Macrophage histone lactylation during ischemia induced-muscle regeneration [CUT&Tag]

After injury, muscles require fully functional macrophages to recover completely. During muscle regeneration, macrophages transition from a pro-inflammatory to a pro-restorative phenotype ensures the proper regeneration. Lactate is a crucial molecule for muscle-residing macrophage polarisation. Histone lactylation, a direct derivative of lactate, has been implicated in macrophage polarisation in vitro . In this work, we show for the first time that macrophages recruited to the muscle after ischemic injury modify their histone lactylome between 2 and 4 days post injury. Absolute histone lactylation levels increase significantly. Although subtly, also the genomic enrichment of H3K18la changes from 2 to 4 days post injury and this correlates with gene expression changes. Interestingly, we find that H3K18la genomic enrichment changes from day 2 to day 4 post injury are predictive for gene expression changes later in time, from day 4 to day 7, rather than being a reflection of past gene expression changes from day 1 to day 2. Our results suggest that histone lactylation dynamics are functionally important for the resolving action of macrophages during muscle regeneration.