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In the realm of biology, visualizing molecular structures is crucial for research. However, capturing a comprehensive view of all molecules within a tissue sample, especially at the single-cell level, remains a significant challenge for scientists.
The ability to identify the precise location of a variety of biomolecules—from lipids to proteins and metabolites—in their natural settings is essential for understanding their roles and interactions. Unfortunately, current imaging technologies fall short in this aspect.
Traditional microscopy techniques can provide insights into the makeup of cellular materials, but they typically only allow researchers to monitor a limited number of biomolecules at a time. Additionally, certain methodologies, such as mass spectrometry, can analyze hundreds of compounds but require samples to be processed in a way that obliterates structural integrity, hindering the study of biomolecule arrangement.
A promising advancement in this field is mass spectrometry imaging, which enables the visualization of many molecules within intact tissues. Nonetheless, challenges remain regarding the spatial resolution necessary for the detection of individual cells.
Meng Wang, Senior Group Leader at Janelia, faced this daunting issue while exploring the mechanisms of aging and longevity. Her research team sought to analyze numerous biomolecules within intact tissues to assess how these components evolve as tissues undergo the aging process.
“Understanding which molecules are present at specific locations and how they interact with neighboring cells is vital for answering key biological questions,” Wang explains.
Fortunately for Wang, her lab is adjacent to that of Paul Tillberg, a Principal Scientist at Janelia and a co-inventor of expansion microscopy. This innovative method, developed during Tillberg’s graduate studies at MIT, employs a swellable hydrogel that allows tissue samples to expand uniformly, revealing intricate details like sub-organelle structures using conventional microscopy techniques.
With a decade of use behind it, the principles of expansion microscopy are being repurposed to enhance other imaging methods. Collaborating with Tillberg and other colleagues at Janelia and the University of Wisconsin-Madison, Wang’s team aimed to employ expansion techniques to solve the spatial resolution limitations of mass spectrometry imaging.
Their efforts culminated in a novel approach that expands tissue samples gradually without compromising molecular integrity, allowing researchers to utilize mass spectrometry imaging to achieve high-resolution views of hundreds of molecules at the single-cell level within their natural environments.
“This technique provides an untargeted perspective of the molecular landscape, bridging the gap between mass spectrometry imaging and the spatial resolution capabilities of microscopy,” says Tillberg.
Utilizing this new method, the team explored the spatial distribution of small molecules across various layers of the cerebellum, discovering that the distribution of biomolecules—including lipids, proteins, peptides, and metabolites—is more complex than previously assumed. Each layer of the cerebellum exhibits a distinct profile of these molecules.
The versatility of their method was further demonstrated through successful application to kidney, pancreas, and tumor tissues, indicating its potential adaptability across diverse biological samples. In tumor tissues, the researchers observed significant variations in biomolecular distribution, potentially providing valuable insights into the molecular dynamics of cancer and informing future drug development strategies.
“Being able to visualize these biomolecules enables us to explore the reasons behind their spatial patterns and their functional implications,” Wang notes. She envisions that this innovative technology will empower scientists to monitor changes in molecular patterns throughout development, aging, and disease, further elucidating their roles in these complex processes.
Since the latest method does not necessitate additional hardware for existing mass spectrometry imaging systems and retains an accessible learning curve for researchers, the team anticipates widespread adoption of this technique across laboratories globally. They have also provided a comprehensive outline for implementing the method across various tissue types.
“Our goal was to create a solution that doesn’t depend on specialized instruments or intricate procedures, making it easy for many researchers to adopt,” Wang concludes.
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