Single-cell RNA-sequencing analysis reveals cellular states and intercellular communication of human lumbar facet-joint degeneration

Figure 2 Identification of lumbar facet joint cartilage chondrocyte subpopulations and their marker-gene expression in different degeneration grades of human lumbar facet joint cartilage. A: Uniform Manifold Approximation and Projection plot showing the single-cell transcriptomic landscape of human lumbar facet joint chondrocytes. Eight subpopulations were identified; B: Heatmap of the top marker genes of each cluster (defined in A); C: Violin plot of representative genes of each chondrocyte population (defined in A); D: Immunohistochemistry staining of representative markers of the indicated cell clusters in different degenerated lumbar facet joint cartilage samples. Scale bar 100 μm. UMAP: Uniform Manifold Approximation and Projection; ProCs: Proliferative chondrocytes; PreHTCs: Prehypertrophic chondrocytes; HTCs: Hypertrophic chondrocytes; FCs: Fibrocartilage chondrocytes; ECs: Effector chondrocytes.