Microchemical studies on acid glycosaminoglycans of the epiphyseal zones during endochondral calcification

Local Changes to the Distal Femoral Growth Plate Following Injury in Mice

Injury to the growth plate is associated with growth disturbances, most notably premature cessation of growth. The goal of this study was to identify spatial changes in the structure and composition of the growth plate in response to injury to provide a foundation for developing therapies that minimize the consequences for skeletal development. We used contrast-enhanced microcomputed tomography (CECT) and histological analyses of a murine model of growth plate injury to quantify changes in the cartilaginous and osseous tissue of the growth plate. To distinguish between local and global changes, the growth plate was divided into regions of interest near to and far from the injury site. We noted increased thickness and CECT attenuation (a measure correlated with glycosaminoglycan (GAG) content) near the injury, and increased tissue mineral density (TMD) of bone bridges within the injury site, compared to outside the injury site and contralateral growth plates. Furthermore, we noted disruption of the normal zonal organization of the physis. The height of the hypertrophic zone was increased at the injury site, and the relative height of the proliferative zone was decreased across the entire injured growth plate. These results indicate that growth plate injury leads to localized disruption of cellular activity and of endochondral ossification. These local changes in tissue structure and composition may contribute to the observed retardation in femur growth. In particular, the changes in proliferative and hypertrophic zone heights seen following injury may impact growth and could be targeted when developing therapies for growth plate injury.

The extracellular matrix of cartilage in the growth plate before and during calcification: changes in composition and degradation of type II collagen

Calcification occurs in the extracellular matrix of the hypertrophic zone of the growth plate when the extracellular matrix volume is reduced to a minimum and alkaline phosphatase content is maximal. The present study shows that significant quantitative and qualitative changes occur in the composition and structure of macromolecules in the extracellular matrix before and during calcification in the proximal tibial growth plate of the bovine fetus. These were detected in part by using microchemical and microimmuno-chemical analyses of sequential transverse frozen sections at defined sites throughout the growth plate. Concentrations of matrix molecules in the extracellular matrix have not previously been determined biochemically. They were measured per unit matrix volume by using combined immunochemical/chemical-histomorphometric analyses. The concentrations within the extracellular matrix of the C-propeptide of type II collagen, aggregating proteoglycan (aggrecan), and hyaluronic acid all progressively increased in the maturing and hypertrophic zones, being maximal (or near maximal) at the time of initiation of mineralization. These results for proteoglycan are contrary to some earlier reports of a loss of proteoglycan are contrary to some earlier reports of a loss of proteoglycan prior to mineralization which measured the tissue content of proteoglycan rather than that present in the extracellular matrix, the volume of which is progressively reduced as the growth plate matures. The C-propeptide data provides a quantitative confirmation of previous immunohistochemical studies. Total collagen concentration (measured as hydroxyproline) in the extracellular matrix initially increased through the proliferating and maturing zones but then rapidly decreased in the hypertrophic zone.(ABSTRACT TRUNCATED AT 250 WORDS)

Chondrons from articular cartilage (II): Analysis of the glycosaminoglycans in the cellular microenvironment of isolated canine chondrons

A chondron rich preparation was isolated from mature canine tibial cartilage using low-speed homogenization techniques. Proteoglycans were extracted from this preparation by exhaustive treatment with 4M guanidine-HCl. A significant proportion of the total proteoglycan, measured as uronic acid, was resistant to extraction and represented 27.9% in intact cartilage chips and 18.6% in the chondron fraction. Histochemical examination of chondrons confirmed that extraction resistant proteoglycans remained within the capsule of the chondron after 4M guanidine-HCl treatment. Electrophoretic analysis of the glycosaminoglycans extracted from intact cartilage chips and the chondron fraction showed approximately equivalent amounts of chondroitin sulphate (79.3%), keratan sulphate (16.3%) and hyaluronic acid (4.3%) present. In contrast, the extraction resistant residue in the chondron fraction was significantly enriched for hyaluronic acid (10.5%, p less than 0.05) but was depleted of chondroitin sulphate (70.9%, p less than 0.05). The major chondroitin sulphate isomer in the resistant fraction was chondroitin 6-sulphate while in the soluble fraction, the quantities of the two isomers were approximately equivalent. Comparison with previously published data suggests a role for minor collagens in the retention of proteoglycans in the cellular microenvironment.

Quantitation of hyaluronic acid in tissues by ion-pair reverse-phase high-performance liquid chromatography of oligosaccharide cleavage products

A method for quantifying hyaluronic acid in biological tissues and fluids is described. The assay uses ion-pair HPLC to resolve and quantify the oligosaccharide end products of Streptomyces hyaluronidase digestion. Tissue samples were solubilized by papain, and the nondiffusate after dialysis was exhaustively digested with Streptomyces hyaluronidase. The resulting tetrasaccharide and hexasaccharide cleavage products were resolved by reverse-phase high-performance liquid chromatography in the presence of the ion-pairing agent, tetrabutylammonium phosphate. The saccharides were detected and quantified by their absorbance at 232 nm due to the alpha, beta-unsaturated carboxyl group generated by the eliminase reaction. In control experiments 93 +/- 3% of a hyaluronic acid standard so treated was reproducibly recovered as its tetra- and hexasaccharide cleavage products. As little as 0.5 microgram of the oligosaccharides could be quantified with no interference from a vast excess of chondroitin sulfate or other tissue components. The assay was applied to various types of human, bovine, and rabbit cartilage and to samples of other tissues including nucleus pulposus, annulus fibrosus, skin, aorta, cervix, cockscomb, synovial fluid, and vitreous humor. Results on human articular cartilage showed a linear increase in the content of hyaluronate from 0.1 to 0.5% of tissue dry weight between birth and 80 years of age.

A possible role for polyamines in cartilage in the mechanism of calcification

The role of polyamines in cartilage is not known: they may be somehow related to the mechanism of calcification. In epiphyseal cartilage from calf scapulas, they are more concentrated in the ossifying area, where calcification takes place, than in the resting region. Spermidine is present in greater amounts than spermine and putrescine. Since ornithine decarboxylase (EC 4.1.1.17) is measurable only in the resting region of the tissue, it is in this area that polyamine biosynthesis occurs, while they accumulate in the ossifying area. Immunohistochemical evidence is obtained that only in the ossifying zone is spermidine extracellular. It is at this level that the matrix is rearranged to become calcified, and proteoglycans are dissociated and partially removed. The effect of polyamines on solutions of proteoglycan subunits has been studied in vitro by following variations of turbidity and viscosity. While in the presence of putrescine the specific viscosity decreases to asymptotic values, in the presence of either 30 mM spermidine or 2.5-10 mM spermine, the decrement is more marked. At the same concentrations, increase of the turbidity of proteoglycan subunit solutions was observed. Only spermidine showed the capacity of displacing proteoglycan subunits from a column of Sepharose 4B-type II collagen: at 15 mM concentration, about 90% of proteoglycans were removed from the column. Alkaline phosphatase activity, which plays an important role in calcification, is enhanced by spermidine and spermine. These results obtained in vitro support the hypothesis that polyamines may be related to calcification of preosseous cartilage.

Effects of 1,25-dihydroxycholecalciferol on fracture healing. Calcium, phosphate, and zinc in callus and serum

The incorporation of calcium, phosphate, and zinc into the callus of closed tibial fractures was studied in adult rats fed a standard diet. Low doses (60 ng/kg per day) of 1,25(OH)2D3 5 days a week greatly increased early callus mineralization. This was not related to an increased serum calcium-phosphate molar product but rather to a decreased ratio. The incorporation of zinc into callus seemed to be correlated to the mineralization process but not to the 1,25(OH)2D3 administration as such. The question of a direct, indirect, or a complex role of 1,25(OH)2D3 in bone formation and mineralization is discussed.

Proteoglycans and glycosaminoglycans of normal and strontium rachitic epiphyseal cartilage

An analytical protocol for the analysis of proteoglycans and proteins extracted from small sections of cartilage has been applied to the upper and lower parts of the epiphyseal growth plate of normal rats and rats with strontium-induced rickets. Only one polydisperse proteoglycan population was found in each of the four tissue portions. In strontium-induced rachitic animals the aggregability of proteoglycan monomers with hyaluronate was considerably increased in the lower part of the growth plate. The proteoglycans in the upper portion of the epiphysis contained somewhat less of chondroitin sulfate and keratan sulfate both in normal and strontium-induced rachitic rats. The chondroitin sulfate chains were somewhat larger in samples from strontium-induced rachitic rats compared with controls while in all groups about 90 per cent of the galactosamine in chondroitin sulfate was sulfated at position four. The findings of an altered composition of proteoglycans in strontium-induced rickets demonstrate that strontium not only prevents the mineral growth but may also induce the chondrocytes to produce a matrix with a different macromolecular composition.

Staining glycol methacrylate embedded cartilage with triethyl-carbocyanin DBTC ("ethyl-stains all") with special reference to the interlacunar network

The dye, triethyl-carbocyanin DBTC, was tested for differential staining of cartilage structures. Femoral head articular cartilage from neonatal rats was processed for histology to demonstrate the interlacunar network. Sections of glycol methacrylate (GMA) embedded cartilage were stained at pH 2.8, 5.4, 6.1 and 8.0 to determine the optimal staining conditions. Only at pH 6.1 were all cartilage structures stained and the best contrast achieved. Streptomyces hyaluronidase, chondroitinase ABC, pepsin, trypsin, and pronase digestions were carried out prior to staining at pH 6.1 to evaluate the selectivity of the stain. Undigested chondrocyte nuclear chromatin stained dark purple; staining intensity was reduced slightly by pepsin or trypsin digestion. Undigested chondrocyte cytoplasm stained light blue but stained purple after hyaluronidase digestion. Undigested extracellular matrix stained light violet; staining was almost entirely eliminated by chondroitinase ABC digestion, was unaffected by hyaluronidase, and was either unaffected or increased after proteinase digestion. Staining of a narrow zone of matrix adjacent to the network was prevented by proteinase digestion while the network element appeared as a thin dark line. The network appears to be a trilaminar structure; a core element of hyaluronic acid and protein surrounded by a protein sheath. Triethyl-carbocyanin DBTC staining of cartilage offers slightly more selectivity and contrast than methylene blue, toluidine blue or safranin O. At pH 6.1, DNA, perhaps RNA, and hyaluronic acid stained deep purple; chondroitin sulfate, light violet; protein (collagen), stained very light violet if at all.

The amount of proteoglycans in cartilage matrix and the onset of mineralization

An electron microscopic investigation of the relationship between proteoglycans and cartilage mineralization has been carried out. On the basis of the number of matrix granules and the affinity of the matrix for colloidal ThO2, we found that in embryonic mouse radii: The amount of proteoglycans does not decline before the onset of mineralization. In the calcified portions of the cartilage matrix the concentration of proteoglycans remains constant during and after mineralization. There is a degradation of proteoglycans in the uncalcified portions of the matrix near the marrow cavity. This last finding explains why chemical analyses of epiphyseal disks so often show a decline in the amount of proteoglycans in the mineralizing zones. It was concluded that degradation of proteoglycans is not a first, necessary step in cartilage mineralization. The loss of proteoglycans in the uncalcified matrix in the lower zones of the epiphyseal disks is probably devoid of any particular significance for calcification but is rather a preparation for the formation of the marrow cavity.

The effect of vitamin A deficiency and fluoride on glycosaminoglycan metabolism in bone

The effects of fluoride intake and vitamin A deficiency on glycosaminoglycan metabolism in vivo were investigated. Weanling female rats were fed either a vitamin A deficient diet ad libitum, a vitamin A supplemented diet pair-fed to the deficient animals, or the vitamin A supplemented diet ad libitum. Additionally, each vitamin A dietary group was divided into three subgroups with the animals receiving water containing 0, 10 or 50 ppm fluoride. The results showed that the groups receiving 10 and 50 ppm fluoride at all dietary levels of vitamin A had significantly higher in vivo 35SO4 incorporation in both the epiphyseal and diaphyseal regions of the bone than the animals receiving 0 ppm fluoride. The vitamin A deficient animals incorporated significantly less 35SO4 into glycosaminoglycans in the epiphyseal and diaphyseal regions of the bone compared to the pair-fed, vitamin A sufficient animals for all three fluoride receiving groups. There was no interaction between fluoride intake and dietary vitamin A levels on 35SO4 incorporation into glycosaminoglycans. Fluoride either increased sulfation or turnover of glycosaminoglycans.

Role of proteoglycans in endochondral ossification: immunofluorescent localization of link protein and proteoglycan monomer in bovine fetal epiphyseal growth plate

The hypothesis is widely held that, in growth plate during endochondral ossification, proteoglycans in the extracellular matrix of the lower hypertrophic zone are degraded by proteases and removed before mineralization, and that this is the mechanism by which a noncalcifiable matrix is transformed into a calcifiable matrix. We have evaluated this hypothesis by examining the immunofluorescent localization and concentrations of proteoglycan monomer core protein and link protein, and the concentrations of glycosaminoglycans demonstrated by safranin 0 staining, in the different zones of the bovine fetal cartilage growth plate. Monospecific antibodies were prepared to proteoglycan monomer core protein and to link protein. The immunofluorescent localization of these species was examined in decalcified and undecalcified sections containing the zones of proliferating and hypertrophic chondrocytes and in sections containing the zones of proliferating and hypertrophic chondrocytes and the metaphysis, decalcified in 0.5 M EDTA, pH 7.5, in the presence of protease inhibitors. Proteoglycan monomer core protein and link protein are demonstrable without detectable loss throughout the extracellular matrix of the longitudinal septa of the hypertrophic zone and in the calcified cartilage of the metaphysis. In fact, increased staining is observed in the calcifying cartilage. Contrary to the prevailing hypothesis, our results indicate that there is no net loss of proteoglycans during mineralization and that the proteoglycans become entombed in the calcified cartilage which provides a scaffolding on which osteoid and bone are formed. Proteoglycans appear to persist unaltered in the calcified cartilage core of the trabeculae, until at last the entire trabeculae are eroded from their surfaces and removed by osteoclasts, when the primary spongiosa is replaced by the secondary spongiosa.

Biochemical studies of the matrix of craniovertebral chordoma and a metastasis

Glycosaminoglycans of human chordoma and a metastasis were studied. The glycosaminoglycans were derived from the extracellular matrix and consisted of chondroitin 4- and 6-sulphate, keratan sulphate and hyaluronate. The ratio of chondroitin sulphate to keratan sulphate was much lower in the metastasis than in the primary. Proteoglycan extracted with 4M guanidinium chloride and purified by associative density-gradient centrifugation was assessed on Sepharose 2B before and after reduction and alkylation. The result of this experiment suggested that only a small proportion of the proteoglycans were aggregated.

Electrophoresis of tissue glycosaminoglycans as an aid in the diagnosis of mesotheliomas

The histologic distinction between mesotheliomas and adenocarcinomas on mesothelial surfaces is sometimes difficult. High concentrations of hyaluronic acid in pleural and peritoneal fluids of mesothelioma patients have been reported. This paper describes results of glycosaminoglycan electrophoresis of papain digests of 7 mesotheliomas and 27 other tumors. Either all or almost all demonstrable glycosaminoglycans in mesotherliomas was hyaluronic acid. Control tissues had variable electrophoretic patterns showing other glycosaminoglycans in addition to hyaluronic acid. In the clinical context of differentiating mesotheliomas and adenocarcinomas in tissue samples, this technique seems simple, economical, and relatively specific.

Biochemical and autoradiographical distribution of hyaluronic acid in calf rib cartilage

In calf rib cartilage, about one half of total hyaluronate is soluble with guanidinium hydrochloride, the other half only after collagenase treatment. Evidence is presented for its pericellular and intracellular distribution.

Correlation of lysozyme activity with proteoglycan biosynthesis in epiphyseal cartilage

Pig epiphyseal cartilage (proximal ulna epiphysis) previously incubated into vitro in the presence of sodium [35S]sulfate or [3H]thymidine was either analyzed by autoradiography or separated into 9 morphologically defined consecutive layers and investigated for 35S-incorporation into the guanidinium chloride-extractable proteoglycans and for lysozyme activity. The lowest 35S incorporation and lysozyme activity were determined in the zone of resting cells, but there is a consecutive increase in the rate of proteoglycan synthesis and lysozyme activity toward the diaphyseal cartilage-bone junction, with the maximum at the lower columnar cell zone and a sharp reduction of both parameters at the hypertrophic zone. The maxima of 35S incorporation and [3H]thymidine incorporation do not coincide. The guanidinium chloride-soluble proteoglycans exhibit macromolecular polydispersity. Fractions excluded from as well as retarded by Sepharose 2B gel could be separated and were detected in all zones. The results indicate a correlation of proteoglycan biosynthesis and lysozyme activity in epiphyseal cartilage.

Hyaluronate in articular cartilage: age-related changes

Articular cartilage of fetal calves, calves, and steers together with normal and osteoarthrotic human cartilage was analyzed for hyaluronate. The hyaluronate content increased with maturation in healthy tissue, particularly in regions of maximum contact, but was low in diseased cartilage.

Regional distribution of water and glycosaminoglycan in immature articular cartilage

The distribution of water and glycosaminoglycan in different functional regions of bovine immature articular cartilage were studied. There was always more water in each articulating than in the corresponding growing zone, but there was less water in both zones in the areas of maximum contact. There was more hyaluronate and much more keratan sulphate in the articulating areas of maximum contact than in the minimum contact areas. In the growing zone the distribution of these two glycosaminoglycans did not vary as significantly but there was slightly more keratan sulphate in the area of maximum contact. Regional variations in chondroitin sulphate content were also present although not as striking as those of keratan sulphate. The results suggest that some keratan sulphate may be synthesized as a reaction to load.

Aggregation of hydroxyapatite crystals

A system to study the aggregation of hydroxyapatite crystals was developed. The effect of several factors (Ca2+ x Pi product, Ca2+/Pi ratio, pH, and various substances) were tested. Pb2+, Zn2+, Mg2+ and methyleneblue had only small effects; citrate inhibited aggregation. Pyrophosphate was a strong inhibitor and the diphosphonates disodium ethane-1-hydroxy-1,1-diphosphonate and disodium dichloromethylene diphosphonate were even more potent. The monophosphonate pentanemonophosphonate had no effect. Potent inhibition also occurred with glycosaminoglycans: heparin greater than hyaluronic acid greater than dermatan sulfate greater than chondroitin 4-sulfate greater than chondroitin 6-sulfate. Urine also showed high inhibitory activity. The inhibition of heparin but not that of hyaluronic acid, PPi or urine was abolished by egg white lysozyme. The effects described might be relevant in the normal mineralization process as well as in the mechanisms leading to pathological calcification, such as urinary stone formation.

Resistant proteoglycans in epiphyseal plate cartilage. Variations in their distribution in relationship to age and species

The localizations of resistant proteoglycans (RPGs) in the epiphyseal plates of rats, dogs, and humans are similar. In the epiphysial plates from young rats, dogs, and humans, the RPGs form a stratum at the junction of the zones of resting and proliferating cells. Non-calcified cartilage RPGs are associated with cells which have the potential for proliferation or column organization. As the individuals age, RPGs are found in intercolumnar regions or at times are even absent. There is also a type of RPGs in calcified cartilage, including the calcified cartilage subjacent to the articular surface, in all species. In human epiphyseal plates, looser fibrillar RPGs change abruptly to a more condensed type in the zone of provisional calcification. Calcified cartilage RPGs stain more intensely with toluidine blue and may represent a different type of RPGs.

The metabolic heterogeneity of glycosaminoglycans of the different zones of the epiphyseal growth plate and the effect of ethane-1-hydroxy-1, 1-diphosphonate (EHDP) upon glycosaminoglycan synthesis in vivo

The synthesis of total and unextractable glycosaminoglycans of rabbit epiphyseal growth plate was studied by determination of the incorporation in vivo of 35S-sulphate into various glycosaminoglycans separated by microfractionation procedures using CPC and ECTEOLA columns. In the narrow hypertrophic zone, hyaluronic acid and chondroitin sulphate of low molecular weight were found to be unextractable with 3M guanidinium chloride for 24 h, thus being firmly bound within the tissue. While the unextractable chondroitin sulphate showed a sharply reduced synthesis rate in the hypertrophic zone compared with that in the columnar and resting zones, a rapid increase in the synthesis of extractable chondroitin sulphate toward the calcification front is indicated. At microfractionation, solubility profiles indicated that the unextractable chondroitin sulphate was of predominantly lower molecular weight and/or charge density compared to that of the whole tissue, most evident in the hypertrophic zone. The distribution pattern of incorporated 35S showed a close correspondence to the distribution of the various chondroitin sulphate fractions both for extracted and unextracted tissue. In the hypertrophic zone, higher radioactivity was found for chondroitin sulphate of predominantly low molecular weight and/or charge density in extracted compared to unextracted tissue. Low doses of EHDP caused no change of distribution of the various glycosaminoglycans but generally inhibited their synthesis.

Light microscopic and ultrastructural observations on the short-term effects of ethylene-1-hydroxy-1, 1-diphosphonate (EHDP) on rat tibia epiphysis

Ethylene-1-hydroxy-1, 1-diphosphonate (EHDP) was administered intraperitoneally to one-day old rats at a concentration of 30 and 40 mg/kg body weight/injection. Two groups of animals received four doses, respectively, over a 44-hour-period and a third group received two high doses with a 15-hour interval, the total amounts corresponding to 30, 40 and 20 mg/P/kg body weight. Animals in the first two experimental groups showed increased width of the hypertrophic zone as compared with normal controls and lack of calcified septa within the zone of provisional calcification. In the calcification zone, persistent atypical chondrocytes were present and in the septa a large number of matrix vesicles which hardly ever contained any crystals. The ground substance of these septa contained fine precipitates, probably representing proteoglycan complexes which were not seen normally in this zone. In the third group, the septa of the calcification zone were calcified and the hypertrophic zone was not clearly widened. In the metaphysis, remnants of cartilage or osteoid were observed as "islands" covered with osteoblast-like cells which showed signs both of collagen and apatite formation, the latter evidenced by the appearance of crystals within the matrix vesicles. It is suggested that the complex effects observed in calcifying cartilage after administration of high doses of EHDP in vivo are not restricted solely to the stage of crystal formation.

Proteoglycans of mineralizing rib and epiphyseal cartilage

Rib cartilage from growing guinea pigs and epiphyseal cartilage from Beagle puppies were separated into three fractions, representing non-mineralized, low mineralized, and high mineralized, tissue, by centrifuging finely ground material in acetone/bromoform density gradients. Following extraction under dissociative conditions, the proteoglycans were fractionated by density gradient ultracentrifugation under associative and dissociative conditions. With the onset of mineralization, the cartilage lost approximately half its content of proteoglycans. The proteoglycans remaining in the calcified cartilage differed in composition and in size from those of nonmineralized tissue. With the increased mineral content of the tissues the ratios of protein to polysaccharide, of chondroitin sulfate to keratan sulfate, and of 4-sulfate to 6-sulfated chondroitin sulfate increased in the proteoglycan fraction. Furthermore, gel chromatograms indicated decreased proportions of very high molecular weight proteoglycans, in mineralized tissue.

The ground substance of the arterial wall. Part 1. Extractability of glycosaminoglycans and the isolation of a proteoglycan from bovine aorta

Water and glycosaminoglycan contents were measured in upper and lower thoracic aortas of claves and steers. The ability of various molarities of guanidine hydrochloride to extract glycosaminoglycans from these tissues was assessed. Some glycosaminoglycans seem to be more resistant to extraction than others. A procedure is described for the isolation of a proteoglycan. The molecule appears to contain both dermatan sulfate and chondroitin sulfate. It also seems to be less dense than cartilage proteoglycans extracted by similar methods as assessed by its behavior in centrifugal fields. The properties, locus and biological activities of this molecule are currently being studied.

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.