Reconstruction of Human Blood-brain-barrier in a Vascularized Brain Organoid Model for in vitro Study of Brain Vascular Disease
Blood-brain-barrier (BBB) is one of critical functional units in our brains, which not only allows oxygen, nutrient/waste and inductive biochemical exchange, but also provides a structural foundation for neural tissue survival. The breakdown of BBB could lead to a variety of neurological conditions and BBB pathology is believed to be highly implicated in neurodegenerative disorders such as Alzheimer’s disease (AD). BBB is also the major hurdle to deliver therapeutic drugs to the brains. Despite the functional importance, studies of human BBB in development and brain vascular disorders have been significantly hindered due to limited access to functional human brain tissues. Patient-derived induced pluripotent stem cells (iPSCs) and their differentiated endothelial cells (ECs), pericytes and astrocytes facilitate mechanistic studies in target cells of BBB in a relevant human genetic background. A major unresolved hurdle in current human cells-based assays is that in vitro cultures weakly recapitulate the physiology of neurovascular unit and thus preclude the reconstruction of structural and functional BBB. In this grant, we propose to fill the critical gap, by reconstructing human BBB in a novel brain organoid model and recapitulating its functional barrier for the study of brain vascular disease. We observed that angiogenesis and establishment of the brain vascular network in forebrain organoids during development. Intriguingly, human astrocytes were highly interactive with ECs and pericytes, and human endothelium began to express BBB-specific markers. We hypothesize that neuronal microenvironment will guide endothelium to acquire brain microvascular endothelial cells properties such as tight junction and the reconstructed human neurovascular unit can recapitulate structural and functional BBB in human brain organoids. Completion of proposed studies will provide novel mechanistic insights into human brain neurovascular unit development, BBB formation/function and drug permeability. The pathological studies using patients-derived iPSCs in future could potentially illustrate the BBB-based etiology and provide novel therapeutic treatment in the context of drug delivery across BBB.
Dr. Ziyuan Guo
The human brain is the most complex organ in the universe. While its unique characteristics allow us to think, abnormalities can lead to brain disorders, such as autism, schizophrenia and Alzheimer’s disease. Unfortunately, due to the inaccessibility of human primary tissue, scientists are limited in their study of disease etiology. This limitation significantly delays the advancement of new therapeutic developments. As a neurobiologist and stem cell scientist, I’m interested in neurodevelopmental and neurodegenerative disorders, autism spectrum disorders, schizophrenia, Alzheimer’s disease, induced pluripotent stem cells (iPSCs), brain organoids, direct reprogramming, in vivo reprogramming, human neural development, human neural stem cells and glia-neuron interaction.
I draw on these interests — and my research experience — to develop a next generation “human nervous system in a petri dish” using cutting-edge stem cell technologies and engineering tools. To that end, my lab applies innovative stem cell technologies (including iPSCs, organoids and trans-differentiation) to study the etiology of neurodevelopmental and neurodegenerative disorders in the context of human genetics. As lead author on an article published in Cell Stem Cell (Feb. 2014), I was among the first to report direct reprogramming of reactive glial cells into functional neurons in adult mouse brains. We accomplished this by overexpressing a single neural transcriptional factor (NeuroD1). This study — which was named one of the best of 2014 by Cell Stem Cell — propelled us in a new direction of utilizing an in vivo reprogramming approach to treating neurological and neurodegenerative disorders. We first published synaptic dysfunction in a human iPSC model of mental disorders carrying a mutation disruption in schizophrenia 1 (DISC1) in the journal Nature (Nov. 2014). These efforts shed light on using human iPSCs to model and study neurodevelopmental disorders, such as schizophrenia.