Fig. 2: PKM2 regulates extracellular matrix (ECM) metabolism in chondrocytes.

a Representative immunoblots and b densitometric quantification of MMP3, MMP13, ADAMTS5, COL2A1, ACAN, SOX9, and PKM2 in chondrocytes transfected with siNC or siPkm2 and stimulated with IL-1β (1 ng mL⁻¹). Data were presented as means ± s.e.m., n = 6, one-way ANOVA with Tukey’s multiple comparisons. c Quantification of type II collagen (Col II) and glycosaminoglycans (GAGs) in the culture supernatant of chondrocytes transfected with siNC or siPkm2 and stimulated with IL-1β (10 ng mL⁻¹). Data were presented as means ± s.e.m., n = 6, one-way ANOVA with Tukey’s multiple comparisons. d Representative immunoblots and e densitometric quantification of MMP3, MMP13, and COL2A1 in IL-1β-stimulated chondrocytes incubated with vehicle, Shikonin (1 μM) or TEPP-46 (50 μM). Data were presented as means ± s.e.m., n = 6, one-way ANOVA with Tukey’s multiple comparisons. f Schematic of intra-articular siNC or siPkm2 administration in DMM mice. Three-month-old WT mice underwent DMM surgery, and intra-articular injections of siNC or siPkm2 were initiated one week later and administered twice weekly for eight weeks. Mice were euthanized eight weeks post-surgery, and cartilage was collected for histological analysis. g Representative images of SO&FG staining and IF staining, and h quantification of PKM2, MMP13, ACAN, and COL2A1 expression in cartilages from DMM mice administered with siNC or siPkm2. Data were presented as means ± s.e.m., n = 6, unpaired Student’s t-test. i Representative immunoblots and j densitometric quantification of MMP3, MMP13, and COL2A1 in chondrocytes transfected with AAV-Vector or AAV-PKM2. Data were presented as means ± s.e.m., n = 6, unpaired Student’s t-test. k Schematic diagram of intra-articular AAV-Vector or AAV-PKM2 administration. Three-month-old WT mice received intra-articular injections once weekly for 8 weeks; mice were then euthanized and cartilage harvested for histological analysis. l Representative SO&FG and IF staining images, and m quantification of PKM2, MMP13, ACAN, and COL2A1 expression in cartilages from mice administered with AAV-Vector or AAV-PKM2. Data were presented as means ± s.e.m., n = 6, unpaired Student’s t-test. *P < 0.05, **P < 0.01, ***P < 0.001. ns not significant.