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UCL welcomes brain cancer researcher and neurosurgeon, Dr Thomas Wälchli

2 January 2025

UCL Cancer Institute is pleased to announce the appointment of neurosurgeon and neuroscientist, Dr Thomas Wälchli as an Honorary Consultant Neurosurgeon and Principal Clinical Research Fellow / Associate Professor (UCLH/UCL).

Thomas Walchli

Dr Wälchli brings a wealth of expertise in brain vascular biology, brain cancer biology, neuroscience, developmental biology, neuro-oncology and single-cell multi-omics, combining clinical work as a brain tumour neurosurgeon with groundbreaking basic and translational research.

Dr Wälchli’s research focuses on understanding how blood vessels in the brain grow and change - from early development through adulthood and in disease. By studying individual cells in brain blood vessels, he aims to discover how they function and how they might be targeted with treatments.

In a recent study, published in Nature, Dr Wälchli and his research team created a ‘single-cell atlas of the human brain vasculature’ – a detailed map of blood vessels in the human brain at the level of individual cells across different developmental stages, in adulthood and in various vascular-dependent diseases such as brain tumours and brain vascular malformations. The group discovered insights into how brain blood vessels form in the fetus, change over time through adulthood, and react to disease states, with key findings including:

  • Blood vessel growth in a healthy adult brain stops almost completely over time and enters a quiescent/resident state, but brain tumors or brain vascular malformations can restart this growth, similar to the blood vessel growth in an early-developing fetal brain.
  • How blood vessels in the brain differ from the vasculature of organs outside the brain, both during early brain development and in adulthood. When disease arises, the brain vasculature and its endothelial cells – the cells that line blood vessels - become more like the vasculature of a peripheral organ.
  • In disease, some typical features of brain blood vessels change. For example, the endothelial cells of the blood-brain barrier, which normally act as a filter for substances, toxins, and drugs, also influence the brain’s interaction with the immune system. During illness, endothelial cells adapt their immune-related functions, allowing them to act like “antigen-presenting cells” that trigger an immune response (e.g. in brain vascular malformations) or to suppress the immune system (e.g. in brain tumours), allowing the brain tumour to escape the body’s immune response.

"It will take many years of additional research, but if we can identify what is happening in an early developing brain and how those blood vessel networks grow over time, how they develop into arteries, capillaries, and veins, how they acquire brain-specific properties, how they interact with the immune system, and how they are reactivated in disease, we can better understand the growth patterns of the brain tumour vasculature," says Dr Wälchli. “And this may open up new avenues for treating these devastating diseases.”

"Both early brain development and brain tumours feature blood vessel growth and immune suppression, allowing tissue to grow in an undisturbed way. If we could dampen or inhibit this blood vessel growth and at the same time strengthen the immune response, that has a potential application to therapy," Dr Wälchli emphasizes. “Addressing the fundamental mechanisms of brain blood vessel growth is not only key for our basic biological understanding of the human brain vasculature but also harbors tremendous translational potential for the treatment of brain tumours.”

Dr Thomas Wälchli joins UCL and UCLH as an academic brain tumor neurosurgeon-neuroscientist, having previously worked at the Krembil Brain Institute and Toronto Western Hospital / University Health Network and the University of Toronto, where he undertook fellowships in cerebrovascular, brain tumour/skull base, and epilepsy neurosurgery, alongside leading a research group. Dr. Wälchli studied engineering at Swiss Federal Institute of Technology Lausanne (EPFL) and medicine at the University of Zurich (UZH) and Harvard Medical School, completing his MD-PhD at Swiss Federal Institute of Technology Zürich (ETHZ), UZH and the University Hospital Zurich (USZ), and leading a research group at the Neuroscience Center Zurich. He performed neurosurgical residency at USZ and the University Hospital Geneva (HUG) and has held clinical and research roles across Switzerland, Canada, and the U.S.

“I am really excited to join UCL and UCLH, both exceptional places with a tremendous amount of outstanding people in a vibrant academic environment. I aim to contribute to patient care via my work as a brain tumor neurosurgeon at National Hospital for Neurology and Neurosurgery (NHNN) at UCLH, and to basic and translational science via my work as a neuroscientist, vascular biologist, and cancer biologist at the UCL Cancer Institute. UCL and UCLH are one of the very few places worldwide which allow these combinatorial activities as a neurosurgeon-neuroscientist and I’m really thrilled and am looking much forward to working together with my clinical, surgical and academic colleagues in this amazing place,” says Dr Wälchli.

"We look forward to Thomas Wälchli joining us at the UCL Cancer Institute and at the National Hospital for Neurology and Neurosurgery at UCLH.  As an academic brain tumour neurosurgeon and neuroscientist, Thomas combines the unique clinical, surgical and research experience and background crucial to unravel our fundamental understanding of human brain vascular biology and to unlocking the potential to impact the way brain cancer is treated in the future.  This is a novel, highly interdisciplinary, and original research niche and a much-needed area of research, which we are excited to see Thomas embark upon," says Prof Gert Attard, UCL Cancer Institute Director.   


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