(A and B) PCA of RNA sequencing data of plantaris tendons from control nonoverloaded (0D) Scx⁺ tendons, as well as from Scx⁺ and Scx^Δ mice at 7D or 14D after synergist ablation/plantaris growth procedure (A), and from cultured Scx⁺ and Scx^Δ tenocytes (B). (C) Proliferating tenocytes, isolated from tail tendons, as quantified by BrdU⁺ nuclei (red) as a percentage of total nuclei (blue) in Scx⁺ and Scx^Δ tenocytes. Representative BrdU^– and BrdU⁺ cells are shown in the inset. Scale bar: 10μm. (D–F) The number of genes that with > 1.5-fold upregulation (red) or > 1.5-fold downregulation (blue), and with q < 0.05, in Scx^Δ tendons compared with Scx⁺ tendons at 7D (D) or 14D (E) after synergist ablation/plantaris growth procedure, or in cultured Scx^Δ tenocytes (F) compared with Scx⁺ tenocytes. (G–I) Heatmaps demonstrating the log₂ fold change in selected genes from RNA sequencing that are components or regulators of the extracellular matrix or tendon differentiation (G), involved in cell migration or proliferation (H), or growth factors, cytokines, and signaling molecules (I). The fold change value is displayed for Scx^Δ relative to Scx⁺ group. (C) Values are mean ± SD. Differences between Scx⁺ and Scx^Δ groups were tested using a t test. (G–I) Differences between groups were tested using DESeq2; a, different (q < 0.05) between Scx⁺ and Scx^Δ groups at a given time point for whole tendons, or for cultured tenocytes. (A, D, E, G–I) N ≥ 3 tendons. (B, C, F–I) N = 6 replicates per tenocyte group.