Trans-Agency Blood-Brain Interface Workshop 2016

Executive Summary
This 1½-day workshop brought together experts in blood science, blood-brain barrier (BBB) biology/modeling and BBB drug delivery. The experts presented their latest findings, examined key challenges, and developed recommendations for further studies on the connection between the circulatory system and the brain. The workshop featured four sessions: 1) Blood Sciences; 2) Exosome Therapeutics; 3) Next Generation in vitro Blood-Brain Barrier Models; and 4) Blood-Brain Barrier Delivery and Targeting. The first day focused on the physiology of the blood and neurovascular unit, biofluid-based molecular markers, and extracellular vesicles associated with brain injury. The sessions explored how these are transported between brain and blood and how they can be used to evaluate injury states or deliver therapeutics. The second day focused on technical advances in in vitro models, BBB manipulations, and nanoparticle-based drug carrier designs, as ways to improve drug delivery to the central nervous system. Each day concluded with a discussion among the speakers and workshop participants. Those interdisciplinary discussions, along with the presentations, highlighted the potential for developing technologies for BBB diagnostics and therapy, as well as the need for collaboration among the groups represented. The discussions also generated recommendations aimed at helping advance this promising, yet underrepresented, cross-disciplinary field.

Research Needs and Challenges
The speaker presentations and panel discussions highlighted several overarching research needs involving the interface between the blood and the brain.  These can be grouped into the following three categories:

1. Biophysical/biochemical properties of the Blood Brain Barrier
   • Standardize procedures to assess changes in the Blood Brain Barrier, employing methods that more accurately reflect changes in physiological analytes and relevant clinical conditions.
   • Develop benchmarks and validate the best practices for developing models of the neurovascular unit and incorporating the blood component as an integral part of the neurovascular unit.
   • Determine reproducible protocols for differentiation of iPS cells into brain-specific endothelial cells, astrocytes, and pericytes for cross-laboratory investigations of the neurovascular unit, including the blood component.
   • Develop a consensus gold standard approach for Blood Brain Barrier opening for delivery of therapeutics from the blood to the brain.
2. Utilization of extracellular vesicles in diagnostics and treatments
   • Develop standardized methods to track how exosomes enter and leave the brain.
   • Develop protocols to stimulate parent cells to produce exosomes of interest with GMP standards.
   • Develop strategies to efficiently load therapeutic cargo into exosomes.
   • Develop methodologies to reduce immunogenicity of exosomes.
   • Optimize methods to deliver exosomes to the brain and target specific cells types.
3. Biomarker discoveries
   • Develop a comprehensive proteomics and RNA sequencing (RNA-Seq) molecular atlas across the blood brain barrier in animals and humans for new targets, a signaling pathway within the neurovascular unit, a drug screen, new transgenic models and new therapies.
   • Determine the origin of extracellular RNA (exRNA) and other biomolecules in peripheral biofluid samples.

Recommendations and Opportunities
The speakers noted the following recommendations and opportunities:

• Membrane transporters can be capitalized to optimize brain exposure of potentially neuroprotective compounds in traumatic brain injury (TBI) and ischemic brain injury; repurposing transporter inhibitors/inducers can expedite clinical translation of such treatment strategies.
• Microparticle populations found in peripheral biofluid samples can be a target for assessment of post-traumatic brain injury or disease progression as well as prophylaxis or amelioration of injury progression.
• Plasma extracellular vesicles of neural origin can be the source of biomarkers and may provide a unique window for studying organ-specific cellular processes in living humans and for following responses to experimental treatments. For example, a profile of exosomal peptides may serve as a blood test for Alzheimer’s disease (AD) and other neurological diseases.
• Nanoparticle and extracellular vesicles (EV)-based therapies hold the promise of personalized medicine.
• Opportunities for developing the building blocks for in vitro models of the neuro/vascular/blood unit exist, despite the challenges. For example, iPSC-derived brain microvascular endothelial cells (BMECs) can be used as a research tool to explore drug permeability and disease at the human BBB.
• Isogenic patient-derived models of the neurovascular unit can be used for biomarker identification, the study of disease progression, and therapeutic testing.
• Patient-specific neurovascular unit models may complement or replace animal models.
• In silico predictive modeling is advancing rapidly and at the current pace will be able to capture most biological processes within 10 years.

As our understanding of both the complex interactions among the various cellular and molecular components of the BBB and the interdependency of the brain and other organ systems with BBB function grows, more opportunities to advance research that leads to new BBB diagnostic and treatment modalities will emerge.

Publication
NIH workshop report on the trans-agency blood–brain interface workshop 2016: exploring key challenges and opportunities associated with the blood, brain and their interface

Published in Fluids and Barriers of the CNS 14, Article number: 12 (2017)
https://doi.org/10.1186/s12987-017-0061-6

NHLBI Contact
Margaret Ochocinska, PhD
Translational Blood Science and Resources Branch
Division of Blood Diseases and Resources
ochocinm@mail.nih.gov

Workshop Chairs and Session Chairs

• Berislav Zlokovic, MD, PhD, Workshop Chair, University of Southern California
• Peter Searson, PhD, Workshop Co-Chair, Johns Hopkins School of Medicine
• Richard Kraig, MD, PhD, Session Chair, University of Chicago Medical Center
• Julia Ljubimova, MD, PhD, Session Chair, Cedars-Sinai Medical Center
• A Tamara Crowder, PhD, Session Chair, Combat Casualty Care Research Program, DoD

Keynote Speakers

• William Banks, MD, FACE, University of Washington
• Todd Mainprize, MD, Sunnybrook Health Sciences Center

Workshop Speakers

• Katerina Akassoglou, PhD, UCSF School of Medicine
• Jacquelyn Brown, PhD, Vanderbilt University
• Robert Clark, MD, University of Pittsburgh
• Scott Diamond, PhD, Penn Center for Molecular Discovery
• Michael Goodman, MD, University of Cincinnati
• Justin Hanes, PhD, Johns Hopkins University
• Dimitrios Kapogiannis, MD, National Institute of Aging, NIH
• Efstathios Karathanasis, PhD, Case Western Reserve University
• Anastasia Khvorova, PhD, University of Massachusetts Medical School
• Donald Marion, MD, Defense and Veterans Brain Injury Center
• A.C. Matin, PhD, Stanford University
• Edward Neuwelt, MD, Oregon Health & Science University and the Portland Veterans Affairs Medical Center
• Sergiu Pasca, MD, Stanford University
• Eric Shusta, PhD, University of Wisconsin – Madison
• Alexander Stegh, PhD, Northwestern University
• Martin Ulmschneider, PhD, Johns Hopkins University
• Alex Valadka, PhD, Virginia Commonwealth University
• Kendall Van Keuren-Jensen, PhD, TGen Center for Noninvasive Diagnostics
• Theresa Whiteside, PhD, University of Pittsburgh
• Huang-Ge Zhang, PhD, University of Louisville

Workshop Steering Committee

• Margaret Ochocinska, PhD, Chair, NHLBI, NIH
• A Tamara Crowder, PhD, Combat Casualty Care Research Program, DoD
• Kristin Fabre, PhD, NCATS, NIH
• Andrei Kindzelski, MD, PhD, NHLBI, NIH
• Lillian Kuo, PhD, NIAID, NIH
• Lei Xiao, MD, PhD, NHLBI, NIH
• Christina Liu, PhD, PE, NCI, NIH
• Tania Lombo, PhD, NCATS, NIH
• Martha Lundberg, PhD, NHLBI, NIH
• Anthony Pusateri, PhD, Combat Casualty Care Research Program, DoD
• Pothur Srinivas, PhD, NHLBI, NIH
• Danilo Tagle, PhD, NCATS, NIH
• William Timmer, PhD, NCI, NIH
• Michel Twery, PhD, NHLBI, NIH
• Ronald Warren, PhD, NHLBI, NIH