Label-Free Detection of Cellular Senescence in Fibroblasts via Third Harmonic Generation

Cellular senescence, a state of irreversible growth arrest in response to stress, plays a dual role in physiology and pathology. While essential for processes such as embryogenesis, wound healing, and tumor suppression, senescence also contributes to aging and age-related diseases, including cancer and neurodegeneration. The accumulation of senescent cells is linked to aging and numerous age-associated pathologies, making the detection of these cells crucial for understanding and potentially mitigating age-related diseases. Lipid metabolism is a key feature of senescent cells, which undergo significant alterations in lipid composition that influence membrane remodeling and cellular function. Here, we propose the use of third harmonic generation (THG) microscopy, a label-free imaging modality, to assess lipid profiles in senescent and nonsenescent cells. Our study demonstrated that THG can discriminate between senescent and nonsenescent fibroblasts based on their lipid content, suggesting a noninvasive approach for the detection and characterization of cellular senescence. In addition, these findings reveal that lipid content is increased in senescent cells. This methodology has potential applications in the diagnosis and study of age-related pathologies where lipid dysregulation is a hallmark feature.