Fig. 3
The maintenance of accumulated LD is associated with the resistance of articular chondrocytes to lipotoxicity. a Representative Nile red and BODIPY staining. Oleate at 1–1.25 mmol·L-1 induced giant LD. The quantification of the BODIPY staining showed that 1 and 1.25 mmol·L-1 oleate significantly increased the total LD volume (n = 4). **P < 0.01 vs. control according to Scheffe’s test. Compared to the cells treated with 1 and 1.25 mmol·L-1 oleate, the LD size was much smaller in cells treated with 1.5 mmol·L-1 oleate. The quantification of the BODIPY staining showed that 1.5 mmol·L-1 oleate significantly reduced the total LD volume (n = 4). **P < 0.01 vs. 1 and 1.25 mmol·L-1 oleate treatment according to Scheffe’s test. Scale bars, 20 μm. b Representative TUNEL, Hoechst and BODIPY triple-labelling showing that more TUNEL-positive cells are observed in cells treated with toxic concentrations of oleate (1.5 mmol·L-1) compared to control cells or cells treated with nontoxic concentrations of oleate (1 and 1.25 mmol·L-1). The quantification of TUNEL staining showed that 1.5 mmol·L-1 oleate significantly increased the population of TUNEL-positive cells. **P < 0.01 vs. control and 1 and 1.25 mmol·L-1 oleate treatment according to Scheffe’s test. The size of the LDs decreased in TUNEL-positive cells compared to TUNEL-negative cells. The quantification of BODIPY staining showed that the total LD volume was significantly decreased in TUNEL-positive cells. **P < 0.01 vs. TUNEL-negative cells according to Scheffe’s test. Scale bars, 20 μm. c Representative western blots showing that 1.5 mmol·L-1 oleate decreased the expression level of FSP27 protein (n = 4). d The knockdown of FSP27 reduced the total LD volume. The quantification shows that the knockdown of FSP27 significantly decreased the total LD volume. **P < 0.01 vs. scRNA control according to Scheffe’s test. Scale bar, 10 μm. e Viability assay showing that FSP27 depletion significantly sensitised chondrocytes to lipotoxicity (n = 4). **P < 0.01 vs. scRNA according to Scheffe’s test. f Immunohistochemistry on cartilages obtained from ACLT model 6 weeks after surgery. The FSP27-positive cells were quantified (n = 4). The population of FSP27-positive articular chondrocytes was significantly smaller in mice fed an HFD than in mice fed an SD. **P < 0.01 vs. mice fed an SD according to Scheffe’s test. BODIPY and Hoechst dual labelling showing that LDs are accumulated in mice fed an HFD. Scale bar, 20 μm
