Background & Aims Loss of leucine-rich repeat-containing G-protein–coupled receptor 5–positive crypt base columnar cells provides permissive conditions for different facultative stem cell populations to dedifferentiate and repopulate the stem cell compartment. In this study, we used a defensin α4-Cre recombinase (Defa4Cre) line to define the potential of Paneth cells to dedifferentiate and contribute to intestinal stem cell (ISC) maintenance during normal homeostasis and after intestinal injury. Methods Small intestine and enteroids from Defa4 Cre ; Rosa26 tandem dimer Tomato (tdTomato), a red fluoresent protein, (or Rosa26 Enhanced Yellow Fluorescent Protein (EYFP)) reporter, Notch gain-of-function ( Defa4 Cre ;Rosa26 Notch Intracellular Domain (NICD)-ires-nuclear Green Fluorescent Protein (nGFP) and Defa4 Cre ;Rosa26 reverse tetracycline transactivator–ires Enhanced Green Fluorescent Protein (EGFP) ;TetO NICD ), A Disintegrin and Metalloproteinase domain-containing protein 10 (ADAM10) loss-of-function ( Defa4 Cre ;ADAM10 flox/flox ), and Adenomatous polyposis coli (APC) inactivation ( Defa4 Cre ;APC flox/flox ) mice were analyzed. Doxorubicin treatment was used as an acute intestinal injury model. Lineage tracing, proliferation, and differentiation were assessed in vitro and in vivo. Results Defa4 Cre -expressing cells are fated to become mature Paneth cells and do not contribute to ISC maintenance during normal homeostasis in vivo. However, spontaneous lineage tracing was observed in enteroids, and fluorescent-activated cell sorter–sorted Defa4 Cre -marked cells showed clonogenic enteroid growth. Notch activation in Defa4 Cre -expressing cells caused dedifferentiation to multipotent ISCs in vivo and was required for adenoma formation. ADAM10 deletion had no significant effect on crypt homeostasis. However, after acute doxorubicin-induced injury, Defa4 Cre -expressing cells contributed to regeneration in an ADAM10–Notch–dependent manner. Conclusions Our studies have shown that Defa4 Cre -expressing Paneth cells possess cellular plasticity, can dedifferentiate into multipotent stem cells upon Notch activation, and can contribute to intestinal regeneration in an acute injury model.

Axial elongation of the neural tube is crucial during mammalian embryogenesis for anterior-posterior body axis establishment and subsequent spinal cord development, but these processes cannot be interrogated directly in humans as they occur post-implantation. Here, we report an organoid model of neural tube extension derived from human pluripotent stem cell (hPSC) aggregates that have been caudalized with Wnt agonism, enabling them to recapitulate aspects of the morphological and temporal gene expression patterns of neural tube development. Elongating organoids consist largely of neuroepithelial compartments and contain TBXT+SOX2+ neuro-mesodermal progenitors in addition to PAX6+NES+ neural progenitors. A critical threshold of Wnt agonism stimulated singular axial extensions while maintaining multiple cell lineages, such that organoids displayed regionalized anterior-to-posterior HOX gene expression with hindbrain (HOXB1) regions spatially distinct from brachial (HOXC6) and thoracic (HOXB9) regions. CRISPR interference-mediated silencing of TBXT, a Wnt pathway target, increased neuroepithelial compartmentalization, abrogated HOX expression and disrupted uniaxial elongation. Together, these results demonstrate the potent capacity of caudalized hPSC organoids to undergo axial elongation in a manner that can be used to dissect the cellular organization and patterning decisions that dictate early human nervous system development.

GI toxicity is a common dose-limiting adverse effect of platin chemotherapy treatment. Up to 50% of cancer survivors continue to experience symptoms of chronic constipation or diarrhea induced by their chemotherapy for many years after their treatment. This drug toxicity is largely attributed to damage to enteric neurons that innervate the GI tract and control GI motility. The mechanisms responsible for platin-induced enteric neurotoxicity and potential preventative strategies have remained unknown. Here, we use human pluripotent stem cell derived enteric neurons to establish a new model system capable of uncovering the mechanism of platin-induced enteric neuropathy. Utilizing this scalable system, we performed a high throughput screen and identified drug candidates and pathways involved in the disease. Our analyses revealed that excitotoxicity through muscarinic cholinergic signaling is a key driver of platin-induced enteric neuropathy. Using single nuclei transcriptomics and functional assays, we discovered that this disease mechanism leads to increased susceptibility of specific neuronal subtypes, including inhibitory nitrergic neurons, to platins. Histological assessment of the enteric nervous system in platin-treated patients confirmed the selective loss of nitrergic neurons. Finally, we demonstrated that pharmacological and genetic inhibition of muscarinic cholinergic signaling is sufficient to rescue enteric neurons from platin excitotoxicity in vitro and can prevent platin-induced constipation and degeneration of nitrergic neurons in mice. These studies define the mechanisms of platin-induced enteric neuropathy and serve as a framework for uncovering cell type-specific manifestations of cellular stress underlying numerous intractable peripheral neuropathies.