Cell Ablation Studies Research Articles

TME-NET: an interpretable deep neural network for predicting pan-cancer immune checkpoint inhibitor responses.

Immunotherapy with immune checkpoint inhibitors (ICIs) is increasingly used to treat various tumor types. Determining patient responses to ICIs presents a significant clinical challenge. Although components of the tumor microenvironment (TME) are used to predict patient outcomes, comprehensive assessments of the TME are frequently overlooked. Using a top-down approach, the TME was divided into five layers-outcome, immune role, cell, cellular component, and gene. Using this structure, a neural network called TME-NET was developed to predict responses to ICIs. Model parameter weights and cell ablation studies were used to investigate the influence of TME components. The model was developed and evaluated using a pan-cancer cohort of 948 patients across four cancer types, with Area Under the Curve (AUC) and accuracy as performance metrics. Results show that TME-NET surpasses established models such as support vector machine and k-nearest neighbors in AUC and accuracy. Visualization of model parameter weights showed that at the cellular layer, Th1 cells enhance immune responses, whereas myeloid-derived suppressor cells and M2 macrophages show strong immunosuppressive effects. Cell ablation studies further confirmed the impact of these cells. At the gene layer, the transcription factors STAT4 in Th1 cells and IRF4 in M2 macrophages significantly affect TME dynamics. Additionally, the cytokine-encoding genes IFNG from Th1 cells and ARG1 from M2 macrophages are crucial for modulating immune responses within the TME. Survival data from immunotherapy cohorts confirmed the prognostic ability of these markers, with p-values <0.01. In summary, TME-NET performs well in predicting immunotherapy responses and offers interpretable insights into the immunotherapy process. It can be customized at https://immbal.shinyapps.io/TME-NET.

Abstract IA001: Cellular and molecular underpinnings of field cancerization and progression to invasive carcinoma in bladder cancer

Abstract Two major concerns in clinical management of bladder cancer are: (i) the high frequency of recurrence; and (ii) the morbidity and mortality associated with progression to invasive disease (invasive urothelial carcinoma, IUC). To gain a better understanding of these issues we have used the murine BBN (N-butyl-N-(4-hydroxylbutyl) nitrosamine) experimental model of bladder cancer, as well as tissue samples from normal human bladders and from bladders of patients at various stages of bladder cancer formation and progression. We have documented in the BBN model a CIS-like stage, prior to invasion, in which clonal expansion from a single cell occupies a significant fraction of the urothelium. With this experimental murine model alongside observations from patient samples and data from The Cancer Genome Atlas (TCGA), we have ascertained that a key event in progression of pre-invasive to invasive carcinoma is the silencing of the Sonic hedgehog (Shh) member of the Hedgehog gene family. Silencing-associated invasion appears due to the loss of SHH-induced differentiation signals, which when present slow growth and block invasion. Despite the consistent loss of SHH expression in invasive murine and human bladder cancers, however, TCGA data show few if any mutations in the SHH gene of IUC cells. Instead, our studies of patient samples and cancer-derived cell lines reveal that the loss of SHH expression is due to tighter chromosomal packaging and reduced accessibility of a bladder-specific enhancer located ~200 kb upstream of the SHH transcription start site. We have found that inhibitors of certain chromatin-modifying enzymes, including an FDA-approved drug, are capable of re-activating SHH expression, and are testing the possibility that these drugs may block or reverse invasion of urothelial carcinoma. The high frequency of bladder cancer recurrence is thought to result from field cancerization, that is, an increased probability of new cancer formation in apparent normal urothelium, even after successful resection of the primary tumor. To understand the basis for this field effect, we compared apparent normal urothelium from cancer patients to truly normal urothelium from bladders never affected by malignancy. We found that apparent normal samples display a dramatically increased basal character in transcriptomic assays, using as a metric of basalization an index constructed from single cell RNA-seq analysis of normal urothelium. We and others have demonstrated previously by lineage tracing and cell ablation studies in the BBN model that IUC arises from basal stem cells of the urothelium. The basalization of urothelium distant from the primary tumor that we observe thus may account for the increased probability of cancer formation in the apparent normal urothelium of bladder cancer patients. We have found that several FDA-approved antagonists of EGF signaling can reverse this basalization in the mouse BBN model as well as in organoid culture, and that these drugs dramatically reduce the formation of tumors following BBN exposure. Citation Format: Philip A. Beachy, Kris B. Prado, Aaron M. Kershner, Karim Mrouj, Bernard M. Kiss, Hua Dong, Ozgu Aydogdu, Ye Tian, Joseph C. Liao. Cellular and molecular underpinnings of field cancerization and progression to invasive carcinoma in bladder cancer [abstract]. In: Proceedings of the AACR Special Conference on Bladder Cancer: Transforming the Field; 2024 May 17-20; Charlotte, NC. Philadelphia (PA): AACR; Clin Cancer Res 2024;30(10_Suppl):Abstract nr IA001.

CRISPR Knock-Ins in Organoids to Track Tumor Cell Subpopulations.

The integration of CRISPR/Cas9 genome editing techniques with organoid technology has revolutionized the field of tumor modeling, enabling the creation of diverse tumor models with distinct mutational profiles. This protocol details the application of CRISPR knock-ins to engineer tumor organoids with reporter cassettes, which are regulated by endogenous promoters of specific genes of interest. This approach facilitates the precise fluorescent labeling, isolation, and subsequent manipulation of targeted tumor cell subpopulations. The utilization of these knock-in reporter cassettes not only allows the visualization and purification of specific tumor cell subsets but also enables conditional cell ablation and lineage tracing studies. In this chapter, we provide a comprehensive guide for the design, construction, delivery, and validation of CRISPR/Cas9 tools tailored for knock-in reporter cassette integration into specific marker genes of interest. By following this protocol, researchers can harness the potential of engineered tumor organoids to decipher intricate tumor heterogeneity, track metastatic trajectories, and unveil novel therapeutic vulnerabilities linked to specific tumor cell subpopulations.

Glial regulators of ions and solutes required for specific chemosensory functions in Caenorhabditis elegans.

Glia and accessory cells regulate the microenvironment around neurons and primary sensory cells. However, the impact of specific glial regulators of ions and solutes on functionally diverse primary cells is poorly understood. Here, we systemically investigate the requirement of ion channels and transporters enriched in Caenorhabditis elegans Amsh glia for the function of chemosensory neurons. Although Amsh glia ablated worms show reduced function of ASH, AWC, AWA, and ASE neurons, we show that the loss of glial enriched ion channels and transporters impacts these neurons differently, with nociceptor ASH being the most affected. Furthermore, our analysis underscores the importance of K+, Cl-, and nucleoside homeostasis in the Amphid sensory organ and uncovers the contribution of glial genes implicated in neurological disorders. Our findings build a unique fingerprint of each glial enriched ion channel and transporter and may provide insights into the function of supporting cells of mammalian sensory organs.

Discovery and functional assessment of a novel adipocyte population driven by intracellular Wnt/β-catenin signaling in mammals.

Wnt/β-catenin signaling has been well established as a potent inhibitor of adipogenesis. Here, we identified a population of adipocytes that exhibit persistent activity of Wnt/β-catenin signaling, as revealed by the Tcf/Lef-GFP reporter allele, in embryonic and adult mouse fat depots, named as Wnt+ adipocytes. We showed that this β-catenin-mediated signaling activation in these cells is Wnt ligand- and receptor-independent but relies on AKT/mTOR pathway and is essential for cell survival. Such adipocytes are distinct from classical ones in transcriptomic and genomic signatures and can be induced from various sources of mesenchymal stromal cells including human cells. Genetic lineage-tracing and targeted cell ablation studies revealed that these adipocytes convert into beige adipocytes directly and are also required for beige fat recruitment under thermal challenge, demonstrating both cell autonomous and non-cell autonomous roles in adaptive thermogenesis. Furthermore, mice bearing targeted ablation of these adipocytes exhibited glucose intolerance, while mice receiving exogenously supplied such cells manifested enhanced glucose utilization. Our studies uncover a unique adipocyte population in regulating beiging in adipose tissues and systemic glucose homeostasis.

Metabolic Regulation of Inflammasome Activity Controls Embryonic Hematopoietic Stem and Progenitor Cell Production.

Embryonic hematopoietic stem and progenitor cells (HSPCs) robustly proliferate while maintaining multilineage potential invivo; however, an incomplete understanding of spatiotemporal cues governing their generation has impeded robust production from human induced pluripotent stem cells (iPSCs) invitro. Using the zebrafish model, we demonstrate that NLRP3 inflammasome-mediated interleukin-1-beta (IL1β) signaling drives HSPC production in response to metabolic activity. Genetic induction of active IL1β or pharmacologic inflammasome stimulation increased HSPC number as assessed by in situ hybridization for runx1/cmyb and flow cytometry. Loss of inflammasome components, including il1b, reduced CD41+ HSPCs and prevented their expansion in response to metabolic cues. Cell ablation studies indicated that macrophages were essential for initial inflammasome stimulation of Il1rl1+ HSPCs. Significantly, in human iPSC-derived hemogenic precursors, transient inflammasome stimulation increased multilineage hematopoietic colony-forming units and Tcell progenitors. This work establishes the inflammasome as a conserved metabolic sensor that expands HSPC production invivo and invitro.

Role of Prx1-expressing skeletal cells and Prx1-expression in fracture repair

The healing capacity of bones after fracture implies the existence of adult regenerative cells. However, information on identification and functional role of fracture-induced progenitors is still lacking. Paired-related homeobox 1 (Prx1) is expressed during skeletogenesis. We hypothesize that fracture recapitulates Prx1's expression, and Prx1 expressing cells are critical to induce repair. To address our hypothesis, we used a combination of in vivo and in vitro approaches, short and long-term cell tracking analyses of progenies and actively expressing cells, cell ablation studies, and rodent animal models for normal and defective fracture healing. We found that fracture elicits a periosteal and endosteal response of perivascular Prx1+ cells that participate in fracture healing and showed that Prx1-expressing cells have a functional role in the repair process. While Prx1-derived cells contribute to the callus, Prx1's expression decreases concurrently with differentiation into cartilaginous and bone cells, similarly to when Prx1+ cells are cultured in differentiating conditions. We determined that bone morphogenic protein 2 (BMP2), through C-X-C motif-ligand-12 (CXCL12) signaling, modulates the downregulation of Prx1. We demonstrated that fracture elicits an early increase in BMP2 expression, followed by a decrease in CXCL12 that in turn down-regulates Prx1, allowing cells to commit to osteochondrogenesis. In vivo and in vitro treatment with CXCR4 antagonist AMD3100 restored Prx1 expression by modulating the BMP2-CXCL12 axis. Our studies represent a shift in the current research that has primarily focused on the identification of markers for postnatal skeletal progenitors, and instead we characterized the function of a specific population (Prx1+ cells) and their expression marker (Prx1) as a crossroad in fracture repair. The identification of fracture-induced perivascular Prx1+ cells and regulation of Prx1's expression by BMP2 and in turn by CXCL12 in the orchestration of fracture repair, highlights a pathway in which to investigate defective mechanisms and therapeutic targets for fracture non-union.

Activation of JAK/STAT Signaling in Megakaryocytes Sustains Myeloproliferation In Vivo.

The myeloproliferative neoplasms (MPN), including polycythemia vera, essential thrombocythemia, and primary myelofibrosis, are characterized by the expansion of the erythroid, megakaryocytic, and granulocytic lineages. A common feature of these disorders is the presence of abnormal megakaryocytes, which have been implicated as causative agents in the development of bone marrow fibrosis. However, the specific contributions of megakaryocytes to MPN pathogenesis remain unclear. We used Pf4-Cre transgenic mice to drive expression of JAK2V617F in megakaryocyte lineage-committed hematopoietic cells. We also assessed the critical role of mutant megakaryocytes in MPN maintenance through cell ablation studies in JAK2V617F and MPLW515L BMT models of MPN. JAK2V617F -mutant presence in megakaryocytes was sufficient to induce enhanced erythropoiesis and promote fibrosis, which leads to a myeloproliferative state with expansion of mutant and nonmutant hematopoietic cells. The increased erythropoiesis was associated with elevated IL6 level, which was also required for aberrant erythropoiesis in vivo. Furthermore, depletion of megakaryocytes in the JAK2V617F and MPLW515L BMT models ameliorated polycythemia and leukocytosis in addition to expected effects on megakaryopoiesis. Our observations reveal that JAK/STAT pathway activation in megakaryocytes induces myeloproliferation and is necessary for MPN maintenance in vivo. These observations indicate that MPN clone can influence the behavior of the wild-type hematopoietic milieu, at least, in part, via altered production of proinflammatory cytokines and chemokines. Our findings resonate with patients who present with a clinical MPN and a low JAK2V617F allele burden, and support the development of MPN therapies aimed at targeting megakaryocytes.

INFLAMMASOME-MEDIATED EXPANSION OF THE HEMATOPOIETIC SYSTEM IN THE VERTEBRATE EMBRYO

Embryonic hematopoietic stem and progenitor cells (HSPCs) have the capacity to rapidly expand while maintaining multilineage potential. As efforts to derive HSPCs in vitro are suboptimal, a better understanding of mechanisms regulating embryonic HSPC formation and expansion is needed. We previously reported that sterile inflammation stimulates embryonic HSPC production, yet it remains unclear how the embryo initiates inflammatory cues. The NLRP3 inflammasome cleaves and activates interleukin-1-beta (IL-1β) in response to sterile stimuli, including reactive oxygen species and metabolic flux. Building on previous findings that glucose exposure expands embryonic HSPCs, we hypothesized that these effects rely on inflammasome activation and IL-1β release. Glucose exposure promoted il1b expression; il1b knockdown suppressed the inductive effects of glucose on numbers of CD41+ HSPCs. Conversely, overexpression of the active form of il1b or pharmacologic inflammasome stimulation increased runx1/cmyb expression and numbers of Flk1+cMyb+ HSPCs. Inflammasome activation required NF-kB priming, and upregulated IL-1β targets IL-6 and IL-8, which are known to expand embryonic HSPCs. Loss of inflammasome components reduced HSPCs, and prevented their expansion in response to glucose stimulation. Furthermore, knockdown of pu.1/spi1l and cell ablation studies indicate that macrophages serve an important role in mediating the effects of inflammasome stimulation on HSPCs. Significantly, inflammasome stimulation of human iPSC-derived hemogenic precursors also increased the frequency of multilineage hematopoietic colony-forming units formed in culture. This work identifies the inflammasome as a conserved metabolic sensor that expands HSPC production in vivo and in vitro, which may ultimately promote human HSPC production for cell therapy.

Inflammasome-Mediated Regulation of Hematopoiesis in the Vertebrate Embryo

Hematopoietic stem and progenitor cells (HSPCs) arise in the embryonic dorsal aorta (DA) through a Runx1-dependent process of endothelial-to-hematopoietic transition (EHT). Subsequently, HSPCs colonize secondary niches to proliferate, differentiate and maintain lifelong hematopoiesis. We previously reported that elevated glucose metabolism and sterile inflammatory signaling each stimulate zebrafish HSPC production from hemogenic endothelium. Consistent with the hypothesis that transient metabolic activation induces an inflammatory response to influence HSPC formation, we found that glucose stimulation from 12-36 hours post fertilization (hpf) increased expression of pro-inflammatory cytokines and receptors by quantitative PCR. In particular, morpholino-mediated knockdown of il1b blunted the inductive effects of glucose metabolism on runx1 expression in the DA and numbers of CD41+ HSPCs in the caudal hematopoietic tissue (CHT). In contrast, overexpression of mature il1b increased HSPC numbers as assessed by flow cytometry and runx1/cmyb in situ hybridization. As IL-1β is cleaved and activated by the inflammasome, which is a well-known sensor of metabolic stimuli, we treated embryos with validated inflammasome activators, such as nigericin, and found that they also increased runx1/cmyb expression and Flk1+cMyb+ HSPCs. Inflammasome stimulation required NF-κB activity, and upregulated canonical IL-1β targets, including IL-6 and IL-8, which have been previously shown by our laboratory to play significant roles in embryonic HSPC formation. Importantly, loss of the inflammasome adapter pycard or effector caspa reduced HSPC numbers, and prevented expansion of the HSPC pool in response to glucose stimulation. In further support of a role for sterile inflammatory activity in regulating HSPC number downstream of metabolic activation, we found that inflammasome-mediated IL-1β action bypassed the suppressive effect of antioxidant treatment on runx1/cmyb expression in the DA. Conversely, inflammasome inhibition partially blocked effects of metabolism-associated HIF1α activation on runx1/cmyb expression, indicating that the inflammasome acts downstream of reactive-oxygen-species (ROS) generation and HIF1α activation to promote HSPC production and/or expansion from hemogenic endothelium. Inflammasome components are highly expressed in myeloid cells; targeted knockdown and cell ablation studies indicate that macrophages are necessary to mediate the effects of inflammasome stimulation on HSPC numbers in the CHT at 72hpf. Interestingly, prolonged inflammasome stimulation also expands myeloid and lymphoid progenitors, as cmyb, rag1 and mpo expression were each elevated at 120hpf; increased numbers of Rag2+ and Mpo+ cells were confirmed by flow cytometry. To determine whether the effects of inflammasome activation were conserved in higher vertebrates, we induced inflammasome activation during differentiation of human induced pluripotent stem cells (iPSC) into hematopoietic progenitors. In this system, nigericin treatment of iPSC-derived hemogenic endothelial cells yielded an increased frequency of functional colony-forming units by day 7 of EHT culture. Taken together, inflammasome-mediated IL-1β action appears to serve as an integrator of metabolic activity, downstream of ROS/ HIF1α, to promote HSPC formation and development of myeloid and lymphoid lineages in vivo and in vitro. These studies identify the inflammasome as a promising target to promote human HSPC production from iPSCs for therapeutic purposes. DisclosuresNo relevant conflicts of interest to declare.

Green monomeric photosensitizing fluorescent protein for photo-inducible protein inactivation and cell ablation

BackgroundPhotosensitizing fluorescent proteins, which generate reactive oxygen species (ROS) upon light irradiation, are useful for spatiotemporal protein inactivation and cell ablation. They give us clues about protein function, intracellular signaling pathways and intercellular interactions. Since ROS generation of a photosensitizer is specifically controlled by certain excitation wavelengths, utilizing colour variants of photosensitizing protein would allow multi-spatiotemporal control of inactivation. To expand the colour palette of photosensitizing protein, here we developed SuperNova Green from its red predecessor, SuperNova.ResultsSuperNova Green is able to produce ROS spatiotemporally upon blue light irradiation. Based on protein characterization, SuperNova Green produces insignificant amounts of singlet oxygen and predominantly produces superoxide and its derivatives. We utilized SuperNova Green to specifically inactivate the pleckstrin homology domain of phospholipase C-δ1 and to ablate cancer cells in vitro. As a proof of concept for multi-spatiotemporal control of inactivation, we demonstrate that SuperNova Green can be used with its red variant, SuperNova, to perform independent protein inactivation or cell ablation studies in a spatiotemporal manner by selective light irradiation.ConclusionDevelopment of SuperNova Green has expanded the photosensitizing protein toolbox to optogenetically control protein inactivation and cell ablation.

Identification of cardiac hemo-vascular precursors and their requirement of sphingosine-1-phosphate receptor 1 for heart development

The cardiac endothelium plays a crucial role in the development of a functional heart. However, the precise identification of the endocardial precursors and the mechanisms they require for their role in heart morphogenesis are not well understood. Using in vivo and in vitro cell fate tracing concomitant with specific cell ablation and embryonic heart transplantation studies, we identified a unique set of precursors which possess hemogenic functions and express the stem cell leukemia (SCL) gene driven by its 5′ enhancer. These hemo-vascular precursors give rise to the endocardium, atrioventricular cushions and coronary vascular endothelium. Furthermore, deletion of the sphingosine-1-phosphate receptor 1 (S1P1) in these precursors leads to ventricular non-compaction cardiomyopathy, a poorly understood condition leading to heart failure and early mortality. Thus, we identified a distinctive population of hemo-vascular precursors which require S1P1 to exert their functions and are essential for cardiac morphogenesis.

Exposure to diphtheria toxin during the juvenile period impairs both inner and outer hair cells in C57BL/6 mice

Diphtheria toxin (DT) administration into transgenic mice that express the DT receptor (DTR) under control of specific promoters is often used for cell ablation studies in vivo. Because DTR is not expressed in mice, DT injection has been assumed to be nontoxic to cells in vivo. In this study, we demonstrated that DT application during the juvenile stage leads to hearing loss in wild-type mice. Auditory brainstem response measurement showed severe hearing loss in C57BL/6 mice administered DT during the juvenile period, and the hearing loss persisted into adulthood. However, ototoxicity did not occur when DT was applied on postnatal day 28 or later. Histological studies demonstrated that hearing loss was accompanied by significant degeneration of inner and outer hair cells (HCs), as well as spiral ganglion neurons. Scanning electron microscopy showed quick degeneration of inner HCs within 3days and gradual degeneration of outer HCs within 1week. These results demonstrated that DT has ototoxic action on C57BL/6 mice during the juvenile period, but not thereafter, and the hearing loss was due to degeneration of inner and outer HCs by unknown DT-related mechanisms.

Near-infrared laser cellular ablation and development in Xenopus laevis embryos

The biological applications of pulsed near-infrared (NIR) lasers are widening due to potential use of this technology to manipulate cellular structure. The present study was conducted to further explore the efficacy of NIR lasers for ablating individual cells in eight-cell stage Xenopus laevis embryos. Ablations were performed with four experimental groups, at magnifications of 10× and 40× (laser beam radius of 0.32 and 0.23 μm, respectively) with either one cell or two adjacent cells targeted. The survivorship, size, and phenotypic mutations of each group were documented and compared to a control group. Survivorship was not affected in any experimental group; however, statistically significant differences were noted in embryonic length (p = 0.02) and in morphology (p < 0.01) for the experimental groups with ablation of two cells at 40× (laser beam radius of 0.23 μm) magnification. The survivorship of targeted embryos in this experiment encourages the use of NIR radiation for cell ablation studies. Our study demonstrated that NIR laser spectroscopy could complement existing X. laevis fate mapping data and improve understanding of developmental plasticity in early embryos as well as serve as a clinical tool for removing pathological cells. Despite visible effects on embryo development, the damages incurred in the most extreme condition did not significantly impact survivorship through the early tadpole stage. This finding does not rule out latent effects that might affect fitness of older tadpoles or even adult frogs.

Silver Sulfide Nanoparticles as Photothermal Transducing Agents for Cancer Treatment

Silver Sulfide Nanoparticles as Photothermal Transducing Agents for Cancer Treatment Silver sulfide (Ag2S) nanoparticles have been recently revealed as attractive nanoagents with near-infrared fluorescence for biological imaging. However, there have been no investigations about their photothermal effect, which can be used to convert nearinfrared light energy to heat for cancer treatment. In this work, the Ag2S nanoparticles are investigated, for the first time, as energy transducing agents on cancer cell destruction. We have used a one-step wet chemistry method in the nanoparticle synthesis. 3-mercaptopropionic acid (MPA) is newly applied as a surfactant to stabilize the obtained Ag2S nanoparticles, allowing them to be highly soluble in water. The nanoparticles have a monoclinic crystal structure with average sizes of ~40 nm, and they display a broad absorption from visible to near-infrared light wavelengths and emissions in 900-1200 nm range. When irradiated by an NIR laser of 808 nm, it is found that the temperature of the aqueous Ag2S nanoparticle solution increases as a function of Ag2S concentration and laser power density. The interesting phenomenon has led us to conduct further photothermal cancer cell ablation studies using human osteosarcoma (U-2OS) cells. Present in several methods, our results have shown that the as-prepared Ag2S nanoparticles can induce efficient photothermal destruction on the U-2OS cells at proper laser doses and nanoparticle concentrations, which may make them a promising heat transducing agent for photothermal cancer therapy.

Neurotensin Is Coexpressed, Coreleased, and Acts Together With GLP-1 and PYY in Enteroendocrine Control of Metabolism

The 2 gut hormones glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) are well known to be coexpressed, costored, and released together to coact in the control of key metabolic target organs. However, recently, it became clear that several other gut hormones can be coexpressed in the intestinal-specific lineage of enteroendocrine cells. Here, we focus on the anatomical and functional consequences of the coexpression of neurotensin with GLP-1 and PYY in the distal small intestine. Fluorescence-activated cell sorting analysis, laser capture, and triple staining demonstrated that GLP-1 cells in the crypts become increasingly multihormonal, ie, coexpressing PYY and neurotensin as they move up the villus. Proglucagon promoter and pertussis toxin receptor-driven cell ablation and reappearance studies indicated that although all the cells die, the GLP-1 cells reappear more quickly than PYY- and neurotensin-positive cells. High-resolution confocal fluorescence microscopy demonstrated that neurotensin is stored in secretory granules distinct from GLP-1 and PYY storing granules. Nevertheless, the 3 peptides were cosecreted from both perfused small intestines and colonic crypt cultures in response to a series of metabolite, neuropeptide, and hormonal stimuli. Importantly, neurotensin acts synergistically, ie, more than additively together with GLP-1 and PYY to decrease palatable food intake and inhibit gastric emptying, but affects glucose homeostasis in a more complex manner. Thus, neurotensin is a major gut hormone deeply integrated with GLP-1 and PYY, which should be taken into account when exploiting the enteroendocrine regulation of metabolism pharmacologically.

Cell-specific ablation in the testis: what have we learned?

SummaryTesticular development and function is the culmination of a complex process of autocrine, paracrine and endocrine interactions between multiple cell types. Dissecting this has classically involved the use of systemic treatments to perturb endocrine function, or more recently, transgenic models to knockout individual genes. However, targeting genes one at a time does not capture the more wide‐ranging role of each cell type in its entirety. An often overlooked, but extremely powerful approach to elucidate cellular function is the use of cell ablation strategies, specifically removing one cellular population and examining the resultant impacts on development and function. Cell ablation studies reveal a more holistic overview of cell–cell interactions. This not only identifies important roles for the ablated cell type, which warrant further downstream study, but also, and importantly, reveals functions within the tissue that occur completely independently of the ablated cell type. To date, cell ablation studies in the testis have specifically removed germ cells, Leydig cells, macrophages and recently Sertoli cells. These studies have provided great leaps in understanding not possible via other approaches; as such, cell ablation represents an essential component in the researchers’ tool‐kit, and should be viewed as a complement to the more mainstream approaches to advancing our understanding of testis biology. In this review, we summarise the cell ablation models used in the testis, and discuss what each of these have taught us about testis development and function.

What have we learned about the testis from cell ablation studies

What have we learned about the testis from cell ablation studies

Macrophage 12/15 lipoxygenase expression increases plasma and hepatic lipid levels and exacerbates atherosclerosis

12/15 lipoxygenase (12/15LO) oxidizes polyunsaturated fatty acids (PUFAs) to form bioactive lipid mediators. The role of 12/15LO in atherosclerosis development remains controversial. We evaluated atherosclerosis development and lipid metabolism in 12/15LO-LDL receptor (LDLr) double knockout (DK) vs. LDLr knockout (SK) mice fed a PUFA-enriched diet to enhance production of 12/15LO products. Compared with SK controls, DK mice fed a PUFA-enriched diet had decreased plasma and liver lipid levels, hepatic lipogenic gene expression, VLDL secretion, and aortic atherosclerosis and increased VLDL turnover. Bone marrow transplantation and Kupffer cell ablation studies suggested both circulating leukocytes and Kupffer cells contributed to the lipid phenotype in 12/15LO-deficient mice. Conditioned medium from in vitro incubation of DK vs. SK macrophages reduced triglyceride secretion in McArdle 7777 hepatoma cells. Our results suggest that, in the context of dietary PUFA enrichment, macrophage 12/15LO expression adversely affects plasma and hepatic lipid metabolism, resulting in exacerbated atherosclerosis.

TRPV1-lineage neurons are required for thermal sensation

The ion-channel TRPV1 is believed to be a major sensor of noxious heat, but surprisingly animals lacking TRPV1 still display marked responses to elevated temperature. In this study, we explored the role of TRPV1-expressing neurons in somatosensation by generating mice wherein this lineage of cells was selectively labelled or ablated. Our data show that TRPV1 is an embryonic marker of many nociceptors including all TRPV1- and TRPM8-neurons as well as many Mrg-expressing neurons. Mutant mice lacking these cells are completely insensitive to hot or cold but in marked contrast retain normal touch and mechanical pain sensation. These animals also exhibit defective body temperature control and lose both itch and pain reactions to potent chemical mediators. Together with previous cell ablation studies, our results define and delimit the roles of TRPV1- and TRPM8-neurons in thermosensation, thermoregulation and nociception, thus significantly extending the concept of labelled lines in somatosensory coding.