Fig. 3

Chondrocyte volume fraction and cartilage thickness measurements medial and lateral femoral condyle articular cartilage across Prg4 ^+/+, Prg4 ^+/- and Prg4 ^-/- mouse knee joints. a Representative median confocal images of FDA (green) + PI (red) + Hoechst (blue) stained medial femoral condyle cartilage presented as a 0 to 14 μm depth projection, (first row) used in the calculation of mean percentage of cellular volume in cartilage. Scale bars indicate 10 μm. Representative microCT coronal sections (second row) illustrating the results of the Mimics cartilage reconstruction. b Superficial and upper intermediate zone living chondrocyte volume fraction (FDA stained cellular volume/superficial + upper intermediate zone volume) measurements for the medial and lateral femoral condyles. Living chondrocyte volume fraction of the medial femoral condyle of Prg4 ^-/- mice was significantly less than Prg4 ^+/+ (p = 0.002) and Prg4 ^+/- (p = 0.002) littermates. c Superficial and upper intermediate zone living + dead chondrocyte volume fraction (FDA + PI stained cellular volume/superficial + upper intermediate zone volume) measurements for the medial femoral lateral femoral condyles. Chondrocyte volume fraction of the medial femoral condyle of Prg4 ^-/- mice was significantly less than Prg4 ^+/+ (p = 0.02) and Prg4 ^+/- (p = 0.04) littermates. d Superficial and upper intermediate zone dead chondrocyte volume fraction (PI stained cellular volume/superficial + upper intermediate zone volume) measurements for medial and lateral femoral condyles. No significant differences were observed between genotypes on medial and lateral condyles. e Mean cartilage thickness determined from microCT, for the medial (blue) and lateral (red) femoral condyle are shown. Cartilage was significantly thicker in Prg4 ^-/- medial femoral cartilage compared to Prg4 ^+/+ (p = 0.03) and Prg4 ^+/- (p = 0.02) littermates. There was a significant increase in thickness for the lateral femoral condyle in Prg4 ^-/- compared to Prg4 ^+/+ (p < 0.0001) and Prg4 ^+/- (p < 0.0001) littermates. FDA fluorescein diacetate, PI propidium iodide