Allison B. Herman

Cardiovascular aging is accompanied by profound remodeling of the extracellular matrix (ECM). Growing evidence suggests that ECM not only acts as a structural scaffold but also actively regulates cell behavior and vascular homeostasis. During aging, the vascular ECM undergoes numerous molecular, architectural, and biochemical changes, including collagen accumulation, elastin fragmentation, pathological crosslinking, matrikines production, and progressive matrix stiffening. These changes reshape the vessel wall’s biochemical and mechanical landscape, reflecting how cells respond to their microenvironment. Vascular cells continuously interpret matrix-derived cues through integrins, discoidin, syndecans, ion channels, and downstream pathways such as FAK, RhoA/ROCK, and YAP/TAZ. As the ECM ages, continuous activation of these pathways promotes endothelial dysfunction, modulation of the vascular smooth muscle cell phenotype, fibroblast activation, inflammation, calcification, and induction of senescence. Consequently, the aging ECM emerges as an instructive niche that can determine and reprogram vascular cell identity and function. Interestingly, the relationship between ECM remodeling and senescent state is bidirectional. Senescent vascular cells profoundly affect matrix composition by producing a plethora of factors involved in ECM production and remodeling, while age-associated ECM alterations, including collagen deposition, increased stiffness, and active matrikines, can induce or reinforce senescence-associated phenotypes. This bidirectional interaction establishes a self-amplifying loop that accelerates vascular dysfunction and cardiovascular aging. In this work, we discuss the molecular and structural hallmarks of ECM aging, the mechanisms by which vascular cells sense and interpret matrix-derived signals, and emerging evidence linking ECM remodeling to senescence and vascular remodeling. In addition, we highlight unanswered questions and opportunities aimed at preserving ECM integrity, modulating mechanotransduction, and restoring a more youthful extracellular environment. In sum, this review supports the notion that aging ECM is not a passive bystander, but a pivotal driver and a promising intervention target for promoting vascular aging and cardiovascular diseases.

Growing evidence suggests that the induction of cellular senescence in vascular cells is causally linked to the etiology of cardiovascular diseases. To investigate systematically the heterogeneity of senescent vascular cells in atherosclerosis, we used a high-fat diet and PCSK9 overexpression to induce atherosclerosis in a senescence reporter mouse model (p16-tdTomato^+/−) and performed single-cell RNA sequencing on whole aortas. Using the SenMayo and CellAge gene sets, we identified four clusters of vascular smooth muscle cells (VSMCs), fibroblasts and T cells enriched in features of senescence, which were reduced upon treatment with the senolytic agent ABT-737. We then derived a global senescence signature of atherosclerosis including Spp1, Ctsb and Tnfrsf11b mRNAs. We validated the enrichment of these mRNAs in senescence by using spatial transcriptomics in a second mouse model of atherosclerosis and senolysis (Ldlr^−/−; p16-3MR), as well as by analyzing in vitro models of human VSMC senescence. Our results uncover a vascular-specific transcriptomic signature of senescence that may be exploited for tracking and treating age-related vascular diseases.

The roles of fibronectin leucine-rich transmembrane protein 2 (FLRT2) in physiological and pathological processes are not well known. Here, we identify a potentially novel function of FLRT2 in preventing endothelial cell senescence and vascular aging. We found that FLRT2 expression was lower in cultured senescent endothelial cells as well as in aged rat and human vascular tissues. FLRT2 mediated endothelial cell senescence via the mTOR complex 2, AKT, and p53 signaling pathway in human endothelial cells. We uncovered that FLRT2 directly associated with integrin subunit beta 4 (ITGB4) and thereby promoted ITGB4 phosphorylation, while inhibition of ITGB4 substantially mitigated the induction of senescence triggered by FLRT2 depletion. Importantly, FLRT2 silencing in mice promoted vascular aging, and overexpression of FLRT2 rescued a premature vascular aging phenotype. Therefore, we propose that FLRT2 could be targeted therapeutically to prevent senescence-associated vascular aging.

Senescent cell accumulation drives aging and related pathologies including metabolic disorders and neurodegeneration, and their selective elimination is a promising therapeutic approach to treat multiple diseases of aging in humans. However, developing drugs to eliminate senescent cells requires specific biomarkers to selectively identify and target these cells in vivo. In this study, we have performed a comprehensive and quantitative proteomic profiling of surface proteomes (surfaceomes) of senescent cells to identify potential senescence biomarker candidates in human tissues. We induced senescence using ionizing radiation in a variety of cell types including lung fibroblasts, monocytes, vascular smooth muscle cells, aortic endothelial cells and preadipocytes. Senescence was validated using a panel of canonical markers including reduced proliferation, increased senescence-associated β-galactosidase activity, and increased expression of p21, p16, IL6, and others. The cell surface proteome was enriched using an optimized surface biotinylation approach (Glyco-cell surface capture) followed by data-independent acquisition (DIA) LC-MS/MS analysis on a Q-Exactive HF Orbitrap mass spectrometer. Our analysis revealed novel cell surface targets that were further validated by flow cytometry and immunohistochemistry. These results provide clinically useful information for establishing biomarkers and therapeutic targets to aid in the translation of senescence-targeted therapies to treat age-associated diseases.

Cardiovascular disease (CVD) is a leading cause of morbidity and mortality worldwide, and senescent cells have emerged as key contributors to its pathogenesis. Senescent cells exhibit cell cycle arrest and secrete a range of proinflammatory factors, termed the senescence-associated secretory phenotype (SASP), which promotes tissue dysfunction and exacerbates CVD progression. Omics technologies, specifically transcriptomics and proteomics, offer powerful tools to uncover and define the molecular signatures of senescent cells in cardiovascular tissue. By analyzing the comprehensive molecular profiles of senescent cells, omics approaches can identify specific genetic alterations, gene expression patterns, protein abundances, and metabolite levels associated with senescence in CVD. These omics-based discoveries provide insights into the mechanisms underlying senescence-induced cardiovascular damage, facilitating the development of novel diagnostic biomarkers and therapeutic targets. Furthermore, integration of multiple omics data sets enables a systems-level understanding of senescence in CVD, paving the way for precision medicine approaches to prevent or treat cardiovascular aging and its associated complications.

Studying cardiovascular senescence is crucial for understanding disease-related changes in the cardiovascular system and their impact on health and disease. To systematically investigate the heterogeneity of senescent vascular cells in atherosclerosis, we employed the senescence reporter mouse p16tdTomato^+/-, overexpressed PCSK9 and fed a high-fat diet (HFD) to induce atherosclerosis, and treated them with the senolytic drug ABT-737. Whole-aorta, single-cell RNA-sequencing (scRNA-seq) and Gene Set Enrichment Analysis (GSEA) using the SenMayo panel uncovered 10 cell clusters displaying senescent features, although not ‘classical’ senescence markers, that were reduced by treatment with ABT-737. Unbiased subclustering revealed subsets of cells increasing by HFD and reduced by ABT-737 treatment that expressed unique transcripts Spp1, Ctsb, and Tnfrsf11b mRNAs. Spatial analysis of these RNAs identified senescent cells in the cap and core of brachiocephalic arteries from atherosclerotic mice. Our results uncover a vascular-specific transcriptomic signature that may be exploited for therapeutic targeting in age-related vascular diseases.

Changes in the transcriptomes of human tissues with advancing age are poorly cataloged. Here, we sought to identify the coding and long noncoding RNAs present in cultured primary skin fibroblasts collected from 82 healthy individuals across a wide age spectrum (22–89 years old) who participated in the GESTALT (Genetic and Epigenetic Signatures of Translational Aging Laboratory Testing) study of the National Institute on Aging, NIH. Using high‐throughput RNA sequencing and a linear regression model, we identified 1437 coding RNAs (mRNAs) and 1177 linear and circular long noncoding (lncRNAs) that were differentially abundant as a function of age. Gene set enrichment analysis (GSEA) revealed select transcription factors implicated in coordinating the transcription of subsets of differentially abundant mRNAs, while long noncoding RNA enrichment analysis (LncSEA) identified RNA‐binding proteins predicted to participate in the age‐associated lncRNA profiles. In summary, we report age‐associated changes in the global transcriptome, coding and noncoding, from healthy human skin fibroblasts and propose that these transcripts may serve as biomarkers and therapeutic targets in aging skin.

Senescent vascular smooth muscle cells (VSMCs) accumulate in the vasculature with age and tissue damage and secrete factors that promote atherosclerotic plaque vulnerability and disease. Here, we report increased levels and activity of dipeptidyl peptidase 4 (DPP4), a serine protease, in senescent VSMCs. Analysis of the conditioned media from senescent VSMCs revealed a unique senescence-associated secretory phenotype (SASP) signature comprising many complement and coagulation factors; silencing or inhibiting DPP4 reduced these factors and increased cell death. Serum samples from persons with high risk for cardiovascular disease contained high levels of DPP4-regulated complement and coagulation factors. Importantly, DPP4 inhibition reduced senescent cell burden and coagulation and improved plaque stability, while single-cell resolution of senescent VSMCs reflected the senomorphic and senolytic effects of DPP4 inhibition in murine atherosclerosis. We propose that DPP4-regulated factors could be exploited therapeutically to reduce senescent cell function, reverse senohemostasis, and improve vascular disease.

Aging causes a progressive decline in the structure and function of organs. With advancing age, an accumulation of senescent endothelial cells (ECs) contributes to the risk of developing vascular dysfunction and cardiovascular diseases, including hypertension, diabetes, atherosclerosis, and neurodegeneration. Senescent ECs undergo phenotypic changes that alter the pattern of expressed proteins, as well as their morphologies and functions, and have been linked to vascular impairments, such as aortic stiffness, enhanced inflammation, and dysregulated vascular tone. Numerous molecules and pathways, including sirtuins, Klotho, RAAS, IGFBP, NRF2, and mTOR, have been implicated in promoting EC senescence. This review summarizes the molecular players and signaling pathways driving EC senescence and identifies targets with possible therapeutic value in age-related vascular diseases.