Isolation of Enteric Glial Cells from the Submucosa and Lamina Propria of the Adult Mouse

The enteric nervous system (ENS) consists of neurons and enteric glial cells (EGCs) that reside within the smooth muscle wall, submucosa and lamina ...

University of Michigan

Stem cell factor (SCF) and its receptor c-Kit have been implicated in tissue remodelling and fibrosis. Alveolar fibroblasts from patients with diffuse interstitial fibrosis secrete more SCF. However, its precise role remains unclear. In this study the potential role of the SCF-c-Kit axis in pulmonary fibrosis was examined. Fibrosis was induced by intratracheal instillation of bleomycin (BLM), which caused increased SCF levels in plasma, bronchoalveolar lavage fluid (BALF) and lung tissue, as well as increased expression by lung fibroblasts. These changes were accompanied by increased numbers of bone marrow-derived c-Kit(+) cells in the lung, with corresponding depletion in bone marrow. Both recombinant SCF and lung extracts from BLM-treated animals induced bone-marrow cell migration, which was blocked by c-Kit inhibitor. The migrated cells promoted myofibroblast differentiation when co-cultured with fibroblasts, suggesting a paracrine pathogenic role. Interestingly, lung fibroblast cultures contained a subpopulation of cells that expressed functionally active c-Kit, which were significantly greater and more responsive to SCF induction when isolated from fibrotic lungs, including those from patients with idiopathic pulmonary fibrosis (IPF). This c-Kit(+) subpopulation was αSMA-negative and expressed lower levels of collagen I but significantly higher levels of TGFβ than c-Kit-negative cells. SCF deficiency achieved by intratracheal treatment with neutralizing anti-SCF antibody or by use of Kitl(Sl)/Kitl(Sl-d) mutant mice in vivo resulted in significant reduction in pulmonary fibrosis. Taken together, the SCF-c-Kit pathway was activated in BLM-injured lung and might play a direct role in pulmonary fibrosis by the recruitment of bone marrow progenitor cells capable of promoting lung myofibroblast differentiation.

Essential role of stem cell factor-c-Kit signalling pathway in bleomycin-induced pulmonary fibrosis.

In addition to its expression in stem cells and many cancers, telomerase activity is transiently induced in murine bleomycin (BLM)-induced pulmonary fibrosis with increased levels of telomerase transcriptase (TERT) expression, which is essential for fibrosis. To extend these observations to human chronic fibrotic lung disease, we investigated the expression of telomerase activity in lung fibroblasts from patients with interstitial lung diseases (ILDs), including idiopathic pulmonary fibrosis (IPF). The results showed that telomerase activity was induced in more than 66% of IPF lung fibroblast samples, in comparison with less than 29% from control samples, some of which were obtained from lung cancer resections. Less than 4% of the human IPF lung fibroblast samples exhibited shortened telomeres, whereas less than 6% of peripheral blood leukocyte samples from patients with IPF or hypersensitivity pneumonitis demonstrated shortened telomeres. Moreover, shortened telomeres in late-generation telomerase RNA component knockout mice did not exert a significant effect on BLM-induced pulmonary fibrosis. In contrast, TERT knockout mice exhibited deficient fibrosis that was independent of telomere length. Finally, TERT expression was up-regulated by a histone deacetylase inhibitor, while the induction of TERT in lung fibroblasts was associated with the binding of acetylated histone H3K9 to the TERT promoter region. These findings indicate that significant telomerase induction was evident in fibroblasts from fibrotic murine lungs and a majority of IPF lung samples, whereas telomere shortening was not a common finding in the human blood and lung fibroblast samples. Notably, the animal studies indicated that the pathogenesis of pulmonary fibrosis was independent of telomere length. 

Telomerase and telomere length in pulmonary fibrosis.

Bone marrow (BM)-derived cells have been implicated in pulmonary fibrosis. However, their precise role in pathogenesis is incompletely understood.

Lung bone marrow-derived hematopoietic progenitor cells enhance pulmonary fibrosis.

Hedgehog signaling plays important roles in cell development and differentiation. In this study, the ability of Sonic Hedgehog (SHH) to induce myofibroblast differentiation was analyzed in isolated human lung fibroblasts, and its in vivo significance was evaluated in rodent bleomycin-induced pulmonary fibrosis. The results showed that SHH could induce myofibroblast differentiation in human lung fibroblasts in a Smo- and Gli1-dependent manner. Gel shift analysis, chromatin immunoprecipitation assay, and site-directed mutagenesis revealed that a Gli1 binding consensus in the α-SMA gene promoter was important for mediating SHH-induced myofibroblast differentiation. Analysis of Hedgehog reemergence in vivo revealed that of all three Hedgehog isoforms, only SHH was significantly induced in bleomycin-injured lung along with Gli1. The induction of SHH was only noted in epithelial cells, and its expression was undetectable in lung fibroblasts or macrophages. transforming growth factor (TGF)-β induced SHH significantly in cultured alveolar epithelial cells, whereas SHH induced TGF-β in lung fibroblasts. Pulmonary fibrosis and α-smooth muscle actin (α-SMA) expression were significantly reduced in mice that were Smo deficient only in type I collagen-expressing cells. Thus, the reemergence of SHH in epithelial cells could result in induction of myofibroblast differentiation in a Smo-dependent manner and subsequent Gli1 activation of the α-SMA promoter.

Reemergence of hedgehog mediates epithelial-mesenchymal crosstalk in pulmonary fibrosis.

DNMT3A mutations are frequent in cytogenetically normal acute myeloid leukemia (cn-AML) patients and associated with poor survival. The role of allogeneic hematopoietic stem cell transplantation (allo-HSCT) in DNMT3A(mut) cn-AML patients remains unclear. In this study, we retrospectively analyzed the prognostic impact of DNMT3A mutations and explored the role of allo-HSCT in 308 cn-AML patients who received consolidation of intensive chemotherapy or allo-HSCT in our center from March 2005 to May 2014. In the whole cohort, 63 patients (20.5%) were identified with DNMT3A exon 23 mutations and R882H was the most frequent variant. DNMT3A(mut) patients had shorter overall survival (3-year OS: 31.9% vs. 52.0%, P = 0.009) and disease-free survival (3-year DFS: 21.8% vs. 40.1%, P = 0.004) compared with DNMT3A(wt) patients. Based on FLT3/NPM1/CEBPA mutations, 308 cn-AML patients were divided into favorable/intermediate group (n = 262) and unfavorable group (n = 46). There were no significant differences in 3-year OS and 3-year DFS between DNMT3A(mut) and DNMT3A(wt) patients in both favorable/intermediate and unfavorable groups. Additionally, in multivariate analysis, DNMT3A mutation remained an independent adverse prognostic factor for the survival. In the DNMT3A(mut) cohort, 23 complete remission (CR) patients received allo-HSCT consolidation and 32 CR patients received chemotherapy consolidation, dramatic differences were observed in 3-year OS (51.7% vs. 28.9%, P = 0.048) and 3-year DFS (41.6% vs. 14.9%, P = 0.024) between allo-HSCT group and chemotherapy group. Collectively, DNMT3A mutation is a poor prognostic factor for cn-AML patients and allo-HSCT could improve survival of cn-AML patients with DNMT3A mutations.

Allogeneic hematopoietic stem cell transplantation could improve survival of cytogenetically normal adult acute myeloid leukemia patients with DNMT3A mutations.

Telomerase is typically expressed in cellular populations capable of extended replication, such as germ cells, tumor cells, and stem cells, but is also induced in tissue injury, repair and fibrosis. Its catalytic component, telomerase reverse transcriptase (TERT) is induced in lung fibroblasts from patients with fibrotic interstitial lung disease and in rodents with bleomycin-induced pulmonary fibrosis. To evaluate the fibroblast specific role of TERT in pulmonary fibrosis, transgenic mice bearing a floxed TERT allele were generated, and then crossed with an inducible collagen α2(I)-Cre mouse line to generate fibroblast specific TERT conditional knockout mice. TERT-specific deficiency in mesenchymal cells caused attenuation of pulmonary fibrosis as manifested by reduced lung hydroxyproline content, type I collagen and α-smooth muscle actin mRNA levels. The TERT-deficient mouse lung fibroblasts displayed decreased cell proliferative capacity and higher susceptibility to induced apoptosis compared with control cells. Additionally TERT deficiency was associated with heightened α-smooth muscle actin expression indicative of myofibroblast differentiation. However the impairment of cell proliferation and increased susceptibility to apoptosis would cause a reduction in the myofibroblast progenitor population necessary to mount a successful myofibroblast-dependent fibrotic response. These findings identified a key role for TERT in fibroblast proliferation and survival essential for pulmonary fibrosis. 

Conditional Knockout of Telomerase Reverse Transcriptase in Mesenchymal Cells Impairs Mouse Pulmonary Fibrosis.

Intestinal metaplasia (IM) is a gastric cancer precursor lesion (GCPL) and an extremely high risk factor for progression to gastric cancer (GC). Clinical guidelines recommend that patients with extensive IM undergo a gastroscopy every 3 years. However, protein biomarkers that indicate a transition from IM to GC are lacking. Our group recently identified an interferon-alpha (IFNα)-responsive gene, Schlafen 4 (Slfn4), in immune cells that correlates with metaplastic changes in Helicobacter-infected mice. We therefore tested the hypothesis that a human homolog of Slfn4, namely, Schlafen 5 (SLFN5), correlates with progression of GCPL to GC.

SCHLAFEN 5 expression correlates with intestinal metaplasia that progresses to gastric cancer.

Amphiregulin (AREG), an epidermal growth factor receptor ligand, is implicated in tissue repair and fibrosis, but its cellular source and role in regeneration versus fibrosis remain unclear. In this study, we hypothesize that AREG induced in bone marrow-derived CD11c(+) cells is essential for pulmonary fibrosis. Thus, the objectives were to evaluate the importance and role of AREG in pulmonary fibrosis, identify the cellular source of AREG induction, and analyze its regulation of fibroblast function and activation. The results showed that lung AREG expression was significantly induced in bleomycin-induced pulmonary fibrosis. AREG deficiency in knockout mice significantly diminished pulmonary fibrosis. Analysis of AREG expression in major lung cell types revealed induction in fibrotic lungs predominantly occurred in CD11c(+) cells. Moreover, depletion of bone marrow-derived CD11c(+) cells suppressed both induction of lung AREG expression and pulmonary fibrosis. Conversely, adoptive transfer of bone marrow-derived CD11c(+) cells from bleomycin-treated donor mice exacerbated pulmonary fibrosis, but not if the donor cells were made AREG deficient prior to transfer. CD11c(+) cell-conditioned media or coculture stimulated fibroblast proliferation, activation, and myofibroblast differentiation in an AREG-dependent manner. Furthermore, recombinant AREG induced telomerase reverse transcriptase, which appeared to be essential for the proliferative effect. Finally, AREG significantly enhanced fibroblast motility, which was associated with increased expression of α6 integrin. These findings suggested that induced AREG specifically in recruited bone marrow-derived CD11c(+) cells promoted bleomycin-induced pulmonary fibrosis by activation of fibroblast telomerase reverse transcriptase-dependent proliferation, motility, and indirectly, myofibroblast differentiation.

Bone Marrow CD11c+ Cell-Derived Amphiregulin Promotes Pulmonary Fibrosis.

Chronic Helicobacter pylori infection triggers neoplastic transformation of the gastric mucosa in a small subset of patients, but the risk factors that induce progression to gastric metaplasia have not been identified. Prior to cancer development, the oxyntic gastric glands atrophy and are replaced by metaplastic cells in response to chronic gastritis. Previously, we identified schlafen 4 (Slfn4) as a GLI1 target gene and myeloid differentiation factor that correlates with spasmolytic polypeptide-expressing metaplasia (SPEM) in mice. Here, we tested the hypothesis that migration of SLFN4-expressing cells from the bone marrow to peripheral organs predicts preneoplastic changes in the gastric microenvironment. Lineage tracing in Helicobacter-infected Slfn4 reporter mice revealed that SLFN4+ cells migrated to the stomach, where they exhibited myeloid-derived suppressor cell (MDSC) markers and acquired the ability to inhibit T cell proliferation. SLFN4+ MDSCs were not observed in infected GLI1-deficient mice. Overexpression of sonic hedgehog ligand (SHH) in infected WT mice accelerated the appearance of SLFN4+ MDSCs in the gastric corpus. Similarly, in the stomachs of H. pylori-infected patients, the human SLFN4 ortholog SLFN12L colocalized to cells that expressed MDSC surface markers CD15+CD33+HLA-DRlo. Together, these results indicate that SLFN4 marks a GLI1-dependent population of MDSCs that predict a shift in the gastric mucosa to a metaplastic phenotype.

Schlafen 4-expressing myeloid-derived suppressor cells are induced during murine gastric metaplasia.

This review focuses on the various experimental models to study gastric cancer pathogenesis, with the role of genetically engineered mouse models (GEMMs) used as the major examples. We review differences in human stomach anatomy compared to the stomachs of the experimental models, including the mouse and invertebrate models such as Drosophila and C. elegans. The contribution of major signaling pathways, e.g., Notch, Hedgehog, AKT/PI3K is discussed in the context of their potential contribution to foregut tumorigenesis. We critically examine the rationale behind specific GEMMs, chemical carcinogens, dietary promoters, Helicobacter infection, and direct mutagenesis of relevant oncogenes and tumor suppressor that have been developed to study gastric cancer pathogenesis. Despite species differences, more efficient and effective models to test specific genes and pathways disrupted in human gastric carcinogenesis have yet to emerge. As we better understand these species differences, "humanized" versions of mouse models will more closely approximate human gastric cancer pathogenesis. Towards that end, epigenetic marks on chromatin, the gut microbiota, and ways of manipulating the immune system will likely move center stage, permitting greater overlap between rodent and human cancer phenotypes thus providing a unified progression model.

Recapitulating Human Gastric Cancer Pathogenesis: Experimental Models of Gastric Cancer.

Since its initial discovery in , Hedgehog (HH) signaling has long been associated with foregut development. The mammalian genome expresses 3 HH ligands, with sonic hedgehog (SHH) levels highest in the mucosa of the embryonic foregut. More recently, interest in the pathway has shifted to improving our understanding of its role in gastrointestinal cancers. The use of reporter mice proved instrumental in our ability to probe the expression pattern of SHH ligand and the cell types responding to canonical HH signaling during homeostasis, inflammation, and neoplastic transformation. SHH is highly expressed in parietal cells and is required for these cells to produce gastric acid. Furthermore, myofibroblasts are the predominant cell type responding to HH ligand in the uninfected stomach. Chronic infection caused by  and associated inflammation induces parietal cell atrophy and the expansion of metaplastic cell types, a precursor to gastric cancer in human subjects. During  infection in mice, canonical HH signaling is required for inflammatory cells to be recruited from the bone marrow to the stomach and for metaplastic development. Specifically, polarization of the invading myeloid cells to myeloid-derived suppressor cells requires the HH-regulated transcription factor GLI1, thereby creating a microenvironment favoring wound healing and neoplastic transformation. In mice, GLI1 mediates the phenotypic shift to gastric myeloid-derived suppressor cells by directly inducing  (). However, the human homologs of SLFN4, designated SLFN5 and SLFN12L, also correlate with intestinal metaplasia and could be used as biomarkers to predict the subset of individuals who might progress to gastric cancer and benefit from treatment with HH antagonists.

Hedgehog Signaling Links Chronic Inflammation to Gastric Cancer Precursor Lesions.

The multiple endocrine neoplasia, type 1 (MEN1) locus encodes the nuclear protein and tumor suppressor menin. MEN1 mutations frequently cause neuroendocrine tumors such as gastrinomas, characterized by their predominant duodenal location and local metastasis at time of diagnosis. Diffuse gastrin cell hyperplasia precedes the appearance of MEN1 gastrinomas, which develop within submucosal Brunner's glands. We investigated how menin regulates expression of the gastrin gene and induces generation of submucosal gastrin-expressing cell hyperplasia.

Gastrin Induces Nuclear Export and Proteasome Degradation of Menin in Enteric Glial Cells.

ZBP-89 () is a Kruppel-type zinc-finger family transcription factor that binds to GC-rich DNA elements. Earlier studies in cell lines demonstrated that ZBP-89 cooperates with Wnt β-catenin signaling by inducing β-catenin gene expression. Since β-catenin levels are normally highest at the crypt base, we examined whether ZBP-89 is required for stem cell maintenance. Lineage-tracing using a  transgenic line demonstrated expression in both intestine and colonic stem cells. Deleting the  locus in the colon using the  transgene, reduced the size and number of polyps formed in the -deleted mice. Since colon polyps form in the presence of butyrate, a short chain fatty acid that suppresses cell growth, we examined the direct effect of butyrate on colon organoid survival. Butyrate induced senescence of colon organoids carrying the  deletion, only when  was deleted. Using quantitative PCR and chromatin immunoprecipitation, we determined that butyrate treatment of colon cell lines suppressed  gene expression, inducing  ( ) gene expression. Collectively,  mRNA is expressed in CBCs, and is required for stem cell maintenance and colonic transformation. Butyrate induces colonic cell senescence in part through suppression of ZBP-89 gene expression and its subsequent occupancy of the  promoter.

Lin Ding

Department of Internal Medicine-Gastroenterology

University of Michigan

Isolation of Enteric Glial Cells from the Submucosa and Lamina Propria of the Adult Mouse

Lin Ding

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Internal Medicine-Gastroenterology

University of Michigan

Isolation of Enteric Glial Cells from the Submucosa and Lamina Propria of the Adult Mouse

Department of Internal Medicine-Gastroenterology