Single-Nucleus and In Situ RNA-Sequencing Reveal Cell Topographies in the Human Pancreas

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 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 showed a different cellular composition of the endocrine tissue, highlighting the tissue dynamics occurring during development. By applying spatial cartography, involving cell proximity mapping through in situ sequencing, we found evidence of specific cell type neighborhoods, dynamic topographies in the endocrine and exocrine pancreas, and principles of morphologic organization of the organ. Furthermore, similar analyses in chronic pancreatitis biopsy samples showed the presence of acinar-REG⁺ cells, a reciprocal association between macrophages and activated stellate cells, and a new potential role of tuft cells in this disease.

CONCLUSIONS

Our human pancreas cell atlas can be interrogated to understand pancreatic cell biology and provides a crucial reference set for comparisons with diseased tissue samples to map the cellular foundations of pancreatic diseases.

Treatment with Allogenic Mesenchymal Stromal Cells in a Murine Model of Systemic Lupus Erythematosus

Objective

Pre-clinical and uncontrolled studies in patients with systemic lupus erythematosus (SLE) showed that mesenchymal stromal cells (MSCs) have a potential therapeutic role in refractory cases. The optimal therapeutic strategy in these patients remain to be elucidated. Our aim was to test the hypothesis that repeated administrations of 1×10⁶/kg body weight of allogenic MSCs, that is a significantly lower dosage with respect to the fixed 1×10⁶ MSC used in animal models, can be effective in improving the clinical course of a murine SLE model.

Methods

Bone marrow derived MSCs were obtained from 12-week-old C57BL/6J mice. Seventy-five 8 weeks old female NZ mice were randomly assigned to receive via caudal vein the following alternative treatments: 1) single infusion of 10⁶ MSCs/kg body weight at 18 weeks of age (NZ_s18) or at at 22 weeks of age (NZ_s22); 2) multiple monthly infusions of 10⁶ MSCs/kg body weight starting at 18 weeks of age (NZ_M18) or at 22 weeks of age (NZ_M22); 3) saline infusions (NZ_c) Fifteen 8 weeks old C57BL/6J mice (Envigo, Huntingdon, UK) were used as untreated controls (C). Weekly, body weight was recorded and twenty-four hour urines were collected by metabolic cages for each animal; proteinuria was detected by dipstick analysis. At sacrifice, peripheral blood samples were collected from mice and anti-dsDNA antibodies were detected by enzyme immunoassorbent assay (ELISA) method using commercial kits. At sacrifice, kidneys were analyzed for histopathology and immunohistochemical analysis for B220, CD4, MPO, CD4^＋Foxp3, F40/80 infiltration was performed.

Results

Proteinuria occurrence was delayed NZ_S and NZ_M mice, no differences were observed in anti-dsDNA autoantibody titer among the groups at the different time-points; at 36 weeks, no significant differences were observed in term of nephritis scores. Inflammatory cells deposition (MPO and F4/80 positive cells) in NZ_M was significantly higher than in NZ and NZ_S. An overexpression of B lymphocytes (B220) was found in NZ_M while T regulatory cells (CD4^＋ Foxp3^＋ cells) were reduced in both NZ_S and NZ_M with respect to NZ_c.

Conclusions

Overall, our study failed to show a positive effect of a treatment with murine MSCs in this model and, for some aspects, even deleterious results seem to be observed.

Preventive Anti-CD2 Treatment does not Impair Parasite Control in a Murine Toxoplasmosis Model

Targeting human CD2 with the monoclonal antibody (mAb) CB.219 reduces intestinal inflammation in a colitis model where T cells carry human CD2. Here, we asked whether this mAb has adverse effects on infection control.

Mice expressing human CD2 on T cells (huCD2tg) were orally infected with Toxoplasma (T.) gondii and treated with the human CD2-specific mAb CB.219 in a preventive setting. The intestinal T. gondii loads in CB.219 treated mice did not differ from the control group. Histologically, huCD2tg mice showed moderate ileal inflammation that did not change with CB.219 treatment. In the ileum, CB.219 treatment reduced the protein levels of interferon-γ, transforming growth factor β and interleukin-6, whereas interleukin-18 mRNA was slightly increased. The infiltration of neutrophils, macrophages, and T cells into the ileum was unaffected by CB.219 treatment. However, CB.219 treatment decreased the numbers of forkhead box P3⁺ regulatory T cells (Treg) in ileum and liver of huCD2tg mice. This was confirmed in vitro using human peripheral blood mononuclear cells.

Taken together, targeting CD2⁺ T cells by the human CD2 mAb CB.219 does not prevent beneficial immune reactions necessary for pathogen control. Further experiments will address gut specificity, underlying mechanisms, and general applicability of CB.219 treatment.

A guide to histomorphological evaluation of intestinal inflammation in mouse models

Histomorphology remains a powerful routine evaluating intestinal inflammation in animal models. Emphasizing the focus of a given animal study, histopathology can overstate differences between established models. We aimed to systematize histopathological evaluation of intestinal inflammation in mouse models facilitating inter-study comparisons. Samples of all parts of the intestinal tract from well-established mouse models of intestinal inflammation were evaluated from hematoxylin/eosin-stained sections and specific observations confirmed by subsequent immunohistochemistry. Three main categories sufficiently reflected the severity of histopathology independent of the localization and the overall extent of an inflammation: (i) quality and dimension of inflammatory cell infiltrates, (ii) epithelial changes and (iii) overall mucosal architecture. Scoring schemata were defined along specified criteria for each of the three categories. The direction of the initial hit proved crucial for the comparability of histological changes. Chemical noxes, infection with intestinal parasites or other models where the barrier was disturbed from outside, the luminal side, showed high levels of similarity and distinct differences to changes in the intestinal balance resulting from inside events like altered cytokine responses or disruption of the immune cell homeostasis. With a high degree of generalisation and maximum scores from 4-8 suitable scoring schemata accounted specific histopathological hallmarks. Truly integrating demands and experiences of gastroenterologists, mouse researchers, microbiologists and pathologists we provide an easy-to-use guideline evaluating histomorphology in mouse models of intestinal inflammation. Standard criteria and definitions facilitate classification and rating of new relevant models, allow comparison in animal studies and transfer of functional findings to comparable histopathologies in human disease.