferative response of mouse splenic T cells and human peripheral blood T cells stimulated with anti-CD3/CD28 antibodies, in a dose-dependent manner. Production of interleukin-2 was decreased in rHuChM-I-treated mouse CD4 T cells. Ten micrograms of rHuChM-I injected intraperitoneally into OVA-primed mice suppressed the induction of the antigen-specific immune response. Finally, rHuChM-I suppressed the development of AIA, and also suppressed the proliferation of synovial cells prepared from the joints of patients with RA.

CONCLUSION

These results suggest that ChM-I suppresses T cell responses and synovial cell proliferation, implying that this cartilage matrix protein has a therapeutic potential in RA.

Identification of promoter regions involved in cell- and developmental stage-specific osteopontin expression in bone, kidney, placenta, and mammary gland: an analysis of transgenic mice

Cell-specific expression of GFP under the control of different lengths of the osteopontin promoter in transgenic mice identified the positive and negative regulatory regions for respective cell types. The results provide new insights for physiological and pathological expression of the osteopontin gene.

INTRODUCTION

Osteopontin (OPN) is a major non-collagenous bone matrix protein that is involved in normal and pathological calcification and is expressed in a tissue-specific manner. To investigate how such tissue-specific OPN gene expression is regulated in vivo, transgenic mice expressing the green fluorescent protein (GFP) reporter gene controlled by different lengths of the OPN promoter were generated.

MATERIALS AND METHODS

Cell- and developmental stage-specific osteopontin expression in transgenic mice was examined by Northern blotting, immunoblotting, fluorescence examination, and in situ hybridization and compared with those of OPN.

RESULTS AND CONCLUSIONS

The line bearing the -5505 to +14 region of the OPN promoter was shown by Northern blotting and immunoblotting to express GFP in the same cells that express endogenous OPN (osteoblasts, hypertrophic chondrocytes, renal and mammary gland epithelial cells, and granulated metrial gland [GMG] placental cells) at the same stage in development. Thus, the 5.5-kb -5505 to +14 promoter region is sufficient for proper tissue-specific OPN expression. The lines carrying shorter segments of the OPN promoter showed different expression patterns. These patterns revealed a putative cis-acting element in the -5269 to -5263 region that restricts OPN expression to hypertrophic chondrocytes and a mammary gland-specific expressing element and a GMG cell-specific enhancing element in the -5505 to -3156 region. Furthermore, the -3155 to -1576 region seems to contain positive renal epithelial cell- and GMG cell-specific expression motif(s) as well as a negative regulatory element that prevents OPN expression in fibroblasts. Moreover, the -1576 to -910 region seems to contain a positive osteoblast-specific-expressing element. Thus, the 5.5-kb OPN promoter contains multiple cis-acting elements encoding positive and negative cell-specific regulatory systems.

Cloning of integral mature peptide gene of human GDF-5

The integral mature peptide gene of human growth differentiation factor-5 (GDF-5) was cloned to provide the essential foundation for study on the biological characteristics of GDF-5 at gene and protein levels. Two primers were chemosynthesized according to the hGDF-5 sequence reported in Genbank. The hGDF-5 gene was gained by RT-PCR methods from the total RNA extracted from human fetus cartilage tissue, and was cloned into vector pMD18-T. The sequence of recombinant plasmid pMD18-T-hGDF-5 was analyzed by sequence analysis. DNA agarose gel electrophoresis showed that the product of RT-PCR was about 380bp, and double enzyme digestion of the recombinant plasmid corresponded with it. The result of sequence assay was in agreement with the reported hGDF-5 sequence in Genbank. Our results showed that the integral mature peptide gene of human GDF-5 was cloned successfully from human fetal cartilage tissue, and totally identified with the sequence of human GDF-5 in Genbank.

Isoflavones extracted from Sophorae fructus upregulate IGF-I and TGF-beta and inhibit osteoclastogenesis in rat bone marrow cells

Isoflavones have been a central subject in research on the natural phytoestrogens found in Leguminosae. Their effects on bone formation and remodeling are important in that they can act like estrogen by binding on estrogen receptors on the target cell surface. We, therefore, believed that isoflavones may help in the treatment of patients with estrogen deficiency disease such as estrogen replacement therapy (ERT) for osteoporosis. As commonly known, osteoporosis is one of the hormonal deficiency diseases, especially in menopausal women. When estrogen is no longer produced in the body a remarkable bone remodeling process occurs, and the associated events are regulated by growth factors in the osteoblast lineage. In the present study, we investigated whether isoflavones (Isocal) extracted from Sophorae fructus affect the growth factors IGF-I and TGF-beta that have been known to be related with bone formation. In the study, we found that the active control (PIII) effectively enhanced the level of nitric oxide (NO) and growth factors, and thereby inhibited osteoclastogenesis. The most efficient concentration was 10(-8)% within five days, whereas the comparative control (soybean isoflavone) was not as effective even at a lower concentration. In conclusion, the products which contain enriched glucosidic isoflavone and nutrient supplements such as shark cartilage and calcium can be used for osteoporosis therapy by enhancing the production of IGF-I and TGF-beta. Furthermore, the NO produced through endothelial constitutive NO synthase (ecNOS) may play a role in inhibiting bone reabsorption.

In situ hybridization and immunohistochemistry of versican, aggrecan and link protein, and histochemistry of hyaluronan in the developing mouse limb bud cartilage

We investigated the expression pattern of versican, aggrecan, link protein and hyaluronan in the developing limb bud cartilage of the fetal mouse using in situ hybridization and/or immunohistochemistry. Versican mRNA and immunostaining were detected in the mesenchymal cell condensation of the future digital bone at E13. Versican mRNA expression rapidly disappeared from the tibial cartilage, as cartilage formation progressed during E13-15, but the immunostaining was gradually replaced by aggrecan immunostaining from the diaphysis. Immunostaining for both molecules thus had a 'nega-posi' pattern and consequently versican immunostaining was still detected at the epiphyseal end at E15. This result indicated that versican functions as a temporary framework in newly formed cartilage matrix. An aggrecan-positive region within the cartilage invariably had intense hyaluronan staining, whereas a versican-positive region also had affinity for hyaluronan within the cartilage, but not in the mesenchymal cell condensation. Therefore, the presence of versican aggregates was not confirmed in the developing limb bud cartilage. Furthermore, although link protein was more closely related with aggrecan than versican during limb bud cartilage formation, there was a discrepancy between the expression of aggrecan and link protein in tibial cartilage at E15. In particular, only a link protein-positive region was present in the marginal area of the metaphysis and the epiphysis at this stage. This finding may indicate a novel role for link protein.

Cleavage of fibromodulin in cartilage explants involves removal of the N-terminal tyrosine sulfate-rich region by proteolysis at a site that is sensitive to matrix metalloproteinase-13

Integrity of cartilage fails in joint disease. The current work aimed to identify candidate active proteinases in joint diseases using an in vitro model for cartilage degradation induced by interleukin-1. A critical event in the process of cartilage destruction in joint disease is the failure of the collagen fiber network to maintain integrity. Proteins binding to the surface of the fibers are likely early points of failure. Fibromodulin, a member of the leucine-rich repeat protein family, is one predominant protein in cartilage and is known for its roles in the formation of collagen fibrils and sustained interaction with these formed fibers. Cleavage removes the tyrosine sulfate-rich region in the N terminus of fibromodulin. Whereas fibromodulin bound to collagen in tissue was digested, purified fibromodulin was not cleaved. In contrast an N-terminal 10-kDa fragment, Gln19-Lys98, of the protein generated by Lys-C digestion contains the cleavage site and was a substrate cleaved by the enzyme in medium from stimulated cultures. In solution, digestion of this substrate with matrix metalloproteinase (MMP)-2, -9, -8, and -13 demonstrated that only MMP-13 was capable to efficiently cleave it. The cleavage product obtained after MMP-13 digestion was identical to that observed in cleaved fibromodulin from cartilage explant cultures stimulated with interleukin-1. MMP-13 treatment of fresh articular cartilage also produced the fragment under study. The elucidation of the enzyme responsible for such cleavage may lead to treatment modalities involving its selective inhibition for patients suffering from arthritis. The known structure of the fragments permits the generation of neo-epitope antibodies to the cleavage site, which can be used to detect ongoing cartilage degradation in patients with arthritic disease, an important adjunct in monitoring disease progression, active disease, and efficacy of treatment.

Elasticity in extracellular matrix 'shape modules' of tendon, cartilage, etc. A sliding proteoglycan-filament model

Connective tissues (CTs), which define bodily shape, must respond quickly, robustly and reversibly to deformations caused by internal and external stresses. Fibrillar (elastin, collagen) elasticity under tension depends on molecular and supramolecular mechanisms. A second intra-/inter-molecular pair, involving proteoglycans (PGs), is proposed to cope with compressive stresses. PG interfibrillar bridges ('shape modules'), supramolecular structures ubiquitously distributed throughout CT extracellular matrices (ECMs), are examined for potential elastic properties. L-iduronate residues in shape module decoran PGs are suggested to be molecular springs, cycling through alternative conformations. On a larger scale, anionic glycosaminoglycan (AGAG) interfibrillar bridges in shape modules are postulated to take part in a sliding filament (dashpot-like) process, which converts local compressions into disseminated tensile strains. The elasticity of fibrils and AGAGs, manifest at molecular and larger-scale levels, provides a graduated and smooth response to stresses of varying degrees. NMR and rheo NMR, computer modelling, electron histochemical, biophysical and chemical morphological evidence for the proposals is reviewed.

Depletion of cartilage collagen fibrils in mice carrying a dominant negative Col2a1 transgene affects chondrocyte differentiation

We have generated transgenic mice harboring the deletion of exon 48 in the mouse alpha1(II) procollagen gene (Col2a1). This was the first dominant negative mutation identified in the human alpha1(II) procollagen gene (COL2A1). Patients carrying a single allele with this mutation suffer from a severe skeletal disorder called spondyloepiphyseal dysplasia congenita (SED). Transgenic mice phenotype was neonatally lethal with severe respiratory failure, short bones, and cleft palate. Transgene mRNA was expressed at high levels. Growth plate cartilage of transgenic mice presented morphological abnormalities and reduced number of collagen type II fibrils. Chondrocytes carrying the mutation showed altered expression of several differentiation markers, like fibroblast growth factor receptor 3 (Fgfr3), Indian hedgehog (Ihh), runx2, cyclin-dependent kinase inhibitor P21CIP/WAF (Cdkn1a), and collagen type X (Col10a1), suggesting that a defective extracellular matrix (ECM) depleted of collagen fibrils affects chondrocytes differentiation and that this defect participates in the reduced endochondral bone growth observed in chondrodysplasias caused by mutations in COL2A1.

Connective tissue growth factor mRNA expression pattern in cartilages is associated with their type I collagen expression

Connective tissue growth factor (CTGF) has been identified as a secretory protein encoded by an immediate early gene and is a member of the CCN family. In vitro CTGF directly regulates the proliferation and differentiation of chondrocytes; however, a previous study showed that it was localized only in the hypertrophic chondrocytes in the costal cartilages of E 18 mouse embryos. We described the expression of CTGF mRNA and protein in chondrocytes of different types of cartilages, including femoral growth plate cartilage, costal cartilage, femoral articular cartilage, mandibular condylar cartilage, and cartilage formed during the healing of mandibular ramus fractures revealed by in situ hybridization and immunohistochemistry. To characterize the CTGF-expressing cells, we also analyzed the distribution of the type I, type II, and type X collagen mRNA expression. Among these different types of cartilages we found distinct patterns of CTGF mRNA and protein expression. Growth plate cartilage and the costal cartilage showed localization of CTGF mRNA and protein in the hypertrophic chondrocytes that expressed type X collagen mRNA with less expression in proliferating chondrocytes that expressed type II collagen mRNA, whereas it was also expressed in the proliferating chondrocytes that expressed type I collagen mRNA in the condylar cartilage, the articular cartilage, and the cartilage appearing during fracture healing. In contrast, the growth plate cartilages or the costal cartilages were negative for type I collagen and showed sparse expression of CTGF mRNA in the proliferating chondrocytes. We found for the first time that CTGF mRNA could be differentially expressed in five different types of cartilage associated with those expressing type I collagen. Moreover, the spatial distribution of CTGF mRNA in the cartilages with type I collagen mRNA suggested its roles in the early differentiation, as well as in the proliferation and the terminal differentiation, of those cartilages.

Compositional changes of the xiphoid process and costal cartilage with aging

To elucidate compositional changes of the cartilage with aging, the authors investigated age-related changes of element contents in the xiphoid process and costal cartilage by inductively coupled plasma-atomic emission spectrometry. After the ordinary dissection by medical students was finished, the xiphoid processes and bilateral the fourth costal cartilages were resected and element contents were determined. The subjects consisted of 17 men and 9 women, ranging in age from 52 to 96 yr. No significant correlations were found between age and the content of elements, such as Ca, P, S, Mg, Na, Zn, Fe, and Si in the xiphoid process and costal cartilage, except for S in the costal cartilage, in which an extremely significant correlation was found. With regard to the relationships among element contents, the common finding that there were significant direct correlations both between Ca and P contents and between Ca and Mg contents, whereas there were significant inverse correlations both between Ca and S contents and between P and S contents obtained in the xiphoid process and costal cartilage.

Diffusion and partition of solutes in cartilage under static load

We describe experimental apparatus, methodology and mathematical algorithms to measure diffusion and partition for typical small ionic solutes and inulin (a medium size solute) in statically loaded cartilage. The partition coefficient based on tissue water (K(H(2)O)) of Na(+) increased from 1.8 to 4.5 and for SO(4)(-2) decreased from 0.5 to 0.1, when the applied pressure was raised from zero to 22 atm K(H(2)O) of inulin decreased from 0.3 to 0.05, for an increase in pressure from zero to 11 atm. Our theoretical interpretation of the results is that the partition coefficient can be expressed as a function of fixed charge density (FCD) for both loaded and unloaded cartilage. The partition coefficient shows good agreement with the ideal Gibbs-Donnan equilibrium, particularly when FCD is based on extrafibrillar water (EFW). The diffusion coefficients, D also decreased with an increase in applied pressure; raising the pressure from 0 to 22 atm resulted in the following changes in the values of D: for Na(+) from 2.86 x 10(-6) to 1.51 x 10(-6) cm(2)/s, for SO(4)(-2) from 1.58 x 10(-6) to 7.5 x 10(-7) cm(2)/s, for leucine from 1.69 x 10(-6) to 8.30 x 10(-7) cm(2)/s and for inulin from 1.80 x 10(-7) to 3.30 x 10(-8) cm(2)/s. For the three small solutes (two charged and one neutral) the diffusion coefficient D is highly correlated with the fraction of fluid volume in the tissue. These experimental results show good agreement with the simple model of Mackie and Meares: hence solute charge does not affect the diffusion of small solutes under load. For inulin D & K show some agreement with a modified Ogston model based on two major components, viz., glycosaminoglycans (GAG) and core protein. We conclude that the changes in the partition and diffusion coefficients of small and medium size solutes in statically loaded cartilage can be interpreted as being due to the reduction in hydration and increase in FCD. The change in the latter affects the partition of small ionic solutes and the partition and diffusion of larger molecules. Our results throw light on the ionic environment of chondrocytes in loaded cartilage as well as on the transport of solutes through the matrix.

Variations in aggrecan structure modulate its susceptibility to aggrecanases

Proteoglycan aggregates and purified aggrecan from adult and fetal bovine cartilage and adult and neonatal human cartilage were subjected to in vitro degradation by recombinant aggrecanase-1 and aggrecanase-2. The ability of the aggrecanases to cleave within the aggrecan IGD (interglobular domain) and CS2 domain (chondroitin sulphate-rich domain 2) was monitored by SDS/PAGE and immunoblotting. Aggrecanase-2 showed a similar ability to cleave within the IGD of adult and immature aggrecan, whereas aggrecanase-1 was less efficient in cleavage in the IGD of immature aggrecan, for both the bovine and the human substrates. Both aggrecanases showed a similar ability to cleave within the CS2 domain of bovine aggrecan irrespective of age, but showed a much lower ability to cleave within the CS2 domain of human aggrecan. Equivalent results were obtained whether aggrecan was present in isolation or as part of proteoglycan aggregates. When proteoglycan aggregates were used, neither aggrecanase was able to cleave link protein. Thus, for aggrecan cleavage by aggrecanases, variations in cleavage efficiency exist with respect to the species and age of the animal from which the aggrecan is derived and the type of aggrecanase being used.

Individual cartilage aggrecan macromolecules and their constituent glycosaminoglycans visualized via atomic force microscopy

Atomic force microscopy was used in ambient conditions to directly image dense and sparse monolayers of bovine fetal epiphyseal and mature nasal cartilage aggrecan macromolecules adsorbed on mica substrates. Distinct resolution of the non-glycosylated N-terminal region from the glycosaminoglycan (GAG) brush of individual aggrecan monomers was achieved, as well as nanometer-scale resolution of individual GAG chain conformation and spacing. Fetal aggrecan core protein trace length (398+/-57 nm) and end-to-end length (257+/-87 nm) were both larger than that of mature aggrecan (352+/-88 and 226+/-81 nm, respectively). Similarly, fetal aggrecan GAG chain trace length (41+/-7 nm) and end-to-end (32+/-8 nm) length were both larger than that of mature aggrecan GAG (32+/-5 and 26+/-7 nm, respectively). GAG-GAG spacing along the core protein was significantly smaller in fetal compared to mature aggrecan (3.2+/-0.8 and 4.4+/-1.2nm, respectively). Together, these differences between the two aggrecan types were likely responsible for the greater persistence length of the fetal aggrecan (110 nm) compared to mature aggrecan (82 nm) calculated using the worm-like chain model. Measured dimensions and polymer statistical analyses were used in conjunction with the results of Western analyses, chromatographic, and carbohydrate electrophoresis measurements to better understand the dependence of aggrecan structure and properties on its constituent GAG chains.

Serum levels of cartilage oligomeric matrix protein. A predicting factor and a valuable parameter for disease management in rheumatoid arthritis

OBJECTIVE

To examine whether cartilage oligomeric matrix protein (COMP) correlates with inflammation and/or joint destruction of patients with rheumatoid arthritis (RA) and to test COMP as predicting factor for the outcome of patients with established RA.

METHODS

Serum levels of COMP were measured in sera of 62 patients, suffering from RA according to the ACR criteria and treated in intervals in our department, over a period of 5 years. A commercially available sandwich--type ELISA-kit developed by AnaMar Medical AB, Sweden, was used. The results of serum COMP were compared with the Disease Activity Score (DAS), the Larsen Score, and clinical and laboratory parameters.

RESULTS

We found a positive correlation between serum levels of COMP at baseline and deterioration of Larsen score even after 5 years (p < 0.007; r = 0.34). To confirm serum COMP as an independent predicting factor for patients with RA we looked at a subgroup of patients (n = 17) with elevated serum levels of COMP (mean 11,7 U/l) and low clinical prognostic factors. In this subgroup we also found a significant correlation with delta Larsen score (p < 0.01; r = 0.59) after 5 years.

CONCLUSION

Serum levels of COMP is known to reflect increased cartilage turnover. The results indicate that serum COMP may be used as a prognostic marker of cartilage degradation in a patient group with established RA.

Osteoarthritis

Osteoarthritis is a chronic degenerative disorder characterised by cartilage loss. It is extremely prevalent in society and is a major cause of disability. It is important to treat osteoarthritis effectively using a multidisciplinary approach tailored to the patient's needs. This paper reviews current thinking on the aetiology, pathogenesis, investigations, and management of osteoarthritis. The paper also discusses the challenges for developing good quality outcome measures for use in large scale multicentre clinical trials for new osteoarthritis treatments, especially disease modifying osteoarthritis drugs.

A comparative dose-response study of cartilage-derived morphogenetic protein (CDMP)-1, -2 and -3 for tendon healing in rats

Cartilage-derived morphogenetic proteins (CDMPs), belonging to the bone morphogenetic protein (BMP) family, are known to be cartilage and bone inducers as well as to induce tendon and ligament-like tissue. In this study we investigated the influence of CDMP-1, -2 or -3 at four different doses (0, 0.4, 2 and 10 microg) on tendon healing in a rat model, as well as differences in osteogenesis between the different CDMPs and doses.In 110 rats, a 3 mm segment of the Achilles tendon was removed via a 2 mm skin incision. CDMP-1, -2 or -3 was injected into the defect 6 h postoperative. The rats were killed 8 days after operation. The tendon regenerates were tested biomechanically. There was a significant dose-related increase in strength and stiffness with all three CDMPs, but no difference between the CDMPs was found. Another 50 rats were used to compare the highest dose of the CDMPs with controls and osteogenic protein 1 (OP-1), as regards cartilage or bone formation after 4 weeks. Cartilage occurred in all groups, including the controls. Some specimens in all groups contained bone, except the controls. No difference between the CDMPs could be demonstrated. The CDMP-1, CDMP-3 and OP-1 groups contained significantly more calcium than controls. Only the CDMP-2 group and the controls contained significantly less calcium than the OP-1 group.In conclusion, the three CDMPs appeared similar as regards improvement of tendon repair and osteogenicity in this setting.

Modulation of CD(4)(+) and CD(8)(+) tumor infiltrating lymphocytes by a fraction isolated from shark cartilage: shark cartilage modulates anti-tumor immunity

Shark cartilage has proven to have some inhibitory effects on angiogenesis, metastasis, cell adhesion and proteolysis. In this study, we wanted to study some of the effects of shark cartilage on tumor immune response. Firstly, by means of chromatographic methods and delayed type hypersensitivity (DTH) test, we optimized a procedure for isolation and purification of a shark cartilage protein fraction with most immunostimulatory effects. Then, we examined its effect on the infiltration of CD(4)(+) and CD(8)(+) lymphocytes into a murine tumor model. Our fraction was composed of two major proteins with molecular weights (MWs) of about 14 and 15 kDa. This fraction highly increases DTH response against sRBC in mice. Furthermore, intraperitoneal injection of this fraction to tumor-bearing mice could increase T-cell infiltration into the tumor. Also, there was a significant increase in the CD(4)/CD(8) ratio in tumor infiltrating lymphocytes, but no such changes were found in the peripheral blood lymphocytes. According to these results, we suppose that this fraction is a good candidate for further studies in cancer therapy. Also, we concluded that this fraction, with previously proven anti-angiogenic effects, can augment cellular immune response and T-cell infiltration into the tumor and thus, there may be a direct relationship between angiogenesis inhibition and T-cell infiltration.

The changes in crosslink contents in tissues after formalin fixation

The aim of this study was to detect crosslinks of collagen and elastin in formalin-fixed tissue, to perform quantification of these crosslinks, and to investigate the effects of formalin fixation on crosslink contents in human yellow ligament and cartilage. Pyridinoline (Pyr) is a stable and nonreducible crosslink of collagen. Pentosidine (Pen) is a senescent crosslink formed between arginine and lysine in matrix proteins, including collagen. Desmosine (Des) and its isomer isodesmosine (Isodes) are crosslinks specifically found in elastin. It is useful to measure crosslink contents of collagen and elastin as a way of investigating the properties of various tissues or their pathological changes. If it is possible to evaluate crosslinks of collagen and elastin in formalin-fixed tissues, we can investigate crosslinks in a wide variety of tissues. We used HPLC to compare the concentrations of Pyr, Pen, Des, and Isodes in the formalin-fixed tissues with their concentrations in the frozen tissues. Pyr and Pen were detected in both the formalin-fixed yellow ligament and the cartilage, and their concentrations were not significantly affected by or related to the duration of formalin fixation. Des and Isodes were detected in the formalin-fixed yellow ligament but in significantly lower amounts compared to the frozen samples. We concluded that crosslinks of collagen were preserved in formalin, but crosslinks of elastin were not preserved in it. The reason for this might be that formalin did not fix elastin tissues sufficiently or it destroyed, masked, or altered elastin crosslinks.

Association of metalloproteinases, tissue inhibitors of matrix metalloproteinases, and proteoglycans with development, aging, and osteoarthritis processes in mouse temporomandibular joint

The temporomandibular joint (TMJ) is an important growth and articulation center in the craniofacial complex. In aging it develops spontaneous degenerative osteoarthritic (OA) lesions. Metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPS) play key roles in extracellular matrix remodeling and degradation. Gelatinase activities and immunohistochemical localization of MMP-2, -3, -8, -9, and -13 and TIMP-1 and -2 were examined in mandibular condyle cartilage of neonatal mice up to 18 months old. The most intense immunostaining for all enzymes and TIMPs and the peak of gelatinase activities were found in animals in the stages of early growth (1 week to 3 months) followed by a decrease during maturation and aging. However, clusters of positively immunoreactive chondrocytes were detected in cartilages of old animals displaying OA lesions. Positive safranin-O staining, indicative of sulfated proteoglycans (PGs), was prominent in the TMJ of newborn mice up to 3 months old followed by reduction during maturation and aging, except in regions displaying OA lesions. Temporal codistribution of PGs, MMPs, and TIMPs during skeletal maturation reflected an active growth phase, whereas their reduction coincided with the more quiescent articulating and maintenance phase in the joint cartilage. Osteoarthritic lesions were associated with both increased PG synthesis and MMP immunoreactivity, indicating limited repair activity during initial stages of osteoarthritis.

Cleavage site specificity of cathepsin K toward cartilage proteoglycans and protease complex formation

Cathepsin K is a potent extracellular matrix-degrading protease that requires interactions with soluble glycosaminolycans for its collagenolytic activity in bone and cartilage. The major sources of glycosaminoglycans in cartilage are aggrecan aggregates. Therefore, we investigated whether cathepsin K activity is capable to hydrolyze aggrecan into fragments allowing the formation of glycosaminoglycan-cathepsin K complexes and determined the cleavage site specificity of cathepsin K toward the cartilage-resident link protein and aggrecan. The cleavage site specificity was compared with those of cathepsins S and L. All three cathepsins released glycosaminoglycans from native bovine cartilage at lysosomal pH and to a lesser degree at neutral extracellular pH. Cathepsin-predigested aggrecan complexes and cartilage provided suitable glycosaminoglycan fragments that allowed the formation of collagenolytically active cathepsin K complexes. A detailed analysis of the degradation of aggrecan aggregates revealed two cathepsin K cleavage sites in the link protein and several sites in aggrecan, including one site within the interglobular domain E1. In summary, these results demonstrate that cathepsin K is capable to degrade aggrecan complexes at specific cleavage sites and that cathepsin K activity alone is sufficient to self-provide the glycosaminoglycan fragments required for the formation of its collagenolytically active complex.

Immunomodulating principles from shark cartilage. Part 1. Isolation and biological assessment in vitro

Extracts from shark cartilage exhibiting powerful immunostimulating activity in vitro are described. The study shows that a simple extraction with water is very effective in producing the immunostimulating principles and implies that it is ideal for scale-up and manufacturing on a large scale. The extracts are potent stimulators of B cells and macrophages isolated from BALB/c mice spleen while stimulation of T cells was insignificant in our in vitro models. The study demonstrates that the active principles are thermally stable proteoglycans with molecular masses exceeding 100 kDa. This in vitro study represents an important step needed for further assessment of the products in vivo and their value for nutraceutical use.

The effect of supplementing layer diets with shark cartilage or chitosan on egg components and yolk lipids

1. An experiment was designed to evaluate the effects of the addition of shark cartilage (SC) or chitosan (CH) to layer diets on egg component weights, yolk lipids and hen plasma lipids. 2. Hy-Line laying hens (80) were used during a 56 d feeding trial. Treatments were: basal diet (BD), BD + 20 g/kg SC, BD + 30 g/kg SC, BD + 20 g/kg CH and BD + 30 g/kg CH. Eggs were analysed on d 14, 28, 42 and 56. 3. Egg weight and egg component weights were not affected by these treatments throughout the experimental period. 4. After 14d of experimental feeding, cholesterol levels were higher in eggs from birds given BD + 20 g/kg CH and BD + 30 g/kg CH than in those from birds given BD. 5. Furthermore, eggs from hens given BD + 20 g/kg SC or BD + 20 g/kg CH were higher in palmitic and stearic acids and lower in oleic acid than those from birds fed on BD. After 56 d feeding, however, palmitic and stearic acid contents in eggs from hens given any of the supplemented diets were lower than in those from hens given BD, and oleic acid in eggs from hens given BD + 20 g/kg SC, BD + 30 g/kg SC and BD + 30 g/kg CH was higher than in those from birds fed on BD. 6. Plasma cholesterol and triacylglycerol levels were not significantly affected by dietary treatment. 7. Shark cartilage or chitosan at up to 30 g/kg in layer diets did not affect egg component weights (yolk, white and shell) and total lipid contents. During the period from 42 to 56d of experimental feeding, diets containing up to 30 g/kg chitosan reduced egg yolk contents of cholesterol, palmitic and stearic acids and increased the content of oleic acid.

Modification of di- and tetrasaccharides from shark cartilage keratan sulphate by refined anhydromethanolic hydrochloric acid-treatments and evaluation of their specific desulphation

Highly sulphated keratan di- and tetrasaccharides were prepared from keratan sulphate (KS) of shark cartilage by enzymatic digestion with keratanase II and subsequent chromatography. The tetrasaccharide fraction carrying four sulphate groups was completely desulphated by 100 mM anhydromethanolic hydrochloric acid (MeOH-HCl) treatment at room temperature for 16 h. The conditions for the desulphation reaction by MeOH-HCl treatment were examined using sulphated keratan di- and tetrasaccharides as substrates by means of reversed phase high performance liquid chromatography (HPLC) and/or capillary electrophoresis, followed by the preparation of partially desulphated keratan oligosaccharides. Sulphate substitution patterns of monosulphated keratan disaccharide and trisulphated keratan tetrasaccharide were evaluated by methylation analysis. The results suggested that 6-O-sulphate groups of Gal moieties are cleaved faster than those of GlcNAc moieties under the present conditions adopted for the MeOH-HCl treatment of KS-derived oligosaccharides.

Matrix fixed-charge density as determined by magnetic resonance microscopy of bioreactor-derived hyaline cartilage correlates with biochemical and biomechanical properties

OBJECTIVE

To use noninvasive magnetic resonance imaging (MRI), biochemical analyses, and mechanical testing of engineered neocartilage grown in a hollow- fiber bioreactor (HFBR) to establish tissue properties, and to test the hypothesis that MRI can be used to monitor biochemical and biomechanical properties of neocartilage.

METHODS

Chondrocytes from day 16 embryonic chick sterna were inoculated into an HFBR and maintained for up to 4 weeks with and without exposure to chondroitinase ABC. The fixed-charge density (FCD) of the cartilage was determined using the MRI gadolinium exclusion method. The sulfated glycosaminoglycan (S-GAG), hydroxyproline, and DNA contents were determined using biochemical procedures, while dynamic and equilibrium moduli were determined from mechanical indentation tests.

RESULTS

S-GAG content, tissue cross-sectional area, and equilibrium modulus of the neocartilage increased with development time. There was a gradient of S-GAG content across the length of control neocartilage at the 4-week time point, with higher values being found toward the inflow region. Exposure to chondroitinase ABC resulted in a decrease in tissue area, negative FCD, proteoglycan content, and equilibrium and dynamic moduli. The treated bioreactors displayed a lengthwise variation in S-GAG content, with higher values toward the outflow end. Linear correlations were established among FCD, proteoglycan content, and biomechanical properties.

CONCLUSION

HFBR-derived neocartilage showed regional variation in S-GAG content under control conditions, and in the decrease of S-GAG in response to enzyme treatment. In addition, the results support the hypothesis that tissue parameters derived from MRI can be used to noninvasively monitor focal neocartilage formation and biochemical and biomechanical properties.

Time-resolved, light scattering measurements of cartilage and cornea denaturation due to free electron laser radiation

Light scattering is used to monitor the dynamics and energy thresholds of laser-induced structural alterations in biopolymers due to irradiation by a free electron laser (FEL) in the infrared (IR) wavelength range 2.2 to 8.5 microm. Attenuated total reflectance (ATR) Fourier-transform IR (FTIR) spectroscopy is used to examine infrared tissue absorption spectra before and after irradiation. Light scattering by bovine and porcine cartilage and cornea samples is measured in real time during FEL irradiation using a 650-nm diode laser and a diode photoarray with time resolution of 10 ms. The data on the time dependence of light scattering in the tissue are modeled to estimate the approximate values of kinetic parameters for denaturation as functions of laser wavelength and radiant exposure. We found that the denaturation threshold is slightly lower for cornea than for cartilage, and both depend on laser wavelength. An inverse correlation between denaturation thresholds and the absorption spectrum of the tissue is observed for many wavelengths; however, for wavelengths near 3 and 6 microm, the denaturation threshold does not exhibit the inverse correlation, instead being governed by heating kinetics of tissue. It is shown that light scattering is useful for measuring the denaturation thresholds and dynamics for different biotissues, except where the initial absorptivity is very high.

Optimum combination of monolayer and three-dimensional cultures for cartilage-like tissue engineering

The autologous chondrocyte transplantation technique has been introduced for the repair of articular cartilage defects. The advantage of transplanting chondrocytes cultured in suspension includes the in vitro expansion of cell numbers. However, the disadvantages include the potential leakage of cells from defects, dedifferentiation of cellular phenotype, and uneven distribution of cells. Transplantation of chondrocytes cultured in collagen gel resolves those problems. However, the expansion of cells in three-dimensional culture is more difficult than in monolayer culture, and for practical reasons only limited numbers of chondrocytes can be obtained from an unloaded area of the knee. To develop a method for the production of high-quality cultured grafts, we investigated the combination of monolayer culture for cell expansion and three-dimensional culture for maintenance of cell phenotype. Articular chondrocytes from rabbits were divided into four groups, exposed to various combinations of culture conditions, and cultured for a total of 3 weeks. Each group was evaluated histologically, biochemically, and biomechanically. Our findings showed that the combination of 2 weeks of monolayer culture followed by 1 week of three-dimensional culture resulted in the highest chondroitin sulfate levels, sufficient cell numbers, and adequate stiffness of the chondrocyte-collagen composites, giving optimal graft preparation.

Collagen type II modification by hypochlorite

Oxidation of proteins is a common phenomenon in the inflammatory process mediated by highly reactive agents such as hypochlorite (HOCl/OCl(-)) produced by activated neutrophils. For instance, in rheumatoid arthritis hypochlorite plays an important role in joint destruction. One of the major targets for HOCl/OCl(-) is collagen type II (CII) - the primary cartilage protein. In our study, HOCl/OCl(-) mediated collagen II modifications were tested using various methods: circular dichroism (CD), HPLC, ELISA, dynamic light scattering (DLS), fluorimetry and spectrophotometry. It was shown that hypochlorite action causes deamination with consecutive carbonyl group formation and transformation of tyrosine residues to dichlorotyrosine. Moreover, it was shown that ammonium chloramine (NH(2)Cl) formed in the reaction mixture reacts with CII. However, in this case the yield of carbonyl groups and dichlorotyrosine is lower than that observed for HOCl/OCl(-) by 50%. CD data revealed that collagen II exists as a random coil in the samples and that chlorination is followed by CII fragmentation. In the range of low HOCl/OCl(-) concentrations (up to 1 mM) 10-90 kDa peptides are predominant whereas massive production of shorter peptides was observed for high (5 mM) hypochlorite concentration. DLS measurements showed that chlorination with HOCl/OCl(-) decreases the radius of collagen II aggregates from 30 to 6.8 nm. Taking into account the fact that chlorinated collagen is partially degraded, the DLS results suggest that smaller micelles are formed of the 10-90 kDa peptide fraction. Moreover, collagen chlorination results in epitope modification which affects CII recognition by anti-CII antibodies. Finally, since in the synovial fluid the plausible hypochlorite concentration is smaller than that used in the model the change of size of molecular aggregates seems to be the best marker of hypochlorite-mediated collagen oxidation.

Controlling the spatial distribution of ECM components in degradable PEG hydrogels for tissue engineering cartilage

In developing a scaffold to support new tissue growth, the degradation rate and mass loss profiles of the scaffold are important design parameters. In this study, hydrogels were prepared by copolymerizing a degradable macromer, poly(lactic acid)-b-poly(ethylene glycol)-b-poly(lactic acid) endcapped with acrylate groups (PEG-LA-DA) with a nondegradable macromer, poly(ethylene glycol) dimethacrylate (PEGDM). The resulting hydrogels exhibited a range of degradation behavior and mass loss profiles. Chondrocytes were photoencapsulated in gels formulated with 50:50, 25:75, and 15:85 (mol % PEGDM: mol % PEG-LA-DA) and cultured for 6 weeks in vitro. The neocartilaginous tissue formed was examined biochemically and histologically. After 6 weeks, the DNA content in gels with 75 and 85% degradable crosslinks was nearly twice that of the DNA content in the 50% gels. The total collagen content was significantly higher in the 85% gel [2.4 +/- 0.8% wet weight (ww)] compared to the 50% gel (0.22 +/- 0.29% ww). In examining the neocartilaginous tissue with immunohistochemistry, type II collagen was localized in the pericellular region in the 50% gel; however, when increased degradation was incorporated into the gel, type II collagen was found throughout the neotissue. In summary, the important role of hydrogel degradation in controlling and influencing the deposition and distribution of extracellular matrix molecules was demonstrated and quantified.

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.

Detection of submicrogram quantities of glycosaminoglycans on agarose gels by sequential staining with toluidine blue and Stains-All

A sensitive method has been developed for the visualization of nonradiolabelled glycosaminoglycans resolved by agarose gel electrophoresis using staining with toluidine blue followed by Stains-All procedure. This method, which can detect as little as 10 ng of a single species, can be used to stain a few micrograms of a complex polysaccharide mixture. The combination of agarose gel electrophoresis and sequential toluidine blue/Stains-All staining can be applied to the analysis of all the complex glycosaminoglycans (i.e., heparin, heparan sulfate, chondroitin/dermatan sulfate) and nonsulfated polyanions (i.e., hyaluronate, defructosylated capsular polysaccharide K4) as well as to comparisons of specificities of the glycosaminoglycan-degrading enzymes and the identification and quantification of the contaminations of other polysaccharides within glycosaminoglycan preparations with great sensitivity (about 0.1%). Furthermore, this method can be used to stain low-molecular-mass fractions and oligosaccharides derived from the natural polyanions, such as heparin. This procedure may be particularly valuable in situations where the availability of glycosaminoglycan is very limited.

Microspectroscopy and imaging in the THz range using coherent CW radiation

A novel THz near-field spectrometer is presented which allows the performance of biological and medical studies with high spectral resolution combined with a spatial resolution down to lambda/100. In the setup an aperture much smaller than the used wavelength is placed in the beam very close to the sample. The sample is probed by the evanescent wave behind the aperture. The distance is measured extremely accurately by a confocal microscope. We use monochromatic sources which provide powerful coherent cw radiation tuneable from 50 GHz up to 1.5 THz. Transmission and reflection experiments can be performed which enable us to study solids and molecules in aqueous solution. Examples for spectroscopic investigations on biological tissues are presented.

A new collagen from the extracellular matrix of Sepia officinalis cartilage

Guanidinium chloride treatment of Sepia officinalis cartilage solubilized a component that contained hydroxyproline. Electron-microscopy observation of rotary-shadowed preparations of this component revealed it to consist of rod-like units themselves consisting of filaments. Dialysis of an acetic acid solution against ATP afforded polymeric aggregates consisting of a succession of two or three thick sections showing transverse electron-opaque banding, separated by thinner sections without banding. Electrophoresis produced a main band of about 140 kDa sensitive to bacterial collagenase. After reduction with mercaptoethanol, electrophoresis afforded a 40-kDa band. Pepsin digestion resulted in additional electrophoretic bands. These data suggest the presence of a collagen in Sepia cartilage with characteristics unlike those of any known collagen.

Effects of L-ascorbic acid on lysyl oxidase in the formation of collagen cross-links

To clarify the role of L-ascorbic acid (AsA) in the formation of pyridinoline, we examined the effects of AsA in vitro using soluble collagen and partially purified lysyl oxidase from bovine aorta. The concentration of dehydrodihydroxylysinonorleucine decreased when AsA was added in the early stage of pyridinoline formation. However, when AsA was added in a later stage of pyridinoline formation, the concentration of pyridinoline was not affected. These findings indicated that AsA was involved in the initial enzymatic reaction in pyridinoline synthesis. We purified lysyl oxidase to confirm its association of AsA. AsA inhibited the enzyme activity. Erythorbic acid and 3,4-dihydroxybenzoate suppressed the enzyme activity as well as AsA did. The inhibition by AsA of the lysyl oxidase activity arose from characteristics of AsA structure. AsA might be important in the regulation of the oxidative reaction of lysine.

Regulation of cell proliferation in rat mandibular condylar cartilage in explant culture by insulin-like growth factor-1 and fibroblast growth factor-2

Insulin-like growth factor-1 (IGF-1) and fibroblast growth factor-2 (FGF-2) regulate the proliferation and differentiation of growth-plate chondrocytes, but surprisingly little is known of the mechanisms underlying growth regulation in secondary cartilages such as the mandibular condylar. The aims here were to investigate whether IGF-1 and FGF-2 receptors are present in mandibular condylar cartilage in vivo from 28-day-old male Sprague-Dawley rats (by immunohistochemistry), how proliferation in that cartilage responds to increasing concentrations of exogenous IGF-1 or FGF-2 in explant culture (by [3H]thymidine incorporation), and whether the expression of these growth factors and their receptors in the cartilage changes during the transition to puberty (quantitative reverse transcriptase-polymerase chain reaction). Immunoreactivity for receptors (R) for IGF-1 and FGF-2 (IGF-1R, FGFR1, and FGFR3) was most pronounced in chondroblasts and hypertrophic chondrocytes, while FGFR2 immunoreactivity was strongest in the articular and prechondroblastic zones. The proliferative response elicited by exogenous IGF-1 was considerably greater than that induced by FGF-2, although the threshold concentration for a significant response was lower for FGF-2. In the transition from prepuberty (31 days) to the beginning of late puberty (42 days), a pronounced trend of increasing IGF-1 and decreasing FGF-2 gene expression was evident. Of the receptors, only FGFR2 and FGFR3 expression increased. These data provide evidence that proliferation in the mandibular condylar cartilage might be regulated in part by IGF-1 and FGF-2, and that expression of these genes changes considerably at puberty. The data also suggest that mechanisms governing proliferation in mandibular condylar cartilage might have as much in common with those regulating cranial sutures as those regulating growth-plate.

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.