17β-estradiol ameliorates age-associated loss of fibroblast function by attenuating IFN-γ/STAT1-dependent miR-7 upregulation

Abstract

SummaryAge‐related defects in fibroblast differentiation and functionality were previously shown to be associated with impaired hyaluronan (HA) synthase 2 (HAS2) and epidermal growth factor receptor (EGFR) function, as a result of upregulated microRNA‐7 (miR‐7) expression. In aging fibroblasts, inhibiting miR‐7 prevented the dysregulation of the HA‐mediated CD44/EGFR signaling pathway. Here, we investigated transcriptional upregulation of miR‐7 and implicated the age‐associated over‐activation of JAK/STAT1 as a primary candidate. STAT1 binding sites were identified on the putative miR‐7 promoter and stimulation of fibroblasts with the inflammatory cytokine, interferon‐γ (IFN‐γ), significantly increased miR‐7 transcriptional activity and resulted in upregulated miR‐7 and loss of EGFR. Additionally, we demonstrated a role for the anti‐inflammatory steroid, 17β‐estradiol (E2), in the attenuation of miR‐7 expression. E2 stimulation promoted estrogen receptor (ER) interactions with the miR‐7 putative promoter and suppressed miR‐7 expression. E2 also attenuated STAT1 expression and activity. Furthermore, treatments with E2 restored fibroblast functionality, including proliferation, migration and differentiation, key events in effective wound healing. In light of our findings, we propose that the regulation of miR‐7 by pro‐ and anti‐inflammatory mediators plays a wider role than previously thought. The modulation of fibroblast functions and ultimately wound healing by miR‐7 activators or inhibitors could provide realistic targets for the restoration of chronic wound healing capabilities in the elderly.

Estrogen Effects on Wound Healing

“…The influence of estrogen on wound healing was investigated in the animal model in 1947 [ 50 ] and in humans in 1953 [ 51 ]. Afterwards, much evidence supports that the estrogen is important on wound healing [ 31 , 41 , 42 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 , 61 ]. It has been shown that primary estrogen deficiency contributes to cutaneous aging and delayed wound repair or impaired wound healing [ 41 , 42 ].…”

Acidic extracellular environment affects miRNA expression in tumors in vitro and in vivo

“…Different aspects have to be considered when explaining this discrepancy between in vivo and in vitro results especially for miR‐7. On the one hand, other factors regulating the miR‐7 expression have been described, for instance INF‐γ or oleic acid . The in vitro experiments were performed in the absence of fetal calf serum (FCS) which is different from the situation in vivo , were many cytokines or growth factors are present.…”

“…On the one hand, other factors regulating the miR-7 expression have been described, for instance INF-γ or oleic acid. 48,49 The in vitro experiments were performed in the absence of fetal calf serum (FCS) which is different from the situation in vivo, were many cytokines or growth factors are present. Since it is known that cytokines affect the expression of miRNAs, it was tried to minimize the impact of these factors on the results of the in vitro experiments.…”

The effect of miR-146a on STAT1 expression and apoptosis in acute lymphoblastic leukemia Jurkat cells

“…Experiments using mutant cell lines and knockout mice have shown that STAT1 plays a significant role in interferon (IFN)-γ and IFN-α/β mediated signaling. The activity of STAT1 is tightly regulated by multiple mechanisms including post-translational modification, regulatory proteins and modulation by other STAT family members (13–15). In a previous study, it was shown that (16) miR-146a can influence STAT1 activity via multiple pathways.…”