Essential role for autophagy protein ATG7 in the maintenance of intestinal stem cell integrity.

The intestinal epithelium acts as a barrier between the organism and its microenvironment, including the gut microbiota. It is the most rapidly regenerating tissue in the human body thanks to a pool of intestinal stem cells (ISCs) expressing Lgr5 The intestinal epithelium has to cope with continuous stress linked to its digestive and barrier functions. Epithelial repair is crucial to maintain its integrity, and Lgr5-positive intestinal stem cell (Lgr5+ISC) resilience following cytotoxic stresses is central to this repair stage. We show here that autophagy, a pathway allowing the lysosomal degradation of intracellular components, plays a crucial role in the maintenance and genetic integrity of Lgr5+ISC under physiological and stress conditions. Using conditional mice models lacking the autophagy gene Atg7 specifically in all intestinal epithelial cells or in Lgr5+ISC, we show that loss of Atg7 induces the p53-mediated apoptosis of Lgr5+ISC. Mechanistically, this is due to increasing oxidative stress, alterations to interactions with the microbiota, and defective DNA repair. Following irradiation, we show that Lgr5+ISC repair DNA damage more efficiently than their progenitors and that this protection is Atg7 dependent. Accordingly, we found that the stimulation of autophagy on fasting protects Lgr5+ISC against DNA damage and cell death mediated by oxaliplatin and doxorubicin treatments. Finally, p53 deletion prevents the death of Atg7-deficient Lgr5+ISC but promotes genetic instability and tumor formation. Altogether, our findings provide insights into the mechanisms underlying maintenance and integrity of ISC and highlight the key functions of Atg7 and p53.

The tumor inflammation signature (TIS) is associated with anti-PD-1 treatment benefit in the CERTIM pan-cancer cohort.

BACKGROUND: The 18-gene tumor inflammation signature (TIS) is a clinical research assay that enriches for clinical benefit to immune checkpoint blockade. We evaluated its ability to predict clinical benefit of immunotherapy in cancer patients treated with PD-1 checkpoint inhibitors in routine clinical care. METHODS: The CERTIM cohort is a prospective cohort which includes patients receiving immune checkpoint inhibitors in Cochin University hospital. RNA extracted from 58 archival formalin fixed paraffin embedded tumor blocks (including 38 lung cancers, 5 melanomas, 10 renal carcinomas, 4 urothelial carcinomas and 1 colon carcinoma) was hybridized to a beta version of the NanoString® PanCancer IO360™ CodeSet using nCounter® technology. Gene expression signatures were correlated with tumor responses (by RECIST criteria) and overall survival. PD-L1 immunostaining on tumor cells was assessed in 37 non-small cell lung cancer (NSCLC) samples and tumor mutational burden (TMB) measured by whole exome sequencing in 19 of these. RESULTS: TIS scores were significantly associated with complete or partial response to anti-PD-1 treatment in the whole cohort (odds ratio = 2.64, 95% CI [1.4; 6.0], p = 0.008), as well as in the NSCLC population (odds ratio = 3.27, 95% CI [1.2; 11.6], p = 0.03). Patients whose tumor had a high TIS score (upper tertile) showed prolonged overall survival compared to patients whose tumor had lower TIS scores, both in the whole cohort (hazard ratio = 0.37, 95% CI [0.18, 0.76], p = 0.005) and in the NSCLC population (hazard ratio = 0.36, 95% CI [0.14, 0.90], p = 0.02). In the latter, the TIS score was independent from either PD-L1 staining on tumor cells (spearman coefficient 0.2) and TMB (spearman coefficient - 0.2). CONCLUSIONS: These results indicate that validated gene expression assay measuring the level of tumor microenvironment inflammation such as TIS, are accurate and independent predictive biomarkers and can be easily implemented in the clinical practice.

Acellular therapeutic approach for heart failure: in vitro production of extracellular vesicles from human cardiovascular progenitors.

Aims: We have shown that extracellular vesicles (EVs) secreted by embryonic stem cell-derived cardiovascular progenitor cells (Pg) recapitulate the therapeutic effects of their parent cells in a mouse model of chronic heart failure (CHF). Our objectives are to investigate whether EV released by more readily available cell sources are therapeutic, whether their effectiveness is influenced by the differentiation state of the secreting cell, and through which mechanisms they act. Methods and results: The total EV secreted by human induced pluripotent stem cell-derived cardiovascular progenitors (iPSC-Pg) and human induced pluripotent stem cell-derived cardiomyocytes (iPSC-CM) were isolated by ultracentrifugation and characterized by Nanoparticle Tracking Analysis, western blot, and cryo-electron microscopy. In vitro bioactivity assays were used to evaluate their cellular effects. Cell and EV microRNA (miRNA) content were assessed by miRNA array. Myocardial infarction was induced in 199 nude mice. Three weeks later, mice with left ventricular ejection fraction (LVEF) ≤ 45% received transcutaneous echo-guided injections of iPSC-CM (1.4 × 106, n = 19), iPSC-Pg (1.4 × 106, n = 17), total EV secreted by 1.4 × 106 iPSC-Pg (n = 19), or phosphate-buffered saline (control, n = 17) into the peri-infarct myocardium. Seven weeks later, hearts were evaluated by echocardiography, histology, and gene expression profiling, blinded to treatment group. In vitro, EV were internalized by target cells, increased cell survival, cell proliferation, and endothelial cell migration in a dose-dependent manner and stimulated tube formation. Extracellular vesicles were rich in miRNAs and most of the 16 highly abundant, evolutionarily conserved miRNAs are associated with tissue-repair pathways. In vivo, EV outperformed cell injections, significantly improving cardiac function through decreased left ventricular volumes (left ventricular end systolic volume: -11%, P < 0.001; left ventricular end diastolic volume: -4%, P = 0.002), and increased LVEF (+14%, P < 0.0001) relative to baseline values. Gene profiling revealed that EV-treated hearts were enriched for tissue reparative pathways. Conclusion: Extracellular vesicles secreted by iPSC-Pg are effective in the treatment of CHF, possibly, in part, through their specific miRNA signature and the associated stimulation of distinct cardioprotective pathways. The processing and regulatory advantages of EV could make them effective substitutes for cell transplantation.

CRISPR/Cas9-mediated inactivation of the phosphatase activity of soluble epoxide hydrolase prevents obesity and cardiac ischemic injury.

INTRODUCTION: Although the physiological role of the C-terminal hydrolase domain of the soluble epoxide hydrolase (sEH-H) is well investigated, the function of its N-terminal phosphatase activity (sEH-P) remains unknown. OBJECTIVES: This study aimed to assess in vivo the physiological role of sEH-P. METHODS: CRISPR/Cas9 was used to generate a novel knock-in (KI) rat line lacking the sEH-P activity. RESULTS: The sEH-P KI rats has a decreased metabolism of lysophosphatidic acids to monoacyglycerols. KI rats grew almost normally but with less weight and fat mass gain while insulin sensitivity was increased compared to wild-type rats. This lean phenotype was more marked in males than in female KI rats and mainly due to decreased food consumption and enhanced energy expenditure. In fact, sEH-P KI rats had an increased lipolysis allowing to supply fatty acids as fuel to potentiate brown adipose thermogenesis under resting condition and upon cold exposure. The potentiation of thermogenesis was abolished when blocking PPARγ, a nuclear receptor activated by intracellular lysophosphatidic acids, but also when inhibiting simultaneously sEH-H, showing a functional interaction between the two domains. Furthermore, sEH-P KI rats fed a high-fat diet did not gain as much weight as the wild-type rats, did not have increased fat mass and did not develop insulin resistance or hepatic steatosis. In addition, sEH-P KI rats exhibited enhanced basal cardiac mitochondrial activity associated with an enhanced left ventricular contractility and were protected against cardiac ischemia-reperfusion injury. CONCLUSION: Our study reveals that sEH-P is a key player in energy and fat metabolism and contributes together with sEH-H to the regulation of cardiometabolic homeostasis. The development of pharmacological inhibitors of sEH-P appears of crucial importance to evaluate the interest of this promising therapeutic strategy in the management of obesity and cardiac ischemic complications.

Long-term cardiovascular disorders in the STOX1 mouse model of preeclampsia.

Adverse long-term cardiovascular (CV) consequences of PE are well established in women. However, the mechanism responsible for that risk remains unknown. Here, we mated wild-type female mice of the FVB/N strain to STOX1A-overexpressing mice to mimic severe PE and investigated the long-term consequences on the maternal cardiovascular system. Ultrasonography parameters were analyzed in mice before pregnancy and at 3 and 6 months post-pregnancy. At 6 months post-pregnancy, cardiac stress test induced by dobutamine injection revealed an abnormal ultrasonography Doppler profile in mice with previous PE. Eight months post-pregnancy, the heart, endothelial cells (ECs) and plasma of females were analyzed and compared to controls. The heart of mice with PE showed left-ventricular hypertrophy associated with altered histology (fibrosis). Transcriptomic analysis revealed the deregulation of 1149 genes in purified ECs and of 165 genes in the hearts, many being involved in heart hypertrophy. In ECs, the upregulated genes were associated with inflammation and cellular stress. Systems biology analysis identified interleukin 6 (IL-6) as a hub gene connecting these pathways. Plasma profiling of 33 cytokines showed that, 8 of them (Cxcl13, Cxcl16, Cxcl11, IL-16, IL-10, IL-2, IL-4 and Ccl1) allowed to discriminate mice with previous PE from controls. Thus, PE triggers female long-term CV consequences on the STOX1 mouse model.

Nanobodies against surface biomarkers enable the analysis of tumor genetic heterogeneity in uveal melanoma patient-derived xenografts.

Monoclonal antibodies specific for biomarkers expressed on the surface of uveal melanoma (UM) cells would simplify the immune capture and genomic characterization of heterogeneous tumor cells originated from patient-derived xenografts (PDXs). Antibodies against four independent tumor antigens were isolated by panning a nanobody synthetic library. Such antibodies enabled flow cytometry-based sorting of distinct cell subpopulations from UM PDXs and to analyze their genomic features. The complexity and specificity of the biochemical and genomic biomarker combinations mirrored the UM tumor polyclonality. The data showed that MUC18 is highly and universally displayed on the surface of UM cells with different genetic background and consequently represents a reliable pan-biomarker for their identification and purification. In contrast, the other three biomarkers were detected in very variable combinations in UM PDX cells. The availability of the identified nanobodies will be instrumental in developing clone-specific drug evaluation and rational clinical strategies based on accurate genomic profiling.