Highlights d A hPSC-derived cell and organoid platform is used to study SARS-CoV-2 tissue tropism d Human pancreatic alpha and beta cells are permissive to SARS-CoV-2 infection d Human hepatocyte and cholangiocyte organoids are permissive to SARS-CoV-2 infection d hPSC-derived cells/organoids show similar chemokine responses as COVID-19 tissues

Summary Tumors are largely classified by histological appearance, yet morphological features do not necessarily predict cellular origin. To determine the origin of pancreatic ductal adenocarcinoma (PDA), we labeled and traced pancreatic cell populations after induction of a PDA-initiating Kras mutation. Our studies reveal that ductal and stem-like centroacinar cells are surprisingly refractory to oncogenic transformation, whereas acinar cells readily form PDA precursor lesions with ductal features. We show that formation of acinar-derived premalignant lesions depends on ectopic induction of the ductal gene Sox9. Moreover, when concomitantly expressed with oncogenic Kras, Sox9 accelerates formation of premalignant lesions. These results provide insight into the cellular origin of PDA and suggest that its precursors arise via induction of a duct-like state in acinar cells.

Pancreas oganogenesis comprises a coordinated and highly complex interplay of signaling events and transcriptional networks that guide a step-wise process of organ development from early bud specification all the way to the final mature organ state. Extensive research on pancreas development over the last few years, largely driven by a translational potential for pancreatic diseases (diabetes, pancreatic cancer, and so on), is markedly advancing our knowledge of these processes. It is a tenable goal that we will one day have a clear, complete picture of the transcriptional and signaling codes that control the entire organogenetic process, allowing us to apply this knowledge in a therapeutic context, by generating replacement cells in vitro, or perhaps one day to the whole organ in vivo. This review summarizes findings in the past 5 years that we feel are amongst the most significant in contributing to the deeper understanding of pancreas development. Rather than try to cover all aspects comprehensively, we have chosen to highlight interesting new concepts, and to discuss provocatively some of the more controversial findings or proposals. At the end of the review, we include a perspective section on how the whole pancreas differentiation process might be able to be unwound in a regulated fashion, or redirected, and suggest linkages to the possible reprogramming of other pancreatic cell-types in vivo, and to the optimization of the forward-directed-differentiation of human embryonic stem cells (hESC), or induced pluripotential cells (iPSC), towards mature b-cells. Developmental Dynamics 240:530-565,

There is an urgent need to create novel models using human disease-relevant cells to study SARS-CoV-2 biology and to facilitate drug screening. As SARS-CoV-2 primarily infects the respiratory tract, we developed a lung organoid model using human pluripotent stem cells (hPSC-LOs). The hPSC-LOs, particularly alveolar type II-like cells, are permissive to SARS-CoV-2 infection, and showed robust induction of chemokines upon SARS-CoV-2 infection, similar to what is seen in COVID-19 patients. Nearly 25% of these patients also have gastrointestinal manifestations, which are associated with worse COVID-19 outcomes 1. We therefore also generated complementary hPSC-derived colonic organoids (hPSC-COs) to explore the response of colonic cells to SARS-CoV-2 infection. We found that multiple colonic cell types, especially enterocytes, express ACE2 and are permissive to SARS-CoV-2 infection. Using hPSC-LOs, we performed a high throughput screen of FDA-approved drugs and identified entry inhibitors of SARS-CoV-2, including imatinib, mycophenolic acid (MPA), and quinacrine dihydrochloride (QNHC). Treatment at physiologically relevant levels of these drugs significantly inhibited SARS-CoV-2 infection of both hPSC-LOs and hPSC-COs. Together, these data demonstrate that hPSC-LOs and hPSC-COs infected by SARS-CoV-2 can serve as disease models to study SARS-CoV-2 infection and provide a valuable resource for drug screening to identify candidate COVID-19 therapeutics. The development of anti-SARS-CoV-2 drugs could change the scope of the ongoing COVID-19 pandemic. While this strategy is being pursued, high throughput screens are typically performed in transformed cell lines which fail to capture the physiologically relevant dynamics of human SARS-CoV-2 infection. To overcome limitations of these cell lines, several adult organoid models have been developed to study SARS-CoV-2 2-4. Here, we developed human pluripotent stem cell-derived lung and colonic organoids (hPSC-LOs and hPSC-COs) optimized as in vitro platforms for high throughput drug screening. hPSC-LOs are permissive to SARS-CoV-2 We differentiated hPSCs to lung organoids (hPSC-LOs) based on previously reported stepwise strategies 5-13 (Extended Data Fig. 1a-1c). qRT-PCR and RNA-seq profiling validates the expression of alveolar type II (AT2) cell markers in the hPSC-LOs (Extended Data Fig. 1d, 1e). Intra-cellular flow cytometry further confirmed the presence of Pro-SP-C + cells in hPSC-LOs (Extended Data Fig. 1f). Single cell transcriptomic profiles of hPSC-LOs identified AT2-like cells, which were enriched for adult human lung AT2 cell markers (Fig. 1a-1c and Extended Data Fig. 2a-2c).

SUMMARYPancreatic multipotent progenitor cells (MPCs) produce acinar, endocrine and duct cells during organogenesis, but their existence and location in the mature organ remain contentious. We used inducible lineage-tracing from the MPC-instructive gene Ptf1a to define systematically in mice the switch of Ptf1a + MPCs to unipotent proacinar competence during the secondary transition, their rapid decline during organogenesis, and absence from the mature organ. Between E11.5 and E15.5, we describe tip epithelium heterogeneity, suggesting that putative Ptf1a