Renin cells are essential for survival and serve as key regulators of blood pressure and fluid-electrolyte homeostasis. Their function and identity are dependent on signals from their local microenvironment afforded by neighboring cells and nerves. Whether and how renin cells contribute to the development and maintenance of this microenvironment remains unclear. Because renin cells are rare — 0.01 % of kidney cells — conventional histological approaches cannot capture their interaction with nerve fibers and surrounding cells within the nephron and its vasculature. Using high-resolution 3D imaging, cell-specific multicolor reporter mice, single-cell RNA-seq, and conditional gene deletions, we mapped how renin cells assemble within arterioles and communicate with axon fibers to organize the growth and orientation of the kidney arterioles during development and disease. This coinductive process is mediated by Ngf produced by renin cell precursors and is necessary for renin cell survival and innervation. Interestingly, renin enzymatic insufficiency elevates Ngf and drives arteriolar hypertrophy with aberrant axon sprouting and hyperinnervation. These findings indicate that renin cells regulate kidney neurovascular development, revealing them as active organizers of their local neuroregulatory microenvironment in health and disease.

BACKGROUND:Diabetic kidney disease (DKD) is a major cause of chronic kidney disease, with glomerular hyperfiltration contributing to its progression. Esaxerenone, a non-steroidal mineralocorticoid receptor antagonist (MRA), reduces albuminuria, but its precise mechanism remains unclear. Mineralocorticoid receptor (MR) activation is implicated in tubuloglomerular feedback (TGF) dysregulation, and we hypothesized that MR inhibition attenuates albuminuria by mitigating glomerular hyperfiltration. METHODS:To investigate the effects of esaxerenone, we used aldosterone-induced MR activation rats and type 2 diabetic (db/db) mice. In vivo multiphoton imaging was performed to assess the single-nephron glomerular filtration rate (SNGFR) and arteriolar diameters. Macula densa (MD) cells were used to examine MR activation's impact on TGF. RESULTS:In aldosterone-infused rats, MR activation induced glomerular hyperfiltration via afferent arteriolar dilation, which was attenuated by esaxerenone. In db/db mice, esaxerenone reduced SNGFR and urinary albumin excretion while increasing urinary adenosine levels, effects reversed by A1aR blockade. In MD cells, MR activation increased nitric oxide (NO) production and reduced Na+-K+-2Cl- cotransporter membrane expression, both of which were mitigated by MRA or neuronal nitric oxide synthase inhibition. CONCLUSION:These findings suggest that esaxerenone restores TGF function via adenosine signalling, attenuating glomerular hyperfiltration and reducing albuminuria. This study provides novel insights into the albuminuria-lowering effects of MR blockade in DKD and supports the therapeutic potential of esaxerenone.

Organ crosstalk, including the gut-kidney axis, plays important roles in the physiological control and maintenance of whole-body energy metabolism and homeostasis. Food intake is known to increases renal blood flow (RBF) and glomerular filtration rate (GFR) to facilitate urinary excretion of metabolic waste postprandially. Gut hormones (incretins) produced in the gastrointestinal tract and pancreas and secreted into the blood act on many organs to aid digestion and whole-body metabolism. While incretins are known to directly regulate the function of many different renal cell types, the key cell and molecular mechanisms of the gut-kidney axis are not fully understood. Macula densa (MD) cells play central roles in controlling renal hemodynamics, renin secretion, and tissue remodeling. We recently reported the high MD-specific expression of gastrin (Cckbr) and glucagon (Gcgr) receptors, suggesting that MD cells may play much more complex sensory and regulatory roles in the kidney and the body than previously thought, including their potential role as a new key element in the gut-kidney axis. Another incretin, amylin is secreted by pancreatic b-cells, controls postprandial glycemia and satiety, and is an exciting new target in anti-obesity drug development. However, the renal effects of amylin and the intrarenal expression of amylin receptors (Amyr) are not fully understood. Amyrs are heterodimers consisting of the calcitonin receptor (Calcr), and one of three receptor activity-modifying proteins (Ramps). This study tested the hypothesis that amylin has direct actions on MD cells as a new mechanism of gut-kidney crosstalk in the control of body metabolism. High-resolution MD bulk and single-cell transcriptome analysis detected Calcr expression and a 6-fold enrichment of Ramp3 in MD vs control cells. Immunofluorescence on human kidney tissue sections translated and validated the MD-specific expression of Ramp3. Single cell MD Ca 2+ signaling was analyzed in vivo using intravital multiphoton microscopy (MPM) of Sox2-GCaMP6/tdTomato mice that express the ratiometric Ca 2+ reporter GCaMP6f/tdTomato in all renal cells. The injection of recombinant amylin (0.25 ug/animal in PBS bolus) into the cannulated carotid artery caused immediate and significant elevations in cell calcium (approximately 3-fold elevations in baseline) in MD cells, but not in other renal cell types. This study uncovered new regulatory mechanisms of systemic metabolism via islet-kidney crosstalk that involves the role of pancreas-derived amylin acting specifically and directly on MD cells in the kidney. MD sensing and responding to amylin may be involved in postprandial adjustments of renal hemodynamics, renin, and renal excretion. This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

Renin synthesis and release is the rate-limiting step of the renin-angiotensin-aldosterone system (RAAS) that controls fluid homeostasis, blood volume, and pressure. A major activator of the RAAS is a decrease in perfusion pressure within the kidneys, suggesting a link between renal mechanotransduction and renin that we hypothesized would be mediated by one or more mechanically activated nonselective cation channel. Prior to this study, the identity of the mechanosensor(s) in the kidneys and their physiological significance to the RAAS was unclear. As such, the primary goal of our study was to identify a physiologically salient ion channel contributing to renin control in the kidneys. Here, we identified PIEZO2 as a key mechanosensitive ion channel expressed in the renin-producing juxtaglomerular granular cells of the kidneys. We found that conditional genetic loss-of-function of the force-gated nonselective cation channel PIEZO2 in cells of renin lineage or the developing or adult stromal cells dysregulated the RAAS by elevating renin in mice. Consistent with the physiological roles of renin, we found that PIEZO2 regulates the RAAS during acute and chronic blood volume challenges. We observed that PIEZO2 is required for the calcium oscillations of juxtaglomerular granular cells in vivo. Notably, PIEZO2 deficiency in cells of renin lineage drives renin- and MAS Receptor-dependent glomerular hyperfiltration and is associated with increased afferent arteriole diameters. Collectively, our work identifies PIEZO2 as an essential regulator of juxtaglomerular granular cell calcium activity and renin in vivo. Disclosure of funding sources: The experiments performed in this study were supported by NIH K99NS133478 (to RZH); AHA 20CDA35320169, NIH K01DK121737, The Collins Medical Trust, and ASN KidneyCure (to JWN); 5R01DK097598 (to SJS); NIH R01HL148044 (to MSSL) NIH R01DK132066 (to JAM); NIH R01DK128660 and R01DK141178 (to JHM); NIH R01DK064324 and S10OD021833 (to JP); and a Howard Hughes Medical Institute Investigator Award (to AP). This abstract was presented at the American Physiology Summit 2026 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.

INTRODUCTION:Diabetic kidney disease (DKD) continues to be the major cause of kidney failure, and its treatment is of key importance. Targeting VEGF-A has yielded conflicting results in DKD models. Here, we investigated the potential benefit of targeting VEGF-A or its receptors for the treatment of advanced mouse DKD. METHODS:Our studies tested the effects of neutralizing antibodies targeting VEGF-A, VEGFR2, and VEGFR1 on kidney function and histopathology, in 4 different mouse models of DKD and chronic kidney disease (CKD). RESULTS:Unlike previous reports, blocking VEGF-A using an anti-VEGF-A monoclonal antibody worsened albuminuria and kidney injury in uninephrectomized (unix) diabetic db/db mice. Similar results were seen with the anti-VEGFR2 antibody (DC101). In contrast, antibody MF1, a VEGFR1 selective monoclonal blocking antibody, dramatically decreased albuminuria, improved kidney function, and reduced renal histological injury in the remnant kidney mice, unix db/db mice with or without renin-AAV injection, and eNOS-/-db/db hypertensive mice. MF1 also improved animal survival. MF1 benefit persisted in albuminuric transgenic mice lacking the VEGFR1 cytoplasmic tyrosine kinase domain. In renin-AAV unix db/db mice with advanced DKD, we observed improved survival, reduced serum creatinine, and regression of established kidney histological changes following delayed MF1 treatment. VEGFR1 antibody increased circulating placental growth factor and VEGF-A as well as phosphorylation of kidney VEGFR2. MF1 reduced blood pressure in diabetic eNOS-/- mice and acutely increased the glomerular filtration rate in db/db mice. CONCLUSIONS:Our studies demonstrate that blocking VEGFR1 improved kidney function and microvascular structure in models of progressive CKD. VEGFR1 blockade provided a promising novel therapeutic approach to reverse DKD progression.

Proteinuria predicts chronic kidney disease progression and cardiometabolic mortality, yet how sustained urinary protein loss reshapes interorgan metabolism remains unclear. Here, we tested whether proteinuric kidney disease alters whole-body amino-acid and nitrogen handling by applying long-term dietary arginine isotope tracing in a proteinuric podocin-mutant mouse model, complemented by ex vivo nephron-segment metabolism and human cohort analyses. Because arginine connects amino acid use in protein synthesis, amino acid catabolism, and the urea cycle, the dietary isotope label allowed us to follow both metabolite flux and protein incorporation across organs over time. Proteinuria did not trigger a broad compensatory increase in protein synthesis. Instead, it caused a kidney-centered rerouting of arginine metabolism. Arginine use shifted away from hepatic ureagenesis and toward renal glutamate-, proline-, and aspartate-linked fate. Across organs, most proteins incorporated recycled arginine, whereas albumin preferentially incorporated diet-derived arginine, identifying albumin as a major non-recycled arginine sink during proteinuric disease. In the kidney, proximal nephron segments showed coordinated remodeling of arginine and proline metabolism in association with tubular albumin handling. This rerouting favored proline synthesis and early collagen incorporation before overt fibrosis was established. Isotope-resolved nitrogen tracing indicated that this renal diversion of arginine occurs at the expense of coordinated nitrogen and acid handling, as reflected by reduced urinary ammonium excretion, tissue accumulation of arginine-derived ammonia, and altered abundance of enzymes involved in ammonium detoxification. In humans, circulating aspartate was elevated during active proteinuric disease and decreased in remission, independently of glomerular filtration rate, and both aspartate and proline associated with histological markers of fibrotic remodeling in biopsies from glomerular disease patients. Consequently, in proteinuric mice, a high dietary content of aspartate/asparagine further aggravated collagen accumulation and fibrosis-related remodeling of high-proline-content proteins, while impairing acid excretion. Together, these findings define proteinuric kidney disease as a chronic interorgan nitrogen-redistribution state that links selective protein turnover, impaired ammonium disposal, acid retention, and a renal profibrotic metabolic environment.

Current kidney organoids do not recapitulate the kidney's complex spatial patterning and function, limiting their applications. The human kidney comprises one million nephrons, derived from nephron progenitor cells, that connect to an arborized ureteric progenitor cell-derived collecting system. Here, we develop spatially organized mouse and human kidney progenitor assembloid (KPA) models in which the nephrons undergo extensive development and fuse to a centrally located collecting system, recapitulating kidney progenitor self-assembly processes observed in vivo. KPAs show dramatically improved cellular complexity and maturity and exhibit several aspects of major kidney functions in vitro and in vivo. Modeling human autosomal dominant polycystic kidney disease (ADPKD) with genome-edited, in vivo-grown human KPAs recapitulated the cystic phenotype and the molecular and cellular hallmarks of the disease and highlighted the crosstalk among cyst epithelium, stroma, and macrophages. The KPA platform opens new avenues for high-fidelity disease modeling and lays a strong foundation for kidney regenerative medicine.

Renin synthesis and release is the rate-limiting step of the renin-angiotensin-aldosterone system (RAAS) that controls fluid homeostasis. A major activator of the RAAS is a decrease in perfusion pressure within the kidneys, suggesting a link between renal mechanotransduction and renin. However, the identity of the mechanosensor(s) in the kidneys and their physiological significance to the RAAS remain unclear. We find that loss of the force-gated nonselective cation channel PIEZO2 in cells of renin lineage dysregulates the RAAS by elevating renin. We observe that PIEZO2 is expressed in renin-producing juxtaglomerular granular cells and is required for their calcium dynamics in vivo. PIEZO2 deficiency in cells of renin lineage drives renin-dependent and MAS-receptor-dependent glomerular hyperfiltration and regulates the RAAS during acute and chronic blood volume challenges. Collectively, our study identifies PIEZO2 as an essential regulator of juxtaglomerular granular cell calcium activity and renin in vivo.

Recent studies using intravital imaging in combination with a multiomics approach identified the neuronal differentiation, novel key sensory and regulatory functions, and an endogenous kidney tissue remodeling and regenerative program of the understudied renal cell type of the macula densa (MD). Molecular-level understanding of new MD cell functions revealed the high, MD-specific expression and secretion of several angiogenic, cell growth, patterning and extracellular matrix remodeling factors including cell communication network (CCN1), and the tissue hypertrophy regulator pregnancy-associated plasma protease A2 (PAPPA2) in both the mouse and human kidney. The present study aimed to provide initial pre-clinical validation of the specificity and efficacy of in injectable MD targeting new therapeutic approaches. Treatment with either MD cell secretome from freshly harvested and conditioned MD cell culture media, or human recombinant CCN1 protein, or AAV9-mediated MD targeting gene therapy with shRNA-mediated CCN1/PAPPA2 overexpression or knockdown specifically in MD cells was performed in vivo in WT and Cdh5-Confetti mice (for genetic cell fate tracking of endothelial cells at the single-cell level) and in Adriamycin-induced focal segmental glomerulosclerosis (FSGS). Chronic administration of hrCCN1 for 5 consecutive days (5 ug/animal/day iv) in Cdh5-Confetti mice induced substantial proliferation and clonal remodeling of endothelial precursor cells at the glomerular vascular pole that propagated to glomerular and peritubular capillaries. In the ADR-BalbC mouse model of FSGS, chronic treatment with either MD cell secretome or hrCCN1 significantly improved GFR, albuminuria (ACR), glomerulosclerosis histology index, and increased podocyte number confirmed by weekly follow-ups for 4 weeks. Systemic iv injection of AAV9-GFP (10^9 GC/animal iv, tissue harvest 1 week later) resulted in highly MD-specific (76.6±2.7%) and efficient (80.2±2.8%) GFP expression in the mouse kidney. Treatment with AAV9-PAPPA2/CCN1 RNA/shRNA (10^9 GC/animal single-dose iv) resulted in highly MD-specific and efficient overexpression/knockdown of PAPPA2/CCN1, improved glomerular and renal blood flow and tissue remodeling. The novel MD program for endogenous kidney tissue remodeling and regeneration can be manipulated and targeted pharmacologically and genetically in pre-clinical mouse models of glomerular and kidney diseases. Short-term MD cell therapeutic targeting in CKD can improve kidney structure and function by regression of pre-existing pathology, opening the doors for the future development of MD mimetics as a new class of renoprotective therapies.

IntroductionThe neuronally differentiated key sensory and regulatory cells of the macula densa (MD) were recently identified to control resident progenitor cells and endogenous kidney tissue remodeling and regeneration. Among the many MD-derived secreted angiogenic, growth, and extracellular matrix remodeling factors, cell communication network 1 (CCN1) is a known positive modulator of angiogenesis. This study aimed to validate and characterize the angiogenic potential and mechanisms of MD-derived biologicals including CCN1 in control healthy and disease conditions.MethodsThe angiogenic effects of secreted MD cell factors including CCN1 on glomerular endothelial cells (GEnC) were studied in vivo using Cdh5-Confetti mice with endothelium-specific expression of multicolor genetic reporters for genetic cell fate tracking, and in vitro using cultured GEnCs in angiogenesis, cell proliferation and migration assays. The effects of treatment with conditioned MD cell culture media (rich in CCN1) were tested in NZM.2328 BAFF transgenic lupus mice using intravital multiphoton microscopy, histology, and classic kidney function phenotyping.ResultsHigh CCN1 expression in MD cells was confirmed in the mouse and human kidney with diminished levels in patients with lupus nephritis. GEnC angiogenesis assays confirmed the strong angiogenic potential of CCN1 and the mechanistic role of integrins β3 and β5, VEGFR2 and Akt signaling in this process. Treatment of NZM.2328 BAFF transgenic lupus mice with MD factors vs control improved GEnC function, halted the progression of albuminuria, and reduced immune cell homing. The implantation of cultured MDgeo cells but not control M1 cells under the renal capsule of Cdh5-Confetti mice induced the growth of new blood vessels radially towards the MD cell epicenter that were formed by clonal expansion of host endothelial cells.DiscussionThe present study confirmed the strong angiogenic effect of MD-derived factors including CCN1 that may be targeted in future biologicals, biofabricated tissue, or cell-based therapeutic developments for kidney diseases.

BACKGROUND:Soluble urokinase plasminogen activator receptor (suPAR) is an innate immune system-derived risk factor for acute and chronic kidney diseases. While suPAR effects on kidney epithelial cells have been reported, its impact on renal vasculature remains unknown. METHODS:We investigated how suPAR affects renal blood flow and glomerular dynamics using a translational approach integrating clinical observations from a propensity-score-matched cardiac surgery cohort, ex vivo porcine kidney perfusion, and intravital multiphoton imaging in mice. FINDINGS:In the matched clinical cohort, we found a significant inverse correlation between suPAR levels and baseline kidney function, with mean eGFR values 14.5 mL/min/1.73 m2 lower in the high suPAR group (≥4 ng/mL) compared to the low suPAR group (<4 ng/mL). Patients with high suPAR levels had significantly higher AKI occurrence (56% vs 33%; relative risk 1.71, 95% CI 1.37-2.12). In experimental models, suPAR caused immediate reduction in renal blood flow and triggered robust calcium responses in renal contractile cells, particularly the extraglomerular mesangium. These effects were absent in brain vasculature and were antagonised by an anti-uPAR antibody. INTERPRETATION:Unlike many immune mediators, suPAR causes predominantly kidney-specific vasoconstriction, establishing a new class of innate-immune vasoconstrictors with direct implications for causing acute kidney injury in high-risk patients. FUNDING:Supported by the National Institutes of Health, University of Southern Denmark, Region of Southern Denmark PhD Fund, OUH-RH Joint Research Fund, Danish Kidney Association's Research Fund, Odense University Hospital Research Fund, Goldsmith A. L. Rasmussen Memorial Fund, Dept. of Anaesthesiology-Intensive Care, OUH Research Fund and the MeCiSu Frontline Centre.