Decelerated osteoarthritis progression in Mmp-13Col2ER mice. Tamoxifen was administered when matrix metalloproteinase (MMP13) conditional knockout (cKO) mice (Mmp13Col2ER) 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 Mmp13Col2ER mice. (B) Type II collagen (Col2) loss following MLI was reduced in Mmp13Col2ER 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 Mmp13Col2ER 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 Mmp13Col2ER mice. (E) Quantification of TUNEL staining positive cells was performed to assess chondrocyte apoptosis.
Wang et al. Arthritis Research & Therapy 2013 15:R5 doi:10.1186/ar4133