Indwelling stents cause obstruction and induce ureteral injury and fibrosis in a porcine model

Objectives: To investigate global changes in ureters at the transcriptional, translational and functional levels, both while stents are indwelling and after removal and recovery, and to study the effects of targeting pathways that play a potential role.

Methods: Pig ureters were stented for varying amounts of time (48 h, 72 h, 14 days) and the impact on peristalsis, dilatation and hydronephrosis were assessed. RNAseq, proteomic, histological and smooth muscle (SM) function analyses were performed on ureteric and kidney tissues to assess changes induced by stenting and recovery. Pathway analysis was performed using Ingenuity Pathway Analysis software. To study the impact of possible interventions, the effects of erythropoeitin (EPO) and a Gli1 inhibitor were assessed.

Results: Stenting triggers massive ureteric dilatation, aperistalsis and moderate hydronephrosis within 48 h. Pathways associated with obstruction, fibrosis and kidney injury were upregulated by stenting. Increased expression of GLI1, clusterin-α (a kidney injury marker) and collagen 4A2 (a fibrosis marker) was found in stented vs contralateral unstented ureters. EPO did not improve peristalsis or contraction force but did decrease non-purposeful spasming seen exclusively in stented ureters. Tamsulosin administration increased contractility but not rate of peristalsis in stented ureters.

Conclusions: Ureters respond to stents similarly to how they respond to an obstruction, that is, with activation of pathways associated with hydronephrosis, fibrosis and kidney injury. This is driven by significant dilatation and associated ureteric SM dysfunction. EPO and tamsulosin induced mild favourable changes in SM physiology, suggesting that targeting specific pathways has potential to address stent-induced complications.