Elimination of <i>p21</i> Highly Expressing Senescent Cells in Transgenic Obese Mice Enhanced Endothelium-dependent Vasodilation and Mitochondrial Respiration

Introduction: Cellular senescence represents a protective biological response to intrinsic and extrinsic stressors; however, the progressive accumulation of senescent cells contributes to tissue aging and dysfunction. In obesity, premature cellular senescence is accelerated, thereby increasing the burden of senescent cells across various tissues. Recent studies revealed that p21 -highly expressing cells ( p21 high cells) accumulate to a greater extent in aged and obese mice. In addition, targeted clearance of p21 high cells can mitigate the adverse effects of senescence, leading to enhanced physical performances in old mice and improved metabolic dysfunction in high-fat diet (HFD)-induced obese mice. Given this, p21 has emerged as a promising target for alleviating aging and aging-related pathologies. Therefore, this study investigates the effects of p21 high cells elimination on endothelium-dependent vasodilation and mitochondrial respiratory capacity in transgenic obese mice. Methods: p21 -Cre/+; +/+; db/db (Pdb) (n=12; 5M and 7F) and p21 -Cre/+; DTA/+; db/db (PDdb) (n=14; 5M and 9F) mice were generated and raised for about 6 months. Tamoxifen was administered monthly starting at 2 months of age for both groups and p21 high cells were depleted in PDdb mice. Using DMT pressure myograph system, femoral arteries were evaluated for endothelium-dependent dilation (EDD) in response to acetylcholine (ACh) and endothelium-independent dilation (EID) with sodium nitroprusside (SNP). Soleus muscles were harvested to measure mitochondrial respiratory capacity using Oroboros O2k high-resolution respirometry. Two-way repeated and one-way ANOVAs with Tukey post-hoc tests were performed to determine statistical differences between groups ( p &lt; 0.05). Results: No significant difference in body mass was observedbetween Pdb (67.2 ± 1.8 g) and PDdb (68.6 ± 1.8 g) mice. However, EDD was significantly improved following p21 high cells clearance (PDdb: 93.7 ± 2.6, Pdb 65.5 ± 2.8 %; p &lt; 0.05), while EID remained unchanged (PDdb: 97.4 ± 1.7, Pdb: 99.6 ± 1.8 %; p &gt; 0.05). Complex I-driven state 3 respiration (CI, State 3) was significantly improved in the PDdb group (PDdb: 28.4 ± 12.6, Pdb: 18.8 ± 2.3 pmol·s -1 ·mg -1 ; p &lt; 0.05). Although complex I+II-driven state 3 maximal (CI + CII, State 3) coupled respiration showed a trend toward enhancement in the PDdb group (PDdb: 44.2 ± 3.8, Pdb: 34.3 ± 2.9 pmol·s -1 ·mg -1 ; p =.055), it did not reach statistical significance. Additionally, respiratory control ratio (RCR), LEAK respiration, and electron transfer (ET) capacity were not significantly different between groups. Furthermore, non-mitochondrial respiration (residual oxygen consumption; ROX) was significantly reduced in the PDdb group (PDdb: 5.9 ± 1.5, Pdb: 8.3 ± 1.0 pmol·s -1 ·mg -1 ; p &lt; 0.05). Conclusion: The selective elimination of p21 high senescent cells in transgenic p21 -Cre obese mice led to improved vascular endothelial function and enhanced mitochondrial oxidative phosphorylation in skeletal muscles. These findings suggest that targeting p21 high cells could be a promising therapeutic strategy to enhance vascular and skeletal muscle function in obese and aging populations, potentially improving physical performance and metabolic health. NIH 5R01AG066679-05 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.