Fig. 4 | Nature Communications

Fig. 4

From: Excessive mechanical loading promotes osteoarthritis through the gremlin-1–NF-κB pathway

Fig. 4

Regulation of osteoarthritis development by gremlin-1. a Safranin O staining and OARSI scores of mouse knee joints of Grem1fl/fl (Cntl) and Col2a1-CreERT2;Grem1fl/fl (cKO) mice 8 weeks after surgery. Tamoxifen induction was performed at 7 weeks. Both experimental groups consist of n = 9 biologically independent animals. Inset boxes indicate regions of immunofluorescence in (c). Scale bars, 100 µm. b TUNEL staining and rate of TUNEL-positive cells in mouse knee joints of Cntl and cKO mice 8 weeks after surgery. Nuclei were stained with DAPI (blue). Scale bars, 100 µm. n = 5 biologically independent experiments. c Safranin O staining and immunofluorescence of Mmp13, Adamts5, IκBα, phosphorylated IκBα (dual Ser32/36), HIF-2α, and gremlin-1 proteins in mouse knee joints of Cntl and cKO mice 8 weeks after surgery. Scale bars, 50 µm. The percentage of positive cells in the immunofluorescence is shown below. n = 5 biologically independent experiments. d Safranin O staining and OARSI scores of mouse knee joints of Cntl and cKO mice at 18 months of age. Tamoxifen induction was performed for 5 days at 8 weeks, 6 months, and 12 months. Both experimental groups consist of n = 8 biologically independent animals. Inset boxes indicate regions of immunofluorescence in (f). Scale bars, 100 µm. e TUNEL staining and rate of TUNEL-positive cells in mouse knee joints of Cntl and cKO mice at 18 months of age. Nuclei were stained with DAPI (blue). Scale bars, 100 µm. n = 5 biologically independent experiments. (f) Safranin O staining and immunofluorescence of Mmp13, Adamts5, IκBα, phosphorylated IκBα (dual Ser32/36), HIF-2α, and gremlin-1 proteins in mouse knee joints of Cntl and cKO mice at 18 months of age. Scale bars, 50 µm. The percentage of positive cells in the immunofluorescence is shown below. n = 5 biologically independent experiments. All data are expressed as mean ± SD. *P < 0.05, **P < 0.01, #P < 0.005, ##P < 0.001 versus Cntl (Student’s unpaired two-tailed t-test)

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