[Comparison of cecal ligation and puncture versus intraperitoneal lipopolysaccharide injection-induced animal models of sepsis-associated acute kidney injury].

Objective: To compare the pathological features and underlying molecular mechanisms of sepsis-associated acute kidney injury (SA-AKI) between two murine sepsis models, cecal ligation and puncture (CLP) and intraperitoneal injection of lipopolysaccharide (LPS), and to provide a basis for the selection of animal models in SA-AKI research. Methods: Male C57BL/6J mice aged 6-8 weeks were randomly divided into the CLP group, the LPS intraperitoneal injection group, the CLP control group, and the LPS control group using a random number table, with 8 mice in each group. The CLP group underwent CLP after intraperitoneal anesthesia. The LPS group received an intraperitoneal injection of 40 mg/kg LPS in saline solution. The CLP control group only had the cecum exposed without ligation or puncture, and the LPS control group received an intraperitoneal injection of an equal volume of saline. Murine sepsis score (MSS) and Kaplan-Meier survival analysis were utilized to evaluate the severity of sepsis and analyze the survival rate, respectively. Serum creatinine (Scr) and urea nitrogen (BUN) were measured 24 hours after model establishment. Renal histopathology was observed, combined with transcriptomic analysis, immunofluorescence, and flow cytometry to validate the relevant mechanisms. Results: The MSS of the CLP and LPS groups were 17.00±2.96 and 16.25±2.77, respectively (P=0.632), and the 48-hour cumulative survival rates were 40% and 60%, respectively (P=0.284), with no significant differences between the two groups. Regarding renal function, Scr and BUN in the CLP group were (56.35±8.59) μmol/L and (76.08±8.64) mg/dl, respectively; in the LPS group, they were (74.20±11.80) μmol/L and (89.82±8.05) mg/dl, respectively. All these values were significantly higher than those in the two control groups (all P<0.001), and renal dysfunction in the LPS group was significantly more severe than that in the CLP group (both P<0.01). Histopathological findings showed that renal injury and inflammatory infiltration were significantly more severe in the LPS group than in the CLP group. Transcriptomic analysis revealed that the hub genes in the LPS model were concentrated in pro-inflammatory pathways such as tumor necrosis factor and interleukin 6, whereas those in the CLP group exhibited higher heterogeneity and were simultaneously enriched in inflammatory as well as anti-inflammatory/oxidative stress-related pathways. Immunofluorescence and flow cytometry showed that macrophage proportions in renal tissues were significantly increased in both models (flow cytometry: CLP group vs. control, 31.39%±3.40% vs. 13.50%±2.98%; LPS group vs. control, 30.85%±4.90% vs. 13.25%±2.57%; both P<0.001). In the LPS group, macrophages were predominantly polarized toward the M1 phenotype (M1 macrophage proportion: LPS group vs. control, 54.05%±6.22% vs. 4.90%±1.28%, P<0.001), while in the CLP group, both M1 and M2 polarization were observed (CLP group vs. control: M1, 50.73%±3.73% vs. 5.08%±0.67%; M2, 16.14%±2.75% vs. 3.45%±1.59%; both P<0.001). Apoptosis was markedly activated in both models, and the levels of inflammatory cytokine expression and tubular epithelial cell pyroptosis in the LPS group were significantly higher than those in the CLP group (all P<0.05). Conclusions: Under comparable sepsis severity, LPS-induced SA-AKI model exhibits more significant renal injury and higher stability than the CLP model. The core mechanistic difference between the two models is associated with the local balance of pro-and anti-inflammatory pathways and macrophage polarization in the kidney. This study provides a reference for choosing animal models for preclinical research on SA-AKI. The LPS-induced murine SA-AKI model has relatively lower heterogeneity.