A Human iPSC-derived Microphysiological 3D model to study CAA/AD

About This Grant

Summary/Abstract Vascular pathology has been identified as a critical driver of Alzheimer’s disease. This proposal aims to establish a human induced pluripotent stem cell (iPSC)-derived model to study the impact of genetic and environmental factors on the development of Alzheimer’s disease-related vascular pathology. Most Alzheimer’s disease patients have cerebral amyloid angiopathy (CAA), the symptoms of which include build-up of amyloid around vessels, cerebral hemorrhages, microbleeds, and inflammation. Studies in multiple mouse models of Alzheimer’s disease have demonstrated that hemopoietic-derived brain-resident microglia and circulating monocytes and perivascular macrophages can be protective against CAA. The APOE44 genotype is the strongest genetic risk factor for Alzheimer’s disease and CAA. Despite the clear interplay between Alzheimer’s disease, CAA, and APOE genotype, the molecular mechanisms underlying the vascular changes are not fully understood. These observations motivate us to create a model using human cells to study the underlying mechanisms of microglia- vascular interactions in cells of different APOE genotypes. In prior published studies, we created a 3D human iPSC-derived vascular model in a hydrogel scaffold. It undergoes vasculogenic and angiogenic events and forms a model plexus (the VAMP model). We showed that the VAMP model can be built inside a microfluidic device to enable regulatable perfusion, mimicking blood flow. We have advanced the model by incorporating microglia (VAMP-MG) to reflect the key cell-cell interactions in CAA better. The work proposed in two specific aims will increase the utility of the VAMP-MG model in five significant ways: We will 1) build the model from a recently established collection of APOE44 versus APOE33 isogenic iPSC lines to incorporate genetic risk factors; 2) incorporate live reporters to monitor the activation states of microglia and vascular cells in real-time; 3) create the VAMP-MG model in microfluidic chips to achieve perfusable vasculature; 4) flow human plasma from Alzheimer’s disease, aged-matched healthy, or young healthy donors through the vessels to improve modeling of disease-relevant environmental factors; 5) use Ribo-Tag technology to identify transcriptomic changes in the vascular endothelial cells and the microglia. The model will be deeply characterized and validated at cellular and molecular levels. Alzheimer’s disease-relevant phenotypes, including amyloid deposition and clearance, A secretion, and inflammatory factor production, will be assessed. We will compare transcriptomic data collected from the model to published human Alzheimer’s disease brain versus healthy control brain transcriptomic data, including single nuclear RNA-seq datasets. Completing the proposed work will enhance our ability to study vascular and microglial responses to inflammatory signals in real time, generate transcriptomic data at cell type levels, and establish APOE44 versus APOE33 phenotypes in microglia-vascular models to a new level of complexity. In the future, this VAMP-MG model can potentially define key genetic and environmental factors that exacerbate or alleviate Alzheimer’s disease-vascular phenotypes.