Characterization of p16-positive stromal cells in age-related cardiac disorders

The heart undergoes structural alterations, including fibrosis and cardiomyocyte hypertrophy with age. These alterations are accompanied by functional decline, resulting in heart failure. Although cardiac stromal cells such as fibroblasts and macrophages are known to play a role in age-related cardiac changes, specific subsets of these cells may have a more pronounced effect on the development of these alterations. In this study, we analyzed p16, a marker of senescence,-positive (p16+) cells in cardiac fibrosis by single-cell RNA sequencing of aged p16-Tom mice, in which p16+ cells can be labeled in the presence of tamoxifen. We found that TGF-β signaling were significantly enriched in the transcriptome of p16+ fibroblasts compared with p16- fibroblasts. Besides, BMP4 was upregulated in p16+ fibroblasts. This activation potentially promoted the expression of collagen genes such as Col4a1 and Col5a3. Selective elimination of p16+ fibroblasts ameliorated cardiac fibrosis in aged p16-Col1a2-LRTD mice, with levels comparable to those observed in young mice. These findings suggest that p16+ fibroblasts play a critical role in age-associated cardiac fibrosis. We further demonstrate the potential use of transcriptomic signatures of p16+ fibroblasts to identify human fibroblast subsets causing age-related cardiac diseases such as dilated cardiomyopathy.