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Comparative analysis of chromatin accessibility during chondrogenesis and in osteoarthritis

ABSTRACT: To reveal the organisation of the cartilage cell chondrocyte genome and identify changes that occur within this organisation during development and due to osteoarthritis (OA). Methods Assay for Transposase -Accessible Chromatin using Sequencing (ATAC-seq) was performed on chondrocytes isolated from 16 patients undergoing total hip replacement because of OA (n=7) or due to a neck of femur fracture (NOF, n=9). ATAC-seq was similarly performed on bone-marrow mesenchymal stem cells (BM-MSC) and differentiated chondrocytes of two donors. DNA sequence reads (av. 50 million/sample) were aligned to human genome Hg38. Peaks were called using MACS2 and differential accessibility identified by DiffBind. Interexperiment comparisons and intersection with published gene expression changes, chondrogenesis ChIP-seq, knee ATAC-seq and human tissue scATAC-seq were performed in Galaxy and R. OA GWAS signal regions were overlapped with our defined chondrocyte ATAC-seq peaks. Results In BM-MSC and derived chondrocytes we mapped 138005 open chromatin regions, of which 20979 and 50699 significantly increased and decreased respectively during cell differentiation. In hip chondrocytes we identified 115295 open chromatin regions, 1383 and 573 were more or less differentially accessible respectively when comparing OA with NOF samples. In both data sets ‘newly accessible regions were enriched at enhancer regions (defined by ChIP-seq). Comparing the data with the ATAC-seq from the single cell ATLAS we identified 11866 open regions exclusive to chondrocytes. Genes associated with these regions were significantly enriched for cartilage-related gene ontology terms. Taking the 420 OA GWAS signals present in the GWAS catalogue, 313 of the OA regions (defined as lead SNP + proxy SNPs with r2 ≥ 0.8) overlapped with a chondrocyte ATAC-seq region. Conclusions Here we have mapped chromatin accessible region changes during chondrogenesis, showing that newly accessible regions are enriched at enhancer regions and positively correlate with gene expression. Open chromatin region changes between OA and NOF cartilage were fewer, and peak differences were subtle. Overall, we have associated OA GWAS loci with accessible regions and defined regions of the genome specific to cartilage and chondrogenesis.

ORGANISM(S): Homo sapiens

PROVIDER: GSE270602 | GEO | 2025/01/01

REPOSITORIES: GEO

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Project description:Autologous chondrocyte transplantation (ACT) is a routine technique to regenerate focal cartilage lesions. However, patients with osteoarthritis (OA) are lacking an appropriate long-lasting treatment alternative, partly since it is not known if chondrocytes from OA patients have the same chondrogenic differentiation potential as chondrocytes from donors not affected by OA. Articular chondrocytes from patients with OA undergoing total knee replacement (Mankin Score >3, AhlbÃ¤ck Score >2) and from patients undergoing ACT, here referred to as normal donors (ND), were isolated applying protocols used for ACT. Their chondrogenic differentiation potential was evaluated both in high-density pellet and scaffold (Hyaff-11) cultures by histological proteoglycan assessment (Bern Score) and immunohistochemistry for collagen types I and II. Chondrocytes cultured in monolayer and scaffolds were subjected to gene expression profiling using genome-wide oligonucleotide microarrays. Expression data were verified by using quantitative RT-PCR. Chondrocytes from ND and OA donors demonstrated accumulation of comparable amounts of cartilage matrix components, including sulphated proteoglycans and collagen types I and II. The mRNA expression of cartilage markers (COL2A1, COMP, aggrecan, CRTL1, SOX9) and genes involved in matrix synthesis (biglycan, COL9A2, COL11A1, TIMP4, CILP2) was highly induced in 3D cultures of chondrocytes from both donor groups. Genes associated with hypertrophic or OA cartilage (COL10A1, RUNX2, periostin, ALP, PTHR1, MMP13, COL1A1, COL3A1) were not significantly regulated between the two groups of donors. The expression of 661 genes, including COMP, FN1, and SOX9, were differentially regulated between OA and ND chondrocytes cultured in monolayer. During scaffold culture, the differences diminished between the OA and ND chondrocytes, and only 184 genes were differentially regulated. Only few genes were differentially expressed between OA and ND chondrocytes in Hyaff-11 culture. The risk of differentiation into hypertrophic cartilage does not seem to be increased for OA chondrocytes. Our findings suggest that the chondrogenic capacity is not significantly affected by OA and OA chondrocytes fulfill the requirements for matrix-associated ACT. Experiment Overall Design: Gene expression profiles of monolayer cultures (ML; passage 2) and Hyaff-11 scaffold cultures (3D; 14 days in vitro) of chondrocytes from 3 normal donors (ND; underwent ACT treatment) and 3 donors suffering from Osteoarthritis (OA; underwent knee replacement surgery) were determined. Comparative analyses between 3D and ML cultures (3D vs. ML) were performed to assess differentiation capacity of ND and OA chondrocytes. Furthermore, OA-related differences were determined comparing OA and ND monolayers as well as scaffold cultures (each OA vs. ND).

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Comparative analysis of chromatin accessibility during chondrogenesis and in osteoarthritis

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