STAT3 promotes bone fracture healing by enhancing the FOXP3 expression and the suppressive function of regulatory T cells

In this study, we examined STAT3‐mediated regulation of immunity in adult patients with closed tibia fracture. In all patients, the expression and activation of STAT3 peaked at around day 7 to day 14 after surgery, and gradually decreased during the rest of the healing period. At day 7 (peak STAT3 expression and phosphorylation), the CD4+CD25+ T cells from bone fracture patients presented the highest level of STAT3 activation among lymphocyte subsets. Therefore, we investigated the role of STAT3 in CD4+CD25+ T cells. The level of FOXP3 expression by CD4+CD25+ T cells was directly correlated with the level of STAT3 phosphorylation in these cells. The level of STAT3 phosphorylation in CD4+CD25+ T cells was also inversely correlated with the level of IFN‐γ and TNF‐α secretion in peripheral blood mononuclear cells. Inhibition of STAT3 significantly suppressed FOXP3 and IL‐10 expression by CD4+CD25+ T cells, as well as the ability of CD4+CD25+ T cells to suppress T‐cell IFN‐γ and TNF‐α secretion. Furthermore, early healers patients presented significantly higher STAT3 expression and phosphorylation than late healers, possibly due to the higher IL‐6 and IL‐10 levels in the serum of early healing patients. Together, these data demonstrated that STAT3 was beneficial to bone fracture healing, possibly by enhancing Treg‐mediated suppression of counteracting inflammations, and suggested that STAT3 could be used as a prognostic marker to identify otherwise undisti...

Source: APMIS - May 11, 2017 Category: Research Authors: Guojing Sun, Zhen Wang, Yunfan Ti, Yicun Wang, Jun Wang, Jianning Zhao, Hongbo Qian Tags: Original Article Source Type: research