ACAN
Aggrecan core protein precursor (Cartilage-specific proteoglycan core protein) (CSPCP) (Chondroitin sulfate proteoglycan core protein 1) (Chondroitin sulfate proteoglycan 1) [Contains: Aggrecan core protein 2] [AGC1] [CSPG1] [MSK16]
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Articular cartilage undergoes biological and morphological changes throughout maturation. The prevalence of osteoarthritis in the aged population suggests that maturation predisposes cartilage to degradation and/or impaired regeneration, but this process is not fully understood. Therefore, the objective of this study was to characterize the cellular and genetic profile of cartilage, as well as biological plasticity in response to mechanical and culture time stimuli, as a function of animal maturity. Porcine articular cartilage explants were harvested from stifle joints of immature (2-4 weeks), adolescent (5-6 months), and mature (1-5 years) animals. Half of all samples were subjected to a single compressive mechanical load. Loaded samples were paired with unloaded controls for downstream analyses. Expression of cartilage progenitor cell markers CD105, CD44, and CD29 were determined via flow cytometry. Expression of matrix synthesis genes Col1, Col2, Col10, ACAN, and SOX9 were determined via qPCR. Tissue morphology and matrix content were examined histologically. Post-loading assays were performed immediately and following 7 days in culture. CD105 and CD29 expression decreased with maturity, while CD44 expression was upregulated in cartilage from mature animals. Expression of matrix synthesis genes were generally upregulated in cartilage from mature animals, and adolescent animals showed the lowest expression of several matrix synthesizing genes. Culture time and mechanical loading analyses revealed greater plasticity to mechanical loading and culture time in cartilage from younger animals. Histology confirmed distinct structural and biochemical profiles across maturity. This study demonstrates differential, nonlinear expression of chondroprogenitor markers and matrix synthesis genes as a function of cartilage maturity, as well as loss of biological plasticity in aged tissue. These findings have likely implications for age-related loss of regeneration and osteoarthritis progression.
Keywords
- Aging
- Articular cartilage
- Osteoarthritis
- Plasticity
- Progenitor cells
Intervertebral disc degeneration (IDD) is a major contributor to back, neck, and radicular pain, and the treatment of IDD is costly and relatively ineffective. Dysregulation of microRNAs (miRNAs) has been reported to be involved in IDD. The purpose of our study is to illustrate the potential that miR-143-5p targeting eEF2 gene mediates IDD. Following the establishment of the IDD rat models, expression of miR-143-5p, eEF2, Bcl-2, Bax, AMPK, mTOR, cyclinD, COL2, ACAN, and DCN was detected. The NP cells isolated from degenerative intervertebral disc (IVD) were introduced with a series of mimic, inhibitor, or AICAR to explore the functional role of miR-143-5p in IDD and to characterize the relationship between miR-143-5p and eEF2. Cell viability, cell cycle, apoptosis, and senescence were also evaluated. A reduction in eEF2, an increase in miR-143-5p, and activation of the AMPK signaling pathway were observed in degenerative IVD. Moreover, increased senescent NP cells were observed in degenerative IVD. eEF2 was confirmed as a target gene of miR-143-5p. miR-143-5p was found to activate the AMPK signaling pathway. The restoration of miR-143-5p or the activation of AMPK signaling pathway decreased COL2, ACAN, and DCN expression, coupled with the inhibition of NP cell proliferation and differentiation, and promotion of NP apoptosis and senescence. On the contrary, the inhibition of miR-143-5p led to the reversed results. The results demonstrated that the inhibition of miR-143-5p may act as a suppressor for the progression of IDD.
MeSH Terms
- AMP-Activated Protein Kinases
- Animals
- Cells, Cultured
- Elongation Factor 2 Kinase
- Intervertebral Disc Degeneration
- Male
- MicroRNAs
- Rats
- Rats, Inbred Lew
- Signal Transduction
Keywords
- AMPK signaling pathway
- Apoptosis
- Differentiation
- EEF2
- MicroRNA-143-5p
- Nucleus pulposus cells
- Senescence
Changes in the content of aggrecan, an essential proteoglycan of articular cartilage, have been implicated in the pathophysiology of osteoarthritis (OA), a prevalent age-related, degenerative joint disease. Here, we examined the effect of SOX9 acetylation on ACAN transactivation in the context of osteoarthritis. Primary chondrocytes freshly isolated from degenerated OA cartilage displayed lower levels of ACAN mRNA and higher levels of acetylated SOX9 compared with cells from intact regions of OA cartilage. Degenerated OA cartilage presented chondrocyte clusters bearing diffused immunostaining for SOX9 compared with intact cartilage regions. Primary human chondrocytes freshly isolated from OA knee joints were cultured in monolayer or in three-dimensional alginate microbeads (3D). SOX9 was hypo-acetylated in 3D cultures and displayed enhanced binding to a -10 kb ACAN enhancer, a result consistent with higher ACAN mRNA levels than in monolayer cultures. It also co-immunoprecipitated with SIRT1, a major deacetylase responsible for SOX9 deacetylation. Finally, immunofluorescence assays revealed increased nuclear localization of SOX9 in primary chondrocytes treated with the NAD SIRT1 cofactor, than in cells treated with a SIRT1 inhibitor. Inhibition of importin β by importazole maintained SOX9 in the cytoplasm, even in the presence of NAD. Based on these data, we conclude that deacetylation promotes SOX9 nuclear translocation and hence its ability to activate ACAN.
MeSH Terms
- Acetylation
- Aged
- Aggrecans
- Animals
- Cartilage, Articular
- Cell Nucleus
- Cells, Cultured
- Chondrocytes
- Enhancer Elements, Genetic
- HEK293 Cells
- Humans
- Mice
- Models, Biological
- Protein Binding
- Protein Stability
- RNA, Messenger
- SOX9 Transcription Factor
- Sirtuin 1
- Stress, Mechanical
- Transcriptional Activation
- Transfection
- Weight-Bearing
Keywords
- Aging
- SIRT1
- SOX9
- acetylation
- aggrecan
- cartilage
- nucleus
- osteoarthritis
Aging and obesity contribute to the initiation and progression of osteoarthritis with little information on their relation to gene expression in joint tissues, particularly the meniscus. Here, we test the hypothesis that patient age and body mass index (BMI) correlate with the expression of osteoarthritis- and obesity-related gene signatures in the meniscus. Meniscus was obtained from patients (N=68) undergoing arthroscopic partial meniscectomy. The mRNA expression of 24 osteoarthritis-related and 4 obesity-related genes in meniscus was assessed by quantitative real-time PCR. The relationship between gene expression and patient age and BMI was analyzed using Spearman's rank-order correlation. Hierarchical cluster dendrogram and heat map were generated to study inter-gene associations. Age was negatively correlated (P<0.05) with the expression of MMP-1 (r=-0.447), NFκB2 (r=-0.361), NFκBIA (r=-0.312), IκBA (r=-0.308), IL-8 (r=-0.305), ADAMTS-4 (r=-0.294), APLN (apelin) (r=-0.250) and IL-6 (r=-0.244). Similarly, BMI was negatively correlated with the expression of APLN (r=-0.328), ACAN (r=-0.268) and MMP-1 (r=-0.261). After adjusting for the correlation between age and BMI (r=0.310; P=0.008), the only independent effect of BMI on gene expression was for APLN (r=-0.272). However, age had an independent effect on the expression on ADAMTS-4 (r=-0.253), MMP-1 (r=-0.399), IL-8 (r=-0.327), COL1A1 (r=-0.287), NFκBIA (r=-0.278), NFκB2 (r=-0.312) and IκBA (r=-0.299). The gene correlation analysis identified four clusters of potentially relevant genes: transcription factors, matrix-degrading enzymes, cytokines and chemokines, and obesity genes. Age and BMI were negatively correlated with several osteoarthritis- and obesity-related genes. Although the bulk of these changes appeared to be driven by age, expression of APLN was related to BMI. Inter-gene correlation analysis implicated a common role for strongly correlated genes. Although age-related variations in gene expression appear to be more relevant than obesity-related differences for the role of the meniscus in osteoarthritis development, further investigation into the role of APLN in meniscus and joint health is warranted.
MeSH Terms
- ADAM Proteins
- ADAMTS4 Protein
- Adolescent
- Adult
- Aged
- Aging
- Apelin
- Body Mass Index
- Cartilage, Articular
- Female
- Gene Expression Profiling
- Gene Expression Regulation
- Humans
- I-kappa B Proteins
- Intercellular Signaling Peptides and Proteins
- Interleukin-8
- Male
- Matrix Metalloproteinase 1
- Menisci, Tibial
- Middle Aged
- NF-KappaB Inhibitor alpha
- NF-kappa B p52 Subunit
- Obesity
- Osteoarthritis
- Procollagen N-Endopeptidase
- Protein Array Analysis
- Real-Time Polymerase Chain Reaction
- Tibial Meniscus Injuries
- United States