Objective: To observe the effects of acupuncture on synovial pathology, synovial mast cell degranulation and tryptase expression and to investigate the relationship between the functions of mast cells and effects of acupuncture on early adjuvant arthritis in rats.
Methods: Forty-six male Wistar rats were randomly divided into normal control group (n=16), untreated group (n=15) and acupuncture group (n=15). Adjuvant arthritis was induced by injection of 0.1 mL Freund's complete adjuvant in right hind limb footpad. Normal control group and untreated group received no acupuncture treatment, while rats in the acupuncture group were treated with sterilized disposable stainless steel needles inserted perpendicularly as deep as 2 to 3 mm at Xuanzhong (GB39), 6 mm at Shenshu (BL23) and 7 mm at Zusanli (ST36) for eight times (15 min each time) every two days. Setting the modeling day as the 0 day of the experiment, the body weight and paw volume of the rats were measured every three days from the 0 day. In the end, synovial tissues of the right hind ankles were sampled and made into paraffin sections. Then they were firstly stained with hematoxylin-eosin for observing synovial pathology to evaluate the effects of acupuncture on adjuvant arthritis, then stained with toluidine blue for observing the number and degranulation ratio of synovial mast cells and finally detected by immunohistochemical staining method to investigate the expression of tryptase in synovium.
Results: Compared with the untreated group, the body weight of rats in the acupuncture group was increased significantly (P<0.05), while the paw volume decreased obviously (P<0.01). Hematoxylin-eosin staining showed that acupuncture significantly inhibited inflammatory cell infiltration, synovial cell hyperplasia, and synovial fibroplasia in synovium of rats with adjuvant arthritis as compared with the untreated group (P<0.05). Toluidine blue staining showed that acupuncture could significantly diminish the numbers of total and degranulated mast cells in rats with adjuvant arthritis (P<0.01), which were significantly higher in the untreated group than in the normal control group (P<0.01). Showing by immunohistochemical staining, the expression of tryptase in synovium in the acupuncture group was decreased as compared with the untreated group (P<0.01). Analyzed by Spearman's bivariate correlation, the number of mast cells and degranulation ratio of mast cells were positively correlated with the pathological scores (r=0.837, P<0.01; r=0.634, P<0.01).
Conclusion: Acupuncture can improve pathological condition of inflammatory synovium in rats with early adjuvant arthritis by inhibiting the function of synovial mast cells, which may play an important underlying role in the immunoregulation of acupuncture on adjuvant arthritis.