Table 1.

Histological score of cartilage damage and synovitis in the knee joint of rats.

	Wild type			TRPV4-KO
	Sham	MIA	P	Sham	MIA	P
Cartilage grade	0.5 ± 0.2	5.1 ± 0.5	<0.001	1.0 ± 0.5	5.6 ± 0.4	<0.001
Synovitis score	0.0 ± 0.0	3.6 ± 0.6	<0.001	0.1 ± 0.1	4.7 ± 0.4	<0.001

MIA or saline (sham) was injected into the knee joint of rats, and histological analysis of the knee joints was performed 2 weeks after injection. All experiments were performed using 6-week-old rats after MIA or saline (sham) injection. The condition of the articular cartilage surface and cartilage morphology was graded as follows: grade 0 (surface intact and cartilage morphology intact), grade 1 (surface intact), grade 2 (surface discontinuity), grade 3 (vertical fissures), grade 4 (erosion), grade 5 (denudation), and grade 6 (deformation). The condition of synovitis was scored by 2 components: enlargement of the synovial lining cell layer from 0 (thickness 1–2 cells) to 3 (thickness ≥10 cells) and density of the cells from 0 (normal) to 3 (greatly increased). The total score of the 2 components (0–6) was used as an indication of the severity of synovitis. Data are presented as the mean ± SEM (wild-type sham: n = 6 and MIA: n = 8; TRPV4-KO sham: n = 8 and MIA: n = 7). Data were analyzed by a two-way ANOVA followed by the Tukey test in each group. No significant differences were observed between wild-type and TRPV4-KO MIA rats (cartilage grade: P = 0.89, synovitis score: P = 0.19).

ANOVA, analysis variance, TRPV4-KO, transient receptor potential vanilloid 4-knockout.