Vitamin B 12 is a limiting factor for induced cellular plasticity and tissue repair.

Transient reprogramming by the expression of OCT4, SOX2, KLF4 and MYC (OSKM) is a therapeutic strategy for tissue regeneration and rejuvenation, but little is known about its metabolic requirements. Here we show that OSKM reprogramming in mice causes a global depletion of vitamin B 12 and molecular hallmarks of methionine starvation. Supplementation with vitamin B 12 increases the efficiency of reprogramming both in mice and in cultured cells, the latter indicating a cell-intrinsic effect. We show that the epigenetic mark H3K36me3, which prevents illegitimate initiation of transcription outside promoters (cryptic transcription), is sensitive to vitamin B 12 levels, providing evidence for a link between B 12 levels, H3K36 methylation, transcriptional fidelity and efficient reprogramming. Vitamin B 12 supplementation also accelerates tissue repair in a model of ulcerative colitis. We conclude that vitamin B 12 , through its key role in one-carbon metabolism and epigenetic dynamics, improves the efficiency of in vivo reprogramming and tissue repair.