MIT researchers have developed a new, noninvasive method to detect biomarkers of cellular senescence—a process in which cells stop dividing but remain alive. These senescent cells can accumulate with age and are linked to various age-related diseases, such as cancer, tissue degeneration, and chronic inflammation. The method combines Raman microscopy, which uses light to reveal the chemical composition of cells without damaging them, with single-cell gene expression data. This combination allows scientists to identify unique "barcodes" that can help quickly recognize senescent cells. The study was conducted using mouse cells, and the team is now working to adapt the technique for human tissue. Cellular senescence often occurs when cells suffer DNA damage, which causes them to stop dividing permanently. These cells undergo significant changes in shape, metabolism, and gene activity. Normally, the immune system removes these "zombie" cells, but this process becomes less effective as people age, leading to their accumulation. This buildup has been linked to physical signs of aging, such as sagging skin and muscle weakness, as well as chronic conditions like osteoarthritis and type 2 diabetes. However, cellular senescence also has important roles, such as aiding in embryonic development and tissue repair. Previously, scientists identified a few senescence markers, like the proteins p16 and p21, but these can only be detected using methods that destroy the cells. MIT researchers aimed to develop a noninvasive approach using Raman microscopy. Unlike RNA sequencing, which requires destroying cells to analyze their genetic material, Raman microscopy is nondestructive. It uses near-infrared or visible light to reveal the chemical composition of tissues or cells, making it a promising tool for studying cellular changes without harming the sample. In their new study, the researchers combined Raman microscopy with spatial RNA sequencing to identify new senescence markers. This dual approach provided a more comprehensive view of the features of senescent cells, including their gene expression, location, and biochemical properties. They examined skin and lung tissue from both young and old mice. One notable finding was an increase in lipid synthesis and accumulation in older cells. However, the impact of these changes on cell function is still unclear. The researchers also found that in senescent skin cells, pathways related to muscle contraction and collagen remodeling were significantly altered. In aged lung tissue, they observed increased activity of genes involved in immune responses and inflammation. The team now hopes to explore how these changes influence the behavior of senescent cells. Using their data, they identified specific Raman peaks—chemical signatures linked to certain molecules—that correlate with senescence. By combining these peaks with key gene expression patterns, they created a barcode that can help identify senescent cells without bias. This could lead to diagnostic tools that detect senescent cells by scanning for specific Raman spectrum bands. To make the technique more practical, the researchers are working on developing a faster version of their Raman imaging system. Currently, analyzing a small tissue sample takes about 30 hours, but they aim to improve the system to process larger samples more quickly. The study was published in the journal Nature Aging, marking a significant step toward understanding and potentially targeting senescent cells in human health.