Breast Regression Protein-39/Chitinase 3-Like 1 Promotes Renal Fibrosis after Kidney Injury via Activation of Myofibroblasts.

The normal response to kidney injury includes a robust inflammatory infiltrate of PMNs and macrophages. We previously showed that the small secreted protein breast regression protein-39 (BRP-39), also known as chitinase 3-like 1 (CHI3L1) and encoded by the Chi3l1 gene, is expressed at high levels by macrophages during the early stages of kidney repair and promotes tubular cell survival via IL-13 receptor α2 (IL13Rα2)-mediated signaling. Here, we investigated the role of BRP-39 in profibrotic responses after AKI. In wild-type mice, failure to resolve tubular injury after unilateral ischemia-reperfusion injury (U-IRI) led to sustained low-level Chi3l1 mRNA expression by renal cells and promoted macrophage persistence and severe interstitial fibrosis. Analysis of macrophages isolated from wild-type kidneys 14 days after U-IRI revealed high-level expression of the profibrotic BRP-39 receptor Ptgdr2/Crth2 and expression of the profibrotic markers Lgals3, Pdgfb, Egf, and Tgfb In comparison, injured kidneys from mice lacking BRP-39 had significantly fewer macrophages, reduced expression of profibrotic growth factors, and decreased accumulation of extracellular matrix. BRP-39 depletion did not affect myofibroblast accumulation but did attenuate myofibroblast expression of Col1a1, Col3a1, and Fn1 Together, these results identify BRP-39 as an important activator of macrophage-myofibroblast crosstalk and profibrotic signaling in the setting of maladaptive kidney repair.

Unusual case of ascites secondary to unilateral distal ureteric obstruction in an infant.

Congenital obstructive uropathy is a rare cause of ascites in infants. Majority of reported cases of genitourinary causes of ascites were due to posterior urethral valve. Here, we report a 6-month-old boy who presented with progressive tense ascites and peritonitis attributed by unilateral left distal ureteric obstruction and acute pyonephrosis. He underwent left nephrostomy placement, after which there was a remarkable improvement of ascites. He then underwent left ureteral diversion procedure a month later with a tentative plan for ureteral reanastomosis in 6 months. To date, there are no reports describing ascites secondary to distal ureteric obstruction beyond the neonatal period. The objective of this case report is to highlight unilateral urinary tract obstruction as a potential cause of transudative ascites. Additionally, the superimposed infection in the obstructed collecting system can lead to acute peritonitis likely due to translocation of bacteria into the peritoneal cavity.