Macrophage-colony stimulating factor (M-CSF) regulates the expression of fibronectin and its alpha5 integrin receptor in human trophoblasts

Interleukin-34 Stimulates Gut Fibroblasts to Produce Collagen Synthesis

BACKGROUND AND AIM

The mechanisms underlying the formation of intestinal fibrostrictures [FS] in Crohn's disease [CD] are not fully understood, but activation of fibroblasts and excessive collagen deposition are supposed to contribute to the development of FS. Here we investigated whether interleukin-34 [IL-34], a cytokine that is over-produced in CD, regulates collagen production by gut fibroblasts.

METHODS

IL-34 and its receptor macrophage colony-stimulating factor receptor 1 [M-CSFR-1] were evaluated in inflammatory [I], FS CD, and control [CTR] ileal mucosal samples by real-time polymerase chain reaction [RT-PCR], western blotting, and immunohistochemistry. IL-34 and M-CSFR-1 expression was evaluated in normal and FS CD fibroblasts. Control fibroblasts were stimulated with IL-34 in the presence or absence of a MAP kinase p38 inhibitor, and FS CD fibroblasts were cultured with a specific IL-34 antisense oligonucleotide, and collagen production was evaluated by RT-PCR, western blotting, and Sircol assay. The effect of IL-34 on the wound healing capacity of fibroblasts was evaluated by scratch test.

RESULTS

We showed enhanced M-CSFR-1 and IL-34 RNA and protein expression in FS CD mucosal samples as compared with ICD and CTR samples. Immunohistochemical analysis showed that stromal cells were positive for M-CSFR-1 and IL-34. Enhanced M-CSFR-1 and IL-34 RNA and protein expression was seen in FS CD fibroblasts as compared with CTR. Stimulation of control fibroblasts with IL-34 enhanced COL1A1 and COL3A1 expression and secretion of collagen through a p38 MAP kinase-dependent mechanism, and wound healing. IL-34 knockdown in FS CD fibroblasts was associated with reduced collagen production and wound repair.

CONCLUSIONS

Data indicate a prominent role of IL-34 in the control of intestinal fibrogenesis.

Fibronectin in Cancer: Friend or Foe

The role of fibronectin (FN) in tumorigenesis and malignant progression has been highly controversial. Cancerous FN plays a tumor-suppressive role, whereas it is pro-metastatic and associated with poor prognosis. Interestingly, FN matrix deposited in the tumor microenvironments (TMEs) promotes tumor progression but is paradoxically related to a better prognosis. Here, we justify how FN impacts tumor transformation and subsequently metastatic progression. Next, we try to reconcile and rationalize the seemingly conflicting roles of FN in cancer and TMEs. Finally, we propose future perspectives for potential FN-based therapeutic strategies.

Changes in gene expression following long-term in vitro exposure of Macaca mulatta trophoblast stem cells to biologically relevant levels of endocrine disruptors

Trophoblast stem cells (TSCs) are crucial for embryo implantation and placentation. Environmental toxicants that compromise TSC function could impact fetal viability, pregnancy, and progeny health. Understanding the effects of low, chronic EDC exposures on TSCs and pregnancy is a priority in developmental toxicology. Differences in early implantation between primates and other mammals make a nonhuman primate model ideal. We examined effects of chronic low-level exposure to atrazine, tributyltin, bisphenol A, bis(2-ethylhexyl) phthalate, and perfluorooctanoic acid on rhesus monkey TSCs in vitro by RNA sequencing. Pathway analysis of affected genes revealed negative effects on cytokine signaling related to anti-viral response, most strongly for atrazine and tributyltin, but shared with the other three EDCs. Other affected processes included metabolism, DNA repair, and cell migration. Low-level chronic exposure of primate TSCs to EDCs may thus compromise trophoblast development in vivo, inhibit responses to infection, and negatively affect embryo implantation and pregnancy.

Cationic antimicrobial peptide, magainin down-regulates secretion of pro-inflammatory cytokines by early placental cytotrophoblasts

BACKGROUND

Human placental villous cytotrophoblasts exhibit relative externalization of negatively charged moieties to the outer leaflet of the plasma membrane during the time of syncytialization rendering their reactivity to positively charged cationic antimicrobial peptides (CAMPs) during the window of implantation and early placentation. Vaginal administration of a synthetic CAMP, Ala(8,13,18)-magainin II amide (AMA) inhibited blastocyst implantation and early placentation in monkeys. Furthermore, the administration of AMA resulted in significant inhibition of cell differentiation, enhancement in apoptosis and loss of viability in first trimester placental villous cytotrophoblasts in primary culture. The present study examines the effect of in vitro application of different doses (0, 1, 10, 100, 1000 ng/ml) of AMA on the secreted cytokine profiles of cytotrophoblasts obtained from placental villi samples (n = 13) collected during 8-9 weeks of gestation and grown on three-dimensional collagen matrix in vitro.

METHODS

A panel of forty-eight (48) cytokines in conditioned medium was analysed using multiplex immunoassays technique. Further, the steady state transcript levels of four cytokines (CCL4, CCL5, IL1B, IL6), the concentrations of which were affected by AMA in the isolated cytotrophoblasts, as well as, two cytokines (IL1A and TNF) which were not affected by AMA were estimated. Input list of cytokines secreted by cytotrophoblasts and showing differential secretion in response to AMA were used in enrichment analysis for the generation of biological networks.

RESULTS

Placental cytotrophoblasts secreted 27 cytokines, 13 of which are affected by AMA in vitro with significantly decreased secretion of CCLs-2, 3, 4, 5, CXCLs-1 and 8, FGF2 and MCSF and that of IL1B, IL6 and MIF, and increased secretion of IL16 and IL-2RA. Of the above cytokines showing differential secretion, only IL-2RA, IL16 and MIF showed significant correspondence in the steady state expression of their respective transcript levels. Post-hoc Enrichment analysis revealed Toll-like receptor (TLR) mediated pathways were the top-scored target pathways that were affected by AMA.

CONCLUSIONS

Administration of a CAMP causes shift in the balance of immune-inflammatory responses involving downstream pathways of TLRs in cytotrophoblast function. Further verification of functions of placental trophoblasts on administration of CAMP with pregnancy outcome is necessary.

Effect of danazol on NK cells and cytokines in the mouse uterus

Danazol, which has been used as a medicine for endometriosis, has a valid effect in pretreatment of patients receiving in vitro fertilization and embryo transfer, although its reproductive mechanism remains unclear. BALB/c mice were subcutaneously injected with danazol for 2 weeks. Blood and uteri were collected and cytokines were assayed. Following danazol treatment, an increase in pregnancy ratio was evident that was accompanied by up-regulation in serum macrophage-colony stimulating factor (M-CSF). RT-PCR analysis revealed that expression of M-CSF and Ly49, a phenotypic marker of natural killer (NK) cells, was up-regulated in the uteri of the danazol-treated mice. In immunohistochemical analysis, M-CSF and Ly49, together with alpha5 integrin, were clearly detected in the endometrium of the danazol-treated mice with very similar pattern of localization. These results suggest that danazol has an effect to promote pregnancy that induces recruitment of NK cells and a concomitant increase in the expression of M-CSF and alpha5 integrin in the uterus.

The fibronectin receptor alpha5 integrin subunit is upregulated by cell-cell adhesion via a cyclic AMP-dependent mechanism: implications for human trophoblast migration

Cell adhesion molecules are implicated in the mechanisms regulating trophoblast migration during human embryo implantation and placentation. We investigated the expression and subcellular organization of the fibronectin receptor alpha5 integrin subunit during the differentiation of human trophoblasts in vitro, and the role of cyclic adenosine monophosphate (cAMP) in the process. Human trophoblasts isolated from chorionic villi expressed no alpha5 integrin, but the molecule was upregulated as cells aggregated in vitro. Low levels of expression of alpha5 integrin subunit and a diffuse cellular distribution pattern were seen in migrating mononuclear trophoblasts. Formation of cell aggregates was accompanied by increased expression of the alpha5 integrin, which translocated to the cytoskeleton-bound pool of proteins and clustered within focal adhesion plaques on the cell surface. This coincided with increased binding to fibronectin. In the absence of cell-cell adhesion, trophoblasts did not display an increase in alpha5 integrin messenger RNA or protein and there was no alpha5 integrin in focal adhesion plaques, suggesting that cell-cell contacts specifically trigger the upregulation of alpha5 integrin subunit and its subcellular translocation. Cyclic AMP is the second messenger mediating the aggregation-induced increase in alpha5 integrin: cAMP increased the de novo synthesis of alpha5 integrin protein, particularly in mononuclear cells, whereas the aggregation-induced increase in alpha5 integrin was strongly inhibited by the antagonist Rp-cAMP in aggregating cells. Our data provide evidence that the alpha5 integrin mediates binding of human trophoblasts to fibronectin and is implicated in the regulation of trophoblast migration. This integrin's expression is specifically triggered by cell-cell adhesion and regulated via cAMP-mediated pathway(s). It is hypothesized that these mechanisms may play an important role in the molecular events controlling human placentation.

Dynamic regulation of expression of colony-stimulating factor 1 in the reproductive tract of cattle during the estrous cycle and in pregnancy

Colony-stimulating factor 1 (CSF-1) is a hematopoetic cytokine that also plays an important role in placental physiology. We report here the molecular cloning of two alternative splice variants of the bovine gene coding for a putative secreted and a membrane-bound form of the cytokine and the dynamic regulation of expression in the reproductive tract of cattle during the estrous cycle and pregnancy. Bovine CSF-1 was expressed mainly as the 3- and 4-kilobase (kb) transcripts, but 1.4- and 0.8-kb mRNAs were also detected in Day 50-70 pregnant uterine tissue. During the estrous cycle, both the 4- and 3-kb mRNAs were present, but the 3-kb putative membrane-bound form was more abundant than the 4-kb secreted form during diestrus. This pattern of expression was reversed in pregnancy, so that the exponential increase in CSF-1 expression seen during pregnancy was due predominantly to increased abundance of the 4-kb transcript. The change in the 4-kb:3-kb ratio was detected between Day 14 and Day 17, approximately the time of maternal recognition of pregnancy. Thus, CSF-1 was identified as one gene whose expression in the uterus might be altered early in response to the presence of the conceptus. CSF-1 was also expressed in the extraembryonic membranes of the conceptus and in the trophoblastic cells of the fetal cotyledons after the formation of the placentomes. The high level of CSF-1 expression during bovine pregnancy in uteroplacental tissues is consistent with its proposed role in placental physiology.

Expression of the alpha 5 integrin subunit gene promoter is positively regulated by the extracellular matrix component fibronectin through the transcription factor Sp1 in corneal epithelial cells in vitro

The accumulation of fibronectin (FN) in response to corneal epithelium injury has been postulated to turn on expression of the FN-binding integrin alpha(5)beta(1). In this work, we determined whether the activity directed by the alpha(5) gene promoter can be modulated by FN in rabbit corneal epithelial cells (RCEC). The activity driven by chloramphenicol acetyltransferase/alpha(5) promoter-bearing plasmids was drastically increased when transfected into RCEC grown on FN-coated culture dishes. The promoter sequence mediating FN responsiveness was shown to bear a perfect inverted repeat that we designated the fibronectin-responsive element (FRE). Analyses in electrophoretic mobility shift assays provided evidence that Sp1 is the predominant transcription factor binding the FRE. Its DNA binding affinity was found to be increased when RCEC are grown on FN-coated dishes. The addition of the MEK kinase inhibitor PD98059 abolished FN responsiveness suggesting that alteration in the state of phosphorylation of Sp1 likely accounts for its increased binding to the alpha(5) FRE. The FRE also proved sufficient to confer FN responsiveness to an otherwise unresponsive heterologous promoter. However, site-directed mutagenesis indicated that only the 3' half-site of the FRE was required to direct FN responsiveness. Collectively, binding of FN to its alpha(5)beta(1) integrin activates a signal transduction pathway that results in the transcriptional activation of the alpha(5) gene likely through altering the phosphorylation state of Sp1.

The role of integrins in reproduction

Fertilization, implantation, and placentation are dynamic cellular events that require not only synchrony between the maternal environment and the embryo, but also complex cell-to-cell communication. This communication involves integrins, a large family of proteins involved in the attachment, migration, invasion, and control of cellular function. Over the past decade, investigators have learned that integrins participate in multiple reproductive events including fertilization, implantation, and placentation in many species. This review will describe: (i) the expression of integrins on gametes and during the establishment and development of the placenta; (ii) regulatory pathways for controlling expression of integrins in the uterus and developing placenta; (iii) the function of integrins as determined by null-mutations; and (iv) reproductive dysfunction in women related to inappropriate integrin expression in the uterus and/or placenta.