Chronic kidney disease (CKD) is associated with persistent low-grade inflammation and immunosuppression. In this study we tested the role of Toll-like receptor 4, the main receptor for endotoxin (LPS), in a mouse model of renal fibrosis and in a model of progressive CKD that better resembles the human disease. C3HeJ (TLR4 mutant) mice have a missense point mutation in the TLR4 gene, rendering the receptor nonfunctional. In a model of renal fibrosis after folic acid injection, TLR4 mutant mice developed less interstititial fibrosis in comparison to wild-type (WT) mice. Furthermore, 4 weeks after 5/6 nephrectomy with continuous low-dose angiotensin II infusion, C3HeOuJ (TLR4 WT) mice developed progressive CKD with albuminuria, increased serum levels of BUN and creatinine, glomerulosclerosis, and interstitial fibrosis, whereas TLR4 mutant mice were significantly protected from CKD progression. TLR4 WT mice also developed low-grade systemic inflammation, splenocyte apoptosis and increased expression of the immune inhibitory receptor PD-1 in the spleen, which were not observed in TLR4 mutant mice. In vitro, endotoxin (LPS) directly upregulated NLRP3 inflammasome expression in renal epithelial cells via TLR4. In summary, TLR4 contributes to renal fibrosis and CKD progression, at least in part, via inflammasome activation in renal epithelial cells, and may also participate in the dysregulated immune response that is associated with CKD.

Interstitial fibrosis is commonly measured by histology. The Masson trichrome stain is widely used, with semiquantitative scores subjectively assigned by trained operators. We have developed an objective technique combining Sirius Red staining, polarization contrast microscopy, and automated analysis. Repeated analysis of the same sections by the same operator (r = 0.99) or by different operators (r = 0.98) was highly consistent for Sirius Red, while Masson trichrome performed less consistently (r = 0.61 and 0.72, respectively). These techniques performed equally well when comparing sections from the left and right kidneys of mice. Poor correlation between Sirius Red and Masson trichrome may reflect different specificities, as enhanced birefringence with Sirius Red staining is specific for collagen type I and III fibrils. Combining whole‐section imaging and automated image analysis with Sirius Red/polarization contrast is a rapid, reproducible, and precise technique that is complementary to Masson trichrome. It also prevents biased selection of fields as fibrosis is measured on the entire kidney section. This new tool shall enhance our search for novel therapeutics and noninvasive biomarkers for fibrosis.To listen to podcast click here

Sepsis is a severe and complex syndrome that lacks effective prevention or therapeutics. The effects of sepsis on the microvasculature have become an attractive area for possible new targets and therapeutics. Microparticles (MPs) are cell membrane-derived particles that can promote coagulation, inflammation, and angiogenesis; and can participate in cell-to-cell communication. MPs retain cell membrane and cytoplasmic constituents of their parental cells, including two pro-coagulants: phosphatidylserine and tissue factor. We highlight the role of microparticles released by endothelial and circulating cells after sepsis-induced microvascular injury, and discuss possible mechanisms by which microparticles can contribute to endothelial dysfunction, immunosuppression, and multi-organ dysfunction--including sepsis-AKI. Once viewed as cellular byproducts, microparticles are emerging as a new class of markers and mediators in the pathogenesis of sepsis.