Semaphorin 7a Expression Research Articles

Semaphorin 7a participants in pterygium by regulating vascular endothelial growth factor.

To investigate the relationship between semaphorin 7a expression and cell proliferation and migration in pterygium fibroblasts. Twenty-six patients with surgically diagnosed pterygium were enrolled, including 15 cases of primary pterygium and 11 cases of recurrent pterygium. In addition, 12 cases of normal conjunctival tissue were collected. The expression of semaphorin 7a in normal conjunctival tissue, primary pterygium and recurrent pterygium was detected by real-time polymerase chain reaction. Recurrent pterygium fibroblasts were isolated and cultured, and the expression of semaphorin 7a was silenced by small interfering RNA (siRNA) interference technique. Furthermore, the effects of si-semaphorin 7a interference on the mRNA and protein levels of β1-integrin, vascular endothelial growth factor A (VEGFA) and vascular endothelial growth factor receptor (VEGFR), and on fibroblast proliferation were analyzed. Transwell assay was used to detect the effect of semaphorin 7a interference on fibroblast migration. Semaphorin 7a was highly expressed in the primary pterygium and recurrent pterygium samples than that of the normal conjunctival tissue. Compared with the primary pterygium, the expression of semaphoring 7a in the recurrent pterygium samples was significantly increased (P<0.05). The mRNA and protein expression levels of β1-integrin, VEGFA and VEGFR were decreased after si-semaphorin 7a transfection, and as well as the cell proliferation and migration. Semaphorin 7a might play important roles in the pathogenesis of pterygium by affecting the expression of β1-integrin, VEGFA and VEGFR.

Semaphorin 7A promotes EGFR-TKI resistance in EGFR mutant lung adenocarcinoma cells.

Although responses to EGFR tyrosine kinase inhibitors (EGFR-TKIs) are initially positive, 30%-40% of patients with EGFR-mutant tumors do not respond well to EGFR-TKIs, and most lung cancer patients harboring EGFR mutations experience relapse with resistance. Therefore, it is necessary to identify not only the mechanisms underlying EGFR-TKI resistance, but also potentially novel therapeutic targets and/or predictive biomarkers for EGFR-mutant lung adenocarcinoma. We found that the GPI-anchored protein semaphorin 7A (SEMA7A) is highly induced by the EGFR pathway, via mTOR signaling, and that expression levels of SEMA7A in human lung adenocarcinoma specimens were correlated with mTOR activation. Investigations using cell culture and animal models demonstrated that loss or overexpression of SEMA7A made cells less or more resistant to EGFR-TKIs, respectively. The resistance was due to the inhibition of apoptosis by aberrant activation of ERK. The ERK signal was suppressed by knockdown of integrin β1 (ITGB1). Furthermore, in patients with EGFR mutant tumors, higher SEMA7A expression in clinical samples predicted poorer response to EGFR-TKI treatment. Collectively, these data show that the SEMA7A-ITGB1 axis plays pivotal roles in EGFR-TKI resistance mediated by ERK activation and apoptosis inhibition. Moreover, our results reveal the potential utility of SEMA7A not only as a predictive biomarker, but also as a potentially novel therapeutic target in EGFR-mutant lung adenocarcinoma.

Effect of dexmedetomidine on expression of Semaphorin 7A during lung ischemia-reperfusion in rats

Objective To evaluate the effect of dexmedetomidine on the expression of Semaphorin 7A during lung ischemia-reperfusion(I/R)in rats. Methods Thirty healthy clean-grade adult male Sprague-Dawley rats, aged 8-12 weeks, weighing 200-240 g, were divided into 3 groups (n=10 each) using a random number table method: sham operation group (S group), I/R group and dexmedetomidine group (D group). Only sternotomy was performed, and the left hilum of lung was not clamped in S group.The model of lung I/R injury was established by clamping the left hilum of lung for 45 min followed by 120 min of reperfusion in I/R group.Dexmedetomidine 50 μg/kg was intraperitoneally injected at 30 min before ischemia, and then the model was established in D group.The rats were sacrificed at the end of reperfusion, and the lungs were removed for examination of the pathological changes(using haematoxylin and eosin staining)which were scored and for determination of the wet to dry weight ratio (W/D ratio), expression of Semaphorin 7A protein and mRNA (by Western blot or real-time polymerase chain reaction), and contents of tumor necrosis factor-alpha (TNF-α) and interleukin-1beta (IL-1β) in lung tissues (by enzyme-linked immunosorbent assay). Results Compared with S group, W/D ratio and pathological scores were significantly increased, the expression of Semaphorin 7A protein and mRNA was up-regulated, and the contents of TNF-α and IL-1β were increased in I/R and D groups (P<0.05). Compared with I/R group, W/D ratio and pathological scores were significantly decreased, the expression of Semaphorin 7A protein and mRNA was down-regulated, and the contents of TNF-α and IL-1β were decreased in D group (P<0.05). Conclusion The mechanism by which dexmedetomidine reduces lung I/R injury may be related to down-regulating Semaphorin 7A expression, thus inhibiting inflammatory responses of rats. Key words: Semaphorins; Dexmedetomidine; Reperfusion injury; Lung

Abstract B54: Investigating semaphorin 7a in hormone receptor-positive breast cancer progression

Abstract While antiestrogen-based treatments are initially effective for hormone receptor-positive (HR+) breast cancer, these tumors often recur, metastasize, and lose responsiveness to endocrine therapies, emphasizing the need for additional therapeutic targets in HR+ disease. We observe that semaphorin 7a (SEMA7A) expression in HR+ patients in the METABRIC dataset confers significantly decreased survival rates by Kaplan-Meier analysis. Thus, we hypothesize that SEMA7A is a potential biomarker for aggressive disease and/or a novel therapeutic target for recurrent HR+ breast cancer. Utilizing multiple 2D and 3D in vitro approaches with human and mouse HR+ tumor cells, we show that shRNA-mediated knockdown (KD) of SEMA7A results in cell growth defects and reduced invasive potential. Loss of SEMA7A also increases apoptosis in attached and forced suspension culture conditions. Finally, we demonstrate that expression of SEMA7A is regulated by the ovarian hormones estrogen and progesterone in a receptor-dependent mechanism. However, we also observe increased expression of SEMA7A with stabilization of HIF1α, suggesting its expression may be context dependent. Overall, these data support SEMA7A as an important driver of multiple hallmarks of cancer in HR+ breast cancer, including cell growth, invasion, and resisting death. As SEMA7A expression is low in normal breast cells, it may be a novel therapeutic target with low toxic side effects. Citation Format: Lyndsey Crump, Alan Elder, Sarah Tarullo, Paris Franz, Traci Lyons. Investigating semaphorin 7a in hormone receptor-positive breast cancer progression [abstract]. In: Proceedings of the AACR Special Conference: Advances in Breast Cancer Research; 2017 Oct 7-10; Hollywood, CA. Philadelphia (PA): AACR; Mol Cancer Res 2018;16(8_Suppl):Abstract nr B54.

Semaphorin 7A in circulating regulatory T cells is increased in autosomal-dominant polycystic kidney disease and decreases with tolvaptan treatment.

Semaphorin 7A (SEMA7A) is an immunomodulating protein implicated in lung and liver fibrosis. In autosomal-dominant polycystic kidney disease (ADPKD), the progressive expansion of renal cysts, inflammation, and subsequent renal fibrosis leads to end-stage renal disease (ESRD). SEMA7A may play a role in renal fibrosis and in ADPKD. We evaluated Sema7a in a mouse model of renal fibrosis and determined the expression of SEMA7A in human ADPKD kidney. We analyzed SEMA7A expression on peripheral blood mononuclear cells (PBMCs), including CD45+ (leukocyte), CD14+(monocyte), CD4+ (T lymphocytes) and CD4+Foxp3+CD25+ [regulatory T lymphocytes (Tregs)] from 90 ADPKD patients (11 tolvaptan treated and 79 tolvaptan naïve), and 21 healthy volunteers, using a Fluorescence-Activated Cell Sorting (FACS). Sema7a is required for renal fibrosis. SEMA7A shows robust expression in ADPKD kidneys, localizing to cysts derived from distal tubules. SEMA7A is higher in circulating monocytes, but unchanged in CD4+ lymphocytes in ADPKD patients. The SEMA7A increase was detected early (stage 1 CKD) and seemed more prominent in patients with smaller kidneys (p = 0.09). Compared to tolvaptan-naïve ADPKD patients, those treated with tolvaptan showed reduced SEMA7A expression on monocytes, T lymphocytes, and Tregs, although the number of PBMCs was unchanged. After 1month of tolvaptan treatment, SEMA7A expression on Tregs decreased. SEMA7A shows potential as both a therapeutic target in mammalian kidney fibrosis and as a marker of inflammation in ADPKD patients. SEMA7A expression was lower after tolvaptan treatment, which may reflect drug efficacy.

Anti-Semaphorin-7A single chain antibody demonstrates beneficial effects on pulmonary inflammation during acute lung injury.

Pulmonary inflammation is a primary characteristic of lung injury initiated by the accession of immune cells into the alveolar space. Neutrophil migration serves an important role in pulmonary inflammation mediated by the migration of neutrophils into hypoxic tissue sites. The elimination of pulmonary inflammation is directly associated with rehabilitation in patients with lung injury. Anti-inflammatory treatment is essential following lung injury and ultimately determines patient outcomes. Semaphorin-7A (SEMA-7A) is a member of the Semaphorin family that influences the migration of neutrophils into hypoxic tissue sites, thus promoting inflammation. However, understanding of the role of SEMA-7A serves during lung injury is limited and the immunological function of SEMA-7A during the migration of neutrophils into acute injury sites remains unknown. The present study investigated SEMA-7A expression and constructed a single chain antibody for SEMA-7A (Anti-SEMA-7A) to study its therapeutic efficacy against pulmonary inflammation in a mouse model of acute injury sites. The data indicated that the expression of SEMA-7A was upregulated due to induction by pro-inflammatory cytokines and demonstrated that Anti-SEMA-7A inhibited SEMA-7A expression in vitro and in vivo. The current study also indicated that the production of pro-inflammatory cytokines induced by SEMA-7A in endothelial and epithelial cells enhanced pulmonary inflammation. Anti-SEMA-7A suppressed the transendothelial migration of neutrophils mediated by SEMA-7A. Anti-SEMA-7A treatment neutralized SEMA-7A expression and reduced signs of pulmonary inflammation, leading to the elimination of pulmonary inflammation in rat with acute lung injury. The current study identified Anti-SEMA-7A as a potential agent to interfere with the inflammatory pathway during acute lung injury, which may be the basis for anti-inflammatory strategies to treat lung injuries in the future.

Semaphorin 7a exerts pleiotropic effects to promote breast tumor progression.

Understanding what drives breast tumor progression is of utmost importance for blocking tumor metastasis; we have identified that semaphorin 7a is a potent driver of ductal carcinoma in situ (DCIS) progression. Semaphorin 7a is a GPI membrane anchored protein that promotes attachment and spreading in multiple cell types. Here we show that increased expression of SEMA7A occurs in a large percentage of breast cancers and is associated with decreased overall and distant metastasis free survival. In both in vitro and in vivo models, shRNA mediated silencing of SEMA7A reveals roles for semaphorin 7a in the promotion of DCIS growth, motility, and invasion as well as lymphangiogenesis in the tumor microenvironment. Our studies also uncover a relationship between COX-2 and semaphorin 7a expression and suggest that semaphorin 7a promotes tumor cell invasion on collagen and lymphangiogenesis via activation of β1-integrin receptor. Our results suggest that semaphorin 7a, may be novel target for blocking breast tumor progression.

Abstract B15: Semaphorin 7a exerts pleiotropic effects to promote breast tumor progression

Abstract Understanding what drives breast tumor progression is of utmost importance for blocking tumor metastasis. We have identified that semaphorin 7a is a potent driver of breast tumor progression. Semaphorin 7a is a GPI membrane anchored protein that promotes attachment and spreading in multiple cell types. We observe that increased expression of SEMA7A occurs in ~45%human breast cancers and its upregulation is associated with decreased overall and distant metastasis free survival. In both in vitro and in vivo models, shRNA mediated silencing reveals roles for semaphorin 7a in the promotion of breast cancer cell growth, motility, and invasion as well as in lymphangiogenesis. Our studies also uncover a relationship between COX-2 and semaphorin 7a expression, and suggest that semaphorin 7a promotes tumor cell invasion on collagen and lymphangiogenesis via activation of β1-integrin receptor. Our results suggest that semaphorin 7a, may be novel target for blocking breast tumor progression. Citation Format: Sarah Black, Andrew Nelson, Natalia Gurule, Bernard Futscher, Traci R. Lyons. Semaphorin 7a exerts pleiotropic effects to promote breast tumor progression. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Breast Cancer Research; Oct 17-20, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(2_Suppl):Abstract nr B15.

Semaphorin 7A Aggravates Pulmonary Inflammation during Lung Injury

The extent of pulmonary inflammation during lung injury ultimately determines patient outcome. Pulmonary inflammation is initiated by the migration of neutrophils into the alveolar space. Recent work has demonstrated that the guidance protein semaphorin 7A (SEMA7A) influences the migration of neutrophils into hypoxic tissue sites, yet, its role during lung injury is not well understood. Here, we report that the expression of SEMA7A is induced in vitro through pro-inflammatory cytokines. SEMA7A itself induces the production of pro-inflammatory cytokines in endothelial and epithelial cells, enhancing pulmonary inflammation. The induction of SEMA7A facilitates the transendothelial migration of neutrophils. In vivo, animals with deletion of SEMA7A expression showed reduced signs of pulmonary inflammatory changes following lipopolysaccharide challenge. We define here the role of SEMA7A in the development of lung injury and identify a potential pathway to interfere with these detrimental changes. Future anti-inflammatory strategies for the treatment of lung injury might be based on this finding.

Gene Expression of Semaphorin 7A During Osteogenic Differentiation in Human Dental Follicle Cells

Gene Expression of Semaphorin 7A During Osteogenic Differentiation in Human Dental Follicle Cells

Semaphorin 7A plays a critical role in IgE-mediated airway inflammation in mice

Elevated allergen-specific IgE levels are a hallmark of allergic asthma, a disease involving chronic airway inflammation characterized by airway hyperresponsiveness (AHR); neutrophilic airway inflammation is found in patients with severe asthma. Furthermore, we have reported that interleukin (IL)-33 and IL-17A contribute to IgE-mediated AHR through neutrophilic inflammation in mice. Meanwhile, semaphorins regulating neuronal and immune function have been focused on in several diseases. Here, we investigated whether semaphorin 7A (SEMA7A) is related to IgE-mediated neutrophilic inflammation in mice. BALB/c mice sensitized with antigen-specific IgE monoclonal antibody were repeatedly challenged by the antigen. When anti-SEMA7A antibody was administered during the fourth to seventh challenges, the infiltration by macrophages, lymphocytes, neutrophils, and eosinophils in the lungs was reduced at the seventh challenge (P<0.05, 0.05, 0.01, and 0.05, respectively). However, the increased production of IL-4, IL-5, IL-13, IL-33, IL-17A, IL-6, and CXCL1 in the lungs was not suppressed. In histological analysis, the epithelial cells, blood vessels, and inflammatory cells in the lungs of IgE-sensitized mice showed SEMA7A expression; plexin C1 for the receptor was expressed in the inflammatory cells. Meanwhile, we examined the effect of anti-SEMA7A antibody on AHR and neutrophilic inflammation enhanced by the collaborative action of IL-33 and IL-17A in normal mice, resulting in the suppression of these responses (P<0.05 and 0.01, respectively). Collectively, we demonstrated that SEMA7A plays a critical role in IgE-mediated neutrophilic airway inflammation. Therefore, SEMA7A may be a potential therapeutic target for severe allergic asthma showing neutrophilic airway inflammation.

Semaphorin7A Inhibition interrupts hypoxia induction of angiogenic factors in murine monocytes (TUM6P.963)

Abstract We discovered that mammary tumor cells express high levels of the protein Semaphorin7A (SEMA7A) and that tumor-derived SEMA7A induces monocytes to secrete pro-angiogenic chemokines to enhance tumor growth. Decreased SEMA7A limits tumor growth and production of angiogenic CXCL-2/MIP-2 and VEGF-A by monocytes. The mechanisms controlling SEMA7A expression during tumor progression are largely unknown. Recent reports describe a hypoxia responsive element in the promoter of SEMA7A. It is well established that hypoxia enhances tumor growth by promoting angiogenesis and alternatively activating monocytes. We hypothesize that SEMA7A may be a hypoxia-inducible factor and its inhibition may deter production of monocyte-derived angiogenic proteins. Monocytes from wild-type (WT) and SEMA7A null BALB/c mice were exposed to CoCl2-induced hypoxia. CoCl2 induced expression of SEMA7A in both mammary cells and WT monocytes. Following hypoxic stimuli, WT monocytes increased production of CXCL2/MIP-2, VEGF-A and Chitinase-3-like protein1 (CHI3L1). However, SEMA7A null monocytes failed to respond to hypoxia, which may be attributed to an impaired MAPK signaling response. Thus, inhibiting SEMA7A may abrogate the detrimental effects of tumor induced hypoxia on monocytes. We are further delineating how the lack of host SEMA7A can impact mammary tumor growth in vivo. Understanding the role of SEMA7A may unravel important tumor-host immune interactions in breast cancer.

Semaphorin7A regulates neuroglial plasticity in the adult hypothalamic median eminence.

Reproductive competence in mammals depends on the projection of gonadotropin-releasing hormone (GnRH) neurons to the hypothalamic median eminence (ME) and the timely release of GnRH into the hypothalamic–pituitary–gonadal axis. In adult rodents, GnRH neurons and the specialized glial cells named tanycytes periodically undergo cytoskeletal plasticity. However, the mechanisms that regulate this plasticity are still largely unknown. We demonstrate that Semaphorin7A, expressed by tanycytes, plays a dual role, inducing the retraction of GnRH terminals and promoting their ensheathment by tanycytic end feet via the receptors PlexinC1 and Itgb1, respectively. Moreover, Semaphorin7A expression is regulated during the oestrous cycle by the fluctuating levels of gonadal steroids. Genetic invalidation of Semaphorin7A receptors in mice induces neuronal and glial rearrangements in the ME and abolishes normal oestrous cyclicity and fertility. These results show a role for Semaphorin7A signalling in mediating periodic neuroglial remodelling in the adult ME during the ovarian cycle.

Endothelial Semaphorin 7A promotes inflammation in seawater aspiration-induced acute lung injury.

Inflammation is involved in the pathogenesis of seawater aspiration-induced acute lung injury (ALI). Although several studies have shown that Semaphorin 7A (SEMA7A) promotes inflammation, there are limited reports regarding immunological function of SEMA7A in seawater aspiration-induced ALI. Therefore, we investigated the role of SEMA7A during seawater aspiration-induced ALI. Male Sprague–Dawley rats were underwent seawater instillation. Then, lung samples were collected at an indicated time for analysis. In addition, rat pulmonary microvascular endothelial cells (RPMVECs) were cultured and then stimulated with 25% seawater for indicated time point. After these treatments, cells samples were collected for analysis. In vivo, seawater instillation induced lung histopathologic changes, pro-inflammation cytokines release and increased expression of SEMA7A. In vitro, seawater stimulation led to pro-inflammation cytokine release, cytoskeleton remodeling and increased monolayer permeability in pulmonary microvascular endothelial cells. In addition, knockdown of hypoxia-inducible factor (HIF)-1α inhibited the seawater induced increase expression of SEMA7A. Meanwhile, knockdown of SEMA7A by specific siRNA inhibited the seawater induced aberrant inflammation, endothelial cytoskeleton remodeling and endothelial permeability. These results suggest that SEMA7A is critical in the development of lung inflammation and pulmonary edema in seawater aspiration-induced ALI, and may be a therapeutic target for this disease.

Abstract 2007: Hypoxia induced TGF-β regulates Semaphorin7A to promote a pro-tumorigenic mesenchymal phenotype in mammary cells

Abstract The study of breast cancer relies heavily upon the identification of tumor-associated proteins that are involved with tumor growth and development. Our lab has discovered that mammary tumor cells express high levels of a novel protein known as Semaphorin7A (SEMA7A). After analyzing breast tissue samples collected at Boca Raton Regional Hospital, we have found that normal human mammary epithelial cells express negligible mRNA levels of SEMA7A, while the malignant mammary tumor cells express elevated levels of SEMA7A. Additionally, our laboratory has established a murine model of mammary cell lines that parallels our human findings. Currently, we have correlated high levels of SEMA7A with increasing tumor malignancy and metastasis. However, it is still unknown what factors could induce the production of SEMA7A in mammary tumors. Recent studies have proven that the expression and induction of SEMA7A in normal endothelial cells is regulated under a hypoxic-response element in the promoter of its gene. Although hypoxia is an established tumorigenic factor, it is unknown if the increased hypoxic conditions in breast tumors could induce SEMA7A. In this study we have investigated if exposing mammary cells to hypoxia induces the expression of pro-tumorgenic SEMA7A. Our results show that SEMA7A is up-regulated in 4T07 and 4T1 mammary tumor cells after hypoxic exposure via TGF-β activation of the PI3/AKT pathway. Furthermore, we have found that shRNA silencing of the SEMA7A in 4T1 mammary cells attenuates the activation of pro-angiogenic and mesenchymal genes even after hypoxic stimuli. In vivo, these cells show a reduced proliferation and metastatic potential. We therefore postulate an exciting new role for SEMA7A as a TGF-β effector that promotes tumorigenesis during breast cancer progression. Citation Format: Ramon A. Garcia-Areas, Stephania Libreros, Samantha Amat, Camila Castro-Silva, Kathy Schilling, Vijaya Iragavarapu-Charyulu. Hypoxia induced TGF-β regulates Semaphorin7A to promote a pro-tumorigenic mesenchymal phenotype in mammary cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2007. doi:10.1158/1538-7445.AM2014-2007

Semaphorin 7A Contributes to TGF-β–Mediated Liver Fibrogenesis

Semaphorin7A (SEMA7A) is a membrane-anchored protein involved in immune and inflammatory responses, exerting an effect on pulmonary fibrosis. Thus, we aimed to investigate the role of SEMA7A in hepatic fibrosis. Liver injury was induced invivo by carbon tetrachloride i.p. injection or bile duct ligation in wild-type and SEMA7A knockout (KO) mice. Human and mouse liver samples and primary mouse hepatic cell populations were used for Western blot analysis, quantitative real-time RT-PCR, and immunohistochemistry. SEMA7A is highly expressed in hepatic stellate cells (HSCs). The expression of SEMA7A and its receptor β1-integrin subunit increase during liver injury and in activated HSCs. Transforming growth factor β-stimulated HSCs showed increased expression of SEMA7A in a SMAD2/3-independent manner, leading to increased expression of fibrogenic and inflammation markers. This pattern was significantly blunted in SEMA7A KO HSCs. Overexpression of SEMA7A in HSCs showed increased fibrogenic and inflammation markers expression. Invivo, SEMA7A KO mice treated with carbon tetrachloride and bile duct ligation developed reduced fibrosis versus wild-type mice. Moreover, SEMA7A expression increased in liver samples of patients with fibrosis versus healthy controls. SEMA7A was expressed in the liver and was increased in the course of liver fibrosis, both in mice and in humans. SEMA7A was mainly expressed in HSCs with respect to other cell types in the liver and plays a critical role in regulating fibrosis.

Semaphorin-7a reverses the ERF-induced inhibition of EMT in Ras-dependent mouse mammary epithelial cells

Epithelial-to-mesenchymal transition (EMT) is a key process in cancer progression and metastasis, requiring cooperation of the epidermal growth factor/Ras with the transforming growth factor-β (TGF-β) signaling pathway in a multistep process. The molecular mechanisms by which Ras signaling contributes to EMT, however, remain elusive to a large extent. We therefore examined the transcriptional repressor Ets2-repressor factor (ERF)-a bona fide Ras-extracellular signal-regulated kinase/mitogen-activated protein kinase effector-for its ability to interfere with TGF-β-induced EMT in mammary epithelial cells (EpH4) expressing oncogenic Ras (EpRas). ERF-overexpressing EpRas cells failed to undergo TGF-β-induced EMT, formed three-dimensional tubular structures in collagen gels, and retained expression of epithelial markers. Transcriptome analysis indicated that TGF-β signaling through Smads was mostly unaffected, and ERF suppressed the TGF-β-induced EMT via Semaphorin-7a repression. Forced expression of Semaphorin-7a in ERF-overexpressing EpRas cells reestablished their ability to undergo EMT. In contrast, inhibition of Semaphorin-7a in the parental EpRas cells inhibited their ability to undergo TGF-β-induced EMT. Our data suggest that oncogenic Ras may play an additional role in EMT via the ERF, regulating Semaphorin-7a and providing a new interconnection between the Ras- and the TGF-β-signaling pathways.

Role of semaphorin 7a signaling in transforming growth factor β1–induced lung fibrosis and scleroderma‐related interstitial lung disease

Semaphorin 7a regulates transforming growth factor β1 (TGFβ1)-induced fibrosis. This study was undertaken to test the hypothesis that semaphorin 7a exerts its profibrotic effects in part by promoting the tissue accumulation of CD45+ fibrocytes. A murine model of pulmonary fibrosis in which an inducible, bioactive form of the human TGFβ1 gene is overexpressed in the lung was used. Fibrosis and fibrocytes were evaluated in TGFβ1-transgenic mice in which the semaphorin 7a locus had been disrupted. The effect of replacement or deletion of semaphorin 7a on bone marrow-derived cells was ascertained using bone marrow transplantation. The role of the semaphorin 7a receptor β1 integrin was assessed using neutralizing antibodies. The applicability of these findings to TGFβ1-driven fibrosis in humans was examined in patients with scleroderma-related interstitial lung disease (ILD). The appearance of fibrocytes in the lungs of TGFβ1-transgenic mice required semaphorin 7a. Replacement of semaphorin 7a on bone marrow-derived cells restored lung fibrosis and fibrocytes. Immunoneutralization of β1 integrin reduced pulmonary fibrocytes and fibrosis. Peripheral blood mononuclear cells (PBMCs) from patients with scleroderma-related ILD showed increased levels of messenger RNA for semaphorin 7a and its receptors, with semaphorin 7a located on collagen-producing fibrocytes and CD19+ lymphocytes. Peripheral blood fibrocyte outgrowth was enhanced in these patients. Stimulation of normal human PBMCs with recombinant semaphorin 7a enhanced fibrocyte differentiation; these effects were attenuated by β1 integrin neutralization. Our findings indicate that interventions that reduce semaphorin 7a expression or prevent the semaphorin 7a-β1 integrin interaction may ameliorate TGFβ1-driven or fibrocyte-associated autoimmune fibroses.

Odontoblast expression of semaphorin 7A during innervation of human dentin

Semaphorin 7A (SEMA 7A) is a membrane-anchored member of the semaphorin family of guidance proteins, previously identified in the immune system. Expressed in central and peripheral nervous system during embryonic and post-natal stages, it can mediate neuronal functions by promoting axonal growth. We show here that SEMA 7A is expressed in human odontoblasts in vivo and in vitro and that its expression is correlated with the establishment of dentin-pulp complex terminal innervation . Co-cultures of trigeminal ganglion (TG) with COS cells overexpressing SEMA 7A demonstrate that SEMA 7A can promote the growth of trigeminal nerve fibers. Finally, by RT-PCR and immunochemistry, we show that beta1-integrin, a SEMA 7A putative receptor, is expressed in pulpal nerve fibers but we failed to detect a co-localization between nerves and odontoblasts through these molecules. On the basis of these data, we suggest that SEMA 7A might be a molecule involved in the terminal innervation of the dentin-pulp complex.