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Asporin is Expressed at Higher Levels in the More Degenerate Human Intervertebral Disc Tissue

ABSTRACT: Asporin, also known as periodontal ligament-associated protein 1 (PLAP1), is a member of the family of small leucine-rich proteoglycan (SLRP) family. It is present within the cartilage extracellular matrix (ECM), and is reported have a genetic association with osteoarthritis. Its D14 allele has recently been found to be associated with lumbar disc degeneration in Asian subjects. There have been no studies, however, of this gene’s normal immunohistochemical localization within the human intervertebral disc, nor of expression levels in Caucasian individuals with disc degeneration. Studies were approved by our human subjects Institutional Review Board. Methods included immunohistochemical localization of asporin in the disc of humans and the sand rat (a small rodent with spontaneous age-related disc degeneration), and Affymetrix microarray analysis of asporin gene expression in vivo and in vitro. mmunohistochemical studies of human discs revealed that some, but not all, cells of the outer annulus expressed asporin. Fewer cells in the inner annulus contained asporin, and it was rarely present in cells in the nucleus pulposus. Similar patterns were found for the presence of asporin in lumbar discs of sand rats. Substantial relative gene expression levels were seen for asporin in both disc tissue and in annulus cells grown in three-dimensional culture. More degenerate human discs (Thompson grade 4) showed higher expression levels of asporin than did less degenerate (grade 1, 2 and 3) discs, p = 0.004. In the discs of Caucasian subjects studied here, and in the sand rat, greater immunolocalization levels were found in the outer compared to inner annulus. Localization was rare in the nucleus. Gene expression studies showed greatest expression of asporin in the more degenerate human discs in vivo.

ORGANISM(S): Homo sapiens

PROVIDER: GSE15227 | GEO | 2009/03/24

SECONDARY ACCESSION(S): PRJNA116483

REPOSITORIES: GEO

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Project description:Asporin, also known as periodontal ligament-associated protein 1 (PLAP1), is a member of the family of small leucine-rich proteoglycan (SLRP) family. It is present within the cartilage extracellular matrix (ECM), and is reported have a genetic association with osteoarthritis. Its D14 allele has recently been found to be associated with lumbar disc degeneration in Asian subjects. There have been no studies, however, of this gene’s normal immunohistochemical localization within the human intervertebral disc, nor of expression levels in Caucasian individuals with disc degeneration. Studies were approved by our human subjects Institutional Review Board. Methods included immunohistochemical localization of asporin in the disc of humans and the sand rat (a small rodent with spontaneous age-related disc degeneration), and Affymetrix microarray analysis of asporin gene expression in vivo and in vitro. mmunohistochemical studies of human discs revealed that some, but not all, cells of the outer annulus expressed asporin. Fewer cells in the inner annulus contained asporin, and it was rarely present in cells in the nucleus pulposus. Similar patterns were found for the presence of asporin in lumbar discs of sand rats. Substantial relative gene expression levels were seen for asporin in both disc tissue and in annulus cells grown in three-dimensional culture. More degenerate human discs (Thompson grade 4) showed higher expression levels of asporin than did less degenerate (grade 1, 2 and 3) discs, p = 0.004. In the discs of Caucasian subjects studied here, and in the sand rat, greater immunolocalization levels were found in the outer compared to inner annulus. Localization was rare in the nucleus. Gene expression studies showed greatest expression of asporin in the more degenerate human discs in vivo. Disc Tissue samples were obtained via the National Cancer Institute Cooperative Tissue Network (CHTN) as well as surgical disc procedures performed on patients with herniated discs and degenerative disc disease. Tissue was fixed and paraffin embedded. Standard laser capture microdissection (LCM) techniques were used to collect the cells from which total RNA was isolated and analyzed via microarray. Based on the Thompson scouring system, unhealthy discs (grade 4) were compared to healthy discs (grades 2,3).

Project description:Autologous stem cell therapy has potential for biologic treatment of disc degeneration. Due to ease of harvest and abundance, adipose-derived mesenchymal stem cells (AD-MSC) are readily available. Our objectives were: 1) To develop/validate methods to harvest AD-MSC and direct them to a disc-like phenotype by three-dimensional (3D) culture and TGF-Ã3 exposure; 2) To perform gene expression profiling for human AD-MSC and annulus cells in 3D culture; 3) To test whether disc cell-AD-MSC co-culture could augment proteoglycan production. Stem cell plasticity offers potential for future biologic therapies for disc degeneration. Data indicated that human AD-MSC can successfully be manipulated in 3D culture to express gene products important in the disc ECM (types I and II collagen, chondroitin sulfate, keratin sulfate, decorin), and that co-culture of annulus cells with AD-MSC enhances proteoglycan production. Studies defined gene expression patterns of AD-MSC and human annulus cells in 3D culture, important as we explore the potential of MSC in biologic therapies for disc degeneration. Experiment Overall Design: AD-MSC were extracted from human adipose tissue, and characterized as stem cells using accepted criteria (direction into osteoblasts or chondrocytes; and cell surface marker criteria). Three AD-MSC cultures were grown in 3D with or without TGF-Ã3 for 2-3 weeks. Disc Tissue samples were obtained from surgical disc procedures performed on patients with herniated discs and degenerative disc disease. Seven disc cultures were also grown in 3-D for 2 weeks. RNA was harvested according to instructions with the Trizol isolation method, checked for quality using the 2100 Bioanalyzer (Agilent Technologies, Inc., Santa Clara, CA USA), reverse-transcribed to double-stranded cDNA, subjected to two rounds of transcription, and hybridized to the DNA microarray in the Affymetrix Fluidics Station 400. Affymetrix human U133 X3P arrays were used. Using Genesifter, gene expression in AD-MSC with and witout TGF-B3 was compared to annulus cells. Gene expression of stem cells with TGF-Ã3 was also compared to stem cells grown in the absence of TGF-Ã3.

Project description:The intervertebral disc (IVD) is a joint in the spine that facilitates daily physical activity, comprising of the central nucleus pulposus (NP), surrounded by the annulus fibrosus (AF) and sandwiched between two cartilage endplates that function together as a unit. Changes to the IVD occur with aging, most drastically in the NP where it experiences dehydration and loss of cellularity, directly impacting on the integrity of the biomechanical functions of the IVD. The proteome reflects the long-term accumulation of proteins and their turnover with time, which cannot be faithfully determined by the transcriptome that reflects only immediate cellular changes. The proteome of the disc, which is predominantly extracellular matrix, may therefore more accurately reflect disc function, and could provide important information about the niche in which disc cells are embedded in and can also impact on cellular function. Unfortunately, the acquisition of young healthy IVD tissues from surgeries are scarce, and it is exceedingly rare to obtain healthy samples with spatial information. Here, we examined three young healthy cadaveric lumbar discs, corresponding to three neighboring levels (L3/4, L4/5 and L5/S1), from one individual (16M); and analysed the proteome profiles of the NP, inner AF (IAF) and outer AF (OAF), in a direction-specific (both lateral and anteroposterior) manner, to gain a reference proteome of healthy discs. We identified that the central-most regions of the disc (including NP and IAF) are similar to each other and there is expression of well characterized NP markers (including KRT8/19, CD109), as well as upregulation of cartilage and cytoskeletal-related proteins (including CHRD, CHRDL2, FRZB). Furthermore, in the PCA plot, there is clear demarcation of inner and outer AF, which was found to express small proteoglycans (BGN, DCN, FMOD, OGN, PRELP) and a unique group of the collagens (COL12A1, COL14A1, COL1A1, COL6A1/2/3) and glycoproteins including CILP, CILP2, COMP, FBN1and THBS1. We also showed that in young disc, the upper levels are more similar to each other than the lower disc levels, and that directional factors (whether the tissue was from an anteroposterior or lateral direction) play minimal roles, although we also identified four modules showing strong directional trends. Using the young proteome as a baseline reference, we then examined three aged cadaveric lumbar discs (with same disc levels as the young) from another older individual (59M) to gain further understanding of age-related changes in the disc. Employing ANOVA, PCA and DEG analyses, the aged inner disc regions (including NP and IAF) were found to have similar profiles, express fewer classical NP markers, and have reduced numbers of differentially expressed proteins (DEPs) in comparison to young disc. Overall, both inner compartments and OAF of the aged disc showed an enrichment of proteins associated with inflammation and degradation. Remarkably, we discovered that in aged disc, the IAF and OAF distinction remains strong, and that the upper lumbar disc was deviated more away from their young counterparts than the lower two levels, with minimal influence by directional differences. Importantly, we further identified an abundance of blood proteins that were highly expressed in inner disc of aged discs, which suggested that age-related changes may have originated from the central NP regions of the disc. We carried out additional validation studies by examining the transcriptome of 2 independent young and aged samples, respectively, and were able to correlate transcriptome to young and aged proteome. Unique and novel to this study, we also correlated MRI imaging of the 3 aged lumbar discs and showed that there is correlation of particular types of proteins with MRI image intensity. In all, this data shed lights on the proteomic changes underlying the ageing IVDs in a region-specific manner.

Project description:Although the degenerating disc is considered to be the key source of pain in patients with low back pain, the relationship between disc cells, nerves, and pain production is poorly understood. Neurotrophins are signaling molecules involved in the survival, differentiation, migration, and neurite outgrowth of central and peripheral neurons. Neurotrophins are now known to be expressed in non-neuronal tissues, including the intervertebral disc. We hypothesize that the inflammatory cytokine interleukin-1 (IL-1beta), which is produced by disc cells during degeneration, is a key element in the cascade of events involving neurotrophins. To test this, we used an in vitro experimental design which challenged 3D-cultured human annulus cells with IL-1beta and utilized microarray analysis to evaluate neurotrophin- and nerve-related gene expression profiles in treated vs. control cells. Analysis of nerve growth factor levels in conditioned media was also performed. Findings presented here support the hypothesis that proinflammatory cytokines (which are produced by disc cells during degeneration) are involved with a significant increase in the expression of neurotrophins and other nerve-related genes. Findings expand previous data on expression of neurotrophins in the degenerating disc, and provide the first documentation of expression of neurotrophin 3 and neuropilin 2. These results have direct translational relevance because they address the primary clinical issue with disc degeneration (low back pain) and open the possibility of novel analgesic therapies based on development of specific small-molecular antagonists to neurotrophins. Human disc tissue samples were obtained from surgical disc procedures performed on patients with herniated discs and degenerative disc disease. Cultured annulus cells were grown in a 3D collagen construct with or without 10 2 pM IL-1 for a total of 14 days. Following homogenization in TRIzol reagent, total RNA was isolated and analyzed via mircoarray.

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Asporin is Expressed at Higher Levels in the More Degenerate Human Intervertebral Disc Tissue

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