OBJECTIVETo observe the effect of Modified Zuoguiwan (MZ) on the balance between helper T cell subsets 17 (Th17) and regulatory T cell subsets (Treg) in estrogen deficiency induced bone loss mice and to explore its mechanism.

METHODSTotally 50 BALB/c mice were divided into the sham-operation group, the ovariectomy model group, the low dose MZ group, the middle dose MZ group, and the high dose MZ group by random digit table, 10 in each group. Mice in the low, middle, and high dose MZ groups were respectively administered with MZ at the daily dose of 7.25, 14.50, and 29.00 g/kg by gastrogavage, 0.5 mL each time for 12 successive weeks. Meanwhile, mice in the sham-operation group and the ovariectomy model group were administered with equal volume by gastrogavage, 0.50 mL each time. The serum estradiol (E2) level was assessed by enzyme linked immunosorbent assay (ELISA). Bone mineral density (BMD) of thigh bone was measured with dual energy X ray absorptiometry. In addition, the population of Th17/Treg subsets in spleen mononuclear cells was analyzed by extracellular and intracellular staining method using flow cytometry. Moreover, the mRNA expression of IL-17A and TGF-β in the spleen mononuclear cells was detected by reverse transcription polymerase chain reaction (RT-PCR).

RESULTSCompared with the sham-operation group, both E2 and BMD significantly decreased, the percentage of Th17 subset and Th17/Treg ratio both increased, the percentage of Treg subset obviously decreased, the expression of IL-17A mRNA significantly increased, and the expression of TGF-β mRNA significantly decreased in the ovariectomy model group (all P < 0.05). Compared with the model group, BMD obviously increased, the percentage of Th17 subset and Th17/Treg ratio both decreased, the percentage of Treg subset obviously increased, the expression of IL-17A mRNA significantly decreased, and the expression of TGF-β mRNA significantly increased in the middle dose MZ group and the high dose MZ group (all P < 0. 05). Correlation analyses showed that BMD was positively related to both the serum E2 level and the percentage of Treg subset (P < 0.05), but negatively related to the percentage of Th17 subset (P < 0.05). In addition, the serum E2 level was positively related to the percentage of Treg subset, but obviously negatively related to that of Th17 subset (P < 0.05).

CONCLUSIONSThere was correlation between Th17/Treg imbalance and E2 deficient bone loss. MZ could decrease the proportion of Th17 subset, but elevate the proportion of Treg subset in E2 deficient bone loss mice. It could achieve therapeutic effect through adjusting the balance of Th17/Treg in E2 deficient bone loss mice.