Protective effect of curcumin on experimentally induced arthritic rats: detailed histopathological study of the joints and white blood cell count

Abstract

Curcuma longa (turmeric) rhizomes contains curcumin, an active compound which possesses anti-inflammatory effects. Collagen-induced arthritis (CIA) is an accepted experimental animal model of rheumatoid arthritis. The present study aimed to observe the histological changes in the joints of experimental arthritic rats treated with curcumin. Twenty four male Sprague-Dawley (approximately 7 weeks-old) rats were randomly divided into four groups. Three groups were immunized with 150 µg collagen. All rats with established CIA, with arthritis scores exceeding 1, were orally treated with betamethasone (0.5 mg/ml/kg body weight), curcumin (110 mg/ml/kg body weight) or olive oil (1.0 ml/kg body weight) daily, for two weeks. One remaining group was kept as normal control. Treatment with 110 mg/ml/kg curcumin showed significant mean differences in the average white blood cell (WBC) count (p<0.05), cell infiltration, bone and cartilage erosion scores (p<0.05) compared to the olive oil treated group. Pannus formation scores showed that curcumin supplementation successfully suppressed the pannus formation process that occurred in the articular cartilage of the CIA joints. The mean difference for histological scores for the curcumin group was insignificant compared to the betamethasone treated group. It is concluded that supplementation of curcumin has protective effect on the histopathological and degenerative changes in the joints of CIA rats which was at par with betamethasone.

Keywords: arthritis; collagen; curcumin; experimental; histopathology; inflammation.

Figure 1. Bar chart of mean white blood cell (WBC) count at day 0, 14 and 28. Each bar represents mean ± SEM. Ctrl - control, beta - betamethasone, olive - olive oil, CL - curcumin groups.

* statistically significant difference compared to the olive oil (negative control) group

Figure 2. Bar charts for histological scores of the rats' ankle joints. A - cell infiltration, B - synovial hyperplasia, C - pannus formation, D - cartilage and bone erosion scores. Each bar represents mean ± SEM. Ctrl - control, beta - betamethasone, olive - olive oil, CL - curcumin groups.

* statistically significant difference compared to olive oil (negative control) group

Figure 3. Photomicrographs of (a) normal joint structure and (b) joint with inflammatory cells infiltration. Infiltration of inflammatory cells into the synovial tissue were shown by the black arrows. B - bone, C - cartilage, Sp - joint space, Syn - synovial tissue

Figure 4. Photomicrographs of (a) normal joint structure and (b) joint with synovial hyperplasia. Synovial hyperplasia is shown by the black arrows. B - bone, C - cartilage, Sp - joint space, Syn - synovial tissue

Figure 5. Photomicrographs of (a) normal articular cartilage and (b) articular cartilage with pannus. Pannus is formed on articular surface of cartilage (black arrows). B - bone, C - cartilage, Sp - joint space

Figure 6. Photomicrographs of (a) normal cartilage and bone and (b) eroded cartilage and eroded bone. Erosion on cartilage (thick arrows) and erosion bone (thin arrows) were shown. B - bone, C - cartilage, Sp - joint space