To investigate the interventional and protective effects of Secale cereale pollen on chondrocyte inflammation and knee osteoarthritis in rats.

In vitro experiment, a chondrocyte inflammation model was established by inducing mouse chondrocyte line ATDC5 with 10 μg/mL lipopolysaccharide(LPS). The experiment was divided into 3 groups: Blank control group, model group (LPS-induced) and experimental groups (LPS+Secale cereale pollen at concentrations of 0, 0.25, 0.50 and 1.00 μg/mL). Reverse transcription-quantitative polymerase chain reaction was performed to detect the gene expressions of inflammatory factors including interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), nerve growth factor(NGF), prostaglandin E₂ (PGE₂), cyclooxygenase-2 (COX-2), as well as cartilage matrix metalloproteinases-1/-2/-3(MMP-1, MMP-2 and MMP-3). In vivo experiment, a knee osteoarthritis model was constructed in SD rats via intra-articular injection of type Ⅱ collagenase. The rats were randomly assigned to 4 groups: Blank control group, model group, positive control group treated with celecoxib at 18 mg/(kg·d), and Secale cereale pollen group treated with 0.167 g/(kg·d). All treatments were administered via gavage for 4 consecutive weeks. Joint swelling was evaluated by measuring the joint circumference. Histopathological changes of the knee joint were observed using histological staining. The levels of IL-2, TNF-α and COX in the synovial tissue of rats were determined by enzyme-linked immunosorbent assay (ELISA), and the expressions of collagen type Ⅱ alpha 1 chain (COL2A1) and matrix metalloproteinase-13 (MMP-13) were detected by immunohistochemistry.

The in vitro results showed that Secale cereale pollen at mass concentrations ranging from 0.2500 to 1.0000 μg/mL promoted chondrocyte proliferation, and dose-dependently down-regulated the gene expressions of LPS-induced pro-inflammatory factors (IL-1β, IL-6, TNF-α, PGE₂) and matrix metalloproteinases (MMP-1/2/3). At the mass concentration of 1 μg/mL, the expressions of the aforementioned genes were restored to the level of the negative control group, while the COX-2 gene expression showed no significant change (P>0.05). The in vivo results demonstrated that the relative difference in joint circumference of rats in the Secale cereale pollen group decreased significantly from (5.84±0.60) mm in the model group to (3.12±0.46) mm (P<0.001), indicating an obvious improvement in joint swelling. Pathological sections of the knee joint revealed ameliorated roughness and folds of the cartilage surface, reduced synovial hyperplasia area, and scattered inflammatory cell infiltration. The Mankin score of the Secale cereale pollen group was significantly lower than that of the model group (P<0.05). The serum COX level decreased from 1.30±0.01 to 1.19±0.01 (P<0.05), whereas the levels of IL-2 and TNF-α showed a slight downward trend without statistical significance (P>0.05). Immunohistochemical results indicated that the positive staining area of COL2A1, a protein related to cartilage matrix synthesis, was increased, while that of MMP13, a protein associated with cartilage matrix degradation, was reduced, thus achieving a bidirectional regulation of cartilage matrix metabolism characterized by “promoting synthesis and inhibiting degradation”.

Secale cereale pollen can inhibit LPS-induced chondrocyte inflammation and matrix degradation, alleviate the pathological severity of knee osteoarthritis in rats, and regulate the metabolic balance of cartilage matrix, thereby exerting interventional and protective effects against osteoarthritis.