How Broken Mitochondria Drive the Scarring That Slowly Kills the Kidneys

Chronic kidney disease now affects hundreds of millions of people worldwide, and its most feared complication is not the failure of any single filter but the slow, silent replacement of working kidney tissue with scar. Renal fibrosis, the accumulation of stiff extracellular matrix that chokes off the delicate tubules and capillaries of the kidney, is the common pathological endpoint of nearly every form of progressive kidney disease. A new narrative review published in Molecular Biology Reports by Shaodan Ni, Zhipeng Li, Xiaolin Pan, Yijia Zhang and Xiaoli Nie of Southern Medical University argues that the deepest roots of that scarring may lie inside an organelle: the mitochondrion. The review, which synthesizes literature searched through mid-2026 with an emphasis on studies published between 2021 and 2026, reframes mitochondrial failure in renal tubular epithelial cells not as a passive consequence of injury but as a context-dependent contributor to, and amplifier of, the multicellular remodeling that drives fibrotic progression.

The vulnerability of the kidney tubule to mitochondrial collapse is no accident of biology; it is a direct consequence of what these cells do for a living. Renal tubular epithelial cells, and particularly the proximal tubular epithelial cells that reabsorb the bulk of the filtrate, are packed with mitochondria and depend overwhelmingly on oxidative metabolism to power the solute transporters that keep the body’s salt, water and pH balance in check. That metabolic specialization makes them exquisitely sensitive to a hostile environment. Hypoxia, lipotoxicity, uremic toxins, aging, chronic inflammation and hemodynamic stress all converge on the same target: the oxidative phosphorylation machinery that these cells cannot live without. When the energy supply falters, the entire tubule begins a descent from adaptive stress response into maladaptive repair, and the review is careful to distinguish the two, noting that the same pathways that protect during acute injury can become destructive when the stress never resolves.

At the biochemical level, the review lays out a cascade of interlocking failures. Persistent mitochondrial injury suppresses fatty acid oxidation, the primary fuel-burning pathway of the proximal tubule, and with it oxidative phosphorylation. Levels of nicotinamide adenine dinucleotide, the electron carrier that shuttles energy into the respiratory chain, become depleted. Mitochondrial reactive oxygen species accumulate, overwhelming the local antioxidant systems that include superoxide dismutase 2, thioredoxin 2 and the peroxiredoxins. Mitochondrial DNA becomes destabilized, in part through disruption of mitochondrial transcription factor A, which normally packages and protects the genome inside the organelle. Biogenesis programs governed by PGC-1α falter, the dynamic balance of fission and fusion controlled by DRP1, the mitofusins and OPA1 tips toward fragmentation, and mitophagy, the selective autophagic disposal of damaged mitochondria, loses its precision. None of these failures occurs in isolation; each feeds the others in a self-reinforcing loop.

One of the most consequential threads in the review concerns what happens when that loop breaches the boundaries of the cell. Damaged mitochondria release their contents, and mitochondrial DNA that escapes into the cytoplasm or the extracellular space acts as a damage-associated molecular pattern, tripping the cGAS-STING pathway and the NLRP3 inflammasome and engaging the mitochondrial antiviral-signaling protein MAVS. The result is a sterile inflammatory response that recruits and activates immune cells without any infection being present. Work cited in the review has shown that mitochondrial damage and STING activation lead directly to renal inflammation and fibrosis, and that NAD+ precursor supplementation can prevent the mtRNA- and RIG-I-dependent inflammation that follows kidney injury. In parallel, severely stressed tubular cells undergo inflammatory forms of cell death, including pyroptosis driven by RIPK3-MLKL signaling and mitochondrial calcium/calmodulin-dependent protein kinase II activation, flooding the interstitium with further danger signals.

The review also emphasizes senescence as a critical transition point between organelle failure and tissue-level disease. Tubular cells that survive mitochondrial stress but cannot restore homeostasis may enter a senescent state, acquiring a senescence-associated secretory phenotype that dumps pro-inflammatory cytokines, chemokines and matrix-remodeling enzymes into the surrounding interstitium. Studies cited include evidence that CXC chemokine receptor 2 accelerates tubular senescence through beta-catenin-induced mitochondrial dysfunction, and that pentraxin 3 drives senescence and fibrosis via beta-catenin signaling. Senescent cells also arrest in the G2/M phase of the cell cycle, a state associated with profuse profibrotic secretion. The tubule, in other words, becomes a chronic source of inflammatory and fibrogenic instruction, converting its own internal energy crisis into a multicellular remodeling program.

That program is executed through paracrine communication with the kidney’s other residents. The review organizes this within what it calls a tubule-to-niche framework, tracing how injured tubular epithelial cells signal to fibroblasts, macrophages, endothelial cells and pericytes. Damaged tubules release exosomes and extracellular vesicles, including TNFAIP8-encapsulated vesicles that steer interstitial fibroblast fate and vesicles that induce macrophage glycolysis by stabilizing HIF-1α in diabetic kidney disease. Tubular cell-specific platelet-derived growth factor subunit B has been shown to drive the formation of fibrogenic niches, while myofibroblast activation, the final common pathway of scarring, is reinforced by YAP/TAZ signaling downstream of mechanical and inflammatory cues. Even the vasculature is drawn in: peritubular endothelial cells shift toward glycolysis and microvascular rarefaction, worsening the hypoxia that started the cascade, and macrophage AMPK activated by oxidative stress drives profibrotic crosstalk with tubular cells after ischemic injury.

What distinguishes this review from many earlier syntheses is its methodological self-awareness. The authors explicitly separate causal perturbation from mere temporal or transcriptomic association, model-specific findings from cross-model convergence, and experimental efficacy from genuine clinical translation. They weigh evidence from human biopsy specimens and urinary biomarkers, including urinary mitochondrial DNA as a marker of tissue injury in non-diabetic chronic kidney disease, alongside single-cell RNA sequencing, spatial transcriptomics and kidney organoid models. Large single-cell atlases of healthy and injured human kidney have mapped the fibrotic microenvironment in unprecedented detail, and multi-omic profiling has implicated that microenvironment in disease progression. The review’s central interpretive claim is deliberately measured: mitochondrial dysfunction is not a universal initiating event for all fibrotic kidney disease, but a context-dependent contributor whose importance varies with the type of injury, the timing of observation and the cellular neighborhood in which it occurs.

On the therapeutic front, the review surveys a pipeline of strategies targeting bioenergetics, redox balance, mitochondrial quality control and tubular drug delivery. Restoring fatty acid oxidation has shown benefit in preclinical models, with tubule-specific overexpression of carnitine palmitoyltransferase 1A protecting against fibrosis by restoring mitochondrial homeostasis, and the natural compound hyperoside stabilizing ACAT1 to promote fatty acid oxidation through an L-carnitine-SIRT3 axis. NAD+ boosting has emerged as a particularly active area, with evidence that NAD+ prevents chronic kidney disease by activating renal tubular metabolism and that CD38-mediated NAD+ decline orchestrates fibrosis in obstructive nephropathy. PGC-1α activation by compounds such as ZLN005 and emodin, mitophagy induction through the Nrf2/PINK1 pathway, inhibition of pathological DRP1-mediated fission, and mitochondria-targeted antioxidants such as Mito-TEMPO have all shown antifibrotic effects in experimental systems. Early-phase clinical exploration includes a pilot randomized trial of a mitochondria-targeted ubiquinol on vascular function in chronic kidney disease and a phase 2a trial of the mitochondrial protectant elamipretide during renal artery stenting.

Yet the review is refreshingly blunt about why none of these approaches has yet changed clinical practice. Translation is constrained by disease heterogeneity, since chronic kidney disease arises from diabetes, hypertension, obstruction, toxins and genetic lesions that converge on fibrosis through partly distinct routes. Intervention timing matters enormously, as pathways that protect during acute injury may behave differently once fibrosis is established, and late intervention in animal models has sometimes attenuated proteinuria without slowing the decline of filtration rate. Target specificity, pharmacokinetics and the scarcity of validated human antifibrotic endpoints further complicate the path forward. The authors also note that much of the supporting evidence comes from rodent models such as unilateral ureteral obstruction, whose fidelity to human disease varies. Their synthesis ultimately delivers a dual message: the mitochondrion has earned its place at the center of fibrosis research, but conquering kidney scarring will require matching mitochondrial interventions to the right patients, at the right stage of disease, with endpoints that regulators and clinicians can trust.

Subject of Research: Mitochondrial dysfunction in renal tubular epithelial cells as a driver of fibrosis in chronic kidney disease

Article Title: Mitochondrial dysfunction of renal tubular epithelial cells in chronic kidney disease-associated fibrosis: from organelle homeostasis to multicellular remodeling

Article References: Ni, S., Li, Z., Pan, X., Zhang, Y., & Nie, X. (2026). Mitochondrial dysfunction of renal tubular epithelial cells in chronic kidney disease-associated fibrosis: from organelle homeostasis to multicellular remodeling. Molecular Biology Reports, 53(1), Article 1675. https://doi.org/10.1007/s11033-026-12861-0

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12861-0

Keywords: chronic kidney disease, renal fibrosis, mitochondria, renal tubular epithelial cells, fatty acid oxidation, NAD+, mitophagy, mitochondrial dynamics, mtDNA, inflammation, senescence, single-cell transcriptomics