Abstract| Volume 355, P9, August 2022

TP53-mutant clonal hematopoiesis accelerates experimental atherosclerosis development

      Background and Aims : Acquired mutations in hematopoietic cells that lead to clonal hematopoiesis (CH) are emerging as new drivers of atherosclerotic cardiovascular disease. The TP53 gene, which encodes the tumor suppressor protein p53, is one of the most frequently mutated genes in individuals exhibiting CH. Here, we investigated the effects of CH driven by inactivating mutations in p53 on experimental atherosclerosis development.
      Methods: Chimeric Ldlr-/- mice carrying 20% Trp53-/- hematopoietic cells (20% KO BMT mice) were generated through competitive bone marrow (BM) transplants. White blood cells (WBC) and BM progenitors were analyzed by flow cytometry. Atherosclerotic plaque development and composition were evaluated by histological techniques. Cultured murine BM derived macrophages (BMDM) were used to perform mechanistic studies.
      Results: Trp53-/- cells expanded progressively in WBCs and BM progenitors, which led to 39% larger atherosclerotic plaques in the aortic root (p=0.009). Increased plaque macrophage content was observed in 20% KO BMT mice, in parallel with higher proliferation of Trp53-/- macrophages within the arterial wall, as revealed by Ki67 immunostaining. Bulk RNA sequencing and in vitro analysis of MCSF-stimulated BMDM showed that p53 deficiency leads to widespread changes in the expression of cell proliferation-related genes and results in accelerated cell cycle progression. Additionally, Trp53-/- BMDM exhibit a marked downregulation of cell-death-related transcripts and reduced apoptosis after UV radiation or MCSF deprivation. Consistent with these findings, 20% KO BMT mice displayed less apoptotic nuclei in atherosclerotic plaques.
      Conclusions: TP53 mutation-driven CH accelerates experimental atherosclerosis development and increases plaque macrophage burden by modulating macrophage proliferation and apoptosis.