PROJECT SUMMARY- PROJECT 5 The underlying mechanisms that drive resiliency or, conversely, rapid decline, remain unclear. Moreover, models of human aging, longevity, and resilience to disease that allow for the functional testing of potential interventions are virtually non-existent. To directly address these gaps in understanding, we propose to build and harness novel, complementary, in vitro human cellular models created from the fibroblasts and/or Peripheral Blood Mononuclear Cells (PBMCs) of healthy young and old subjects and those experiencing mild cognitive impairment (MCI) or clinically verified Alzheimer's Disease and Related Dementias (ADRD). We will also study and compare cells generated from individuals who display exceptional longevity (EL) and/or resistance to or resilience against ADRD. First (1), in combinatorial efforts, fibroblasts and PBMCs will be reprogrammed into iPSCs and differentiated into neurons (iPSC-derived neurons) while, in parallel, the same starting material will undergo direct conversion into induced neurons (iNs) which retain aging-associated signatures. Using this approach, we harness both the flexibility and unlimited cell source provided by iPSCs while also capturing potential epigenetic drivers of longevity or resilience by using iNs. Next (2), we will exploit these complementary cell-based models to identify mechanisms underlying prevention (iPSC model) or reversal (iN model) of aging-related decline including studies and models of dynamic resilience, DNA repair hotspots, and metabolic functionality. Lastly (3), we will leverage iPSCs and iNs in functional validation studies of the genes, genetic variants, proteins, metabolites, and other analytes found to be associated with longevity or decline across all projects in the Longevity Consortium. These overlapping strategies present a unique opportunity for the cross validation of the functional results, identified pathways, and signatures observed across systems and laboratories, a major point of concern in the rapidly emerging geroscience field. This work combines innovative, complementary human cell-based models capable of recapitulating human development with next generation omics and functional assays to identify and validate the transcription factors, signaling pathways, and protein interaction networks that are linked to longevity and act to sustain cellular integrity and functionality during disease and in old age. The described work, to be performed by a collaborative team of uniquely skilled individuals, has the potential to make substantial and meaningful advances in the fields of regenerative medicine and aging while unlocking a detailed roadmap to healthful living and longevity.