Cells behave differently when removed from their environments, just as cells that develop in cultures do not behave like cells in living creatures. To study the effects of Alzheimer’s disease in a more natural environment, scientists from the lab of Bart De Strooper (VIB-KU Leuven, Dementia Research Institute-UK) in collaboration with scientists from ULB (Pierre Vanderhaeghen and Jean-Pierre Brion) successfully circumscribed this challenge by transplanting human neural cells into mouse brains containing amyloid plaques, one of the hallmarks of Alzheimer’s disease. The results of their research showed that, unlike mouse neurons, human neurons that developed in this environment were extremely susceptible to Alzheimer’s disease. Their high-impact results are published in leading academic journal Neuron.
The study of the development of Alzheimer’s disease on a molecular level presents unique challenges, as neurons behave differently in vivo vs. in vitro. Using mice as models presents useful insights, but mouse models never fully develop the disease, despite the fact that their brains and neurons share many similarities with those of humans.
A new, humanized model
A team of researchers has now transplanted human neurons into mouse brains which mimick some of the hallmarks of Alzheimer’s disease, including the presence of amyloid plaques. They found that, compared to mouse neurons, human neurons were much more sensitive to amyloid plaque pathology. This novel model allows for a better characterization of the disease processes that actually take place in the brain of human patients.
Much of the work was performed in close cooperation with Pierre Vanderhaeghen, professor at ULB-WELBIO and VIB-KULeuven, whose lab previously pioneered the technology to differentiate human pluripotent stem cells into neural cells in vitro, and then transplant them in the mouse brain, generating a human/mouse chimera.
De Strooper: “We relied heavily on the insights and expertise of Pierre Vanderhaeghen and his lab to set up this new AD model. With this novel experimental technique, we can study how different cell types in the human brain respond to the Alzheimer pathology, hopefully unraveling the link between amyloid and tau protein pathology – which leads to neuron death and is the holy grail of current Alzheimer’s research.”
Vanderhaeghen: “While many features of the brain are conserved between different species such as humans and mice, the human brain displays a number of characteristics, which make us what we are, as a species and as individuals. However, studying this human-specific part remains a big challenge in neuroscience. This study is exciting because it constitutes a first proof of principle that stem cell-based models of transplanted human neurons can be applied to study an important neurological disease.”
Identifying genetic components
Moving forward, De Strooper and his team are already planning a screen to identify human genes that protect against cell death associated with Alzheimer’s disease.
De Strooper: “Now that we are able to investigate the disease by observing human cells directly, we can make progress in this field of research at a considerably faster pace. The eventual end goal of the screening is to identify new drug targets within human cells themselves, something that was never possible before.”
Espuny-Camacho, Ira, et al. "Hallmarks of Alzheimer’s Disease in Stem-Cell-Derived Human Neurons Transplanted into Mouse Brain." Neuron (2017).