Modeling Alpha-Synuclein Pathology in a Human Brain-Chip to Assess Blood-Brain Barrier Disruption in Parkinson’s Disease

Abstract

Parkinson’s disease and related synucleinopathies are characterized by the abnormal accumulation of alpha-synuclein aggregates, loss of dopaminergic neurons, and gliosis in the substantia nigra. Although clinical evidence and in vitro studies indicate disruption of the Blood-Brain Barrier in Parkinson’s disease, the mechanisms mediating the endothelial dysfunction remain elusive. Lack of relevant models able to recapitulate the order of events driving the development of the disease in humans has been a significant bottleneck in the identification of specific successful druggable targets. Here we leveraged the Organs-on-Chips technology to engineer a human Brain-Chip representative of the substantia nigra area of the brain containing dopaminergic neurons, astrocytes, microglia, pericytes, and microvascular brain endothelial cells, cultured under fluid flow. Our αSyn fibril-induced model was capable of reproducing several key aspects of Parkinson’s disease, including accumulation of phosphorylated αSyn (pSer129-αSyn), mitochondrial impairment, neuroinflammation, and compromised barrier function. This model is poised to enable research into the dynamics of cell-cell interactions in human synucleinopathies and to serve as testing platform for novel therapeutic interventions, including target identification and target validation.

The Contribution of Microglia to Neuroinflammation in Parkinson’s Disease

“…Significant scientific efforts are currently ongoing to configure cell culture media compositions that will facilitate the simultaneous growth of all cell types, thereby achieving a more physiological microenvironment that prevents the activation of microglia (which is, for instance, commonly observed in the dead core of organoids). Furthermore, cell-based microfluidics systems (also known as Brain-on-Chip technology) have been developed to investigate microglia interactions with astrocytes and neurons under the impact of a continuous fluid flow [ 143 , 144 , 145 ]. To mimic the BBB composition, some systems are designed to contain a layer of microvascular endothelial cells and pericytes.…”

“…To mimic the BBB composition, some systems are designed to contain a layer of microvascular endothelial cells and pericytes. Exposing a human Brain-Chip (which mirrored the microenvironment of the substantia nigra) to α-synuclein fibrils initiated dopaminergic neuron death, mitochondrial dysfunction and neuroinflammation, while BBB was significantly compromised [ 145 ]. Due to their capacity to model the BBB, both organoids and microfluidic systems have emerged as highly promising resources for therapeutic testing in brain diseases [ 146 , 147 ].…”

Blood–Brain Barrier and Neurodegenerative Diseases—Modeling with iPSC-Derived Brain Cells

“…ECs are plated in the first cell culture channel and the other cell type(s) to the second channel or open-top chamber. The porous membrane between the cell culture chamber enables the transfer of substances and interactions between ECs and other cell types, similarly to transwells [ 236 , 237 , 238 , 239 , 240 ]. However, the chip structure can have a lot of variation due to different requirements of the users; for example, a membrane is not always used in chips, and there may be more than two cell culture chambers and additional medium channels.…”

“…However, there are many differences—for example, in used organ-on-chip platforms, cells, culture conditions, membranes, and methods for generating the flow through it. Some of the studies are made only with iPSC-derived brain ECs [ 236 ], while others have used iPSC-derived astrocytes [ 239 ], neural cells [ 237 , 240 ], or primary astrocytes and pericytes [ 237 , 238 , 240 ]. more specific information on these studies and their differences has been collected ( Table 2 ).…”

Lab-on-a-Chip Platforms as Tools for Drug Screening in Neuropathologies Associated with Blood–Brain Barrier Alterations

“…Several strategies have evolved to mimic neurological disorders on a chip ( Figure 4 ). The simplest in vitro model on a chip is to expose brain cells (e.g., cell lines) or neurospheroids of human or rodent origin to peptides/proteins, such as α-synuclein, β-amyloid, tau-protein etc., in order to obtain similar conditions at the BBB/NVU level that have elevated levels in brain parenchyma, cerebral spinal fluid, or cerebral blood flow associated with specific neurological pathologies [ 42 , 151 , 152 ]. In order to preserve the biochemical and morphological properties of brain cells, a good alternative is to cultivate on a chip primary cultures obtained from rodents or larger species (e.g., bovine, porcine, and nonhuman primate) [ 153 ].…”