The wrong kind of cells have been used to make in vitro models of the blood-brain barrier, which now throws a decade’s worth of research into question.
The present in vitro human blood-brain barrier model was developed in 2012. By inducing differentiated adult cells, such as skin cells, into developing into stem cells, the pluripotent stem cells obtained from the process are then transformed into nearly any type of mature cell. This includes the type of endothelial cell that lines brain and spinal cord blood vessels, and making a unique barrier that acts as a gatekeeper, restricting potentially dangerous substances, antibodies, and immune cells from entering the brain from the bloodstream.
“The blood-brain barrier is difficult to study in humans and there are many differences between the human and animal blood-brain barrier. So it’s very helpful to have a model of the human blood-brain barrier in a dish,” said co-study leader Dritan Agalliu, PhD, associate professor at Columbia University Vagelos College of Physicians and Surgeons.
Agalliu had noticed that these endothelial cells produced in this manner, did not behave like normal endothelial cells in the human brain. “This raised my suspicion that the protocol for making the barrier’s endothelial cells may have generated cells of the wrong identity,” said Agalliu.
“At the same time the Weill Cornell Medicine team had similar suspicions, so we teamed up to reproduce the protocol and perform bulk and single-cell RNA sequencing of these cells.”
Upon analysis, the researchers discovered that the supposed human brain endothelial cells were missing several key proteins found in natural endothelial cells and had more in common with epithelial cells, which is not usually found in the brain.
The team also identified three genes that, when activated within induced pluripotent cells, lead to the creation of cells that behave more like actual endothelial cells. More work is still needed, Agalliu says, to create endothelial cells that produce a reliable model of the human blood-brain barrier. His team is working to address this problem.
“The misidentification of human brain endothelial cells may be an issue for other types of cells made from induced pluripotent cells such as astrocytes or pericytes that form the neurovascular unit,” said Agalliu. The protocols to produce these cells were drawn up prior to the advent of single-cell technologies that are better at identifying cells.
“Cell misidentification remains a major problem that needs to be addressed in the scientific community in order to develop cells that mirror those found in the human brain. This will allow us to use these cells to study the role of genetic risk factors for neurological disorders and develop drug therapies that target the correct cells that contribute to the blood-brain barrier.”
Source: Medical Xpress
