Ranking Biomarkers of Aging by Citation Profiling and Effort Scoring

Abstract

Aging affects most living organisms and includes the processes that reduce health and survival. The chronological and the biological age of individuals can differ remarkably, and there is a lack of reliable biomarkers to monitor the consequences of aging. In this review we give an overview of commonly mentioned and frequently used potential aging-related biomarkers. We were interested in biomarkers of aging in general and in biomarkers related to cellular senescence in particular. To answer the question whether a biological feature is relevant as a potential biomarker of aging or senescence in the scientific community we used the PICO strategy known from evidence-based medicine. We introduced two scoring systems, aimed at reflecting biomarker relevance and measurement effort, which can be used to support study designs in both clinical and research settings.

Keywords: aging; biomarker; health; senescence; survival.

FIGURE 1

Simplified graphic of the PICO-based queries employed at NCBI-PubMed. The search strategy was conducted as “((aging) AND (potential biomarker)) AND (biomarker)” for establishing the “c-score” and “((aging) AND (potential biomarker)) AND (biomarker),” filtered for reviews, for establishing the “rc-score.”

FIGURE 2

Representative microscopy pictures of cellular senescence biomarkers. Note the clear difference in overt morphology due to age of the respective individual at biopsy (cells are larger in size and more flattened; cells were immunostained for vimentin.) SAHF are formed in old fibroblasts and are enriched in heterochromatin markers. (Cells were immunostained for H3K9Me3.) SA-ßGal activity increases with age at pH 6.0. (Cells were treated with X-Gal to make SA-βGal visible in senescent cells.); scale bar: 10 μM for morphology and SAHF column, 50 μM for SA-βGAL column.