Nociceptive neurons innervate the skin with complex dendritic arbors that respond to pain-evoking stimuli such as harsh mechanical force or extreme temperatures. Here we describe the structure and development of a model nociceptor, the PVD neuron of C. elegans, and identify transcription factors that control morphogenesis of the PVD dendritic arbor. The two PVD neuron cell bodies occupy positions on either the right (PVDR) or left (PVDL) sides of the animal in posterior lateral locations. Imaging with a GFP reporter revealed a single axon projecting from the PVD soma to the ventral cord and an elaborate, highly-branched arbor of dendritic processes that envelop the animal with a web-like array directly beneath the skin. Dendritic branches emerge in a step-wise fashion during larval development and may use an existing network of peripheral nerve cords as guideposts for key branching decisions. Time-lapse imaging revealed that branching is highly dynamic with active extension and withdrawal and that PVD branch overlap is prevented by a contact-dependent self-avoidance, a mechanism that is also employed by sensory neurons in other organisms. With the goal of identifying genes that regulate dendritic morphogenesis, we used the mRNA tagging method to produce a gene expression profile of PVD during late larval development. This microarray experiment identified > 2,000 genes that are 1.5 X elevated relative to all larval cells. The enriched transcripts encode a wide range of proteins with potential roles in PVD function (e.g., DEG/ENaC and Trp channels) or development (e.g., UNC-5 and LIN-17/frizzled receptors). We used RNAi and genetic tests to screen 86 transcription factors from this list and identified eleven genes that specify PVD dendritic structure. These transcription factors appear to control discrete steps in PVD morphogenesis and may either promote or limit PVD branching at specific developmental stages. For example, time-lapse imaging revealed that the MEC-3 (LIM homeodomain) is required for branch initiation in early larval development whereas EGL-44 (TEAD domain) prevents ectopic PVD branching in the adult. A comparison of PVD-enriched transcripts to a microarray profile of mammalian nociceptors revealed homologous genes with potentially shared nociceptive functions. We conclude that PVD neurons display striking structural, functional and molecular similarities to nociceptive neurons from more complex organisms and can thus provide a useful model system in which to identify evolutionarily conserved determinants of nociceptor fate.

Purpose: Major barriers to effective adenovirus-based gene therapy include induction of an immune response and tumor-specific targeting of vectors. The use of mesenchymal stem cells (MSC) as systemic delivery vehicles for therapeutic genes has been proposed as a result of their combined ability to home in on the tumor site and evade the host immune response. This study is aimed at investigating factors mediating homing of human MSCs to breast cancer primary cultures and cell lines in vitro and in vivo. Experimental Design: Fluorescently labeled MSCs were given to mice bearing breast cancer xenografts, and tumor tissue was harvested to detect MSC engraftment. MSC migration in response to primary breast tumors in vitro was quantified, and chemokines secreted by tumor cells were identified. The role of monocyte chemotactic protein-1 (MCP-1) in cell migration was investigated using antibodies and standards of the chemokine. Serum MCP-1 was measured in 125 breast cancer patients and 86 healthy controls. Results: Engrafted MSCs were detected in metastatic breast tumors in mice after systemic administration. There was a significant increase in MSC migration in response to primary breast tumor cells in vitro (6-fold to 11-fold increase). Tumor explants secreted a variety of chemokines including GROa, MCP-1, and stromal cell^derived factor-1a. An MCP-1antibody caused a significant decrease (37-42%) in MSC migration to tumors. Serum MCP-1 levels were significantly higher in postmenopausal breast cancer patients than age-matched controls (P < 0.05).Conclusions: These results highlight a role for tumor-secreted MCP-1in stimulating MSC migration and support the potential of these cells as tumor-targeted delivery vehicles for therapeutic agents.

Background Bone-marrow derived mesenchymal stem cells (MSCs) reduce the severity of evolving acute lung injury (ALI), but their ability to repair the injured lung is not clear. A study was undertaken to determine the potential for MSCs to enhance repair after ventilatorinduced lung injury (VILI) and elucidate the mechanisms underlying these effects. Methods Anaesthetised rats underwent injurious ventilation which produced severe ALI. Following recovery, they were given an intravenous injection of MSCs (2310 6 cells) or vehicle immediately and a second dose 24 h later. The extent of recovery following VILI was assessed after 48 h. Subsequent experiments examined the potential for non-stem cells and for the MSC secretome to enhance VILI repair. The contribution of specific MSC-secreted mediators was then examined in a wound healing model. Results MSC therapy enhanced repair following VILI. MSCs enhanced restoration of systemic oxygenation and lung compliance, reduced total lung water, decreased lung inflammation and histological lung injury and restored lung structure. They attenuated alveolar tumour necrosis factor a concentrations while increasing concentrations of interleukin 10. These effects were not seen with non-stem cells (ie, rat fibroblasts). MSCsecreted products also enhanced lung repair and attenuated the inflammatory response following VILI. The beneficial effect of the MSC secretome on repair of pulmonary epithelial wounds was attenuated by prior depletion of keratinocyte growth factor. Conclusion MSC therapy enhances lung repair following VILI via a paracrine mechanism that may be keratinocyte growth factor-dependent.

Mesenchymal stem cells (MSCs) inhibit proliferation of allogeneic T cells and express low levels of major histocompatibility complex class I (MHCI), MHCII and vascular adhesion molecule-1 (VCAM-1). We investigated whether their immunosuppressive properties and low immunophenotype protect allogeneic rat MSCs against cytotoxic lysis in vitro and result in a reduced immune response in vivo. Rat MSCs were partially protected against alloantigen-specific cytotoxic T cells in vitro. However, after treatment with IFN-γ and IL-1β, MSCs upregulated MHCI, MHCII and VCAM-1, and cytotoxic lysis was significantly increased. In vivo, allogeneic T cells but not allogeneic MSCs induced upregulation of the activation markers CD25 and CD71 as well as downregulation of CD62L on CD4+ T cells from recipient rats. However, intravenous injection of allo-MSCs in rats led to the formation of alloantibodies with the capacity to facilitate complement-mediated lysis, although IgM levels were markedly decreased compared with animals that received T cells. The allo-MSC induced immune response was sufficient to lead to significantly reduced survival of subsequently injected allo-MSCs. Interestingly, no increased immunogenicity of IFN-γ stimulated allo-MSCs was observed in vivo. Both the loss of protection against cytotoxic lysis under inflammatory conditions and the induction of complement-activating antibodies will likely impact the utility of allogeneic MSCs for therapeutic applications.

Bone marrow derived Mesenchymal Stem Cells (MSCs) are known to specifically migrate to and engraft at tumor sites. Understanding interactions between cancer cells and MSCs has become fundamental to determining whether MSC-tumour interactions should be harnessed for delivery of therapeutic agents or considered a target for intervention. Breast Cancer Cell lines (MDA-MB-231, T47D & SK-Br3) were cultured alone or on a monolayer of MSCs, and retrieved using epithelial specific magnetic beads.Alterations in expression of 90 genes associated with breast tumorgenicity were analyzed using low density array. Expression of markers of Epithelial-Mesenchymal transition and array results were validated using RQ-PCR. Co-cultured cells were analyzed for changes in protein expression, growth pattern, and morphology. Gene expression and proliferation assays were also performed on indirect co-cultures. Following direct co-culture with MSCs, breast cancer cells expressed elevated levels of oncogenes (NCOA4, FOS), protooncogenes (FYN, JUN), genes associated with invasion (MMP11), angiogenesis (VEGF)and anti-apoptosis (IGF1R, BCL2). However, universal downregulation of genes associated with proliferation was observed (Ki67, MYBL2), and reflected in reduced ATP production in response to MSC-secreted factors. Significant upregulation of Epithelial-Mesenchymal Transition specific markers (N-cadherin, Vimentin, Twist and Snail) was also observed following co-culture with MSCs, with a reciprocal downregulation in E-cadherin protein expression. These changes were predominantly cell contact mediated and appeared to be MSC specific. Breast cancer cell morphology and growth pattern also altered in response to MSCs. Mesenchymal Stem Cells may promote breast cancer metastasis through facilitation of Epithelial-Mesenchymal Transition.