Abstract
Background:
Necrotizing enterocolitis (NEC) is a life-threatening intestinal inflammatory disorder characterized by the breakdown of the epithelial barrier and bacterial translocation, resulting in systemic inflammation. Developing an ideal animal model is essential for gaining a deeper insight into its pathomechanism. Dextran sodium sulfate (DSS) has been widely used to induce NEC-like intestinal injury; however, the precise concentration of DSS that consistently reproduces NEC features remains uncertain.

Aim:
This study aimed to determine the optimal DSS concentration for inducing NEC-like inflammation in the ileal tissue of BALB/c mice by evaluating the disease activity index (DAI), NEC histological scores, and proinflammatory cytokine expression.

Methods:
A true in vivo experimental design with a randomized post-test-only controlled group was conducted using 30 male BALB/c mice (weight, 20–25 g; age, 8–10 weeks). The mice were divided into five groups (n = 6): a control group receiving water and treatment groups receiving 3%, 3.5%, 4%, and 4.5% DSS in their drinking water for a duration of 9 days. The clinical parameters, including DAI scores, were recorded. Ileal tissue was collected for NEC histological score, nuclear factor kappa B (NF-кB), interleukin-1 beta (IL-1β), and tumor necrosis factor alpha (TNF-α) expression. Data were analyzed using one-way ANOVA (p ≤ 0.05).

Results:
Mice treated with 4% DSS showed significantly elevated DAI and NEC histological scores and increased NF-кB, IL-1β, and TNF-α expression compared with controls. The 4.5% DSS groups exhibited more severe inflammation and higher mortality, whereas the 3%–3.5% DSS group induced only mild to moderate lesions.

Conclusion:
A DSS concentration of 4% effectively induces consistent NEC-like intestinal injury in BALB/c mice, characterized by higher DAI and NEC histological scores, as well as proinflammatory cytokine upregulation. This concentration provides an optimal model for future mechanistic and therapeutic studies of NEC.

Key words: IL-1β; Necrotizing enterocolitis; NEC histological score; NF-кB; TNF-α.