Polysaccharides of Atractylodes macrocephala Koidz alleviate bursa of Fabricius involution in Magang geese by inhibiting the Wnt signaling pathway

Involution of the bursa of Fabricius (BF) with increasing age in avian species leads to decreases in lymphocyte counts and pathogen recognition, thereby compromising immune function and increasing susceptibility to infections. Polysaccharides of Atractylodes macrocephala Koidz (PAMK), a major component of the traditional Chinese medicine Atractylodes macrocephala, increase immunity. This study aimed to explore the impact of PAMK on the BF during involution in Magang geese. Following the prefeeding period, 54 four-month-old Magang geese were selected for the experiment. These geese were evenly divided into three groups. Each group consisted of three replicates, with six geese per replicate. One group was immediately euthanized to collect serum and BF samples. The remaining 36 geese were further divided into two groups: one group was maintained on a standard diet, and the other group was provided a diet supplemented with 400 mg/kg PAMK. One month later, serum and BF samples were collected for analysis. Morphological, organ index and histological observations indicate that PAMK can alleviate the significant reduction in the organ index of the BF during the involution process in Magang geese and mitigate the disorder of follicular arrangement and the decrease in the ratio of the cortical area to the medullary area in the BF. Immunoglobulin and oxidative stress results revealed that PAMK can increase the levels of immunoglobulins and reduce oxidative stress in involuting Magang geese. Functional enrichment analysis revealed that the Wnt signaling pathway plays a significant role in alleviating the involution of the BF in Magang geese. Further cellular studies revealed that the addition of PAMK inhibited apoptosis and promoted cell cycle progression into the S and G2 phases. In summary, PAMK effectively mitigates the involution of the BF in Magang geese by inhibiting the Wnt signaling pathway, thereby enhancing humoral immunity and improving antioxidant status.