A UUO Mouse Model Approach to Explore the Pathophysiological Role of Uremic Toxins in Renal Damage

運用單側輸尿管阻塞小鼠模型探討尿毒素於腎損傷中的病理生理作用

Ta-Chin Lin¹, Chih-Wei Su², Chung-Jen Lee³

¹Department of Surgery, Tri-Service General Hospital Penghu Branch, ²Department of Surgery, Hualien Armed Forces General Hospital, ³Department of Nursing, Tzu Chi University

林大欽¹、蘇志偉²、李崇仁³

¹三軍總醫院澎湖分院外科部，²國軍花蓮總醫院外科部，³慈濟大學護理系

Introduction

Obstructive nephropathy is a common clinical condition that can lead to both acute kidney injury (AKI) and chronic kidney disease (CKD). The unilateral ureteral obstruction (UUO) model is widely used to investigate this form of nephropathy and is considered a bridge between AKI and CKD. Protein-bound uremic toxins-particularly indoxyl sulfate (IS) and p-cresyl sulfate (PCS)-are known to accumulate as renal function declines in both AKI and CKD. In this study, we aim to further elucidate the pathological roles and tissue levels of IS and PCS in kidney injury using the UUO animal model.

Materials and Methods

Twenty-four male C57BL/6 mice underwent UUO surgery to induce obstructive nephropathy and were categorized into three groups: UUO Day 1, UUO Day 4, and UUO Day 7, representing 1, 4, and 7 days post-surgery, respectively. Additionally, eight male C57BL/6 mice were designated as the sham group (Control). The transdermal glomerular filtration rate (GFR) in mice was assessed using the excretion kinetics of fluorescein-isothiocyanate conjugated sinistrin. Blood samples were procured for the analysis of uremic toxins and biochemistry. Kidneys were harvested for H&E and immunohistochemistry staining.

Results

Seven days after UUO, levels of PCS and IS were significantly elevated compared with the control group. UUO resulted in a reduction in GFR and an increase in the inflammatory cytokines IL‑6 and IL‑1β on Days 1, 4, and 7. Morphological examination of the obstructed kidneys revealed tubular dilation, interstitial expansion, and loss of proximal tubular mass. Immunohistochemical staining for KIM‑1 and NF‑κB showed progressively increased expression in the UUO Day 1, Day 4, and Day 7 groups, with semi-quantitative analysis using Image-Pro Plus 6.0 demonstrating significant differences. The regression equation for PCS and GFR was f(X) = −1.29 × 10⁻⁷ X³ + 6.64 × 10⁻⁴ X² − 1.23 X + 1184, and the regression model for IS and GFR was f(X) = 1.18 × 10⁴ × X⁻^0.512.

Conclusions

This study employed regression analyses to characterize the relationships between PCS, IS, and GFR. Our findings indicate that inflammation driven by elevated uremic toxins contributes to tubular toxicity, interstitial fibrosis, reduced glomerular filtration rate, and progressive loss of kidney function. Using a unilateral ureteral obstruction mouse model, we demonstrated a clear association between uremic toxin accumulation and the development of kidney injury.

Key Word: unilateral ureteral obstruction, glomerular filtration rate, indoxyl sulfate, p-cresyl sulfate