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The heterogeneity of the non-aggregating proteoglycans of the human intervertebral disc.

ABSTRACT: Non-aggregating proteoglycans of differing average hydrodynamic volumes were prepared from nuclei pulposi and anuli fibrosi of three human lumbar spines and characterized by biochemical and immunochemical analyses. The hexose-to-hexuronate and protein-to-hexuronate ratios increased with decreasing hydrodynamic volume. Analysis by composite agarose/polyacrylamide-gel electrophoresis has demonstrated two aggregating subpopulations [McDevitt, Jahnke & Green (1982) Trans. Annu. Meet. Orthop. Res. Soc. 7, 50]. In the present study, electrophoresis of the non-aggregating pools has shown three additional subpopulations, here named bands III, IV and V. The two smallest proteoglycan pools from each tissue contained two and three components respectively. These components were isolated by preparative electrophoresis and analysed. Band III was a proteoglycan richer in keratan sulphate than in chondroitin sulphate; band IV was a proteoglycan richer in chondroitin sulphate than in keratan sulphate; band V contained only chondroitin sulphate. Unsaturated disaccharides prepared from the chondroitin sulphate of all bands were predominantly 6-sulphated, with only 5-15% 4-sulphated. The molecular masses of the chondroitin sulphate and keratan sulphate did not differ between the bands. The amino acid composition of band III differed from that of band IV. Thus three distinct subpopulations of non-aggregating proteoglycan were demonstrated in the human intervertebral disc.

SUBMITTER: DiFabio JL

PROVIDER: S-EPMC1147948 | biostudies-other | 1987 May

REPOSITORIES: biostudies-other

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Project description:Nuclei pulposi were dissected from lumbar discs of radiologically normal human spines of cadavers aged 17, 20 and 21 years. Proteoglycans were extracted with 4 M guanidine hydrochloride (dissociative conditions) with proteinase inhibitors and isolated as A1 fractions by associative density-gradient centrifugation. Aggregating and non-aggregating proteoglycans were separated by Sepharose 2B chromatography. Both aggregating and non-aggregating proteoglycans contained a keratan sulphate-rich region as isolated by chondroitinase/trypsin/chymotrypsin digestion and Sepharose CL-6B chromatography. Agarose/acrylamide-gel electrophoresis of individual fractions of a Bio-Gel A-50m dissociative-column separation of the aggregating proteoglycans revealed two, well-separated bands: S and F, the slower and faster migrating bands respectively. The non-aggregating proteoglycan fractions were eluted under associative conditions (0.5 M-sodium acetate, pH 6.8) and migrated as a single band in the electrophoretic system. The gel-electrophoretic heterogeneity of the aggregating proteoglycans was still evident after hydroxylamine fragmentation and removal of the hyaluronate-binding portion of the molecule. Dissociative density-gradient centrifugation of the aggregating proteoglycans partially separated the Band-S proteoglycans from the Band-F population. Subsequent dissociative chromatography of the high-buoyant-density Band F proteoglycans permitted discrimination of this band into two gel-electrophoresis-distinguishable populations (Bands F-1 and F-2). Enzyme-linked immunosorbent assays with a monoclonal antibody that recognized keratan sulphate demonstrated that the D1 fraction containing the Band F-1 proteoglycans was enriched in keratan sulphate compared with the total aggregating or non-aggregating pool of proteoglycans. The proteoglycans of young adult nucleus pulposus could then be ascribed to one of four structurally and/or electrophoretically distinct populations: (1) the non-aggregating population, which comprised about 70% of the total extractable proteoglycans; (2) the aggregating pool, comprising: (a) Band F-1 proteoglycans, which had a relatively large hydrodynamic size, uronate/protein weight ratio, were enriched in keratan sulphate and had a high buoyant density; (b) Band S proteoglycans, which migrated slower in agarose/acrylamide gels, had a smaller hydrodynamic size, lower buoyant density and a lower uronate/protein ratio than the Band F-1 population; (c) Band F-2 proteoglycans, which were lower in buoyant density, smaller in hydrodynamic size and slightly faster in electrophoretic mobility than the Band F-1 proteoglycans.

Project description:Nucleus pulposus (NP) cells have a phenotype similar to articular cartilage (AC) cells. However, the matrix of the NP is clearly different to that of AC suggesting that specific cell phenotypes exist. The aim of this study was to identify novel genes that could be used to distinguish bovine NP cells from AC and annulus fibrosus (AF) cells, and to further determine their expression in normal and degenerate human intervertebral disc (IVD) cells.Microarrays were conducted on bovine AC, AF and NP cells, using Affymetrix Genechip(R) Bovine Genome Arrays. Differential expression levels for a number of genes were confirmed by quantitative real time polymerase chain reaction (qRT-PCR) on bovine, AC, AF and NP cells, as well as separated bovine NP and notochordal (NC) cells. Expression of these novel markers were further tested on normal human AC, AF and NP cells, and degenerate AF and NP cells.Microarray comparisons between NP/AC&AF and NP/AC identified 34 NP-specific and 49 IVD-specific genes respectively that were differentially expressed > or =100 fold. A subset of these were verified by qRT-PCR and shown to be expressed in bovine NC cells. Eleven genes (SNAP25, KRT8, KRT18, KRT19, CDH2, IBSP, VCAN, TNMD, BASP1, FOXF1 & FBLN1) were also differentially expressed in normal human NP cells, although to a lesser degree. Four genes (SNAP25, KRT8, KRT18 and CDH2) were significantly decreased in degenerate human NP cells, while three genes (VCAN, TNMD and BASP1) were significantly increased in degenerate human AF cells. The IVD negative marker FBLN1 was significantly increased in both degenerate human NP and AF cells.This study has identified a number of novel genes that characterise the bovine and human NP and IVD transcriptional profiles, and allows for discrimination between AC, AF and NP cells. Furthermore, the similarity in expression profiles of the separated NP and NC cell populations suggests that these two cell types may be derived from a common lineage. Although interspecies variation, together with changes with IVD degeneration were noted, use of this gene expression signature will benefit tissue engineering studies where defining the NP phenotype is paramount.

Project description:Human intervertebral disc tissue was obtained from patients (average age 51 yrs) undergoing surgery for lumbar interbody fusion (n=3) or lumbar disc herniation (n=1). Cells were isolated by sequential pronase-collagenase digestion [3]. Cells were passaged twice in monolayer and suspended at a density of 2 x 106 cells/ml in 1.2% alginate (low viscosity, Sigma Chemical, St Louis, MO) dissolved in 150 mM NaCl. Alginate beads were formed by dropwise addition of the alginate from a 22 gauge needle into 102 mM CaCl2, followed by 10 minutes of curing, as described previously [13, 27]. Cell-gel beads were incubated in cell culture media consisting of Ham’s F-12 medium (Gibco BRL, Grand Island, NY), supplemented with 10% FBS (HyClone, Logan, UT), 25 μg/ml ascorbic acid (Sigma, St. Louis, MO), 100 U/ml penicillin, 100 μg/ml streptomycin, and 1 μg/ml Fungizone at 5% CO2 and 37° C. After 24 h, the cell culture medium was removed via pipette and exchanged for one of three osmotically active solutions, representing iso-osmotic, hyper-osmotic and hypo-osmotic media [12, 23, 34]. The iso-osmotic solution consisted of a defined cell culture medium (Ham’s F-12 with supplements as described above; 293 mOsm/kg H2O). The hypo-osmotic solution consisted of the same cell culture media diluted with de-ionized water to a final osmolarity of 250 mOsm/kg H2O. The hyper-osmotic solution consisted of the same cell culture media supplemented with sucrose to a final osmolarity of 450 mOsm/kg H20. The osmolarity of all solution formulations was determined using a freezing-point osmometer (Advanced Laboratory Wide Range 3W2, Advanced Instrument, Needham Heights, MA) as described previously [12]. Cell-alginate beads were cultured for a 4 hour period under one of these conditions, after which the cells were released from alginate in a dissolving buffer (55 mM Na-citrate and 150 mM NaCl), lysed and stored at –80°C. Intervertebral disc (IVD) cells experience a broad range of physical stimuli under physiologic conditions, including alterations in their osmotic environment. In this study, the gene expression profile of human IVD cells was quantified with gene array technology following exposure to varying osmolarity in order to capture the biological responses for a broad set of targets. A total of 42 genes were identified in IVD cells as significantly changed following culture under hyper-osmotic conditions, while a total of 18 genes were identified as significantly changed under hypo-osmotic conditions. Gene expression patterns were verified using RT-PCR. Genes identified in this study include those related to cytoskeleton remodeling and stabilization (ephrin-B2, sarcoglycan beta, IQGAP1), as well as membrane transport (ion transporter SLC21A12, osmolyte tranporter SLC5A3, monocarboxylic acid SLC16A6, and amino acid transporter SLC7A8). An unexpected finding was the differential regulation of the gene for the neurotrophin brain-derived neurotrophic factor by hyper-osmotic stimuli that may be indicative of a physiological response of IVD cells to physical stimuli important in regulating discogenic pain. Keywords = intervertebral disc Keywords = osmotic stimuli Keywords: other

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The heterogeneity of the non-aggregating proteoglycans of the human intervertebral disc.

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