Prediction of biological age by morphological staging of sarcopenia in Caenorhabditis elegans.

Sarcopenia encompasses a progressive decline in muscle quantity and quality. Given its close association with aging, it may represent a valuable healthspan marker. Given the commonalities with human muscle structure and facile visualization possibilities, C. elegans represents an attractive model for studying the relationship between sarcopenia and healthspan. However, classical visual assessment of muscle architecture is subjective and has low throughput. To resolve this, we have developed an image analysis pipeline for the quantification of muscle integrity in confocal microscopy images from a cohort of aging myosin::GFP reporter worms. We extracted a variety of morphological descriptors and found a subset to scale linearly with age. This allowed establishing a linear model that predicts biological age from a morphological muscle signature. To validate the model, we evaluated muscle architecture in long-lived worms that are known to experience delayed sarcopenia by targeted knockdown of the daf-2 gene. We conclude that quantitative microscopy allows for staging sarcopenia in C. elegans and may foster the development of image-based screens to identify modulators that mitigate age-related muscle frailty and thus improve healthspan in C. elegans.