Kidney, Vessels, Inflammation and Metabolism – KVIM

Our team study the role of cell communications in pathologies that arise secondary to glomerular capillary dysfunctions or cause them. We have a common interest in how local signalling crosstalk regulate vascular integrity and how the loss of vascular integrity exacerbates inflammatory diseases, and we both use genetic and pharmacological tools to address these questions in mouse models.

We closely work with the Department of Nephrology at the Hôpital Européen Georges-Pompidou and the Department of Internal Medicine at Hôpital Cochin, Paris, on translational and clinical aspects. Our main scientific goals are to 1. Identify mechanisms of (peri)vascular signalling in development and disease, 2. Improve our understanding of the pathogenesis of immune-mediated and metabolic vascular and glomerular diseases (primarily focal segmental glomerulosclerosis (FSGS), crescentic rapidly progressive glomerulonephritis (RPGN), diabetic retinopathy and kidney disease), 3. Identify the roles of immune cells in sickle cell vasculopathy and nephropathy

Tharaux Group

Aims
The Tharaux group study the pathophysiological mechanisms of glomerular injury in rare glomerulopathies and common chronic kidney diseases (CKD).

• Stratify and treat FSGS and CGN: Crescentic glomerulonephritis (CGN) and focal segmental glomerulosclerosis (FSGS) are severe kidney diseases responsible for irreversible renal failure, which is also a major risk factor for cardiovascular mortality. CGN can even result in a loss of kidney function within days or weeks. Despite the aggressiveness of immunosuppressive protocols applied, treatments against CGN have limited effectiveness. Similarly, there is no approved, specific treatment for FSGS.
  We aim to identify druggable pathways and invasive and non-invasive markers of pathogenic glomerular epithelial cells in CGN and FSGS.
• Disrupt the fibrotic niche: severe glomerular diseases are followed by tubular injury and progressive interstitial fibrosis, markedly associated with progression of chronic kidney disease.
  Whereas most effort has focused on fibroblasts, our research ambition is instead to restore epithelial functions.
  We aim to identify key cellular and molecular actors of the fibrotic niche and druggable targets.

Recent Achievements
We dissected mechanisms driving the development of extracapillary lesions in FSGS and CGN. We addressed the key question of how parietal epithelial cells (PECs) invade glomerular capillaries, promoting injury and kidney failure. We showed that expression of the tetraspanin CD9 increases markedly in PECs in mouse models of CGN and FSGS and in the kidneys of individuals diagnosed with these diseases. Cd9 gene targeting in PECs prevents glomerular damage in CGN and FSGS mouse models. Mechanistically, CD9 deficiency prevents the oriented migration of PECs into the glomerular tuft and their acquisition of CD44 and β1 integrin expression. These findings highlight a critical role for de novo expression of CD9 as a common pathogenic switch driving the PEC phenotype in CGN and FSGS while offering a potential therapeutic avenue to treat these conditions. Our findings reinforce this paradigm that “activation” of resident glomerular cells play a key role in disease progression and extend the concept by examining interactions between surrounding cellular and molecular systems involved in CGN.

• Lazareth et al. Nat Commun 2019; commented in Wang M. Nat Rev Nephrol. 2019 and in Smeets B, Miesen L, Shankland SJ. Am J Kidney Dis. 2020

We uncovered the roles of the ET-1 receptors in myeloid cells in vascular diseases. Myeloid ETB receptors command the concentration of the ET-1 vasoconstrictor in the arterial wall and tissues. Two studies demonstrated the key role for the myeloid ETB receptors in the control of systemic vascular resistance and blood pressure as well as in hypertensive kidney and retina injuries. We also demonstated that ET-1 acts as a chemokine in sickle cell crises, recruiting and promoting neutrophils adhesion to the microvascular endothelium and transmigration in tissues.

• Czopek et al. Eur Heart J. 2019; Guyonnet et al. Kidney Int. 2020; Koehl et al. Haematologica. 2017

Lenoir Group

Aims
The Lenoir group study the pathophysiological mechanisms of kidney and vessels injury in common chronic kidney diseases (CKD). Despite the strong prevalence of diabetic kidney disease worldwide and the emergence of the recent sodium glucose cotransporter 2 inhibitors and glucagon-like peptide 1 receptor agonists, providing significant but only partial efficacy to prevent cardiovascular events and kidney failure, there are currently no therapies to specifically prevent glomerular cells injury during diabetes and hypertension.

We aim to identify mechanisms of kidney and vessels tolerance during diabetes and hypertension.

Developing new tools to study cell-cell interactions within glomeruli is a necessity. Animal models are informative, but they are increasingly criticized by the civil society. In addition, they do not allow to monitor phenotypic changes in cells in real time. In collaboration with the Ecole Polytechnique (LOB Laboratory, C. Bouzigues), we are developing a glomerulus-on-a-chip, enabling to study phenotypic changes in glomerular cells and the function of the glomerular filtration barrier during the mimicked pathology. We also develop Imaging Mass Cytometry and image analysis algorithms to study the multiple phenotypic switches and cellular cross-communications in kidneys in human pathologies.

Autophagy is a highly regulated lysosomal protein degradation pathway that removes protein aggregates and damaged or excess organelles to maintain intracellular homeostasis and cell integrity. Growing evidence suggests that autophagy is implicated in cell injury during renal diseases, both in the tubulointerstitial compartment and in glomeruli. We previously demonstrated that the autophagy gene, Atg5, is essential in endothelial cells and podocyte to maintain kidney microvascular integrity during diabetes mellitus in mice (Lenoir et al. Autophagy 2015). In collaboration with T. Huber’s group we further demonstrated that unlike the majority of cells whose autophagy is regulated by the mTOR pathway, autophagy in podocytes is regulated independently of the mTOR pathway (Bork et al. Autophagy 2020).

We aim to understand the mechanisms regulating autophagy in glomerular cells and the pharmacological means of modulating autophagy in CKD.

Recent Achievements
We highlighted mechanisms of podocyte injury in chronic kidney disease linking the hypertensive and diabetic environment to the dysregulation of podocyte autophagy. We demonstrated that aberrant TRPC6-mediated calpain activation in podocytes promotes autophagy impairment and subsequent podocyte injury. Calpain or TRPC6 inhibition restored podocyte autophagy, limiting podocyte injury in disease models of hypertension and diabetes.

• Bensaada et al. Kidney International 2021 and Salemkour, Yildiz et al., J Am Soc Nephrol, 2023

We unraveled a fundamental role of autophagy in endothelial function, linking cell proteostasis to mechanosensing. We demonstrated that autophagy regulates VEGF-dependent VEGFR signaling and VEGFR-mediated and flow-mediated eNOS activation. Endothelial ATG5 deficiency in vivo resulted in selective loss of flow-induced vasodilation in mesenteric arteries and kidneys and increased cerebral and renal vascular resistance in vivo. We found a crucial pathophysiological role for autophagy in endothelial cells in flow-mediated outward arterial remodeling, prevention of neointima formation following wire injury, and recovery after myocardial infarction.

• Nivoit, Mathivet, Wu et al. Cellular and Molecular Life Sciences 2023 and punctum in Autophagy Reports 2023

Terrier Group

Aims
The Terrier group study the mechanisms driving inflammation in autoinflammatory diseases and systemic vasculitis, especially large vessel vasculitis and ANCA-associated vasculitis.

Work on autoinflammatory diseases has focused primarily on VEXAS syndrome. Acquired mutations in the UBA1 gene, which occur in myeloid cells and result in the expression of a catalytically impaired isoform of the enzyme E1, have recently been identified in patients with a severe adult-onset autoinflammatory syndrome called VEXAS (vacuoles, E1 enzyme, X-linked, autoinflammatory, somatic). The exact physiological and clinical effects of these mutations remain poorly defined. Using cell lines and patient cells, we are studying perturbations in inflammatory and cell death pathways induced by this mutation.
We aim to identify inflammatory pathways that are involved in VEXAS syndrome that could be targeted to reduce or prevent inflammation.

Work in systemic vasculitis focuses on large vessel vasculitis, primarily giant cell arteritis, the most common cause of vasculitis in adults over 50 years of age, and small vessel vasculitis, characterized by the presence of antineutrophil cytoplasmic antibodies (ANCA) and frequent involvement of the lungs and kidneys, called ANCA-associated vasculitis.
In large vessel vasculitis, we study the crosstalk between inflammatory cells and resident cells with the vessel wall. In ANCA-associated vasculitis, we are studying the inflammatory determinants of renal involvement, which is characterized by rapidly progressive glomerulonephritis, a severe form of kidney disease responsible for irreversible renal failure.
As previously, we aim to identify pathways that could be targeted to reduce or prevent inflammation and vascular damage in such diseases.

Recent Achievements
We dissected the mechanisms driving systemic inflammation in UBA1-mutant monocytes in VEXAS syndrome. We performed an integrated immune analysis including multiparameter phenotyping of peripheral blood leukocytes, cytokine profiling, bulk and single cell gene expression analysis, and skin tissue imaging mass cytometry. We showed that monocytes from UBA1 mutant individuals were quantitatively and qualitatively impaired and exhibited features of exhaustion with aberrant expression of chemokine receptors. In the peripheral blood of VEXAS patients, we identified a significant increase in circulating levels of many proinflammatory cytokines, including IL-1β and IL-18, which reflect inflammasome activation and markers of myeloid cell dysregulation. Whole blood gene expression analysis confirmed the role of circulating cells in IL-1β and IL-18 dysregulation in VEXAS patients and revealed a significant enrichment of TNF-a and NFkB pathways that could mediate cell death and inflammation. Single-cell analysis confirmed the inflammatory state of monocytes from VEXAS patients and allowed us to identify specific molecular pathways that could explain monocytopenia. Taken together, these findings provide important insights into the molecular mechanisms involved in mature myeloid commitment in VEXAS syndrome and suggest that control of the undescribed inflammasome activation and inflammatory cell death may be novel therapeutic targets in this disease.

• Kosmider et al. VEXAS syndrome is characterized by inflammasome pathway activation and monocyte dysregulation. Nature Communications. In press.