Senescent cells, which accumulate in tissues as we age, are known to play a role in organ aging and the overall aging process. These cells cause a halt in the proliferation of functional cells and induce chronic inflammation. However, researchers have hypothesized the existence of a subset of cells in an intermediate stage of cellular senescence, which they call “mid-old cells,” that significantly impact and contribute to organic dysfunction in the elderly. Their study found that mid-old cells exhibit distinct gene expression patterns and retain their capacity to respond to external stimuli. These cells were also observed in elderly tissues, specifically in fibroblasts and smooth muscle cells.
https://www.nature.com/articles/s41467-023-43491-w