Glycosaminoglycans of human bone tissue. I. Pattern of compact bone in relation to age

Anti-inflammatory Effect of DNA Polymeric Molecules in a Cell Model of Osteoarthritis

The DNA polymeric molecules polydeoxynucleotide (PDRN) and polynucleotide (PN) can be used as new alternative treatment for osteoarthritis (OA); however, the underlying mechanisms are not fully understood. In this study, we investigated the effect of PDRN and PN on gene-expression profiles in a cell model of OA using transcriptome analysis. Under hypoxic conditions, human chondrosarcoma cells were stressed for 24 h in the presence of interleukin (IL)-1β and subsequently treated with PDRN, PN, or hyaluronic acid (HA) for another 24 h, followed by transcriptome analysis. The results of the transcriptome study comprising differentially expressed genes were analyzed using the Database of Annotation Visualization and Integrated Discovery program, which yielded Kyoto Encyclopedia of Genes and Genomes pathways. Toll-like receptor (TLR)- and nucleotide-binding oligomerization domain-like receptor (NLR)-signaling pathways were related between the IL-1β group and the group treated with DNA polymeric molecules. The genes involved in the TLR- and NLR-signaling pathways were validated using real-time quantitative polymerase chain reaction and western blot. Among these genes, IL-6, IL-1β, IL-8, and chemokine (C-C motif) ligand 3 were dramatically upregulated in the IL-1β group, but significantly downregulated in the group treated with DNA polymeric molecules. Specifically, PN treatment resulted in a greater decrease in the expression of these genes as compared with PDRN treatment. Both PDRN and PN treatments were involved in the anti-inflammatory response associated with OA progression, with PN treatment exhibiting additional anti-inflammatory properties relative to PDRN treatment. These results provide insight into potential therapeutic approaches involving PDRN and PN treatment of OA.

The pearl oyster Pinctada fucata martensii genome and multi-omic analyses provide insights into biomineralization

Nacre, the iridescent material found in pearls and shells of molluscs, is formed through an extraordinary process of matrix-assisted biomineralization. Despite recent advances, many aspects of the biomineralization process and its evolutionary origin remain unknown. The pearl oyster Pinctada fucata martensii is a well-known master of biomineralization, but the molecular mechanisms that underlie its production of shells and pearls are not fully understood. We sequenced the highly polymorphic genome of the pearl oyster and conducted multi-omic and biochemical studies to probe nacre formation. We identified a large set of novel proteins participating in matrix-framework formation, many in expanded families, including components similar to that found in vertebrate bones such as collagen-related VWA-containing proteins, chondroitin sulfotransferases, and regulatory elements. Considering that there are only collagen-based matrices in vertebrate bones and chitin-based matrices in most invertebrate skeletons, the presence of both chitin and elements of collagen-based matrices in nacre suggests that elements of chitin- and collagen-based matrices have deep roots and might be part of an ancient biomineralizing matrix. Our results expand the current shell matrix-framework model and provide new insights into the evolution of diverse biomineralization systems.

The Components of Bone and What They Can Teach Us about Regeneration

The problem of bone regeneration has engaged both physicians and scientists since the beginning of medicine. Not only can bone heal itself following most injuries, but when it does, the regenerated tissue is often indistinguishable from healthy bone. Problems arise, however, when bone does not heal properly, or when new tissue is needed, such as when two vertebrae are required to fuse to stabilize adjacent spine segments. Despite centuries of research, such procedures still require improved therapeutic methods to be devised. Autologous bone harvesting and grafting is currently still the accepted benchmark, despite drawbacks for clinicians and patients that include limited amounts, donor site morbidity, and variable quality. The necessity for an alternative to this "gold standard" has given rise to a bone-graft and substitute industry, with its central conundrum: what is the best way to regenerate bone? In this review, we dissect bone anatomy to summarize our current understanding of its constituents. We then look at how various components have been employed to improve bone regeneration. Evolving strategies for bone regeneration are then considered.

The identification of proteoglycans and glycosaminoglycans in archaeological human bones and teeth

Bone tissue is mineralized dense connective tissue consisting mainly of a mineral component (hydroxyapatite) and an organic matrix comprised of collagens, non-collagenous proteins and proteoglycans (PGs). Extracellular matrix proteins and PGs bind tightly to hydroxyapatite which would protect these molecules from the destructive effects of temperature and chemical agents after death. DNA and proteins have been successfully extracted from archaeological skeletons from which valuable information has been obtained; however, to date neither PGs nor glycosaminoglycan (GAG) chains have been studied in archaeological skeletons. PGs and GAGs play a major role in bone morphogenesis, homeostasis and degenerative bone disease. The ability to isolate and characterize PG and GAG content from archaeological skeletons would unveil valuable paleontological information. We therefore optimized methods for the extraction of both PGs and GAGs from archaeological human skeletons. PGs and GAGs were successfully extracted from both archaeological human bones and teeth, and characterized by their electrophoretic mobility in agarose gel, degradation by specific enzymes and HPLC. The GAG populations isolated were chondroitin sulfate (CS) and hyaluronic acid (HA). In addition, a CSPG was detected. The localization of CS, HA, three small leucine rich PGs (biglycan, decorin and fibromodulin) and glypican was analyzed in archaeological human bone slices. Staining patterns were different for juvenile and adult bones, whilst adolescent bones had a similar staining pattern to adult bones. The finding that significant quantities of PGs and GAGs persist in archaeological bones and teeth opens novel venues for the field of Paleontology.

High-throughput bone and cartilage micropellet manufacture, followed by assembly of micropellets into biphasic osteochondral tissue

Engineered biphasic osteochondral tissues may have utility in cartilage defect repair. As bone-marrow-derived mesenchymal stem/stromal cells (MSC) have the capacity to make both bone-like and cartilage-like tissues, they are an ideal cell population for use in the manufacture of osteochondral tissues. Effective differentiation of MSC to bone-like and cartilage-like tissues requires two unique medium formulations and this presents a challenge both in achieving initial MSC differentiation and in maintaining tissue stability when the unified osteochondral tissue is subsequently cultured in a single medium formulation. In this proof-of-principle study, we used an in-house fabricated microwell platform to manufacture thousands of micropellets formed from 166 MSC each. We then characterized the development of bone-like and cartilage-like tissue formation in the micropellets maintained for 8–14 days in sequential combinations of osteogenic or chondrogenic induction medium. When bone-like or cartilage-like micropellets were induced for only 8 days, they displayed significant phenotypic changes when the osteogenic or chondrogenic induction medium, respectively, was swapped. Based on these data, we developed an extended 14-day protocol for the pre-culture of bone-like and cartilage-like micropellets in their respective induction medium. Unified osteochondral tissues were formed by layering 12,000 osteogenic micropellets and 12,000 chondrogenic micropellets into a biphasic structure and then further culture in chondrogenic induction medium. The assembled tissue was cultured for a further 8 days and characterized via histology. The micropellets had amalgamated into a continuous structure with distinctive bone-like and cartilage-like regions. This proof-of-concept study demonstrates the feasibility of micropellet assembly for the formation of osteochondral-like tissues for possible use in osteochondral defect repair.

Chondroitin sulfate-E mediates estrogen-induced osteoanabolism

Osteoporosis is an age-related disorder of bone remodeling in which bone resorption outstrips bone matrix deposition. Although anticatabolic agents are frequently used as first-line therapies for osteoporosis, alternative anabolic strategies that can enhance anabolic, osteogenic potential are actively sought. Sex steroid hormones, particularly estrogens, are bidirectional regulators for bone homeostasis; therefore, estrogen-mediated events are important potential targets for such anabolic therapies. Here, we show that estrogen-induced, osteoanabolic effects were mediated via enhanced production of chondroitin sulfate-E (CS-E), which could act as an osteogenic stimulant in our cell-based system. Conversely, estrogen deficiency caused reduced expression of CS-E-synthesizing enzymes, including GalNAc4S-6ST, and led to decreased CS-E production in cultures of bone marrow cells derived from ovariectomized mice. Moreover, Galnac4s6st-deficient mice had abnormally low bone mass that resulted from impaired osteoblast differentiation. These results indicated that strategies aimed at boosting CS-E biosynthesis are promising alternative therapies for osteoporosis.

NMR investigation of the role of osteocalcin and osteopontin at the organic-inorganic interface in bone

Mechanical resilience of bone tissue decreases with age. The ability to comprehensively probe and understand bone properties could help alleviate this problem. One important aspect of bone quality that has recently been made evident is the presence of dilatational bands formed by osteocalcin (OC) and osteopontin (OPN), which contribute to fracture toughness. However, experimental evidence of the structural role of these two proteins at the organic-mineral interface in bone is still needed. Solid state nuclear magnetic resonance (SSNMR) is emerging as a useful technique in probing molecular level aspects of bone. Here, we present the first SSNMR study of bone tissue from genetically modified mice lacking OC and/or OPN. Probing the mineral phase, the organic matrix and their interface revealed that, despite the absence of OC and OPN, the organic matrix and mineral were well preserved, and the overall exposure of collagen to hydroxyapatite (HA) nanoparticles was hardly affected. However, the proximity to the HA surface was slightly increased for a number of bone components including less abundant amino acids like lysine, suggesting that this is how the tissue compensates for the lack of OC and OPN. Taken together, the NMR data supports the recently proposed model, in which the contribution of OC-OPN to fracture toughness is related to their presence at the extrafibrillar organic-mineral interfaces, where they reinforce the network of mineralized fibrils and form dilatational bands. In an effort toward further understanding the structural role of individual amino acids of low abundance in bone, we then explored the possibility of specific (13)C enrichment of mouse bone, and report the first SSNMR spectra of 97% (13)C lysine-enriched tissue. Results show that such isotopic enrichment allows valuable molecular-level structural information to be extracted, and sheds light on post-translational modifications undergone by specific amino acids in vivo.

Applications and emerging trends of hyaluronic acid in tissue engineering, as a dermal filler and in osteoarthritis treatment

Hyaluronic acid (HA) is a naturally occurring biodegradable polymer with a variety of applications in medicine, including scaffolding for tissue engineering, dermatological fillers and viscosupplementation for osteoarthritis treatment. HA is available in most connective tissues in body fluids such as synovial fluid and the vitreous humor of the eye. HA is responsible for several structural properties of tissues as a component of extracellular matrix and is involved in cellular signaling. Degradation of HA is a stepwise process that can occur via enzymatic or non-enzymatic reactions. A reduction in HA mass or molecular weight via degradation or slowing of synthesis affects physical and chemical properties such as tissue volume, viscosity and elasticity. This review addresses the distribution, turnover and tissue-specific properties of HA. This information is used as the context for considering recent products and strategies for modifying the viscoelastic properties of HA in tissue engineering, as a dermal filler and in osteoarthritis treatment.

A biochemical and immuno-electron microscopical analysis of chondroitin sulphate-rich proteoglycans in human alveolar bone

This study used biochemical and immunohistochemical methods to characterize the chondroitin sulphate-rich proteoglycans from human alveolar bone obtained from an oral source. Proteoglycans were extracted from bone by a sequential 4 M guanidine HCl extraction process, and purified by DEAE-ion exchange chromatography. SDS-PAGE and Western blot analysis, using CS-56 monoclonal antibody, demonstrated one major proteoglycan species with a core protein of 58 kDa, glycosaminoglycan chains of 45-66 kDa and a mean molecular weight of 205 kDa. This work confirmed the biochemistry of chondroitin sulphate-rich proteoglycans from a novel source of adult human alveolar bone, and pointed towards a proteoglycan with a high glutamate, glycine, aspartate, alanine, serine and leucine content. Sections of alveolar bone were embedded in LR White resin, labelled with CS-56 antibody and examined with the light and electron microscopes. At the light microscope level, labelling was restricted to the osteocyte lacunae and canaliculi. Ultrastructural observations showed that the labelling was localized to fine filamentous material in the walls of the osteocytes and canaliculi. Sparse labelling was associated with the collagen fibres immediately subjacent to the lamina limitans, but no labelling of the mineralized matrix was observed. These findings also indicated subtle differences in the distribution of chondroitin sulphate compared with previously reported work, which may indicate species or age differences in the samples used in this study. Ultrastructural analysis confirmed and extended observations of glycosaminoglycan localization at the osteocyte cell membrane of mature human alveolar bone.

Time and position-specific expression of glycosaminoglycans in rat molar cementum related to physiological tooth movement

The role of glycosaminoglycans (GAGs) and proteoglycans during cementogenesis is not known. In this study, we have analysed the temporal and spacial expression of GAGs in the cellular cementum of 10-30 weeks old rats, immunohistochemically using monoclonal antibodies 2B6 and 3B3, specific for chondroitin 4-sulfate/dermatan sulfate and chondroitin 6-sulfate, respectively. Both 2B6- and 3B3-epitopes were expressed at similar position and time in the rat cellular cementum. Two types of cellular cementum were identified; GAG-positive and GAG-negative cementum. The former corresponded to the lightly stained and the latter to the darkly stained cementum in sections stained with haematoxylin and eosin. The GAG-positive cementum was seen at the distal side of dentine surface and appeared most thick at, middle of the apical half roots, whereas the other parts of the cementum were the GAG-negative. Distribution of GAG-positive cementum showed changes with age of animals. In 10-15 week old rats, the GAG-positive cementum occupied most of the cementum layer, covering a thin layer of the GAG-negative cementum. The cellular cementum of 20-30 week old rats consisted of three layers; GAG-negative, GAG-positive and GAG-negative cementum from dentine to cementum surface, reducing the GAG-positive area. Because our previous study has demonstrated that the lightly stained cementum is uncalcified, the present result suggests a correlation between calcification and contents of GAGs in the cellular cementum. Further, time- and position-specific expression of GAGs indicates their relation to the physiological tooth movement, which has been known in the rat molars.

An electron microscopic study on the presence of proteoglycans in the mineralized matrix of rat and human compact lamellar bone

The presence of proteoglycans (PGs) was studied in compact lamellar rat and human bone at the electron microscopic level. With the cationic dye cuprolinic blue (CB1), PGs could be demonstrated in the mineralized bone matrix. The amounts of PGs appeared to be equal in the different lamellae and osteons. More CBl-positive material was found in the outermost lamella of the cortex, in the perilacunar matrix around the osteocyte lacunae, and around the canaliculi. Enzyme digestion with chondroitinase ABC demonstrated that the CBl-positive rods consisted of PGs. These observations amplify biochemical studies in which PGs have been isolated from the mineralized bone matrix. The presence of CBl-positive rods in the mineralized matrix suggest that PGs do not have to be removed completely to make the matrix calcifiable.

Age-related bone changes

Bone changes occur during normal aging in both men and women. Changes are both quantitative and qualitative in nature, and include: 1) alterations in the dynamics of bone cell populations, resulting in uncoupling of the normal process of bone resorption and formation; 2) changes in bone architecture (e.g., rearrangement of trabecular struts) and cross-sectional geometry (characterized by subperiosteal expansion and enlargement of the medullary cavity); 3) accumulation of microfractures; 4) localized disparity in the concentration of deposited minerals, with hypomineralization in some areas and hypermineralization in others; 5) changes in the crystalline properties of mineral deposits; and 6) changes in the protein content of matrix material. In addition, there are age-related changes in the status of calcium and phosphate regulating hormones: parathyroid hormone increases, and production of the most active metabolites of vitamin D3 decreases. These hormonal changes undoubtedly affect the maintenance of normal bone homeostasis. Other important factors which can profoundly influence bone status in the elderly are decreased physical activity and dietary inadequacies. Bone tissue is particularly responsive to mechanical loading, and the magnitude of bone mass loss as a consequence of decreased physical activity may not be fully appreciated. Interactions of the above mentioned changes are not completely understood, and the degree to which these changes have been documented in humans varies considerably. Clearly, however, the overall net result is the occurrence of age-related loss of bone tissue and bone strength. This process is accelerated after menopause in women, resulting in the clinical condition commonly known as osteoporosis. In addition to loss of bone mass (usually reported as a decrease in bone mineral content), osteoporosis is accompanied by bone pain, spinal deformity, loss of height, and fractures.

Structural characterization of human alveolar bone proteoglycans

Proteoglycans were extracted from EDTA-demineralized human alveolar bone under dissociative conditions using 4 M guanidinium chloride in the presence of protease inhibitors. The extract was further purified by anion-exchange chromatography on DEAE-Sephacel, using a step-wise salt gradient. The proteoglycan-rich fraction was analysed for carbohydrate, protein and amino acid composition and molecular size by SDS-PAGE. Glycosaminoglycan content was determined by cellulose acetate electrophoresis after proteolysis. The sulphate isomers of the glycosaminoglycans were confirmed by Fourier-transformed infra-red spectroscopy. Two chondroitin sulphate-proteoglycan species were identified with molecular weights of 79 and 55-65 kDa, respectively. The core proteins had molecular weights of 49 kDa for both proteoglycans, with the amino acid content rich in glycine, leucine, glutamate and aspartate. The chondroitin sulphate chains were mainly as the 4-sulphate isomer forms although low but detectable amounts of 6-sulphate isomer were also present.

A biochemical and immunohistochemical study of the proteoglycans of alveolar bone

The purpose of this investigation was to study the proteoglycans in alveolar bone of three animal species. Alveolar bone was obtained from humans, pigs, and rabbits. Portions were fixed, sectioned, and stained with monoclonal antibodies against keratan sulfate and chondroitin sulfate. In other samples, biochemical analyses were performed. After removal of the organic matrix by 4 mol/L guanidinium HCl extraction in the presence of proteinase inhibitors, proteoglycans in the mineralized matrix were extracted with 4 mol/L guanidinium HCl/0.5 mol/L EDTA/proteinase inhibitors, and characterized on the basis of their glycosaminoglycan content (cellulose acetate membrane electrophoresis), charge (DEAE-Sephacel and hydroxylapatite chromatography), size (Sepharose CL-6B chromatography and agarose/polyacrylamide gel electrophoresis), and amino acid content. The results indicated that keratan sulfate could be detected immunohistochemically and biochemically in rabbit bone only. The predominant glycosaminoglycan in pig and human alveolar bone was chondroitin sulfate, although some hyaluronate, dermatan sulfate, and heparan sulfate were also detected. The proteoglycans were found to be slightly smaller than gingival proteoglycans, but similar to those in cementum, dentin, and other bones. In addition to intact proteoglycans, some free glycosaminoglycan chains were also extracted from the mineralized matrix. Amino acid analyses showed some subtle differences between alveolar bone proteoglycan and those of the soft tissues of the periodontium.

Glycosaminoglycans of human alveolar bone

Bone proteoglycan was extracted and the glycosaminoglycan (GAG) components identified. Chondroitin-4-sulphate was the major GAG detected and represented 93.8% of the total GAG extracted. In addition, hyaluronic acid (1.3%), dermatan sulphate (3.1%) and heparan sulphate (1.8%) were identified as minor constituents.

Bone mineral and glycosaminoglycans in newborn and mature rabbits

The relation between bone mineralization and glycosaminoglycans (GAG) was investigated in newborn and mature rabbit diaphyseal bone. Using the density fractionation technique, the bone was separated into fractions of increasing density from 1.4 to 2.3 grams/ml. Each fraction was analyzed by X-ray diffraction to determine the average crystal size. The GAG content of each fraction and of the unfractionated bone was determined by direct extraction and on a few fractions by sequential extraction in guanidine hydrochloride and guanidine/EDTA. There was a decrease in the GAG content with animal age and with increasing fraction density in the newborn rabbit. In one overlapping fraction (2.0-2.1 grams/ml), the GAG content was twice as high in the newborn as in the mature animal. Finally, the crystal size substantially increased from newborn to mature rabbits. Therefore, calcification and maturation of bone is associated with a decrease in the proteoglycan content of the organic matrix.

The glycosaminoglycan constituents of alveolar and basal bone of the rabbit

Proteoglycan was extracted from alveolar and basal bone of New Zealand White rabbits using a sequential extraction procedure. Proteoglycans not associated with the bone mineral represented 1% of the total organic matrix whereas proteoglycans associated with the mineral represented 20% of the alveolar organic matrix and 12% of the basal organic matrix. Chondroitin-4-sulphate and keratan sulphate were identified in both alveolar and basal bone following protease treatment of the proteoglycan extracts and enzymic digestion with chondroitinase AC, ABC and keratanase. Differences were observed in the percentage of each glycosaminoglycan (GAG) in the total organic matrix. In alveolar bone samples, keratan sulphate and chondroitin-4-sulphate is present in equal proportions. In basal bone chondroitin-4-sulphate represents approximately half the value found in alveolar bone and keratan sulphate about a quarter. The extracts were examined by gel filtration on Sepharose 4B under associative conditions. The 280 nm absorbance profiles of proteoglycan from alveolar and basal bone were essentially similar with three main peaks evident, including molecular weight material in excess of 2 X 10(6). The bulk of the bone GAG appeared in the medium molecular weight range with trace amounts in lower molecular weight fractions.

Changes with age in the non-collagenous proteins of human bone

Little is known about the function of the non-collagenous proteins in the organic matrix of bone. Information about these proteins was obtained from studies of human cortical bone. Analysis of fractions of bone differing in density showed that 96% of the alpha 2HS-glycoprotein and 58% of the albumin was associated with the mineralized phase. A study of age-related changes in the composition of bone showed that the amounts present of alpha 2HS-glycoprotein, albumin, sialoprotein, soluble collagen and of EDTA-soluble protein were all higher in bone from children than in adults. In subjects aged over 60 y the content in bone of albumin, sialoprotein and of total protein was similar to that of children. These differences could not be correlated with age-related changes in the calcium/hydroxyproline ratio nor with previous reports of alterations in the crystal structure and the physical properties of human cortical bone. This suggests that these proteins are unlikely to be involved in stabilization of the mineralized matrix or in influencing the physical properties of bone; their function appears more likely to be related to bone formation and turnover.

Chemical composition of human bone

The mineral and non-collagenous organic components of normal human femoral cortex were examined following powdering, demineralization with EDTA and digestion with bacterial collagenase. The protein, hexose, sialic acid and uronic acid contents of the matrix were determined. Neonatal bone had lower levels of mineral and calcium and higher levels of organic material and sialic acid than adult bone, suggesting increased glycoprotein content in neonatal bone. The soluble non-collagenous matrix of human femoral cortex was examined by gel filtration on Sephadex G100 and by ion-exchange chromatography on DEAE-cellulose. Four fractions were eluted off Sephadex-G100: a large molecular weight fraction, a shoulder on the descending portion of this, both of which contained sialic acid and two smaller molecular weight fractions. The material eluted off DEAE-cellulose was separated into 6 fractions which were similar to those found for beef and rabbit bone matrix. Human bone matrix appeared more resistant to collagenase digestion than beef bone, soluble collagen eluted later off DEAE-cellulose than beef bone; sialic acid gave 3 peaks: a major and two lesser ones. The sialic acid-containing material in the fifth fraction was probably bound to proteoglycan. Rabbit bone has 2 to 3 sialic acid peaks whereas beef bone has one, indicating species differences in cortical bone matrix.

The acidic macromolecules in rabbit cortical bone tissue

Rabbit cortical bone powder was extracted with EDTA solutions at neutral pH and the soluble constituents fractionated by DEAE-cellulose chromatography. The acidic fractions obtained were further investigated by gel chromatography and chemical analysis. Two classes of proteoglycans were present; one containing chondroitin sulphate and the other containing material resembling keratan sulphate mixed with a smaller amount of chondroitin sulphate. Sialoglycoproteins were detected by specific chemical introduction of tritium label into the sialic acid residues of the acidic glycoprotein fraction. Following sodium dodecyl sulphate-polyacrylamide gel electrophoresis and fluorography, the presence of numerous distinct sialoglycoprotein components was demonstrated.

Stimulation of aryl sulfatase in rat peritoneal macrophages exposed to bone in vitro

Rat peritoneal macrophages elicited by injection of thioglycollate were cultured in the absence and presence of non-vital, milled rat bone or latex beads. After 0, 48, 96, and 144 hours exposure to these substances, the levels of aryl sulfatase B were determined. Cells exposed to bone demonstrated a significant (p less than .001) time-dependent increase in the specific activity of aryl sulfatase B. After 144 hours the specific activity of aryl sulfatase in cells exposed to bone was 20 fold higher than that in the 144 hour controls. There were no significant differences in the levels of aryl sulfatase B in controls over time, nor were the levels of enzyme in those exposed to latex beads difference from controls. We conclude that the specific activity of aryl sulfatase B increases when macrophages resorb bone and suggest that this enzyme could be used as a marker or index for bone resportion.

The occurrence of chondroitin-6-sulphate in adult human compact bone tissue

Compact bone tissue chondroitin sulphate, previously considered to be pure chondroitin-4-sulphate, was isolated from three adult human femoral diaphyses and digested with chondroitinase ABC. Assaying these digests by means of high performance liquid chromatography we could demonstrate that 12 to 14% of the disaccharide residues were 6-sulphated. The 4/6-ratios were also studied in chondroitin sulphate fractions of different molecular size. Slightly increasing amounts of 6-sulphated disaccharides were found with increasing size of the chondroitin sulphates.

Ultrahistochemical analysis of glycosaminoglycan hydrolysis in the rat periodontal ligament. II. Aryl sulfatase and bone resorption

The distribution of aryl sulfatase in the rat periodontal ligament was investigated by ultrastructural histochemistry. In the periodontal ligament aryl sulfatase was localized specifically in osteoclasts and in vicinal perivascular macrophages. Macrophages associated with bone formation did not stain. The authors interpret this specificity as a potential marker for osteoclast differentiation from macrophages--or as a further indication of the capacity of macrophages to modulate their enzymatic complement in response to the environment. To explain the absence of aryl sulfatase in areas of bone formation we suggest that different sulfate esters are mobilized from resorbing and mineralizing matrices, and that only the enzyme associated with bone resorption is histochemically detectable with the artificial substrates currently used.

Glycosaminoglycans of cartilage and bone tissue in two cases of osteogenesis imperfecta congenita

Epiphyseal cartilage and bone tissue from two cases of osteogenesis imperfecta congenita and one control case with similar skeletal age were examined regarding their glycosaminoglycan content. The diseased bone tissue showed a 3-fold increase in glycosaminoglycans, and 20-25 per cent of the chondroitin sulphate disaccharides seemed to be disulphated. The diseased cartilages showed only traces of material with characteristics of disulphates disaccharides. No disulphates disaccharides were isolated from the control materials. No difference between diseased and control material was indicated regarding molecular size, chondroitin-4-sulphate/chondroitin-6-sulphate ratio or contents of keratan sulphate and hyaluronic acid. The disease is thus associated with fundamental changes of the glycosaminoglycan structure, and these changes may be of functional importance to the mineralization process as well as to the organisation of collagen.

Glycosaminoglycans and proteoglycans of human bone tissue at different stages of mineralization

Using ultracentrifugation, compact bone from a growing 15 years old man was separated into three fractions with different degrees of mineralization. The finely powdered material was fractionated in a density gradient of acetone and bromoform in varying proportions. The glycosaminoglycans were isolated after papain digestion of the tissue fractions. The glycosaminoglycan elution profiles from CPC-cellulose microcolumns indicated the presence of chondroitin-4-sulphate and, possibly, minor traces of hyaluronic acid. The degree of sulphatation was the same in all three fractions, while the total amount and molecular size of the glycosaminoglycans decreased somewhat with increasing degree of mineralization. The glycosaminoglycans of the tissue fractions were also extracted with 4 M guanidinium chloride and then purified chromatographically on DEAE. Gel chromatography of the isolated material showed three different peaks, two probably representing low molecular weight proteoglycans. The proportion of intermediate molecular size material increased with increasing degree of mineralization. The results are discussed briefly in relation to the mineralization process.

Chondroitin sulphate of calf knee-joint cartilage

Chondroitin sulphate from different layers of calf knee-joint cartilage has been isolated and purified. Analysis for hexosamine, uronic acid, sulphate and relative proportions of the 4- and 6-isomers revealed no differences between the layers. However, an increase in the average molecular weight of the chondroitin sulphate was found to correspond with distance from the articular surface. In particular, the average molecular weight in the epiphyseal cartilage was significantly higher than that in the articular cartilage. The chondroitin sulphate of the 40-mu-mthick articular surface layer was found to have a higher molecular weight than the rest of the articular part of the cartilage and also to be more polydisperse. These results, regarding molecular size, are in agreement with the cetylpyridinium chloride cellulose microcolumn fractionation patterns.