(A) Fluorescence images depicting intracellular Ca²⁺ (green) within early passage WT and TRPC1^–/– chondrocytes loaded with Fluo-4 Ca²⁺ indicator, during stimulation with 5 ng/mL thapsigargin. Scale bar: 200 μm. (B) Comparison of basal intracellular Ca²⁺ levels as measured by fluorescence intensity of early passage WT and Trpc1^–/– chondrocytes. Unpaired t test (n = 8). (C–E) Time course analysis of intracellular Ca²⁺ levels as measured by fluorescence intensity of loaded Fluo-4 Ca²⁺ indicator in WT and Trpc1^–/– chondrocytes during stimulation with either ionomycin (200 nM), thapsigargin (5 ng/mL), or bFGF (50 ng/mL). Two-way ANOVA with multiple comparisons (n = 4). *P < 0.05 and **P < 0.01. (F) Immunofluorescence detection of TRPC1 (green) in WT murine chondrocytes in resting conditions and 3 minutes following bFGF (50ng/mL) stimulation. Cell cytoskeleton is counterstained with phalloidin (white) and nuclei with DAPI (blue). Scale bar: 20 μm. For isotype negative control staining, see Supplemental Figure 3A. (G) Immunohistological detection of TRPC1 in human cartilage sections comparing healthy (OARSI score 0), early OA (OARSI score 1.0–2.5) and advanced OA (OARSI score 3.0+). Scale bar: 100 μm. For isotype negative control staining, see Supplemental Figure 3B. (H) Graph showing quantification of TRPC⁺ cells within the cartilage expressed as percentage of total number of cells identified (n = 4 participants). One-way ANOVA with Tukey’s multiple-comparison test. (I) Immunohistological detection of TRPC1 in murine knee joint 2 weeks and 8 weeks following sham control or DMM surgery. Dotted red outline indicates area used for analysis of articular cartilage. Scale bar: 100 μm. For isotype negative control staining, see Supplemental Figure 3C. (J) Quantification of the relative number of TRPC1⁺ cells within the tibial articular cartilage expressed as a percentage of cells present P values: unpaired t test (n = 5 mice).