Molecular characterization of cell types using single-cell transcriptome sequencing is revolutionizing cell biology and enabling new insights into the physiology of human organs. We created a human reference atlas comprising nearly 500,000 cells from 24 different tissues and organs, many from the same donor. This atlas enabled molecular characterization of more than 400 cell types, their distribution across tissues, and tissue-specific variation in gene expression. Using multiple tissues from a single donor enabled identification of the clonal distribution of T cells between tissues, identification of the tissue-specific mutation rate in B cells, and analysis of the cell cycle state and proliferative potential of shared cell types across tissues. Cell type–specific RNA splicing was discovered and analyzed across tissues within an individual.

Acute lung injury (ALI) is an inflammatory disease with a high mortality rate. Although typically seen in individuals with sepsis, ALI is also a major complication in severe acute pancreatitis (SAP). The pathophysiology of SAP-associated ALI is poorly understood, but elevated serum levels of IL-6 is a reliable marker for disease severity. Here, we used a mouse model of acute pancreatitis–associated (AP-associated) ALI to determine the role of IL-6 in ALI lethality. Il6-deficient mice had a lower death rate compared with wild-type mice with AP, while mice injected with IL-6 were more likely to develop lethal ALI. We found that inflammation-associated NF-κB induced myeloid cell secretion of IL-6, and the effects of secreted IL-6 were mediated by complexation with soluble IL-6 receptor, a process known as trans-signaling. IL-6 trans-signaling stimulated phosphorylation of STAT3 and production of the neutrophil attractant CXCL1 in pancreatic acinar cells. Examination of human samples revealed expression of IL-6 in combination with soluble IL-6 receptor was a reliable predictor of ALI in SAP. These results demonstrate that IL-6 trans-signaling is an essential mediator of ALI in SAP across species and suggest that therapeutic inhibition of IL-6 may prevent SAP-associated ALI.

Chronic pancreatitis (CP) is a continuing inflammatory disease of the pancreas, which typically presents with attacks of severe upper abdominal pain. CP causes structural and functional alterations, often leading to irreversible tissue damage.

The transcription factor nuclear factor-κB (NF-κB) (a heterodimer of NF-κB1p50 and RelA) is activated rapidly in acute pancreatitis (AP). However, it is not clear whether NF-κB promotes or protects against AP. We used the NF-κB inhibitor protein, inhibitor of κB (IκB)α, to study the roles of NF-κB in the development of AP in mice. IκBα or the combination of IκBα and RelA selectively were deleted from pancreas of mice using the Cre/locus of cross-over P strategy; cerulein or L-arginine were used to induce AP. We performed microarray analyses of the IκBα- and RelA-deficient pancreata. DNA from healthy individuals and patients with acute or chronic pancreatitis were analyzed for variants in coding regions of alpha-1-antichymotrypsin. Mice with pancreas-specific deletion of IκBα had constitutive activation of RelA and a gene expression profile consistent with NF-κB activation; development of AP in these mice was attenuated and trypsin activation was impaired. However, AP was fully induced in mice with pancreas-specific deletion of IκBα and RelA. By using genome-wide expression analysis, we identified a cluster of NF-κB-regulated genes that might protect against the development of AP. The serine protease inhibitor 2A (Spi2a) was highly up-regulated in IκBα-deficient mice. Lentiviral-mediated expression of Spi2A reduced the development of AP in C57BL/6 and RelA-deficient mice. However, we did not correlate any variants of alpha-1-antichymotrypsin, the human homologue of Spi2a, with acute or chronic pancreatitis. Pancreas-specific deletion of IκBα results in nuclear translocation of RelA and reduces AP induction and trypsin activation in mice after administration of cerulein or L-arginine. Constitutive activation of RelA up-regulates Spi2A, which protects mice against the development of AP.