Project Summary In this MOSAIC K99/R00 Pathway to Independence application, Dr. Brian O’Grady proposes training in models of subarachnoid hemorrhage (SAH) and development of therapeutics that will strategically compliment his expertise in the development of arteriole-specific growth of ex vivo brain tissue in a biomimetic hydrogel and 3D printed microfluidic fabrication. The training plan is paired with scientific studies that will develop and apply a novel microfluidic device for modeling subarachnoid hemorrhage stroke events and for use as a screening platform for a dual-targeted nanoparticle as a potential therapeutic for the damage caused by SAH and delayed cerebral ischemia. Dr. O’Grady’s primary goal is to become an independent researcher focused on creating biomimetic in vitro models of the brain vasculature and developing novel therapeutics for neurological diseases. The rigorous training described and the outstanding team of mentors in vascular biology (Dr. Lippmann), neurological disease pathology (Dr. Jefferson), and nanoparticle development and therapeutics (Dr. Duvall) will ensure his success in transitioning to independence. Through his training plan, Dr. O’Grady will gain 1) deeper knowledge of blood-brain barrier physiology and the neurovascular unit; 2) experience synthesizing and characterizing nanoparticles; 3) knowledge of modeling SAH and neurological disorders in vitro; and 4) strategies for running a successful interdisciplinary and collaborative research lab. SAH is defined as a cerebrovascular disease with the initial event of a ruptured brain aneurysm and accounts for 5% of all types of strokes. Despite this small percentage, SAH accounts for one third of all stroke-related years of potential life lost before the age of 65. While a new era of neurocritical care management has contributed to improved outcomes for SAH, the secondary consequences result in delayed cerebral ischemia (DCI). DCI has varying degrees of patient functional outcome and has no known interventions to improve quality of life. This lack of effective treatments is largely attributed to the high failure rate of translating brain-targeting drugs from animals to humans. Recently, there has been a global effort to produce a tissue engineered, in vitro model system that can represent the complex vascular anatomy and microenvironment of the neurovascular unit. Dr. O’Grady’s preliminary work demonstrates that a novel biomimetic hydrogel supports induced pluripotent stem cell-derived neural, mural, and glial cells and induces arteriole-specific growth of ex vivo human brain vasculature. This new vasculature consists of anatomically correct, concentric layered structures that were previously unobtainable. When supported by a microfluidic device, the arterioles anastomose and can be lumen- perfused and photoablated. Based on his preliminary data, Dr. O’Grady hypothesizes that the dynamic neurovascular microenvironment of a stroke-like event can be accurately m...