Periodic Reporting for period 2 - EXTREME (EXTRacEllular matrix MEchanochemistry: a solid-state NMR approach)
Reporting period: 2023-04-01 to 2024-09-30
All our tissues consist of cells set into a complex extracellular matrix of proteins and sugars. The extracellular matrix not only embeds the cells in the tissue, it provides the essential mechanical properties of each tissue: the hardness of bone, the elasticity of skin and the toughness of tendons, for instance. Down at the nanoscopic lengthscale, the extracellular matrix instructs cells how to behave in that tissue. The instructions are delivered by molecules in the extracellular matrix binding to specific proteins on the surface of the tissue’s cells. So, the detailed molecular structure and organization of the extracellular matrix determines the instructions given to cells. But that extracellular matrix structure is subject to constant movement because of the external forces we subject our tissues to. This project investigates how the extracellular matrix molecular structures change as tissues are stretched and even torn, and then linking those structural changes to altered cell behaviour. Understanding how tissue mechanics affects cell behaviour is fundamental to understanding how our tissues work – and how they fail. The extracellular matrix structure changes hugely with injury and in diseases like cancer, and the changed matrix structure drives altered cell behaviours that often lead to poor outcomes, like imperfect tissue repair or progression of cancer. However, knowledge of how the extracellular matrix molecular structure translates to instructions to cells is still a work in progress in science. Understanding what is actually changing in the extracellular matrix structure and how that impacts cell behaviour is the essential starting point to design therapeutic interventions, to improve tissue repair and even to inhibit cancer progression.
The project has developed techniques to study extracellular matrix structure in intact tissues whilst they are held under mechanical strain, the fundamental block to work in this area. The primary technique we have developed is based on solid-state nuclear magnetic resonance (NMR) spectroscopy. In solid-state NMR spectroscopy, it is necessary to spin the sample at kHz frequencies. Our first challenge was to develop ways to spin intact tissue samples whilst they are held strained. We have achieved this and are building a comprehensive database on how collagen and elastin in a range of tissues change their molecular structure and dynamics when the tissue is strained or torn. This includes investigating how collagen and elastin molecules alter their structure with strain in differently structured extracellular matrices and matrices with different overall composition. We suspect that collagen molecules, the main structural component in nearly all our tissues, are protected from breakage by the presence of proteoglycans and/ or elastin, and that altered extracellular matrix compositions in cancer may remove this protection. To test how collagen and elastin molecules react to strain in different extracellular matrix compositions, we have used gene-editing methods on matrix-producing cells to make the cells themselves produce different matrices. We anticipate building a library of matrix-producing cells that can be used by other to mimic extracellular matrix in a wide variety of tissues, for e.g. improved drug discovery, as well as for this current project.
There are few experimental methods to investigate tissue molecular structures and dynamics in intact tissues and NMR spectroscopy is arguably one of the few. Developing solid-state NMR spectroscopy methods to investigate these aspects for the extracellular matrix of tissues whilst they are held under strain takes the existing toolbox of methods beyond the state-of-the-art. Through our new methods, we have directly observed changes in collagen molecular structure and chemistry resulting from mechanical strain in intact tissues for the first time. This has led us to intriguing new hypotheses about how the extracellular matrix delivers instructions to cells that we are now working on.
One of the most important observations we have made is the alteration of chemical crosslinks between collagen molecules as a result of mechanical strain. In the next phase of the project, we will follow in detail the chemistry behind the alterations in the collagen crosslinks with strain and carry out work to understand how cells react to the products of this chemistry. We will also probe how mechanical strain from cancer cells pulling on extracellular matrix as the cancer cells migrate affects the matrix structure. We have early results that suggest that cancer cells can alter matrix structure through strain in ways that have significant effects on surrounding cells. It is important to understand all the effects that cancer cells have on a tissue if medicine is to design more effective approaches to treating cancer. If we find that cancer cells can change surrounding cell behaviour by straining the extracellular matrix that the tissue’s cells share, we will investigate further how we can prevent these modifications. This will be essential knowledge for future drug discovery.
One of the most important observations we have made is the alteration of chemical crosslinks between collagen molecules as a result of mechanical strain. In the next phase of the project, we will follow in detail the chemistry behind the alterations in the collagen crosslinks with strain and carry out work to understand how cells react to the products of this chemistry. We will also probe how mechanical strain from cancer cells pulling on extracellular matrix as the cancer cells migrate affects the matrix structure. We have early results that suggest that cancer cells can alter matrix structure through strain in ways that have significant effects on surrounding cells. It is important to understand all the effects that cancer cells have on a tissue if medicine is to design more effective approaches to treating cancer. If we find that cancer cells can change surrounding cell behaviour by straining the extracellular matrix that the tissue’s cells share, we will investigate further how we can prevent these modifications. This will be essential knowledge for future drug discovery.