Project description:The tissue dynamics that govern maintenance and regeneration of the pancreas remain largely unknown. In particular, the presence and nature of a cellular hierarchy remains a topic of debate. Previous lineage tracing strategies in the pancreas relied on specific marker genes for clonal labeling, which left other populations untested and failed to account for potential widespread phenotypical plasticity. Here we employed a tracing system that depends on replication-induced clonal marks. We found that in homeostasis, steady acinar replacement events characterize tissue dynamics, to which all acinar cells have an equal ability to contribute. Similarly, regeneration following pancreatitis was best characterized by an acinar self-replication model, as no evidence for a cellular hierarchy was detected. In particular, rapid regeneration in the pancreas was found to be driven by an accelerated rate of acinar fission-like events. Together these results provide a comprehensive and quantitative model of cell dynamics in the exocrine pancreas.
Project description:BACKGROUND & AIMS: Acinar cells produce digestive enzymes that impede transcriptomic characterization of the exocrine pancreas. Thus, single-cell RNA-sequencing (scRNA-seq) studies of the pancreas underrepresent acinar cells relative to histological expectations, and a robust approach to capture pancreatic cell responses in disease states is needed. We sought to innovate a method that overcomes these challenges to accelerate study of the pancreas in health and disease. METHODS: We introduce FixNCut, a scRNA-seq approach where tissue is reversibly fixed with dithiobis(succinimidyl propionate) prior to dissociation and single-cell preparation. We apply FixNCut to an established mouse model of acute pancreatitis, validate findings using GeoMx whole transcriptome atlas (WTA) profiling, and integrate our data with prior studies to benchmark our method in both mouse and human pancreas datasets. RESULTS: FixNCut achieves unprecedented definition of challenging pancreatic cells including acinar and immune populations in homeostasis and acute pancreatitis, and identifies changes in all major cell types during injury and recovery. We define the acinar transcriptome during homeostasis and acinar-to-ductal metaplasia and establish a unique gene set to measure deviation from normal acinar identity. We characterize pancreatic immune cells, and analysis of T-cell subsets reveals a polarization of the homeostatic pancreas towards type-2 immunity. We report immune responses during acute pancreatitis and recovery, including early neutrophil infiltration, expansion of dendritic cell subsets, and a substantial shift in the transcriptome of macrophages due to both resident macrophage activation and monocyte infiltration. CONCLUSIONS: FixNCut preserves pancreatic transcriptomes to uncover novel cell states during homeostasis and following pancreatitis, establishing a broadly applicable approach and reference atlas for study of pancreas biology and disease.
Project description:Pancreas volume or mass varies more than 3-fold among adult humans. The heterogeneity is likely the result of genetics, diseases, and nutrition. Dietary protein intake and blood amino acid levels are known to affect pancreas mass, but the underlying mechanism is not well understood. The goal of this study is to determine how increased blood amino acid level (hyperaminoacidemia) induces pancreas expansion.Multiple complementary mouse and zebrafish models were used to study the impact of hyperaminoacidemia on pancreatic mass, acinar cell size and proliferation. Blood amino acid levels were manipulated by dietary protein content, or by pharmacologic or genetic interruption of glucagon signaling (IGS). The activation of mammalian target of rapamycin complex 1 (mTORC1) and Yes-associated protein 1 (YAP) were determined by pS6 and YAP staining. Sirolimus administration in mice and knockdown of solute carrier family 38 member 5b (slc38a5b) and yap/taz in zebrafish were used to determine the role of mTORC1, SLC38A5 and YAP/TAZ in acinar cell proliferation and pancreas expansion. We found that the IGS-induced pancreas expansion was the result of acinar cell proliferation and hypertrophy. Hyperaminoacidemia was the likely mediator as pancreas expansion was blunted by a low protein diet in mice and by knocking down the most highly expressed amino acid transporter gene, slc38a5b, in zebrafish lacking both glucagon receptor genes (gcgr-/-). In GCGR-Ab treated mice, inhibition of mTORC1 attenuated both hyperplasia and hypertrophy of acinar cells. There was a gene expression signature of YAP activation in acinar cells, consistent with increased YAP-expressing acinar cells in GCGR-Ab treated mice and increased fraction of acinar cells with nuclear YAP1 in gcgr-/- zebrafish. Knocking down yap1 or taz decreased mTORC1 activity and acinar cell hyperplasia and hypertrophy in gcgr-/- zebrafish. Hyperaminoacidemia leads to acinar cell proliferation and hypertrophy via activation of both mTORC1 and YAP pathways. The study discovered a previously unrecognized role of the YAP/Taz pathway in hyperaminoacidemia-induced acinar cell hypertrophy and hyperplasia.
Project description:To investigate the role of the E3 ubiquitin ligase Thyroid Receptor Interacting Protein 12 (TRIP12) in pancreatic acinar cell identity and pancreatic carcinogenesis, we used genetically engineered mouse models of pancreas-selective Trip12 deletion, mutant Kras (G12D) and mutant P53 (R172H). We performed gene expression analysis using RNA-seq data from adult acinar cells. We established cell lines from murine pancreatic tumors.
Project description:Serine protease inhibitor Kazal type 3 (Spink3) is a trypsin inhibitor in the pancreas. Spink3-/- pancreatic acinar cells are dead with excessive autophagy at birth (p0.5). To prove the role of nonapoptotic cell death with autophagy, we generated by transgenic technology the pancreas of Spink3-/-;XKI/+ mice contained both normal and dying acinar cells with autophagy. In this new mouse model, chronic inflammation occurred in the pancreas, indicating that some signals from nonapoptotic dead cell induce chronic inflammation in the pancreas. All samples were the pancreas at p0.5. Sample 1 and 2 are the pancreas from wild type (Spink3+/+, control) mice. Sample 3 and 4 are the pancreas from Spink3-/-, which all pancreatic acinar cells show induced nonapoptotic cell death with autophagy. Sample 5 and 6 are the pancreas from Spink3-/-XKI/+, about half acinar cells are normal, but other acinar cells show induced nonapoptotic cell death with autophagy.
Project description:The expansion procedure strengthened the pancreas progenitor identity while efficiently repressed endocrine differentiation and liver fate as well as acinar and duct differentiation programs
Project description:To identify putative procarcinogenic gene changes associated with pancreatic acinar cell neoplasia in rats exposed to peroxisome proliferator activated receptor alpha agonists, we performed transcription profiling in the pancreas of rats fed diets containing the pancreatic carcinogen Wyeth 14,643 (Wy) at procarcinogenic (50ppm) and non-carcinogenic (20ppm) doses for 1, 7, 28 and 90 days. The effects of these treatments were compared to those of ammonium perfluorooctanoate (APFO) 300 ppm, an agent shown to induce pancreatic acinar cell adenomas in rats, and diethylhexylphthalate (DEHP) 12,000 ppm, an agent not shown to produce pancreatic acinar cell tumors. To assess whether this putative mechanism(s) of carcinogenesis occurs in ‘target’ cells we have also performed transcriptional profiling in isolated pancreatic acinar cells obtained from animals exposed to these compounds in vivo.
Project description:Acinar cells make up the majority of all cells in the pancreas, yet the source of new acinar cells during homeostasis remains unknown. Using multicolor lineage-tracing and organoid-formation assays, we identified the presence of a progenitor-like acinar cell subpopulation. These cells have long-term self-renewal capacity, albeit in a unipotent fashion. We further demonstrate that binuclear acinar cells are terminally differentiated acinar cells. Transcriptome analysis of single acinar cells revealed the existence of a minor population of cells expressing progenitor markers. Interestingly, a gain of the identified markers accompanied by a transient gain of proliferation was observed following chemically induced pancreatitis. Altogether, our study identifies a functionally and molecularly distinct acinar subpopulation and thus transforms our understanding of the acinar cell compartment as a pool of equipotent secretory cells.
Project description:Pancreas development involves a coordinated process in which an early phase of cell segregation and patterning is proceeded by a longer phase of lineage restriction, expansion and extensive tissue remodeling. By combining quantitative clonal lineage tracing and whole-mount reconstruction with proliferation kinetics and single-cell transcriptional profiling, we define the functional basis of pancreas morphogenesis. Our results show that the large-scale organization of tissue can be traced to the activity of self-renewing precursors that localize at the termini of growing ductal branches and act collectively to drive serial rounds of stochastic ductal bifurcation balanced by termination. During this process, multipotent precursors give rise to self-renewing acinar-committed precursors, which are conveyed with growing ducts, as well as fate-restricted ductal progenitors that expand the trailing ducts and give rise to delaminating islet precursors. Together, these findings define quantitatively how the functional behavior and lineage progression of heterogeneous pools of the pancreatic precursors that define the organization of the organ.