Objective      To determine the role and significance of the balance of Treg/Th17 cells in pathogenesis of aplastic anemia (AA)

and to investigate the regulatory effect of umbilical cord-derived mesenchymal stem cells (UC-MSCs) on the

ratio of Treg/Th17 cells in patients with AA.        Methods      UC-MSCs were isolated

cultured and identified in vitro. Flow cytometry (FCM) was used to detect the percentage of Treg cells and Th17 cells in the peripheral blood mononuclear cells (PBMCs) from 10 healthy volunteers and 15 AA patients

respectively by FCM

and the ratio of Treg/Th17 cells was compared. After PBMCs of the patients with AA was cultured solely or co-cultured with UC-MSCs for 72 h

the percentages of Treg and Th17 cells in PBMCs

and the ratio of Treg/Th17 were compared respectively in the PBMCs in present or absent of UC-MSCs.        Results      FCM indicated that the obtained MSCs were ≥98% positive to CD90 and CD105

and ≤1% positive to CD34 and CD45. The percentage of Treg cells was significantly lower

while that of Th17 cells was significantly higher in the peripheral blood samples from AA patients than those from healthy control group (

P

0.05)

and the ratio of Treg/Th17 cells was significantly lower in the patients than the normal control (

P

0.05). After the PBMCs from AA patients were co-cultured with UC-MSCs

the percentage of Treg cells was significantly higher

while the percentage of Th17 cells was significantly lower than those without co-culture (

P

0.05)

and the ratio of Treg/Th17 cells was also significantly increased (

P

0.05).        Conclusion      There is a differential imbalance between Treg cells and Th17 cells in the peripheral blood from AA patients. UC-MSCs may regulate the imbalance by inducing the production and aggregation of Treg cells

and thus

restore the imbalance to some extent.