Inman, Christina

ABSTRACT The senescent cell (SC) fate is linked to aging, multiple disorders and diseases, and physical dysfunction. Senolytics, agents that selectively eliminate 30%–70% of SCs, act by transiently disabling the senescent cell antiapoptotic pathways (SCAPs), which defend those SCs that are proapoptotic and pro‐inflammatory from their own senescence‐associated secretory phenotype (SASP). Consistent with this, a JAK/STAT inhibitor, Ruxolitinib, which attenuates the pro‐inflammatory SASP of senescent human preadipocytes, caused them to become “senolytic‐resistant”. Administering senolytics to obese mice selectively decreased the abundance of the subset of SCs that is pro‐inflammatory. In cell cultures, the 30%–70% of human senescent preadipocytes or human umbilical vein endothelial cells (HUVECs) that are senolytic‐resistant (to Dasatinib or Quercetin, respectively) had increased p16 INK4a , p21 CIP1 , senescence‐associated β‐galactosidase (SAβgal), γH2AX, and proliferative arrest similarly to the total SC population (comprising senolytic‐sensitive plus‐resistant SCs). However, the SASP of senolytic‐resistant SCs entailed less pro‐inflammatory/apoptotic factor production, induced less inflammation in non‐senescent cells, and was equivalent or richer in growth/fibrotic factors. Senolytic‐resistant SCs released less mitochondrial DNA (mtDNA) and more highly expressed the anti‐inflammatory immune evasion signal, glycoprotein non‐melanoma‐B (GPNMB). Transplanting senolytic‐resistant SCs intraperitoneally into younger mice caused less physical dysfunction than transplanting the total SC population. Because Ruxolitinib attenuates SC release of proapoptotic SASP factors, while pathogen‐associated molecular pattern factors (PAMPs) can amplify the release of these factors rapidly (acting as “senosensitizers”), senolytic‐resistant and senolytic‐sensitive SCs appear to be interconvertible.

Marfan Syndrome (MFS) is often associated with progressive aortic root dilation, ultimately leading to aortic aneurysm and dissection. While recent work showed increased transforming growth factor beta (TGF-β) signaling contributes to aneurysm formation in aorta, efficacious therapeutic targets remain elusive. Consistent with prior reports of progeroid phenotypes in a subset of Marfan patients we previously demonstrated increased cellular senescence in a MFS mouse model. Here, we sought to determine whether administration of senolytic drugs reduces cellular senescent markers, TGF-β signaling, and aortic root dilation in aged MFS mice by assessing aortic root dimensions by echocardiography and gene expression levels by quantitative real time PCR at 15 months of age following treatment with vehicle (VEH) or the senolytic compound Fisetin for one month. As expected, aortic sinus dimensions were increased dramatically in fibrillin-1 mutant mice compared to wild-type controls and were associated with increased expression of TGF-β1, the senescence marker CDKN2A, the matrix remodeling enzyme MMP2, and the osteogenic and proliferative gene RUNX2. Consistent with previous data from our group, Fisetin treatment dramatically reduced CDKN2A expression in marfanoid mice compared to VEH, which was associated with reductions in TGF-β1, MMP2, and RUNX2. Phenotypically, we observed modest reductions in aortic sinus dimensions compared to VEH, but no substantive change in ascending aortic dilatation. Collectively, these data suggest that senescent cells are significant contributors to molecular changes occurring in MFS and clearance of senescent cells with Fisetin slows the progression aortic root-dilation in fibrillin-1 mutant mice.