Imaging Technique Reveals Biomolecule Distribution at Single-Cell Resolution in Intact Tissues

Biologists face challenges in visualizing hundreds of biomolecules simultaneously within intact tissues at single-cell resolution. Existing methods, like most types of microscopy, track only a few molecules at a time and cannot detect all types, such as certain lipids. Mass spectrometry imaging detects hundreds of molecules but lacks the spatial resolution to pinpoint their locations within individual cells. 

Meng Wang, from Howard Hughes Medical Institute, Janelia Research Campus, sought to address this gap while studying aging mechanisms. Collaborating with expansion microscopy co-inventor Paul Tillberg, her team developed tissue expansion mass spectrometry imaging (TEMI), a method combining mass spec imaging with a modified expansion technique. Unlike traditional expansion microscopy, which degrades molecules, their approach gradually enlarges intact tissue samples using a swellable hydrogel, preserving molecular integrity while improving spatial resolution.

The refined process allows researchers to detect hundreds of biomolecules—including lipids, proteins, metabolites, and glycans—in their native locations at single-cell resolution. Applying the method to mouse cerebellum layers, the team discovered distinct molecular signatures in each layer, challenging assumptions of uniform distribution. Similar analyses in kidney, pancreas, and tumor tissues revealed biomolecule variations that could aid disease research.

“Knowing at each specific location what molecules are there and what is in the neighboring cells is very important for any kind of biological question,” Wang explains. The technique’s ability to map biomolecule patterns during aging, development, or disease could clarify their functional roles. In tumors, visualized molecular heterogeneity may help identify drug targets.

The method, described in Nature Methods, requires no specialized hardware, relying on existing mass spectrometry systems and accessible hydrogel protocols. “We wanted to develop something that did not require specialized instruments or procedures, but can be broadly adopted,” Wang says. By providing a detailed roadmap for adapting the approach to diverse tissues, the team aims to make mass spectrometry imaging a more versatile tool for biologists worldwide.

Tillberg notes the method bridges microscopy’s high-resolution imaging with mass spectrometry’s broad molecular detection: “This lets you have an untargeted look in the molecular space, and we are trying to bring it closer to what microscopy can do in terms of spatial resolution.” The technique’s accessibility and precision may accelerate discoveries in aging, cancer, and other fields reliant on spatial biomolecule analysis.