Jellyfish mucin may have potential disease-modifying effects on osteoarthritis

Abstract

Background: We aimed to study the effects of intra-articular injection of jellyfish mucin (qniumucin) on articular cartilage degeneration in a model of osteoarthritis (OA) created in rabbit knees by resection of the anterior cruciate ligament. Qniumucin was extracted from Aurelia aurita (moon jellyfish) and Stomolophus nomurai (Nomura's jellyfish) and purified by ion exchange chromatography. The OA model used 36 knees in 18 Japanese white rabbits. Purified qniumucin extracts from S. nomurai or A. aurita were used at 1 mg/ml. Rabbits were divided into four groups: a control (C) group injected with saline; a hyaluronic acid (HA)-only group (H group); two qniumucin-only groups (M groups); and two qniumucin + HA groups (MH groups). One milligram of each solution was injected intra-articularly once a week for 5 consecutive weeks, starting from 4 weeks after surgery. Ten weeks after surgery, the articular cartilage was evaluated macroscopically and histologically.

Results: In the C and M groups, macroscopic cartilage defects extended to the subchondral bone medially and laterally. When the H and both MH groups were compared, only minor cartilage degeneration was observed in groups treated with qniumucin in contrast to the group without qniumucin. Histologically, densely safranin-O-stained cartilage layers were observed in the H and two MH groups, but cartilage was strongly maintained in both MH groups.

Conclusion: At the concentrations of qniumucin used in this study, injection together with HA inhibited articular cartilage degeneration in this model of OA.

Figure 1

Nomura's jellyfish. The world's largest jellyfish, growing to over 1 m in diameter and weighing more than 200 kg.

Figure 2

Macroscopic findings in the femur of the knee joint 10 weeks after OA model preparation. a (group C): Cartilage defects are observed on both the medial and lateral sides. These extend to the subchondral bone and range across the entire weight-bearing area. b (group H): Irregularity of the cartilage surface is apparent on both medial and lateral sides in the photo. A cartilage defect extending to the subchondral bone can be seen in some sections. c, d (group M1, moon jellyfish extract; group M2, Nomura's jellyfish extract, respectively): As with group C, a cartilage defect extending to the subchondral bone is observed. No difference is apparent in the range of the defect. e, f (group MH1, moon jellyfish extract; group MH2, Nomura's jellyfish extract, respectively): Irregularity of the cartilage surface is apparent on the medial side in the photo. No exposure of the subchondral bone is observed and the range of the defect is very limited. No differences are seen in the M or MH groups where the qniumucin had been extracted from the two different species of jellyfish. Arrowheads indicate areas of exposed subchondral bone.

Figure 3

Histological findings. The femoral condyle in the knee joint was resected and fixed in 4% neutral-buffered formalin (pH 7.4). The tissue was then decalcified with 10% EDTA and the cross-section was embedded in paraffin wax. Dewaxed sections were processed for safranin-O (a--f) and toluidine blue (g--l) staining. a (group C): The cartilage defect reaches the subchondral bone. b (group H): The fissure in the cartilage extends to the deep layer and reduced staining is observed in the upper layer from the tide mark. Cell sequences are not maintained and a reduction in the number of cells is observed. c, d (group M1, moon jellyfish extract; group M2, Nomura's jellyfish extract, respectively): Only a small portion of the cartilage layer remains and the cells have been obliterated. e, f (group MH1, moon jellyfish extract; group MH2, Nomura's jellyfish extract, respectively): Peeled cartilage layers are seen, but fissure have generally extended to the middle layer. Cell sequences are relatively well maintained and the reduction in staining is minor compared with that in group H. g (group C): No metachromasia is observed with toluidine blue staining in the cartilage layer. h (group H): Slight metachromasia is observed in the cartilage layer. i, j (group M1, moon jellyfish extract; group M2, Nomura's jellyfish extract, respectively): No metachromasia is observed in the cartilage layer. k, l (group MH1, moon jellyfish extract; group MH2, Nomura's jellyfish extract, respectively): The cartilage layer shows metachromasia with toluidine blue staining, which is specific for articular cartilage. Magnification: a-l, × 4; m-r, × 10.

Figure 4

Osteoarthritis score. Samples were histologically evaluated based on the standard grading and staging of OA cartilage histopathology. Evaluation was quantified using the following formula: most degenerated site in the cartilage (grades 1-6, Table 2) × area of degeneration (stages 1-4, Table 3) = OA score (1-24, Table 3). Columns and vertical lines represent mean values and standard deviations for each group, respectively. No significant differences were observed between group C and groups M1 and M2. Significant differences were observed between groups H and C, between groups H and M1 or M2, between groups H and MH1, and between groups M1 or M2 and groups MH1 or MH2. *Significant differences between groups, corresponding to the last column in Table 1. After analysis of variance, least significant differences were used for post hoc testing (Scheffé's method). Mean OA scores were compared and values of * P < 0.05 were considered significant. Groups M1 and MH1: moon jellyfish extract. Groups M2 and MH2: Nomura's jellyfish extract.

Figure 5

Protocol. Intra-articular injections were commenced from week 4 after preparation of the osteoarthritis (OA) model. Treatment solutions were injected once weekly until week 8. The rabbits were killed 10 weeks after surgery. Surgery and intra-articular injections were performed with the rabbits under general anesthesia. ACL-T, anterior cruciate ligament transection.