PROJECT SUMMARY Pulmonary neuroendocrine cells (PNECs) are sensory epithelial cells that signal to the brain through sensory neurons and locally through neuropeptides and neurotransmitters. We used scRNA-seq to comprehensively profile and analyze mouse and human PNECs, which revealed over 40 PNEC neuropeptides and hormones in diverse combinations. Here, we propose to map the innervation and molecular subtypes of human pulmonary neuroendocrine cells and identify the functional subsets in human lung, beginning with an investigation of functionally distinct neuroendocrine stem cells. Using precision cut lung slice cultures to establish an injury model inducing proliferation, we will identify the location of proliferative PNECs and measure their complete transcriptomic profiles by scRNA-seq. In parallel, we will use multiplex single molecule in situ hybridization methods to localize the human PNEC neuropeptides, identify their combinations in situ, and their cognate receptors in human lung. Collectively, these studies will comprehensively characterize the cellular and molecular features of human PNECs, their stem cells and niches. PNEC expansions and ectopic pulmonary neuroendocrine cells are the distinguishing pathologic features underlying a common form of pediatric diffuse lung disease, neuroendocrine cell hyperplasia of infancy (NEHI), which is characterized by diffuse obstructive ventilatory defect. In adults, a pre-neoplastic condition called diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is also associated with airway obstruction and prominent respiratory symptoms thought to be due to bioactive peptides from neuroendocrine cells. We will identify the neuropeptide and receptor expression in pathological cell niches during NE stem cell transformation in DIPNECH. This work establishes a molecular foundation for the diverse clinical presentations associated with pulmonary neuroendocrine lesions and identifies panels of neuropeptides and hormones localized to precise anatomic locations that will provide the basis for developing novel diagnostic and therapeutic approaches.