A multicentre study of 95 biopsy-proven cases of renal disease in primary Sjögren's syndrome.

OBJECTIVE.: Renal involvement is a rare event during primary SS (pSS). We aimed to describe the clinico-biological and histopathological characteristics of pSS-related nephropathy and its response to treatment. METHODS.: We conducted a French nationwide, retrospective, multicentre study including pSS patients fulfilling American-European Consensus Group criteria or enlarged American-European Consensus Group criteria, and with biopsy-proven renal involvement. RESULTS.: A total of 95 patients were included (median age 49 years). An estimated glomerular filtration rate (eGFR) of <60 ml/min was found in 82/95 patients (86.3%). Renal biopsy demonstrated tubulointerstitial nephritis (TIN) in 93 patients (97.9%), and frequent (75%) plasma cell infiltrates. Glomerular lesions were found in 22 patients (23.2%), mainly related to cryoglobulin. The presence of anti-SSA (76.8%) and anti-SSB (53.8%) antibodies was particularly frequent among patients with TIN and was associated with a worse renal prognosis. Eighty-one patients (85.3%) were treated, with CSs in 80 (98.8%) and immunosuppressive agents (mostly rituximab) in 21 cases (25.9%). Despite marked interstitial fibrosis at initial biopsy, kidney function improved significantly during the 12-month period following diagnosis (final eGFR 49.9 vs 39.8 ml/min/1.73 m 2 at baseline, P < 0.001). No proven benefit of immunosuppressive agents over steroid therapy alone was found in this study. CONCLUSION.: Renal involvement of pSS is mostly due to TIN with marked T, B and especially plasma cell infiltration. Renal dysfunction is usually isolated but can be severe. Use of CSs can improve the eGFR, but further studies are needed to define the best therapeutic strategy in this disease.

Endothelial cell and podocyte autophagy synergistically protect from diabetes-induced glomerulosclerosis.

The glomerulus is a highly specialized capillary tuft, which under pressure filters large amounts of water and small solutes into the urinary space, while retaining albumin and large proteins. The glomerular filtration barrier (GFB) is a highly specialized filtration interface between blood and urine that is highly permeable to small and midsized solutes in plasma but relatively impermeable to macromolecules such as albumin. The integrity of the GFB is maintained by molecular interplay between its 3 layers: the glomerular endothelium, the glomerular basement membrane and podocytes, which are highly specialized postmitotic pericytes forming the outer part of the GFB. Abnormalities of glomerular ultrafiltration lead to the loss of proteins in urine and progressive renal insufficiency, underlining the importance of the GFB. Indeed, albuminuria is strongly predictive of the course of chronic nephropathies especially that of diabetic nephropathy (DN), a leading cause of renal insufficiency. We found that high glucose concentrations promote autophagy flux in podocyte cultures and that the abundance of LC3B II in podocytes is high in diabetic mice. Deletion of Atg5 specifically in podocytes resulted in accelerated diabetes-induced podocytopathy with a leaky GFB and glomerulosclerosis. Strikingly, genetic alteration of autophagy on the other side of the GFB involving the endothelial-specific deletion of Atg5 also resulted in capillary rarefaction and accelerated DN. Thus autophagy is a key protective mechanism on both cellular layers of the GFB suggesting autophagy as a promising new therapeutic strategy for DN.