Age-related changes in physical and chemical properties of proteoglycans synthesized by costal and matrix-induced cartilages in the rat

The effects of prenatal protein-energy malnutrition on ossification of fetal rat bones: a biochemical study

In fetal rats whose dams were fed a low-protein diet, 35S sulfate uptake into the growth plate of the long bone and rib was higher than in the control group. The elution pattern of guanidine-HCl extract in gel chromatography revealed that the malnourished group had more high molecular weight proteoglycans in the dissociative condition and a larger aggregated portion in the associative condition than did the control group; however, the same chondroitin-sulfate chain size existed. Calcium content did not differ in both groups. Aggregated proteoglycan or a high molecular weight proteoglycan that existed in the malnourished group probably played an inhibitory role in calcification. Prenatal protein-energy malnutrition may delay the change of proteoglycan character, which could affect mineralization of fetal bones.

Changes in proteoglycans of cultured pig aortic smooth muscle cells during subculture

Smooth muscle cells were cultured from pig aorta. Changes in both the growth and the properties of sulfated proteoglycans were observed during passage. The population doubling time during log phase growth was 34 h from Passages 3 to 7-8 but 20 h at the Passage 11, and the cell density at the stationary phase, was 86,000 and 136,000 cells/cm2 at Passages 3 and 11, respectively. Structural characteristics of sulfated proteoglycans secreted into the medium were investigated after metabolic labeling with [35S]-sulfate. Significant differences were observed with age in vitro: a) [35S]proteoglycan complexes were in a greater amount at Passage 10 than at Passage 3; b) the hydrodynamic size of at least 45% of subunits and about 90% of monomers decreased with in vitro aging; c) this decrease in the size of proteoglycans was partly due to a decrease in the size of their glycanic chains; d) an increase of 15% in the proportion of dermatan sulfate was observed when cells were subjected to 10 passages.

Glycosaminoglycans and proteoglycans synthesized by rat limb buds during prechondrogenic and chondrogenic stages

The sulfated glycosaminoglycans synthesized in the forelimb plates of rats on days 12, 13, 14, and 15 of gestation were characterized by their susceptibility to various glycosaminoglycan lyases. On days 12 and 13, heparan sulfate accounted for approximately 65% of the newly synthesized sulfated glycosaminoglycans. Small amounts of dermatan sulfate and chondroitin sulfates were also observed. On day 14, the relative amount of chondroitin 4-sulfate began to increase, there being a compensatory decrease in the amount of heparan sulfate. 35S-Sulfate-labeled material was extracted from day-13 forelimb plates with 4 M guanidine/HCl without proteolysis. Using ultracentrifugation on a sucrose density gradient, the extract was separated into two peaks: a light peak (L) mainly composed of heparan sulfate, and a faster-sedimenting peak (M) mainly composed of chondroitin sulfate. The cartilage-type proteoglycan (H) was first detectable on day 14 of gestation, indicating that chondrogenesis in rat forelimb plates starts on day 14 of gestation. In addition to these previously identified glycosaminoglycans or proteoglycans, we isolated an unknown component in the glycosaminoglycan preparations obtained from limb plates during these developmental stages. This component was not found in glycosaminoglycan preparations obtained either from the brain or tail of rat fetuses at the same stages.

Stable phenotypic expression by chick chondroblasts in long-term suspension cultures as determined by proteoglycan analysis

The influence of cell shape on phenotypic expression was studied in chick vertebral chondroblasts maintained for several weeks in suspension culture. To monitor phenotypic expression, synthesis of proteoglycans was studied in cultures of freshly-isolated 1-day-old chondroblasts and 1-to-6-week-old chondroblasts. The rate of proteoglycan synthesis was virtually identical in 1-week or older chondroblasts; however, this rate was 3- to 5-fold higher than in 1-day-old cells. When compared to the latter cells, the various populations of older chondroblasts synthesized monomers of the major cartilage proteoglycan (KS: CS-PG) of slightly lower molecular size and a lower level of unsubstituted N-acetylgalactosamine residues on their core protein but with similar chondroitin sulfate chains and levels of O-linked oligosaccharides. At no time of culture were changes in the proportions of the major vs the minor cartilage proteoglycans detected. The results suggest that in contrast to epithelioid chondroblasts in standard monolayer cultures studied previously, the round floating chondroblasts express very stable biosynthetic properties for a prolonged time in suspension. The distinct biosynthetic properties of 1-day-old chondroblasts are discussed in terms of an initial, transitory response to the culture condition and in relation to regulatory mechanisms for proteoglycan elaboration.

Disappearance of the cartilage interlacunar network during histological dehydration

The interlacunar network connects adjacent chondrocytes in rapidly growing cartilage and with anionic dyes stains more intensely than the surrounding matrix. The network is seen in fresh-frozen sections and sections treated with a variety of fixatives, dehydration agents and embedding media. The network is not seen after using such common dehydrating fluids as ethanol and acetone. Polyanionic glycosaminoglycans (GAG) are abundant in the cartilage matrix and it has been suggested that the network is an artifact caused by a rearrangement of the matrix GAG during histological processing. Extraction of GAG from neonatal rat cartilage with guanidine hydrochloride removes stainable extracellular matrix but not the interlacunar network. However, after extraction of GAG and immersion of the cartilage in either 50% or 100% aqueous ethanol or acetone, the network was no longer visible. The network apparently is not an artifact formed by soluble matrix GAG, but a real structure which is extracted, collapsed or otherwise destroyed during dehydration in ethanol or acetone.

Structural changes during development in bovine fetal epiphyseal cartilage

Sedimentation coefficients of approximately 150 S show that proteoglycan aggregates from bovine fetal epiphyseal cartilage are exceptionally large. To determine the structural basis for the unusually large size of these proteoglycan aggregates, identify changes in proteoglycan structure with changing developmental age, and provide a basis for demonstrating the structural modifications which may occur in growth plate proteoglycan aggregates during endochondral ossification, we examined the molecular architecture and dimensions of fetal epiphyseal proteoglycans by electron microscopy. The eight bovine epiphyseal cartilages studied ranged in fetal age from 168 to 241 days. Proteoglycans were extracted in 4 M guanidinium hydrochloride containing protease inhibitors and isolated by equilibrium density gradient centrifugation under associative and dissociative conditions. Electron micrographs were made from monolayer preparations of proteoglycan-cytochrome c mixtures on nitrocellulose support films. The overall molecular architecture of the proteoglycan aggregates from fetal epiphyseal cartilages was similar to that of aggregates from other cartilages and showed a single, unbranched central hyaluronic acid filament to which many proteoglycan monomers were attached. However, the dimensions of the fetal proteoglycans differed strikingly from those of proteoglycans from mature cow nasal or immature calf nasal cartilage. Specifically, proteoglycan aggregates from bovine fetal epiphyseal cartilage showed: (a) longer hyaluronic acid central filaments; (b) greater numbers of proteoglycan monomers per aggregate; (c) closer spacing of proteoglycan monomers along the hyaluronic acid central filament; and (d) longer proteoglycan monomer core proteins. Proteoglycan monomers bound to hyaluronate consisted of two segments: (1) a peripheral thick segment, composed of the chondroitin sulfate chains condensed along the peripheral portion of the protein core, which corresponds to the chondroitin sulfate-rich region; and, (2) a central thin segment, devoid of visible glycosaminoglycan chains, which attaches directly to the hyaluronic acid central filament and contains the hyaluronic acid binding region and a portion of the keratan sulfate-rich region. The contribution of the thin segment to total monomer length decreased as total monomer length increased. Thus, in longer monomers the thick segment contributed more to total monomer length and the thin segment contributed less. Both the thin and thick segments of monomers from fetal epiphyseal cartilage were longer than the corresponding segments of calf nasal cartilage and mature bovine nasal cartilage monomers.(ABSTRACT TRUNCATED AT 400 WORDS)

Werner's syndrome: a review of recent research with an analysis of connective tissue metabolism, growth control of cultured cells, and chromosomal aberrations

Werner's syndrome is a rare, autosomal recessive condition with multiple progeroid features, but it is an imitation of aging rather than accelerated or premature senescence. Somatic chromosome aberrations occur in multiple tissues in vivo and in vitro, and there is an increased incidence of neoplasia. Thus. Werner's syndrome can be classified in the group of chromosome instability syndromes. Recent findings provide additional support for the concept that there is an aberration of connective tissue metabolism in Werner's syndrome, but it is unclear whether this is a primary or secondary manifestation of the underlying genetic defect. Abnormal growth characteristics are observed in cultured skin fibroblast-like cells and this provides another avenue for current research. Identification of the basic genetic defect in Werner's syndrome might clarify our understanding of the normal aging process in general, or might elucidate specific aspects such as the development of neoplasia, atherosclerosis, diabetes, or osteoporosis.

Human cartilage proteoglycans isolated from normally ossifying and congenitally malformed leg bones

Proteoglycans were extracted with 4 M guanidine HCl solution containing protease inhibitors from various zones of human epiphyseal cartilages of the normally ossifying fibula and cartilaginous rudiment of the tibia of a 12-month-old boy with congenital absence of the tibia, when the knee disarticulation was performed. All the proteoglycan preparations from the epiphyseal cartilages were separated with a sucrose density gradient centrifugation into two components: a heavy, major component and a light one. The molecular size and the proportion of isomeric chondroitin sulfates of polysaccharides of the heavy component differed from those of the light one. The relative amounts of isomeric chondroitin sulfates in the polysacharide moieties of the components also varied among these zones. The glycosaminoglycan content in the rudimentary tibia was equal to that of the epiphyseal cartilage of the fibula. However, proteoglycan preparations showed neither the normal sedimentation profile with two peaks nor the zonal differences as to the proportion of isomeric chondroitin sulfates. These results suggest that the alterations in proteoglycan metabolism might be involved in the pathogenetic mechanisms producing the congenital limb defect.