How Senescent Cells Drive Kidney Injury and What New Therapies Can Do About It

Ischemia-reperfusion injury (IRI) is the leading cause of acute kidney injury (AKI), affecting more than 20% of hospitalized patients and contributing substantially to morbidity, mortality, and progression to chronic kidney disease (CKD) and end-stage renal disease (ESRD). The kidney is particularly vulnerable to IRI because its proximal tubules depend on aerobic metabolism for energy-intensive ion transport, making rapid depletion of energy reserves during ischemia highly damaging. When blood flow is restored, reactive oxygen species (ROS) are generated in a burst, compounding DNA damage and oxidative stress beyond what the cell can repair. This review from the Institute of Nephrology at Peking University First Hospital provides a detailed synthesis of how these events culminate in cellular senescence — and why that matters for long-term kidney health.

Cellular senescence is defined as a stable, irreversible cell cycle arrest triggered by damaging stimuli such as DNA double-strand breaks, telomere dysfunction, oncogene activation, and oxidative stress. In the kidney, tubular epithelial cells (TECs) are the most vulnerable cell type and can become arrested in either G1/S or G2/M phase following IRI. The review details two major signaling axes driving this arrest: the p53–p21(CDKN1A) pathway, activated rapidly after DNA damage via ATM/ATR kinase signaling, and the p16(INK4a)–Rb pathway, which becomes dominant during sustained or repeated injury. Persistent G2/M arrest in TECs is particularly pathological — cells in this state produce profibrotic factors including TGF-β1, connective tissue growth factor (CTGF), and PAI-1, directly linking TEC senescence to interstitial fibrosis.

The senescence-associated secretory phenotype (SASP) is a defining and damaging hallmark of senescent cells. SASP components identified in IRI-AKI models include pro-inflammatory cytokines (IL-1β, IL-6, IL-8), chemokines (CCL2, CCL3, CCL5, CCL8), matrix metalloproteinases (MMP12, MMP13), and growth factors. Beyond soluble factors, the review highlights that senescent cells also release small extracellular vesicles and non-coding RNAs that propagate senescence signals to neighboring healthy cells — a phenomenon termed paracrine senescence. This SASP-driven amplification loop overwhelms immune surveillance, fosters chronic inflammation, remodels the extracellular matrix, and promotes progressive fibrosis, all of which contribute to the AKI-to-CKD transition. Pre-existing senescent cells in donor kidneys prior to transplantation have been shown to correlate significantly with subsequent development of interstitial fibrosis and tubular atrophy in allograft recipients.

The review describes two main therapeutic approaches: senolytics, which selectively kill senescent cells, and senomorphics, which suppress the SASP without eliminating the cells. Among senolytics, the combination of dasatinib (a BCR-ABL/Src kinase inhibitor) plus quercetin (a flavonoid) is the most clinically advanced, with studies showing clearance of p16-positive and SA-β-gal-positive senescent cells in tissues and improvement in physical function in early human trials. Navitoclax (ABT-263), a BCL-2/BCL-xL inhibitor, demonstrated senolytic efficacy in mouse IRI models. Among senomorphics, rapamycin (mTOR inhibition) suppresses SASP secretion, and metformin reduces senescence burden partly through AMPK activation and ROS reduction. Notably, pharmacological CDK4/6 inhibition using palbociclib induced temporary G1 arrest in bilateral IRI mouse models, protecting TECs from DNA damage and caspase activation without permanent senescence induction.

The authors underscore important emerging tools: single-cell RNA sequencing has enabled identification of distinct senescent TEC subpopulations in both human and mouse IRI kidneys, and SenNet consortium biomarkers (including CDKN1A, TP53BP1, SERPINE1, PTGS1, PTGS2) now provide a more precise molecular atlas of renal senescence. Novel in vivo senescence detection methods — including fluorescent SA-β-gal probes (SPiDER-βgal, C12FGD) and PET tracers (FPyGal) — allow real-time monitoring of senescent cell burden, which may prove critical for clinical dosing and response assessment. The authors acknowledge that most therapeutic evidence remains preclinical, that senolytic/senomorphic dosing regimens for the kidney are not yet standardized, and that some senescent cells may serve beneficial roles (e.g., wound healing) requiring careful therapeutic targeting to avoid off-target harm.