Tissue Engineered Blood Vessels as a Model for Drug Discovery in Alzheimer’s Disease
- Humanized 3D blood vessels are improved in vitro tools for cerebrovascular studies
- Model for Alzheimer’s disease and blood brain barrier function
- Screening system for therapeutic candidates that target Aβ deposition or enhance Aβ clearance
- Screening system for therapeutic candidates that target apoE secretion
Alzheimer’s disease (AD) is a chronic neurodegenerative disease that progressively affects memory, behavior and intellectual abilities. Between 60-90% of AD brains show evidence of cerebral small vessel disease and cerebral amyloid angiopathy (CAA) in addition to amyloid-β (Aβ) plaques and neurofibrillary tangles which are the known hallmarks of AD. Apolipoprotein (Apo)E is primarily secreted from astrocytes in the brain and is the principal lipid carrier within the CNS. ApoE is thought to contribute to both plaque formation and cerebrovascular dysfunction. A major route for Aβ clearance from the brain involves the cerebrovasculature, and understanding the contributions of the cerebrovascular to dementia is of great interest.
Almost all of the current knowledge about Aβ egress through cerebral vessels is from murine models engineered to express human amyloid precursor protein (APP), but these models may have limited translational relevance. In vitro studies using human cells represents an alternative approach, however, most studies of the blood brain barrier (BBB) use monotypic cultures of brain endothelial cells (ECs), which do not mimic the complexity of cell-cell and/or cell-matrix interactions found in the native vessel. Transwell cultures or static co-cultures of brain endothelial cells, astrocytes, and smooth muscle cells are also used, but these models systems are unable to mimic the physical and biochemical behavior of the native cerebrovasculature.
Our Solution: To address key limitations of the existing experimental models, UBC scientists have generated three-dimensional (3D) bioengineered human blood vessels using a scaffold-directed dynamic pulsatile flow bioreactor system, where primary human endothelial cells (EC) and smooth muscle cells (SMC) are cultivated in the presence or absence of human astrocytes to generate bipartite or tripartite vessels. The bioengineered vessels display the histological features of native peripheral (bipartite) and cerebral (tripartite) arteries with correct vascular anatomy (EC lumen surrounded by layers of SMC, +/- layers of antelumenal astrocytes).
Technology Details: The inventors have developed a humanized 3D platform to facilitate investigation of AD-related cerebrovascular disease. As a model system for AD, the vessel system can be used to investigate (i) the role of ApoE genotype in Aβ accumulation/clearance; (ii) the co-operation between ApoE and circulating HDL in Aβ accumulation/clearance. The vessel system can also function as a drug-screening tool to investigate therapeutic candidates designed to prevent Aβ deposition, to stimulate Aβ clearance or to stimulate apoE secretion.
Figure 1: Aβ40 and Aβ42 accumulation bipartite vessels. Aβ40 or Aβ42 monomers (0, 0.1, 1.0 and 10 μM) were injected into the tissue chamber (antelumen) and incubated for 48 h under flow conditions. Aβ deposition within bioengineered vessels was measured using ELISA. L: lumen
Figure 2: ApoE2 lipoprotein reduces Aβ42 accumulation as compared with ApoE4 lipoprotein within bioengineered bipartite vessels. Aβ42 monomers (1 μM) were incubated without or with recombinant ApoE (ratio 25:1) for 2 h at 37 °C before injection into the antelumenal tissue chamber. The level of accumulated Aβ was measured by ELISA at 24 h after Aβ injection. Graphs represent mean ± SEM for at least four independent experiments. * p=0.05