Impact of genetic background and experimental reproducibility on identifying chemical compounds with robust longevity effects

Abstract

Limiting the debilitating consequences of ageing is a major medical challenge of our time. Robust pharmacological interventions that promote healthy ageing across diverse genetic backgrounds may engage conserved longevity pathways. Here we report results from the Caenorhabditis Intervention Testing Program in assessing longevity variation across 22 Caenorhabditis strains spanning 3 species, using multiple replicates collected across three independent laboratories. Reproducibility between test sites is high, whereas individual trial reproducibility is relatively low. Of ten pro-longevity chemicals tested, six significantly extend lifespan in at least one strain. Three reported dietary restriction mimetics are mainly effective across C. elegans strains, indicating species and strain-specific responses. In contrast, the amyloid dye ThioflavinT is both potent and robust across the strains. Our results highlight promising pharmacological leads and demonstrate the importance of assessing lifespans of discrete cohorts across repeat studies to capture biological variation in the search for reproducible ageing interventions.

Automated Lifespan Determination Across Caenorhabditis Strains and Species Reveals Assay-Specific Effects of Chemical Interventions

“…(b,d,f) Survivorship curves from data of combined trials for all C. elegans (b), C. briggsae (d) and C. tropicalis (f) strains. Manual data are from Lucanic et al (2017). Table 1 Comparison of reproducibility of longevity estimates from manual and automated lifespan assays within and between labs for the baseline analysis of 22 strains across three species with no added compounds.…”

“…Table 1 Comparison of reproducibility of longevity estimates from manual and automated lifespan assays within and between labs for the baseline analysis of 22 strains across three species with no added compounds. Results for manual assays are from Lucanic et al (2017).…”

“…The qualitatively bimodality of survivorship curves observed in manual analysis in at least two of the three independent sites for each of the C. briggsae strains does not stand out in the ALM data set. Manual data are from Lucanic et al (2017).…”

“…Most compounds that extended lifespan in the manual assays also extended lifespan in ALMs. However, two compounds failed to extend lifespan on the ALMs, including thioflavin T (ThT), which is highly robust and reproducible in manual assays (Alavez et al 2011;Lucanic et al 2017). We found ThT to be photo-sensitive, such that modification of the ALM with the addition of a blue light filter restored the beneficial effects of ThT.…”

A long journey to reproducible results

“…After more than a year of pilot experiments and discussion of methods in excruciating detail, we eliminated systematic differences in survival outcomes across our labs almost completely. 12 …”