Fig. 1

Development of the CellPopAge Clock for monitoring subtle ageing difference in cells in culture. A Predicted age of control samples using three existing epigenetic clocks. Predicted epigenetic age for control samples across all experiments as estimated by the Multi-Tissue clock (green), the Skin and Blood clock (orange), and the PhenoAge clock (yellow). Fitted lines are shown with 95% confidence intervals (semi-transparent). All three clocks show a trend to increase in predicted age with progressing passage; however, there is considerable variability in predictions, particularly for the PhenoAge clock. The Multi-Tissue clock consistently predicted cells to have the highest epigenetic age, whilst the PhenoAge clock consistently predicted cells to have the lowest epigenetic age, which even reached below zero for several samples at various passages. B Heatmap representing 23 CpG probes that undergo hypomethylation with increasing cell passage and 19 CpGs that undergo hypermethylation with increasing cell passage. These 42 CpG probes were used to develop the CellPopAge Clock. Probes that undergo hypomethylation and hypermethylation with increasing passage were separated and ordered by their methylation values per row. The mean absolute difference between passage 20 and passage 10 among clock CpGs is 0.2. C Testing the CellPopAge Clock on HMF and HDF samples that were not used to train the clock. The grey dashed line represents the diagonal (perfect prediction). The fitted line of the actual data is shown in blue, with a 95% confidence interval (semi-transparent). Cell passages are predicted accurately