As the brain develops, neurons grow long extensions known as axons. These structures connect different areas of the brain and send signals both within the brain and throughout the body. To establish these connections, axons must travel along very specific routes within brain tissue. Their journey depends not only on the physical properties of their surrounding environment, but also on chemical signals.
Until now, scientists did not fully understand how these two types of guidance work together. An international team of researchers has discovered that the stiffness of brain tissue can control the production of key signaling molecules. The survey results are natural materialsreveals a direct relationship between mechanical forces and chemical signaling in the brain. This insight could also help researchers better understand how other organs develop, potentially leading to new medical strategies.
Chemical and physical cues work together
Scientists have known for years that chemical signals guide how tissues grow and organize. Gradients of signaling molecules act like directional cues, helping cells move to the correct location and develop.
More recent studies have shown that physical factors such as tissue stiffness also influence cell behavior. However, the relationship between these mechanical cues and chemical signals remains unclear. Understanding how the two interact is important for explaining how complex tissues such as the brain form during development.
Study reveals tissue stiffness controls key brain signals
Researchers from the Max Planck Center for Physics and Medicine (MPZPM), Friedrich-Alexander Erlangen-University of Nuremberg (FAU), and the University of Cambridge investigated this question using the Xenopus laevis (Xenopus laevis), a model organism widely used in developmental biology. Their experiments showed that tissue stiffness can modulate the generation of important chemically induced signals.
This process is controlled by a mechanosensitive protein called Piezo1. The research team, led by Professor Christian Franze, found that when tissue stiffness increases, cells begin to produce signaling molecules that are not normally present in that area. One example is the guidance molecule semaphorin 3A. Remarkably, this response only occurred when Piezo1 levels were sufficiently high.
“We did not expect that Piezo1 would function both as a force sensor and as a sculptor of the chemical landscape in the brain,” said study co-lead Eva Pillai, a postdoctoral researcher at the European Molecular Biology Laboratory (EMBL). “Not only does it detect mechanical forces, but it also helps form chemical signals that guide neuron growth. This kind of connection between the physical and chemical worlds of the brain gives us a whole new way of thinking about how the brain develops.”
Piezo1 also helps maintain tissue structure
The researchers also found that Piezo1 affects the physical stability of the brain tissue itself. Decreasing the amount of Piezo1 reduces the levels of important cell adhesion proteins such as NCAM1 and N-cadherin. These proteins are important for maintaining cell-cell contacts that glue cells together.
“What’s interesting is that Piezo1 not only helps neurons sense the environment, but also helps build it,” said Sudipta Mukherjee, a postdoctoral researcher and co-director of the study at FAU and MPZPM. He and Pillai were both PhD students at the University of Cambridge, where the project began. “By controlling the levels of these adhesion proteins, Piezo1 keeps cells well connected, which is essential for stable tissue architecture. Environmental stability influences the chemical environment.”
The results indicate that Piezo1 plays two important roles. It acts as a sensor that converts mechanical signals from the surrounding environment into cellular responses. At the same time, it also acts as a modulator that helps organize the mechanical properties of the tissue itself.
Impact on development and disease
These findings may have broad implications for developmental biology and medical research. Errors in neuron growth are associated with congenital and neurodevelopmental disorders. Additionally, tissue stiffness is thought to be associated with diseases such as cancer.
This study provides new insights into how tissues form and function by demonstrating that mechanical forces can shape chemical signaling. It also suggests new directions for research into the disease and potential treatments.
“Our study shows that the brain’s mechanical environment is not just a background, but an active director of development,” said lead author Christian Franze. “It not only modulates cell function directly, but also indirectly by modulating the chemical landscape. This work could lead to a paradigm shift in the way we think about chemical signals, which impact many processes from early embryonic development to regeneration to disease.”
The researchers also found that tissue stiffness can affect chemical signaling over long distances, influencing the behavior of cells far from where the mechanical forces are generated. Overall, this study highlights mechanical forces as powerful regulators of development and organ function.
