Nonviral CRISPR/Cas9 mutagenesis for streamlined generation of mouse lung cancer models.

Functional analysis in mouse models is necessary to establish the involvement of a set of genetic variations in tumor development. A modeling platform to facilitate and cost-effectively analyze the role of multiple genes in carcinogenesis would be valuable. Here, we present an innovative strategy for lung mutagenesis using CRISPR/Cas9 ribonucleoproteins delivered via cationic polymers. This approach allows the simultaneous inactivation of multiple genes. We validate the effectiveness of this system by targeting a group of tumor suppressor genes, specifically Rb1, Rbl1, Pten, and Trp53, which were chosen for their potential to cause lung tumors, namely small cell lung carcinoma (SCLC). Tumors with histologic and transcriptomic features of human SCLC emerged after intratracheal administration of CRISPR/polymer nanoparticles. These tumors carried loss-of-function mutations in all four tumor suppressor genes at the targeted positions. These findings were reproduced in two different pure genetic backgrounds. We provide a proof of principle for simplified modeling of lung tumorigenesis to facilitate functional testing of potential cancer-related genes.

Low Levels of Amyloid Precursor Protein (APP) Promote Neurogenesis and Decrease Gliogenesis in Human Neural Stem Cells.

Amyloid precursor protein (APP) has been widely studied due to its association with Alzheimer's disease (AD). However, the physiological functions of APP are still largely unexplored. APP is a transmembrane glycoprotein whose expression in humans is abundant in the central nervous system. Specifically, several studies have revealed the high expression of APP during brain development. Previous studies in our laboratory revealed that a transient increase in APP expression induces early cell cycle exit of human neural stem cells (hNSCs) and directs their differentiation towards glial cells (gliogenesis) while decreasing their differentiation towards neurons (neurogenesis). In the present study, we have evaluated the intrinsic cellular effects of APP down-expression (using siRNA) on cell death, cell proliferation, and cell fate specification of hNSCs. Our data indicate that APP silencing causes cellular effects opposite to those obtained in previous APP overexpression assays, inducing cell proliferation in hNS1 cells (a model line of hNSCs) and favoring neurogenesis instead of gliogenesis in these cells. In addition, we have analyzed the gene and protein expression levels of ß-Catenin as a possible molecule involved in these cellular effects. These data could help to understand the biological role of APP, which is necessary to deepen the knowledge of AD.

Hedgehog Signalling Modulates Immune Response and Protects against Experimental Autoimmune Encephalomyelitis.

The Hedgehog (Hh) pathway is essential for the embryonic development and homeostatic maintenance of many adult tissues and organs. It has also been associated with some functions of the innate and adaptive immune system. However, its involvement in the immune response has not been well determined. Here we study the role of Hh signalling in the modulation of the immune response by using the Ptch-1-LacZ+/- mouse model (hereinafter referred to as ptch+/-), in which the hemizygous inactivation of Patched-1, the Hh receptor gene, causes the constitutive activation of Hh response genes. The in vitro TCR stimulation of spleen and lymph node (LN) T cells showed increased levels of Th2 cytokines (IL-4 and IL-10) in ptch+/-cells compared to control cells from wild-type (wt) littermates, suggesting that the Th2 phenotype is favoured by Hh pathway activation. In addition, CD4+ cells secreted less IL-17, and the establishment of the Th1 phenotype was impaired in ptch+/- mice. Consistently, in response to an inflammatory challenge by the induction of experimental autoimmune encephalomyelitis (EAE), ptch+/- mice showed milder clinical scores and more minor spinal cord damage than wt mice. These results demonstrate a role for the Hh/ptch pathway in immune response modulation and highlight the usefulness of the ptch+/- mouse model for the study of T-cell-mediated diseases and for the search for new therapeutic strategies in inflammatory diseases.

Restrained Th17 response and myeloid cell infiltration into the central nervous system by human decidua-derived mesenchymal stem cells during experimental autoimmune encephalomyelitis.

BACKGROUND: Multiple sclerosis is a widespread inflammatory demyelinating disease. Several immunomodulatory therapies are available, including interferon-ß, glatiramer acetate, natalizumab, fingolimod, and mitoxantrone. Although useful to delay disease progression, they do not provide a definitive cure and are associated with some undesirable side-effects. Accordingly, the search for new therapeutic methods constitutes an active investigation field. The use of mesenchymal stem cells (MSCs) to modify the disease course is currently the subject of intense interest. Decidua-derived MSCs (DMSCs) are a cell population obtained from human placental extraembryonic membranes able to differentiate into the three germ layers. This study explores the therapeutic potential of DMSCs. METHODS: We used the experimental autoimmune encephalomyelitis (EAE) animal model to evaluate the effect of DMSCs on clinical signs of the disease and on the presence of inflammatory infiltrates in the central nervous system. We also compared the inflammatory profile of spleen T cells from DMSC-treated mice with that of EAE control animals, and the influence of DMSCs on the in vitro definition of the Th17 phenotype. Furthermore, we analyzed the effects on the presence of some critical cell types in central nervous system infiltrates. RESULTS: Preventive intraperitoneal injection of DMSCs resulted in a significant delay of external signs of EAE. In addition, treatment of animals already presenting with moderate symptoms resulted in mild EAE with reduced disease scores. Besides decreased inflammatory infiltration, diminished percentages of CD4(+)IL17(+), CD11b(+)Ly6G(+) and CD11b(+)Ly6C(+) cells were found in infiltrates of treated animals. Early immune response was mitigated, with spleen cells of DMSC-treated mice displaying low proliferative response to antigen, decreased production of interleukin (IL)-17, and increased production of the anti-inflammatory cytokines IL-4 and IL-10. Moreover, lower RORγT and higher GATA-3 expression levels were detected in DMSC-treated mice. DMSCs also showed a detrimental influence on the in vitro definition of the Th17 phenotype. CONCLUSIONS: DMSCs modulated the clinical course of EAE, modified the frequency and cell composition of the central nervous system infiltrates during the disease, and mediated an impairment of Th17 phenotype establishment in favor of the Th2 subtype. These results suggest that DMSCs might provide a new cell-based therapy for the control of multiple sclerosis.

Intraepithelial paracrine Hedgehog signaling induces the expansion of ciliated cells that express diverse progenitor cell markers in the basal epithelium of the mouse mammary gland.

The Hedgehog signaling pathway regulates embryo patterning and progenitor cell homeostasis in adult tissues, including epidermal appendages. A role for the Hh pathway in mammary biology and breast cancer has also been suggested. The aim of this study was to analyze Hh signaling in the mouse mammary gland through the generation of transgenic mice that express Sonic Hedgehog (Shh) under the control of the mammary-specific WAP promoter (WAP-Shh mice). To identify mammary cells capable of activating the Hh pathway we bred WAP-Shh mice to Ptch1-lacZ knock-in mice, in which the expression of a nuclear-targeted ß-galactosidase reporter protein (ß-gal) is driven by the endogenous Patched 1 gene regulatory region. After two cycles of induction of transgenic Shh expression, we detected areas of X-gal reactivity. Immunohistochemical analysis showed nuclear ß-gal staining in clusters of mammary cells in WAP-Shh/Ptch1-lacZ bitransgenic mice. These were epithelial cells present in a basal location of displastic ducts and alveoli, adjacent to Shh-expressing luminal cells, and overexpressed epithelial basal markers keratin 5, 14 and 17 and transcription factor p63. Absence of smooth muscle actin expression and a cuboidal morphology differentiated Hh-responding cells from flat-shaped mature myoepithelial cells. Groups of cells expressing stem cell markers integrin ß3 and keratins 6 and 15 were also detected within Hh-responding areas. In addition, we found that Hh-responding cells in the mammary glands of WAP-Shh/Ptch1-lacZ mice were ciliated and exhibited a low proliferation rate. Our data show the paracrine nature of hedgehog signaling in the epithelial compartment of the mouse mammary gland, where a subset of basal cells that express mammary progenitor cell markers and exhibit primary cilia is expanded in response to secretory epithelium-derived Shh.

Hepatocyte growth factor is a lymphangiogenic factor with an indirect mechanism of action.

Hepatocyte growth factor (HGF) has previously been reported to act as a hemangiogenic factor, as well as a mitogenic factor for a variety of tumor cells. Here, we demonstrate that HGF is a lymphangiogenic factor, which may contribute to lymphatic metastasis when overexpressed in tumors. In a mouse corneal lymphangiogenesis model, implantation of HGF induces sprouting and growth of new lymphatic vessel expressing the lymphatic vessel endothelial specific marker hyaluronan receptor-1 (Lyve-1). Unlike blood vessels, the Lyve-1-positive structures consist of blunt-ended vessels of large diameters that generally lack expression of CD31. The growth of HGF-induced lymphatic vessels can be partially blocked by a soluble VEGFR-3, suggesting that HGF may stimulate lymphatic vessel growth through an indirect mechanism. Consistent with this finding, the HGF receptor (c-Met) is only localized on corneal blood vessels but is absent on lymphatic vessels in a mouse corneal assay. In a transgenic mouse model that expresses HGF under the control of the whey acidic protein (WAP) gene promoter, transgenic females develop tumors in the mammary glands after several pregnancies. Interestingly, dilated Lyve-1-positive lymphatic vessels accumulate in the peritumoral area and occasionally penetrate into the tumor tissue. Our findings indicate that HGF may play a critical role in lymphangiogenesis and potentially contribute to lymphatic metastasis.

Targeted expression of HGF/SF in mouse mammary epithelium leads to metastatic adenosquamous carcinomas through the activation of multiple signal transduction pathways.

Overexpression of hepatocyte growth factor (HGF), also called scatter factor (SF), and its receptor c-Met are associated with poor prognosis for cancer patients. In particular, breast cancer cells can produce HGF that acts in a paracrine as well as in an autocrine manner. Therefore, HGF and c-Met are putative targets for cancer therapy. To explore HGF/c-Met signaling in breast cancer, we have generated transgenic mice expressing HGF specifically in mammary epithelium under the transcriptional control of the whey acidic protein (WAP) gene promoter. WAP-HGF transgenic females developed hyperplastic ductal trees and multifocal invasive tumors after several pregnancies, some of which progressed to lung metastases. Tumors produced HGF and displayed phosphorylated c-Met, which correlated with increased Akt as well as c-myc activation. A high growth rate, as demonstrated by Ki67 nuclear antigen staining, and a lack of progesterone receptor were characteristic of the tumors. Immunohistochemical analysis revealed areas of osteopontin (Opn) expression in WAP-HGF tumors and lung metastases in agreement with a previously reported role for Opn in invasive growth. We suggest that these mice may serve as a new breast cancer model for the evaluation of the effects of unscheduled HGF expression in breast cancer.

Differential requirements for shh in mammary tissue and hair follicle morphogenesis.

Sonic Hedgehog (Shh) is a secreted morphogen that directs patterning and cellular differentiation through binding to its receptor Patched (Ptc). It is required for the development of skin-derived organs, such as hair, whiskers, and teeth. The mammary gland is a skin-derived organ that develops mainly during adult life in which Shh is expressed from puberty to lactation. We have investigated the role of Shh in mammary gland morphogenesis and differentiation by two transplantation approaches. Since Shh-null fetuses die at late embryogenesis, we transplanted Shh-null mammary anlagen into cleared fat pads and under the renal capsule of wild type host mice. Pregnancy-mediated functional differentiation of Shh-null mammary epithelium was indistinguishable from wild type transplants, while hair follicles derived from cotransplanted skin only developed in wild type transplants. Transplants of Ihh-null anlagen also developed normally. To assess the molecular consequences of Shh deletion in mammary tissue, we compared mRNA levels of patched 1, a target gene of Hedgehog signaling, in Shh-null and wild type mammary epithelial transplants. No reduction of Ptc1 transcripts was observed in Shh-null mammary tissues. Our results demonstrate that neither Shh nor Ihh is required for mammary gland morphogenesis and functional differentiation, suggesting that the two members of the Hedgehog family may have redundant function in activating the Ptc1 signaling pathway during mammary gland development.