The intervention effect of nicotine on cervical fibroblast-myofibroblast differentiation in lipopolysaccharide-induced preterm birth model through activating the TGF-β1/Smad3 pathway

Currently, the clinical treatment of preterm birth, mainly using uterine contraction inhibitors, does not fundamentally reduce the incidence of premature birth (PTB). Premature cervical ripening is an important factor in PTB. We previously found that nicotine-treated pregnant murine had significant cervical resistance to stretch and higher collagen cross-links compared to the control animals, and nicotine prolonged gestation and inhibited cervical ripening. However, the regulatory effects of nicotine on premature cervical ripening and its role in PTB remain unclear. To investigate the effects of nicotine on cervical TGF-beta 1/Smad3 pathway and fibroblastmyofibroblast differentiation regulated by this pathway in PTB-like models. Intraperitoneal injection with 15 mu g lipopolysaccharide (LPS) in 200 mu l PBS into pregnant mice was used to induce the PTB-like model. Mice were randomly divided into four groups: control group, LPS-treated group, LPS + Nicotine co-treated group and LPS + Nicotine+alpha-BGT co-treated group. Pregnancy outcomes were monitored. The collagen content was assessed by Picrosirius red staining. Expressions of genes and proteins in the TGF-beta/Smad3 pathway were detected by double immunofluorescence staining and quantitative Real-time PCR (qRT-PCR). myofibroblast differentiation were investigated by double immunofluorescence staining and qRT-PCR. Ultrastructures were analyzed by conventional transmission electron microscopy. The rate of PTB and neonatal mortality at birth was significantly higher in the LPS-treated group than in the control group; collagen content also decreased remarkably; the expression of TGF-beta 1 in macrophages and p-Smad3 in fibroblasts were reduced; the expression of alpha-smooth muscle actin (alpha-SMA, markers for activated fibroblasts) was down-regulated while the expression of calponin and smoothelin (markers for fibroblasts at rest) was up-regulated. Nicotine improved pregnancy outcomes and inhibited collagen degradation, activated the TGF-beta 1/Smad3 pathway and promoted cervical fibroblast-myofibroblast differentiation in PTB-like mice; such effects could be reversed by alpha-bungarotoxin (alpha-BGT). Nicotine inhibited premature cervical ripening in PTB-like models in relation with up-regulating the TGF-beta/Smad3 pathway and promoting fibroblast to differentiate into myofibroblasts.