DNAm Skin & Blood clock (Horvath 2018)

The DNAm Skin & Blood clock, published by Horvath and colleagues in 2018, is an epigenetic age estimator based on 391 CpG sites selected from methylation arrays applied to skin fibroblasts and blood samples. It was developed partly to overcome the observation that the original 2013 Horvath clock systematically underestimated age in keratinocytes and fibroblasts, tissues central to studies of in-vitro reprogramming and rejuvenation. Because it was trained on a tissue type directly accessible in longevity intervention studies, it is frequently used as a readout in partial reprogramming experiments alongside the multi-tissue Horvath clock.