Amélie Calmont

Chronic kidney disease (CKD) is a major global health challenge affecting over 10% of the adult population. A hallmark of CKD progression is the transdifferentiation of kidney fibroblasts into extracellular matrix‐producing myofibroblasts, a key mechanism involved in the decline of kidney function and the development of kidney failure. Fibroblasts maintain the structural integrity of the kidney and support epithelial survival, repair, and regeneration after acute kidney injury. Maladaptive repair is a failure to resolve fibroblast activation, which ultimately progresses to chronic injury and CKD. In this study, we showed that the membrane‐bound coreceptor neuropilin 1 (NRP1) was essential to maintain fibroblast function and prevent their transdifferentiation into myofibroblasts. We used the myelin protein zero‐Cre ( P0‐Cre ) to specifically abrogate Nrp1 in kidney resident fibroblasts during fibrosis progression. We employed kidney‐induced interstitial fibrosis models combined with a lineage‐tracing strategy, single‐cell RNA sequencing analysis, and ex vivo explant cultures to reveal a cell autonomous protective role for NRP1 in limiting fibrosis. Furthermore, we extended the analysis by showing that Nrp1 conditional mutants were more prone to develop cardiac fibrosis in a mouse model of heart failure. Collectively, these findings provide new insights into the signalling pathways controlling the transition from acute to chronic kidney disease conversion and identify NRP1 as a novel regulator of fibroblast supportive function. © 2025 The Author(s). The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Renin is the key enzyme of the systemic renin-angiotensin-aldosterone system, which plays an essential role in regulating blood pressure and maintaining electrolyte and extracellular volume homeostasis. Renin is mainly produced and secreted by specialized juxtaglomerular (JG) cells in the kidney. In the present study, we report for the first time that the conserved transmembrane receptor neuropilin-1 (NRP1) participates in the development of JG cells and plays a key role in renin production. We used the myelin protein zero-Cre (P0-Cre) to abrogate Nrp1 constitutively in P0-Cre lineage-labelled cells of the kidney. We found that the P0-Cre precursor cells differentiate into renin-producing JG cells. We employed a lineage-tracing strategy combined with RNAscope quantification and metabolic studies to reveal a cell-autonomous role for NRP1 in JG cell function. Nrp1-deficient animals displayed abnormal levels of tissue renin expression and failed to adapt properly to a homeostatic challenge to sodium balance. These findings provide new insights into cell fate decisions and cellular plasticity operating in P0-Cre-expressing precursors and identify NRP1 as a novel key regulator of JG cell maturation.

Background: Alterations of renal hemodynamics play an essential role in renal homeostasis and kidney diseases. Recent data indicated that semaphorin 3C (SEMA3C), a secreted glycoprotein involved in vessel development, can modulate renal vascular permeability in acute kidney injury, but whether and how it might impact systemic and renal hemodynamics is unknown. Objectives: The objective of the study was to explore the effect of SEMA3C on systemic and renal hemodynamics. Methods: SEMA3C recombinant protein was administered intravenously in two-month-old wild-type mice, and the variations of mean arterial pressure, heart rate, renal blood flow, and renal vascular resistance were measured and analyzed. Results: Acute administration of SEMA3C induced (i) systemic hemodynamic changes, including mean arterial pressure decrease and heart rate augmentation; (ii) renal hemodynamic changes, including reduced vascular resistance and elevated renal blood flow. Continuous perfusion of SEMA3C had no significant effect on systemic or renal hemodynamics. Conclusion: SEMA3C is a potent vasodilator affecting both systemic and renal hemodynamics in mice.

Background: Vascular permeability (VP) is a fundamental aspect of vascular biology. A growing number of studies have revealed that many signalling pathways govern VP in both physiological and pathophysiological conditions. Furthermore, emerging evidence identifies VP alteration as a pivotal pathogenic factor in acute kidney injury, chronic kidney disease, diabetic kidney disease, and other proteinuric diseases. Therefore, perceiving the connections between these pathways and the aetiology of kidney disease is an important task as such knowledge may trigger the development of novel therapeutic or preventive medical approaches. In this regard, the discussion summarizing VP-regulating pathways and associating them with kidney diseases is highly warranted. Summary: Major pathways of VP regulation comprise angiogenic factors including vascular endothelial growth factor/VEGFR, angiopoietin/Tie, and class 3 semaphorin/neuropilin and inflammatory factors including histamine, platelet-activating factor, and leukocyte extravasation. These pathways mainly act on vascular endothelial cadherin to modulate adherens junctions of endothelial cells (ECs), thereby augmenting VP via the paracellular pathway. Elevated VP in diverse kidney diseases involves EC apoptosis, imbalanced regulatory factors, and many other pathophysiological events, which in turn exacerbates renal structural and functional disorders. Measures improving VP effectively ameliorate the diseased kidney in terms of tissue injury, endothelial dysfunction, kidney function, and long-term prognosis. Key Messages: (1) Angiogenic factors, inflammatory factors, and adhesion molecules represent major pathways that regulate VP. (2) Vascular hyperpermeability links various pathophysiological processes and plays detrimental roles in multiple kidney diseases.

Haploinsufficiency of the T-box transcription factor TBX1 is responsible for many features of 22q11.2 deletion syndrome. Tbx1 is expressed dynamically in the pharyngeal apparatus during mouse development and Tbx1 homozygous mutants display numerous severe defects including abnormal cranial ganglion formation and neural crest cell defects. These abnormalities prompted us to investigate whether parasympathetic (vagal) innervation of the heart was affected in Tbx1 mutant embryos. In this report, we used an allelic series of Tbx1 mouse mutants, embryo tissue explants and cardiac electrophysiology to characterise, in detail, the function of Tbx1 in vagal innervation of the heart. We found that total nerve branch length was significantly reduced in Tbx1^+/− and Tbx1^neo2/− mutant hearts expressing 50% and 15% levels of Tbx1. We also found that neural crest cells migrated normally to the heart of Tbx1^+/−, but not in Tbx1^neo2 mutant embryos. In addition, we showed that cranial ganglia IX^th and X^th were fused in Tbx1^neo2/− but neuronal differentiation appeared intact. Finally, we used telemetry to monitor heart response to carbachol, a cholinergic receptor agonist, and found that heart rate recovered more quickly in Tbx1^+/− animals versus controls. We speculate that this condition of decreased parasympathetic drive could result in a pro-arrhythmic substrate in some 22q11.2DS patients.