Introduction: One of the principal limitations of drug delivery to the brain is the blood brain barrier, formed by the cooperation of glial and vascular cells in a functional system termed the gliovascular unit (GVU). Both in vitro laboratory and animal models fail to accurately represent the properties of the blood brain barrier seen in adult humans. Through the process of three-dimensional bioprinting, we seek to develop a standardized laboratory model of the human GVU.
Methods: A computer-designed 3D microvascular structure was developed. Isolated human primary astrocytes, pericytes and smooth muscle cells were integrated into separate fibrin gels in preparation for microextrusion bioprinting. Pericytes and/or human brain microvascular endothelial cells were integrated into a dissolvable gelatin for printing of a pre-planned vessel lumen. Printed structures were maintained in stationary media culture at 37C. On Day 4 and 7, structures were analyzed and/or processed for staining.
Results: Haematoxylin and eosin (H&E) stained sections of the 3-D printed microvessels reveal that they maintained a well-defined lumen on Day 4 with cell growth into the lumen on Day 7. Immunohistochemistry was performed for the astrocyte marker GFAP and endothelial cell marker CD31, which revealed defined cellular layers on Day 4 with an endothelial cell-lined lumen with astrocytes in the surrounding region. Viability assessment on Day 10 revealed the majority of cells to be viable.
Conclusions: Current studies are ongoing of adapting the bioprinted GVU to a dynamic, microfluidic culture environment and assessing the cellular expression of tight-junction markers characteristic of the blood brain barrier. We foresee bioprinted models such as this will help improve our understanding of the etiology of human neurologic disorders and eventually assist in the development of novel therapeutics for neurodegenerative and neuro-oncologic diseases.
Patient Care: Development of a 3D bioprinted human gliovascular unit (GVU) with an accurately modeled blood brain barrier will allow for high-throughput assessment of potential therapeutics or toxins delivery to the brain. Through the application of induced pluripotent stem cells differentiation, patient-specific cell types integrated within the modeled GVU are foreseeable.
Learning Objectives: By the conclusion of this session, participants should:
1) Describe both the components of the human gliovascular unit and the importance of the blood brain barrier to drug delivery and disease.
2) Understand the steps necessary to apply 3D bioprinting technology to build in vitro tissue models.
3) Identify potential applications of 3d bioprinting to the study of drug delivery and neurologic disease.