BACKGROUND & AIMS: Molecular evidence of cellular heterogeneity in the human exocrine pancreas has not been yet established because of the local concentration and cascade of hydrolytic enzymes that can rapidly degrade cells and RNA upon pancreatic resection. We sought to better understand the heterogeneity and cellular composition of the pancreas in neonates and adults in healthy and diseased conditions using single-cell-sequencing approaches. METHODS: We innovated single-nucleus RNA-sequencing protocols and profiled more than 120,000 cells from pancreata of adult and neonatal human donors. We validated the single-nucleus findings using RNA fluorescence in situ hybridization, in situ sequencing, and computational approaches. RESULTS: We created the first comprehensive atlas of human pancreas cells, to our knowledge Q9 , including epithelial and nonepithelial constituents, and uncovered 3 distinct acinar cell types, with possible implications for homeostatic and inflammatory processes of the pancreas. The comparison with neonatal single-nucleus-sequencing data

Here, we describe a novel approach that allows pathologists to three-dimensionally analyse malignant tissues, including the tumour-host tissue interface. Our visualization technique utilizes a combination of ultrafast chemical tissue clearing and light-sheet microscopy to obtain virtual slices and 3D reconstructions of up to multiple centimetre sized tumour resectates. For the clearing of tumours we propose a preparation technique comprising three steps: (a) Fixation and enhancement of tissue autofluorescence with formalin/5-sulfosalicylic acid. (b) Ultrafast active chemical dehydration with 2,2-dimethoxypropane and (c) refractive index matching with dibenzyl ether at up to 56 °C. After clearing, the tumour resectates are imaged. The images are computationally post-processed for contrast enhancement and artefact removal and then 3D reconstructed. Importantly, the sequence a–c is fully reversible, allowing the morphological correlation of one and the same histological structures, once visualized with our novel technique and once visualized by standard H&E- and IHC-staining. After reverting the clearing procedure followed by standard H&E processing, the hallmarks of ductal carcinoma in situ (DCIS) found in the cleared samples could be successfully correlated with the corresponding structures present in H&E and IHC staining. Since the imaging of several thousands of optical sections is a fast process, it is possible to analyse a larger part of the tumour than by mechanical slicing. As this also adds further information about the 3D structure of malignancies, we expect that our technology will become a valuable addition for histological diagnosis in clinical pathology.

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The cellular heterogeneity of the human pancreas has not been previously characterized due to the presence of extreme digestive enzymatic activities, causing rapid degradation of cells and RNA upon resection. Therefore, previous cellular mapping studies based on gene expression were focused on pancreatic islets, leading to a vast underrepresentation of the exocrine compartment. By profiling the transcriptome of more than 110,000 cells from human donors, we created the first comprehensive pancreas cell atlas including all the tissue components. We unveiled the existence of four different acinar cell states and suggest a division of labor for enzyme production within the healthy exocrine pancreas, which has so far been considered a homogeneous tissue. This work provides a novel and rich resource for future investigations of the healthy and diseased pancreas. Main textSingle-cell RNA sequencing (scRNA-seq) has tremendously expanded our understanding of heterogeneous human tissues and made the identification of novel functional cell types in the lung, brain and liver possible 1-5 . The development of single-nucleus RNA-seq (sNuc-seq) has further broadened its application to tissues which are difficult to dissociate or already archived, such as clinical samples 6 . Pancreatic exocrine tissues contain among the highest level of digestive enzymatic activities in the human body 7 , hindering the preparation of undegraded RNA from this organ. Therefore, previous scRNA-seq studies of the human pancreas have been restricted to the islets of Langerhans (the endocrine part of the organ) in order to remove the exocrine compartment, namely the acinar and ductal cells responsible for the production and transport of digestive enzymes. Following their isolation, the endocrine islets were cultured in vitro, enzymatically dissociated and processed on microfluidics devices before next-generation sequencing [8][9][10][11][12][13][14] . While this strategy proved to be successful in generating a draft of the endocrine human pancreas cell atlas, it has distinct disadvantages. For example, only a very small number of exocrine cells have been captured and their numbers are largely underrepresented relative to homeostatic physiological conditions (approximately 5% rather than 95%). Moreover, in vitro culture and dissociation steps are known to introduce technical artefacts in gene expression measurements 15 . In this work we opted to use flash-frozen tissue biopsies isolated from pancreata of six human donors followed by sNuc-seq ( Fig. 1a), avoiding in vitro expansion and dissociation procedures, aiming to obtain an unbiased sampling of the organ.

Sirolimus and its derivatives have similar effects on endothelial regrowth and neointimal thickening. The observation of greatest fibrin deposition in the experimental EES group indicates that everolimus may affect vascular healing differently.

Background: Pseudohypoxic tumors activate pro-oncogenic pathways typically associated with severe hypoxia even when sufficient oxygen is present, leading to highly aggressive tumors. Prime examples are pseudohypoxic pheochromocytomas and paragangliomas (p-PPGLs), neuroendendocrine tumors currently lacking effective therapy. Previous attempts to generate mouse models for p-PPGLs all failed. Here, we describe that the rat MENX line, carrying a Cdkn1b (p27) frameshift-mutation, spontaneously develops pseudohypoxic pheochromocytoma (p-PCC). Methods: We compared rat p-PCCs with their cognate human tumors at different levels: histology, immunohistochemistry, catecholamine profiling, electron microscopy, transcriptome and metabolome. The vessel architecture and angiogenic potential of pheochromocytomas (PCCs) was analyzed by light-sheet fluorescence microscopy ex vivo and multi-spectral optoacoustic tomography (MSOT) in vivo. Results: The analysis of tissues at various stages, from hyperplasia to advanced grades, allowed us to correlate tumor characteristics with progression. Pathological changes affecting the mitochrondrial ultrastructure where present already in hyperplasias. Rat PCCs secreted high levels of norepinephrine and dopamine. Transcriptomic and metabolomic analysis revealed changes in oxidative phosphorylation that aggravated over time, leading to an accumulation of the oncometabolite 2-hydroxyglutarate, and to hypermethylation, evident by the loss of the epigenetic mark 5-hmC. While rat PCC xenografts showed high oxygenation, induced by massive neoangiogenesis, rat primary PCC transcriptomes possessed a pseudohypoxic signature of high Hif2a, Vegfa, and low Pnmt expression, thereby clustering with human p-PPGL. Conclusion: Endogenous rat PCCs recapitulate key phenotypic features of human p-PPGLs. Thus, MENX rats emerge as the best available animal model of these aggressive tumors. Our study provides evidence of a link between cell cycle dysregulation and pseudohypoxia.

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AimsProgrammed death-ligand 1 (PD-L1) status in triple-negative breast cancer (TNBC) is important for immune checkpoint inhibitor therapies but may vary between different immunohistochemical assays, scorings and the type of specimen used for analysis.MethodsWe compared the analytical concordance of three clinically relevant PD-L1 assays (VENTANA SP142, VENTANA SP263 and DAKO 22C3 pharmDx) assessing immune cell score (IC), tumour proportion score and combined positive score (CPS) in preoperative biopsies and resection specimens of primary TNBC. PD-L1 expression was scored on virtual whole slide images and compared with expression data from corresponding surgical specimens.ResultsThe mean PD-L1 positivity in TNBC biopsies defined as IC ≥1% and CPS ≥1 ranged between 11% and 61% with the lowest positivity for SP142 and highest for SP263. The corresponding surgical specimens showed overall higher positivity rates (53%–75%). When comparing biopsies with surgical specimens, the agreement for PD-L1 positivity with SP263 and 22C3 at IC score ≥1% and CPS ≥1 was fair (kappa 0.47–0.52) and poor for SP142 (kappa 0.15–0.19). Using CPS ≥10 cut-off, the agreement for SP263 was excellent (kappa 0.751) but poor for 22C3 (kappa 0.261). Spearman correlation coefficients ranged between 0.489 and 0.75 indicating a generally moderate to strong correlation between biopsies and surgical specimens for all assays and scores.ConclusionsWe demonstrate high accordance between biopsies and surgical specimens for SP263 and 22C3 scoring but less for SP142. Generally, biopsies are suitable for PD-L1 testing in TNBC but the appropriate assay, scoring and cut-off must be considered.