Figure 2.

Decelerated osteoarthritis progression in Mmp-13^Col2ER mice. Tamoxifen was administered when matrix metalloproteinase (MMP13) conditional knockout (cKO) mice (Mmp13^Col2ER) and Cre-negative control mice were two-weeks-old (1 mg/10 g body weight, intraperitoneal injection, daily for five days). Meniscal-ligamentous injury (MLI) surgery was performed when the mice were 10-weeks-old. Knee joints were harvested eight weeks post-surgery. (A) Safranin O/Fast Green staining was performed to evaluate proteoglycan content. Proteoglycan loss following MLI was reduced in Mmp13^Col2ER mice. (B) Type II collagen (Col2) loss following MLI was reduced in Mmp13^Col2ER mice. Immunohistochemistry (IHC) of Col2 was performed to assess its protein level. (C) IHC of ColX was performed to assess its protein level. Type X collagen (ColX) induction following MLI was reduced in Mmp13^Col2ER mice. (D) Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining (in green) and 4',6-diamidino-2-phenylindole (DAPI) nuclear counterstaining (in blue) were performed to assess chondrocyte apoptosis. Chondrocyte apoptosis following MLI was reduced in Mmp13^Col2ER mice. (E) Quantification of TUNEL staining positive cells was performed to assess chondrocyte apoptosis.