We have reported that mPGES-1/PGE2 induced blood flow recovery from ischemia by promoting accumulation of Tregs. Expression of chemokines and the SDF-1/CXCR4 axis has been implicated in Tregs migration in angiogenesis. Therefore, we examined whether the SDF-1/CXCR4 axis plays a role in the accumulation of Tregs in angiogenesis.
Male 6-8 week-old wild-type mice (WT), mPGES-1-deficient mice (mPges-1-/-) were used. Recovery from ischemia was estimated by laser Doppler imaging. Contribution of Tregs was estimated by immunohistichemical study against FoxP3.The expression of Sdf-1 and Cxcr4 in ischemic muscle and accumulated Tregs were estimated by real time RT-PCR. The function of Tregs was estimated by in vitro suppression assay.
In WT, recovery from ischemia was significantly suppressed in CXCR4 antibody treated mice compared to Control IgG. In contrast, there was no significant changes in mPges-1-/-. In ischemic muscle tissue, expression of Sdf-1 and Cxcr4 mRNA was significantly decreased in mPges-1-/- mice compared with WT mice. In accumulated CD4+CD25+ Tregs in ischemic muscle tissue, expression of Cxcr4 mRNA was significantly decreased in mPges-1-/- mice compared with WT mice. Furthermore, in vitro analysis revealed that expression of Cxcr4 mRNA was induced in Tregs from WT mice upon anti-CD3 stimulation but not in Tregs from mPges-1-/- mice. In vitro suppression assay showed there was no difference in Treg function between WT and mPges-1-/- mice.
These results suggested that SDF-1/CXCR4 axis induces ischemic recovery by the accumulation of Tregs in ischemic muscle which was depended on mPGES-1/PGE2 axis.