Involvement of MAPK signalling in human villous trophoblast differentiation.

Human villous trophoblast differentiation is a complex and highly regulated process essential for the well-being of the pregnancy and fetal development. In this review, we present an overview of the role of MAPKs signalling in morphological and functional differentiation of villous trophoblast.

Mechanical strain increases cytokine and chemokine production in bronchial fibroblasts from asthmatic patients.

BACKGROUND: Mechanical strain and cytokine stimulation are two important mechanisms leading to airway remodeling in asthma. The effect of mechanical strain on cytokine secretion in airway fibroblasts is not known. The aim of this study was to determine whether bronchial and nasal fibroblasts differentially alter cytokine secretion in response to mechanical strain. METHODS: We measured secretion of the pro-fibrotic cytokine, interleukin-6 (IL-6), and the pro-inflammatory cytokines, IL-8 and monocyte chemotactic protein 1, before and after mechanical strain in bronchial fibroblasts obtained from asthmatic patients [asthmatic bronchial fibroblasts (BAF)] and normal volunteers [normal bronchial fibroblasts (BNF)], and in nasal fibroblasts (NF) obtained from nasal polyps. Cells were grown on flexible membranes and a mechanical strain of 30% amplitude, 1 Hz frequency was applied for 3, 6 and 24 h. Control cells were unstrained. IL-6, IL-8 and monocyte chemotactic protein 1 was measured after 24 h strain using enzyme-linked immunoassay; mRNA was measured by real time polymerase chain reaction. We also measured mRNA for versican, a matrix proteoglycan, known to be upregulated in the asthmatic airway wall. RESULTS: In unstrained conditions, no differences in cytokine secretion were observed. After 24 h strain, BAF secreted more IL-6 than BNF. Mechanical strain increased IL-8 mRNA in BAF, BNF and NF; and IL-6 and versican mRNA, in BAF, only. CONCLUSIONS: Cytokine responses to mechanical strain varied in different airway fibroblast populations, and depended on the site of origin, and the underlying inflammatory state. Strain resulted in IL-6 upregulation and increased message for extracellular matrix protein in bronchial fibroblasts from asthmatic patients only, and may reflect these patients' propensity for airway remodeling.

PP2 regulates human trophoblast cells differentiation by activating p38 and ERK1/2 and inhibiting FAK activation.

Throughout gestation, fetal growth and development depend, in part, on placental transfer of nutrients from the maternal circulation. This latter function depends on multinucleated, terminally differentiated syncytiotrophoblasts. In vitro, freshly isolated cytotrophoblast cells differentiate spontaneously into syncytiotrophoblast in the presence of fetal bovine serum (FBS). We have previously showed that trophoblast differentiation is regulated by ERK1/2 and p38. Moreover, we showed that PP2 [4-amino-5-(4-chlorophenyl)-7-(t-butyl)pyrazolo[3, 4-d]pyrimidine], a Src family kinase (SFK) specific inhibitor, stimulates biochemical trophoblast cells differentiation while it inhibits cell adhesion and spreading without affecting cell fusion. Therefore, we examined the mechanisms by which PP2 modulates trophoblast cells differentiation. This study shows that PP2 stimulates ERK1/2 and p38 activation after 24h of treatments and up to 3 days while it inhibits focal adhesion kinase (FAK) phosphorylation at many sites including Tyr-397, 407, 576 and 577. Furthermore, we showed that transient activation of ERK1/2 by FBS is independent of SFK and that PP2 induces rapid activation of p38. Moreover, the kinase activity of SFK is negatively regulated by the phosphorylation of their carboxy (C)-terminal regulatory tyrosines by specific proteins called carboxyl-terminal Src kinase (Csk) and Csk homologous kinase (CHK). We showed the expression of Csk and CHK in human trophoblast cells. In summary, this study showed that PP2 stimulates the biochemical differentiation of trophoblast cells by stimulating p38 and ERK1/2 while it inhibits the morphological differentiation by inhibiting FAK activation.

Induction of trophoblast cell fusion by a protein tyrosine phosphatase inhibitor.

In the placenta, trophoblast cell fusion leads to the formation of the syncytiotrophoblast, which plays an essential role in the diffusion of nutrients and hormones from the mother to the fetus. Different protein tyrosine kinases are involved in the modulation of this biological process. Herein, we investigated the impact of a protein tyrosine phosphatase (PTP) inhibitor (bpV[pic]) on trophoblast fusion. Upon bpV[pic] or forskolin treatment, primary and BeWo trophoblastic cells demonstrated higher cAMP levels and a more potent induction of cell fusion, while non-fusogenic JEG-3 cells were non-responsive to these treatments. RT-PCR analyses on stimulated BeWo cells or primary cytotrophoblast cells demonstrated an increase in syncytin-1 mRNA levels, which was more pronounced upon forskolin/bpV[pic] treatment. Using the luciferase gene upstream of the syncytin-1 promoter, similar results were obtained in BeWo cells after stimulation. These results demonstrate that PTPs act negatively on cell fusion in human trophoblasts and could control the timing of syncytiotrophoblast formation during placenta development.

Laminin-alpha6beta1 integrin interaction enhances survival and proliferation and modulates steroidogenesis of ovine granulosa cells.

This study aimed to determine the physiological role of laminin (LN) and its receptor, alpha(6)beta(1) integrin, in controlling the functions of granulosa cells (GC) during follicular development in sheep ovary. Immunohistochemistry experiments showed the presence of increasing levels of LN (P<0.0001), and high levels of mature alpha(6)beta(1) integrin in GC layers of healthy antral follicles during the follicular and the preovulatory phases of the estrous cycle. In vitro, the addition of a function-blocking antibody raised against alpha(6) subunit (anti-alpha(6) IgG) to the medium of ovine GC cultured on LN impaired cell spreading (P<0.0001), decreased the proliferation rate (P<0.05) and increased the apoptosis rate (P<0.05). Furthermore, addition of anti-alpha(6) IgG enhanced estradiol (E2) secretion by GC in the presence or absence of follicle-stimulating hormone (FSH), luteinizing hormone or insulin-like growth factor-I in culture medium (P<0.0001), and inhibited progesterone (P4) secretion in basal conditions or in the presence of low (0.5 ng/ml) FSH concentrations only (P<0.0001). The anti-alpha(6) IgG effect was specific to an interaction of LN with alpha(6)beta(1) integrin since it was ineffective on GC cultured on heat-denatured LN, RGD (arginine-glycine-aspartic acid) peptides and non-coated substratum. Hence, this study established that alpha(6)beta(1) integrin 1) was expressed in GC of antral follicles, 2) mediated the actions of LN on survival, proliferation and steroidogenesis of GC, and 3) was able to dramatically modulate P4 and E2 secretion by GC in vitro. It is suggested that during the follicular and the preovulatory phases of the estrous cycle, the increasing levels of LN in GC of large antral follicles might support their final development to ovulation.