Abstract Body: Introduction: Acute kidney injury (AKI) is a major clinical problem characterized by rapid loss of renal function and limited treatment options. Current preclinical models often fail to replicate the complex immune and microbial environment found in humans. Wildling mice, which harbor a natural microbiome and exhibit an immune system more similar to humans, offer a promising alternative compared to conventional specific pathogen-free (SPF) mice models.

Hypothesis: We assessed the hypothesis that wildling mice would exhibit a more severe AKI phenotype and heightened systemic inflammation compared to SPF mice due to their natural microbiota and matured immune state.

Methods: AKI was induced in uninephrectomized wildling and SPF mice by 17.5 minutes of renal ischemia followed by reperfusion. Sham-operated animals underwent uninephrectomy only. Male and female mice were used in equal numbers in the groups (in total n=14-20 per group). After 24 hours, urine and blood were collected. Serum creatinine and cystatin C levels were measured as markers of renal injury. Serum cytokines were analyzed to assess systemic inflammation.

Results: Serum creatinine was significantly elevated in wildling AKI mice (0.35±0.20 mg/dl) compared to wildling sham (0.15±0.02 mg/dl, P<0.0001) and SPF AKI (0.22±0.07 mg/dl, P=0.0009). Serum cystatin C followed a similar pattern, with wildling AKI animals reaching 0.50±0.14 mg/l compared to wildling sham (0.32±0.02 mg/l, P<0.0001) and SPF AKI (0.44±0.10 mg/l, P=0.2773). Wildling mice showed elevated baseline and post-AKI levels of pro-inflammatory cytokines. Serum IL-6, GM-CSF, TNF-alpha, and IP-10 were significantly higher in wildling sham and AKI mice compared to SPF controls. No significant differences in these markers were observed between wildling sham and wildling AKI.

Conclusions: Wildling mice developed more severe AKI and exhibited significantly enhanced systemic inflammation at baseline and following injury compared to SPF mice. These findings support the use of the wildling model to better reflect human immune-microbiome interactions in kidney injury and highlight its potential to improve the translational relevance of AKI research.