American journal of physiology. Renal physiology最新文献

Background: The mechanisms contributing to progressive kidney damage in autosomal dominant polycystic kidney disease (ADPKD) remain unclear. Renal microvascular (MV) rarefaction plays an important role in kidney disease, but its natural history, underlying mechanisms, and contributions to renal disease progression in ADPKD remain unknown. We hypothesized that intrarenal MV rarefaction is present early on and is preceded by vascular transcriptional and metabolic changes. Methods: Pkd1^RC/RC and WT mice (n=16 each) were studied at 1, 6, and 12 months. Total kidney volume (TKV) was measured in vivo (MRI), whereas renal MV architecture (3D-micro-CT), capillary density, perivascular fibrosis, and histomorphometric parameters were assessed ex vivo. In randomly selected Pkd1^RC/RC and WT kidneys (n=5, each/time point), mRNA-sequencing was performed to identify differentially expressed vasculature-related genes (DEGs). Next, in young humans with ADPKD and matched controls (n=10 each), plasma cellular energy metabolites were determined (LC-MS/MS), validated in an extended cohort (n=32 and n=16, respectively), and correlated with markers of disease severity and progression. Gene-metabolite interaction networks were generated to integrate DEGs in Pkd1^RC/RC at 1 month with metabolites dysregulated in individuals with ADPKD, which were further quantified in WT and Pkd1^RC/RC kidneys. Results: Renal MV density was preserved at 1 month but progressively decreased at 6 and 12 months, associated with capillary loss and perivascular fibrosis. A total of 110, 48, and 201 DEGs were identified at 1, 6, and 12 months, respectively. Plasma gamma-aminobutyric acid (GABA), homocysteine (Hcy) and asymmetric dimethyl arginine (ADMA) levels were higher in humans with ADPKD versus controls, interacted with DEGs implicated in inflammatory and innate immune response and Hcy metabolism, and correlated with TKV and renal blood flow. Conclusions: Our data demonstrate that intrarenal MV abnormalities present early in ADPKD and are preceded by vascular transcriptional and metabolic changes. The renal microcirculation may constitute an important therapeutic target in ADPKD, and its underlying biomarkers may serve to monitor its progression.

The stromal compartment of the developing kidney arises from Foxd1-expressing progenitors and gives rise to diverse cell types essential for nephrogenesis, including the renal stroma, capsule, mesangial cells, renin cells, pericytes, and vascular smooth muscle cells (VSMCs). However, the molecular mechanisms guiding their fate specification remain incompletely defined. Here, we identify the basic helix-loop-helix transcription factor Tcf21 as a critical determinant of stromal cell identity during kidney development. We performed single-cell RNA sequencing (scRNA-seq) on Foxd1-lineage cells isolated from embryonic day 14.5 (E14.5) Tcf21 conditional knockout (Tcf21-cKO) Foxd1^Cre/+;Rosa26^mTmG;Tcf21^f/f and control kidneys, revealing seven transcriptionally distinct stromal subpopulations. Loss of Tcf21 resulted in marked depletion of Medullary/Perivascular stroma, Collecting duct associated stroma, Proliferating stroma, and Nephrogenic zone associated subpopulations, confirmed by immunostaining, which revealed severe constriction of medullary and collecting duct stromal spaces. Additionally, we identified a novel cluster unique to Tcf21-cKO kidneys, characterized by high expression of Endomucin (Emcn). These cells spanned pseudotime trajectories and were distributed broadly across the mutant kidney. These findings were corroborated by E14.5 single-cell ATAC sequencing (scATAC-seq), which confirmed altered chromatin accessibility in Tcf21-deficient stroma. To assess the persistence and downstream impact of these defects, we performed bulk and scRNA-seq at E18.5, revealing sustained expansion of Emcn⁺ cells with pro-fibrotic and perivascular transcriptional programs. Histological analyses at 2 months demonstrated lasting architectural disruption, interstitial fibrosis, and impaired renal function in Tcf21-cKO mice. Our results identify Tcf21 as a key regulator of stromal progenitor fate and establish a developmental origin for fibrotic remodeling and kidney dysfunction.

This study investigates the effects of environmental circadian disruption and high-fat diet (HFD) on cardiovascular and renal functions in Bmal1 knockout (KO) and wild-type (WT) rats. Under 12:12-h light:dark conditions, Bmal1 KO males and females on a normal fat diet (NFD) exhibit lower mean arterial pressure (MAP) compared with WT. These genotype differences were attenuated after subjecting rats to a weekly 6 h advance in the 12:12-h light:dark protocol to induce chronic circadian stress (CCS). CCS modestly elevated MAP in males, eliminating pre-existing genotypic differences, whereas in females, CCS had no significant effects on MAP and heart rate. Under HFD, genotype-based MAP differences are attenuated, and sex differences in heart rate are diminished. CCS further elevated MAP in male Bmal1 KO, accompanied by reduced blood pressure amplitude. Diurnal variations in sodium excretion are abolished post-CCS in both WT and Bmal1 KO males on HFD. In Bmal1 KO females, CCS combined with HFD disrupts sodium excretion rhythms, thus eliminating the protective effects seen on NFD. These findings highlight the complex interplay between circadian regulation, dietary fat, and environmental stress in modulating cardiovascular and renal physiology. This study further supports a "two-hit hypothesis," where CCS and HFD may synergistically disrupt sodium homeostasis and blood pressure circadian rhythms in both males and females.NEW & NOTEWORTHY We investigate the role of Bmal1, a core circadian clock gene, and diet in impairment of blood pressure and renal function during a chronic circadian stress protocol. This study finds that the endogenous molecular clock responds to circadian stress and high-fat diet in a sex-specific manner, warranting further investigation in the role of these systems in the regulation of blood pressure control and organ function.

Chronic kidney disease (CKD) is one of the leading causes of global morbidity, and early diagnosis is essential to prevent complications. Estimated glomerular filtration rate (eGFR) is a key biomarker for assessing renal function. However, its value is influenced by various factors, including circadian variations. Previous studies have documented a circadian rhythm in eGFR, but population-level investigations using the cosinor method have not been conducted. We conducted a retrospective study in two hospitals in Spain (Toledo and Lorca) between 2017 and 2019. The circadian rhythm of eGFR was studied by fitting it to a cosine function, analyzing the effects of age and CKD stage. The results showed a statistically significant circadian rhythm in both populations, with the acrophase occurring at the beginning of the active phase of the day. The amplitude of the rhythm decreased in older patients (70-85 yr), whereas patients with advanced CKD had lost their circadian rhythm entirely. This study, for the first time, uses the cosinor method to demonstrate the existence of a population-level circadian rhythm of eGFR. The cosinor analysis was performed on different CKD stages and ages, revealing the existence of significant rhythms, although none at advanced ages or post-G1 CKD stage. The loss of circadian variability in advanced CKD emphasizes the importance of considering these rhythms in clinical practice to improve the diagnosis and management of kidney disease.NEW & NOTEWORTHY This study, for the first time, uses the cosinor method to demonstrate the existence of a population-level circadian rhythm of estimated glomerular filtration rate, which is influenced both by age and the progression of chronic kidney disease.

Epigenetic regulation through histone modifications plays a crucial role in driving cellular state transitions. Regulating gene transcription through bivalency, the co-occurrence of activating histone H3 lysine 4 trimethylation (H3K4me3) and repressive histone H3 lysine 27 trimethylation (H3K27me3) histone marks, drives cell fate in development; however, its role in kidney injury is not known. Here, we investigated bivalent gene activation in the adult male Mus musculus kidney following ischemia-reperfusion injury (IRI). We developed and validated a novel per-gene scoring method for identifying bivalent domains from CUT&RUN (Cleavage Under Targets and Release Using Nuclease) data. Our analysis revealed that bivalent genes in the mature kidney substantially overlap with known embryonic bivalent domains. Following IRI, a subset of bivalent genes became activated, defined by a loss of H3K27me3, enrichment of H3K4me3, and a corresponding increase in gene transcription. Activated bivalent genes were differentially expressed in kidney epithelial cells and strongly enriched for pathways involving inflammation and fibrosis. To uncover the regulatory mechanism associated with activated bivalent genes, we identified key transcription factors linking these genes which converged on the pioneer transcription factor, Spi1. We demonstrated that Spi1 targets are differentially expressed in both mouse and human kidney epithelial cells after injury and preferentially depleted of H3K27me3 and gain H3K4me3 enrichment after IRI, supporting its role in mediating the epigenetic switch. Our findings reveal a common epigenetic mechanism where transcription factors, acting on bivalent chromatin, contribute to inflammatory and fibrotic responses to kidney injury. This suggests that the progression from acute to chronic kidney injury is an active, transcriptionally driven failure of repair that is epigenetically mediated by histone modifications.NEW & NOTEWORTHY We performed the first identification of bivalent domains in the adult mouse kidney. We identified bivalent genes that, when activated after kidney injury, drive inflammation, proliferation, and fibrosis. Activation of bivalent genes is coordinated by transcription factors such as Spi1. Our research not only provides a valuable database of bivalent genes in the kidney but also demonstrates that activation of bivalent genes is crucial for the progression from acute to chronic kidney injury.

Chronic kidney disease (CKD) is associated with hypervolemia and sympathetic nervous system (SNS) overactivity that both contribute to heightened cardiovascular risk. Classically, extracellular fluid volume (ECFV) is inversely related to SNS activity, whereby increased ECFV suppresses SNS activation. However, ECFV and SNS activity could be concomitantly elevated if there is failure to suppress SNS activity or if SNS activity plays a contributory role in ECFV expansion. Therefore, we examined the clinical determinants of increased ECFV, the association between ECFV and SNS activity, and whether kidney function accounts for this relationship in CKD. In this cross-sectional study, patients with stage II-IV CKD (62 ± 12 yr, 67% men, 90% with hypertension, n = 104) underwent an assessment of ECFV via extracellular water/total body water ratio, using multifrequency bioimpedance, and a subset had SNS activity via muscle sympathetic nerve activity (MSNA, n = 39). We examined linear associations between ECFV and clinical factors, including MSNA, and group comparisons of MSNA across ECFV tertiles. Multivariable regression analyses were used to assess the relative contribution of kidney function [i.e., estimated glomerular filtration rate (eGFR)] and MSNA to ECFV. ECFV was inversely associated with eGFR and positively associated with age, systolic blood pressure, and pulse pressure (P < 0.05 for all). MSNA was different across ECFV tertiles (P = 0.009), with higher MSNA in tertiles 2 and 3 compared with tertile 1 (41 ± 14 and 35 ± 12 vs. 26 ± 9 bursts/min, P = 0.002 and 0.081, respectively), even after adjusting for eGFR, age, sex, and antihypertensive medications. MSNA (r = -0.376, P = 0.018) was inversely associated with eGFR. In multivariable models, eGFR remained a significant predictor of ECFV (β = -0.341, P = 0.045), whereas MSNA showed no independent association with ECFV (β = 0.124, P = 0.457). An inverse relationship between ECFV and SNS activity is not observed in stage II-IV CKD; rather, MSNA is higher in patients with higher ECFV. These findings suggest that the sympathoexcitatory effects of reduced kidney function may override the sympathoinhibitory effects of increased ECFV in CKD.NEW & NOTEWORTHY Patients with chronic kidney disease (CKD) face high cardiovascular risk from both fluid overload and heightened sympathetic nervous activity. In healthy individuals, fluid expansion suppresses sympathetic tone; however, this inverse relationship was absent in our cohort with CKD stage II-IV. Using direct intraneural recordings and validated volume measures, we found that extracellular fluid and muscle sympathetic nerve activity increased in parallel, highlighting disrupted volume-autonomic interplay and underscoring the need to better understand neurogenic contributions to fluid dysregulation in CKD.

Despite advances in drug delivery technologies, there is still an unmet demand for noninvasive kidney-targeted drug delivery systems that enhance therapeutic efficacy while minimizing systemic side effects. In the present study, we conducted a proof-of-concept study to evaluate the feasibility and effectiveness of intravesical delivery as a kidney-targeting strategy in mice. We demonstrated that intravesical infusion could retrogradely deliver molecules with a size up to 500 kDa to both the medulla and cortex of the kidney. In particular, empagliflozin, an antagonist of sodium-glucose cotransporter 2 (SGLT2), could effectively target the uppermost segment of the renal tubular system, that is, the proximal tubules, when administered via the intravesical route, thereby promoting glucose excretion. In an orthotopic renal carcinoma model, intravesical delivery of a chemotherapeutic agent achieved superior tumor suppression with markedly reduced adverse effects on extrarenal organs, compared with systemic administration at an equivalent dose. This improvement was attributed to a higher renal drug concentration and substantially lower systemic exposure achieved by intravesical delivery, demonstrating its kidney-targeting specificity. Thus, these findings indicated that the intravesical delivery route offers a promising strategy for kidney-targeted therapy and related translational research.NEW & NOTEWORTHY Intravesical infusion is valid for retrograde delivery of molecules up to 500 kDa to both the medulla and cortex of the kidney. This route is highly selective in targeting the urinary system with limited leakage to extrarenal organs, providing great potential as a noninvasive means for kidney-targeted research and therapy.

Podocytes are highly specialized, terminally differentiated visceral epithelial cells that are critical for the maintenance of the glomerular filtration barrier. In subtypes of glomerulonephritis and focal segmental glomerulosclerosis (FSGS), injured podocytes trigger the activation and proliferation of neighboring parietal epithelial cells (PECs) which line Bowman's capsule. Mechanisms by which injured podocytes trigger the activation of PECs remain poorly understood. In three independent murine models of proliferative glomerulopathy, we observed that rapid podocyte loss triggered the formation of novel intercellular bridges (or tunneling nanotubes) extending between podocytes and PECs. Immunofluorescence staining of a coculture of mouse podocytes and PECs also revealed the presence of vesicle-like structures within intercellular bridges. In addition, these vesicle-like structures stained positive for Ras-related protein Rab-11A (RAB11A), a RabGTPase involved in the regulation of vesicle transport, and cytoplasmic dynein 1 heavy chain 1, a critical motor protein involved in cargo transport. Finally, we identified intercellular bridges in human kidney biopsies with subtypes of glomerulonephritis and collapsing FSGS, suggesting relevance to human disease.NEW & NOTEWORTHY To date, this is the first study to demonstrate that intercellular bridges form between podocytes and parietal epithelial cells in the setting of rapid podocyte loss in subtypes of glomerulonephritis and FSGS.

NaCl restriction upregulates pendrin, in part, through increased circulating aldosterone and the intercalated cell (IC) mineralocorticoid receptor (MR). Since 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) enhances aldosterone binding to this receptor in other cells, we asked if pendrin abundance is reduced in NaCl-restricted 11β-HSD2 knockout (KO) rats. However, pendrin abundance was greater in 11β-HSD2 KOs than in controls, possibly from enhanced glucocorticoid MR activation. Moreover, the MR antagonist, spironolactone, reduced pendrin abundance in mice that do not produce aldosterone (aldosterone synthase KO). IC MR gene ablation also reduced pendrin protein abundance in corticosterone-treated, adrenalectomized mice. Therefore, the MR regulates pendrin independently of aldosterone. As such, we asked whether glucocorticoids, the other MR ligands, change pendrin abundance and/or subcellular distribution in adrenalectomized wild-type mice. We observed that corticosterone upregulated pendrin in a dose-dependent manner through both increased total protein abundance and subcellular redistribution. At higher doses, corticosterone increased pendrin abundance from greater pendrin-positive cell number within the late distal convoluted tubule 2 (DCT2) rather than increased pendrin abundance per cell. Finally, we asked whether pendrin contributes to the hypertension seen in rodent models of Cushing syndrome. Although corticosterone increased blood pressure in wild-type mice, it had no effect in pendrin KOs. In conclusion, glucocorticoids upregulate pendrin by increasing pendrin total protein abundance through an MR-dependent pathway and subcellular redistribution. Glucocorticoids increase pendrin abundance by increasing the number of pendrin-positive cells within the DCT2. In doing so, pendrin contributes to the hypertension seen in rodent models of Cushing syndrome.NEW & NOTEWORTHY Pendrin participates in the hypertension seen in Cushing syndrome.