[Imbalance of immunological functions of Treg and TGF-β1 aggravated cerebral ischemia damage in mice].

Aim: To investigate the changes of proportion of CD4(+);CD25(+); regulatory T cells (Treg) in Splenocytes and concentration of serum TGF-β1 in diverse period after transient middle cerebral artery occlusion(tMCAO) in mice and correlation between Treg and TGF-β1, so as to elucidate their roles in the immunological injury of acute ischemic stroke.

Methods: 60 male Kunming mice were randomly divided into six groups, i.e. sham group (24 h, n=10) and five tMCAO groups(ischemia/reperfusion 12 h, 24 h, 48 h, 72 h and 5 d, n=10/group), amount to six groups. The models of tMCAO were established by modified monofilament method; Neurologic deficit score was performed at each time point after tMCAO, and then, to sacrifice mice and measure the volume of cerebral infarction by TTC staining; the expression of Foxp3 in spleen was observed by frozen section and immunofluorescence method; the proportions of Treg in splenocytes were analyzed by flow cytometry(FCM) and the concentrations of serum TGF-β1 were measured by ELISA.

Results: This study observed that there was obvious immunological injury and it was gradually worse. Similarly, TTC staining indicated that the volume of cerebral infarction gradually enlarged and peaked at 48 h following reperfusion, subsequently, exhibited slight decrease. Neurological function gradually improved after reperfusion. There were positive expressions of Foxp3 in the mice spleens and significant different in every groups. FCM indicated, compared with sham group, the percentage of Treg was decrease at 24 h after ischemia/reperfusion (P<0.05), and recovered normal level at 72 h, and significantly increased at 5 d (P<0.05). The level of serum TGF-β1 also showed the similar tendency, the concentration of serum TGF-β1 was lower at 24 h after ischemia/reperfusion than sham group, and recovered to sham's level at 48 h, and was significantly higher at 5 d than sham group (P<0.05). Otherwise, there was a positive correlation between serum level of TGF-β1 and percentage of Treg.

Conclusion: The levels of Treg and TGF-β 1 were decrease in the acute period after ischemia/reperfusion, and they were significant increase in the recovery progress, which closely associated with the change of the ischemia volume. Therefore, Imbalance of Treg and TGF-β1 is very likely to play an important role in the immunological injury of acute ischemic stroke.