Transcriptome sequencing reveals dynamic changes in matrix metalloproteinases in facet joint osteoarthritis

Abstract

Osteoarthritis is a general joint disease characterized by articular cartilage degeneration. The extracellular matrix is a principal component in articular cartilage. The dynamic remodeling of the extracellular matrix is involved in the pathological degradation of the articular cartilage. Facet joint osteoarthritis (FJOA) is a common form of osteoarthritis that occurs in the posterior aspect of the vertebral column. However, to the best of our knowledge, the current understanding of the genetic changes in FJOA is limited. The most significantly differentially expressed genes and Gene Ontology categories in FJOA were identified by transcriptome sequencing analysis. The extracellular matrix, matrix metalloproteinases (MMPs) and proteinases of the extracellular matrix were highly involved in FJOA. The canonical signaling pathway 'inhibition of matrix metalloproteinases' was further studied in detail by identifying and validating differentially expressed genes in the signaling pathway. Taken together, the present study revealed changes in MMP-related genes in FJOA and showed the importance of extracellular matrix remodeling in FJOA from a genetic aspect.

Keywords: bioinformatics analysis; extracellular matrix; facet joint osteoarthritis; matrix metalloproteinases; transcriptome sequencing.

Figure 1.

Expression patterns of genes in healthy and lesioned facet joint tissues. The expression levels of genes are shown in a heatmap and indicated by a color bar. Red indicates upregulated genes while blue indicates downregulated genes.

Figure 2.

Top enriched GO categories in facet joint osteoarthritis. The ten most enriched GO biological processes, molecular functions and cellular components. Red represents GO biological processes, blue represents GO molecular functions and green represents GO cellular components. GO, gene ontology.

Figure 3.

Schematic diagram of the canonical signaling pathway ‘inhibition of matrix metalloproteinases’. Differentially expressed genes in the canonical signaling pathway ‘inhibition of matrix metalloproteinases’ are represented in red and green. Red indicates upregulated genes while green indicates downregulated genes. TIMP, tissue inhibitor of metalloproteinases; MMP, matrix metalloproteinase; RECK, reversion-inducing cysteine-rich protein with Kazal motifs; HSPG, basement membrane-specific heparan sulfate proteoglycan core protein; ADAM, disintegrin and metalloproteinase domain-containing protein; TSP2, thrombospondin-2; A2M, α-2-macroglobulin; TFPI2, tissue factor pathway inhibitor 2; LRP1, prolow-density lipoprotein receptor-related protein 1; MT1-MMP, matrix metallopeptidase 14 (membrane-inserted).

Figure 4.

Heatmap of differentially expressed genes in the canonical signaling pathway ‘inhibition of matrix metalloproteinases’. Red indicates upregulated genes while green indicates downregulated genes. CTRL, control group; FJOA, facet joint osteoarthritis; TIMP, tissue inhibitor of metalloproteinases; MMP, matrix metalloproteinase; RECK, reversion-inducing cysteine-rich protein with Kazal motifs; HSPG, basement membrane-specific heparan sulfate proteoglycan core protein; ADAM, disintegrin and metalloproteinase domain-containing protein; TSP2, thrombospondin-2; A2M, α-2-macroglobulin; TFPI2, tissue factor pathway inhibitor 2; LRP1, prolow-density lipoprotein receptor-related protein 1.

Figure 5.

Reverse transcription-quantitative PCR analysis of differentially expressed genes in the canonical signaling pathway ‘inhibition of matrix metalloproteinases’. The relative expression levels of MMP7, ADAM12, TIMP3 and TIMP4 were calculated. The red arrows indicate the expression trends of genes, as revealed by sequencing. Data were summarized from three independent experiments. ^*P<0.05 vs. control. FJOA, facet joint osteoarthritis; MMP7, matrix metalloproteinase 7; ADAM12, disintegrin and metalloproteinase domain-containing protein 12; TIMP, tissue inhibitor of metalloproteinases.