Boiogito, a Kampo medicine, improves hydrarthrosis in a rat model of knee osteoarthritis

Abstract

Background: Hydrarthrosis, which is associated with knee pain and limited range of motion, decreases the quality of life (QOL) of patients with osteoarthritis (OA). The Kampo medicine boiogito is prescribed for the treatment of knee OA with hydrarthrosis; however, its precise mechanisms of action remain unknown. The purposes of this study were to assess the pharmacological effects of boiogito and its mechanisms of action on joint effusion in rats with surgically induced OA.

Methods: A rat OA model was produced by transecting the anterior (cranial) cruciate ligament, medial collateral ligament, and medial meniscus in the right knee joints of 7-week-old female Wistar rats. The rats were given chow containing boiogito (1 or 2%) or indomethacin (0.002 %) for 4 weeks after surgical transection. Levels of interleukin-1β (IL-1β) and hyaluronic acid (HA) were measured by enzyme-linked immunosorbent assay. Knee joint pain was assessed using an incapacitance tester. Osmotic water permeability in cultured rabbit synovial cells was assessed using stopped-flow analysis.

Results: Increased synovial fluid volume and knee joint pain were observed in rats with surgically induced OA. In rats with OA, levels of IL-1β and HA in the articular cavity were higher but concentration of HA in synovial fluid was lower than in sham-operated rats, suggesting excessive synovial fluid secretion. Administration of boiogito improved hydrarthrosis, IL-1β, and HA concentrations and alleviated knee joint pain in rats with OA. Indomethacin reduced IL-1β and knee joint pain but failed to improve hydrarthrosis or HA concentration in rats with OA. Osmotic water permeability in synovial cells, which is related to the function of the water channel aquaporin, was decreased by treatment with boiogito.

Conclusion: Boiogito ameliorates the increased knee joint effusion in rats with OA by suppressing pro-inflammatory cytokine IL-1β production in the articular cavity and regulating function of water transport in the synovium. The improvement of hydrarthrosis by boiogito results in the increased HA concentration in synovial fluid, thus reducing joint pain. Boiogito may be a clinically useful treatment of QOL in patients with OA with hydrarthrosis.

Fig. 1

A three-dimensional high-performance liquid chromatography profile of boiogito, provided by Tsumura & Co

Fig. 2

Effects of boiogito and indomethacin on hydrarthrosis in a rat model of knee osteoarthritis (OA). Rats with OA were given chow containing boiogito (1 or 2 %, n = 12) or indomethacin (Ind; 0.002 %, n = 11) for 4 weeks. Increased synovial fluid volume and interleukin-1β in the articular cavity were observed in rats with surgically induced OA. a: Synovial fluid volume in rats with OA was decreased by boiogito. b: The level of interleukin-1β in the articular cavity in rats with OA was reduced by boiogito and Ind. Results are expressed as mean ± standard error (SE). ^## P < 0.01 vs. sham-operated rats (Sham, n = 8), *P < 0.05, **P < 0.01 vs. non-treated control rats with OA (Con, n = 12)

Fig. 3

Effects of boiogito and indomethacin on hyaluronic acid (HA) in a rat model of knee osteoarthritis (OA). The contents of HA in the articular cavity (a) were increased but HA concentrations in the synovial fluid (b) were decreased in rats with OA (Con, n = 12) compared with those in sham-operated rats (Sham, n = 8). Daily administration of boiogito (2 %, n = 12) did not change the HA content but recovered the decreased HA concentration in synovial fluid. These parameters were not influenced by indomethacin (Ind, n = 11). Results are expressed as mean ± SE. ^## P < 0.01 vs. Sham, **P < 0.01 vs. non-treated control rats with OA (Con)

Fig. 4

Effects of boiogito and indomethacin on gene expressions in the synovial membranes in a rat model of knee osteoarthritis (OA). Data are shown as the relative mRNA expression of matrix metalloprotease 3 (MMP3; a), hyaluronan synthase 2 (HAS2; b), hyaluronidase 1 (HYAL1; c) and aquaporin 1 (AQP1; d), normalized to reference gene of beta actin (ACTB). The expressions of MMP3 (a) and HAS2 (b) increased and that of HYAL1 (c) decreased in the synovial membranes of rats with OA (Con, n = 12) compared with those of sham-operated rats (Sham, n = 8). Expressions of these genes were not influenced by boiogito (n = 12). Indomethacin (Ind, n = 11) decreased HAS2 mRNA and slightly increased AQP1 mRNA in the synovial membranes of rats with OA. Results are expressed as mean ± SE. ^## P < 0.01 vs. Sham, *P < 0.05, **P < 0.01 vs. non-treated control rats with OA (Con)

Fig. 5

Effects of boiogito and indomethacin on joint pain in a rat model of knee osteoarthritis (OA). Joint pain was assessed by the weight ratio of the right (osteoarthritic) to left (contralateral control) hind limbs using an incapacitance tester. Rats with OA showed weight-bearing deficits associated with knee pain. Boiogito (n = 12) and indomethacin (n = 11) significantly alleviated weight-bearing deficits in rats with OA. Results are expressed as mean ± SE. ^## P < 0.01 vs. sham-operated rats (Sham, n = 8), *P < 0.05, **P < 0.01 vs. non-treated control rats with OA (Con, n = 12)

Fig. 6

Effect of boiogito on water permeability in cultured synovial cells. a Boiogito (0.25–1 mg/mL) and the aquaporin inhibitor mercuric chloride (10 μmol/L) inhibited water permeability in synovial cells (n = 8–9). b, c Sinomenium Stem, one of six boiogito constituents, decreased water permeability of the synovial cells (n = 4–5) in a dose-dependent manner (n = 4–6). Results are expressed as mean ± SE. *P < 0.05, **P < 0.01 vs. vehicle