Rat Model of Cystic Neutrophilic Granulomatous Mastitis by Corynebacterium Kroppenstedtii.

BACKGROUND: Cystic neutrophilic granulomatous mastitis (CNGM) poses a significant threat to the physical and mental health of women due to its increasing incidence, complex clinical manifestations. Developing an appropriate animal model will help further study the pathogenesis of CNGM. METHODS: Seventy-two rats were randomly assigned to seven groups: group A (n=12, tissue suspension 0.2mL), group B (n=12, 1×10^8 CFU/mL Corynebacterium kroppenstedtii (CK) suspension 0.1mL), group C (n=12, 1×10^9 CFU/mL CK suspension 0.1mL), group D (n=12, tissue suspension 0.1mL + 1×10^8 CFU/mL CK suspension 0.1mL), group E (n=12, tissue suspension 0.1mL + 1×10^9 CFU/mL CK suspension 0.1mL), group F (n=6, phosphate buffer saline solution 0.1mL), and group G (n=6, physiological saline 0.1mL + Complete Freund's adjuvant suspension 0.1mL). Groups A to E constitute the experimental groups with 12 rats each, while groups F and G served as control groups with 6 rats each. Tissue suspension of patients with granulomatous mastitis and different concentrations of CK solution were injected into the fourth pair of mammary glands of rats. Tissue samples were harvested on the 3rd, 7th, and 14th days post-implantation. The breast tissue specimens were stained with HE stain and Gram stain to observe the histopathological characteristics and the presence of Gram-positive bacteria. Bacterial culture was performed to observe the presence of CK. The expression levels of C-reactive protein and interleukin-1 beta were detected. RESULTS: Rats in groups A, D, and E exhibited breast masses with erythema, with some showing ulceration, and granulomatous structures in pathological. Lipid vacuoles and Gram-positive rods observed in groups D and E. Pus cultures from groups D and E showed growth of CK. Histopathology revealed minimal inflammatory cell infiltration and no granulomatous formation in groups B and C. Group F showed no masses or inflammatory cell infiltration. Rats in group G presented with masses without ulceration, only chronic and acute inflammatory cell infiltration in pathological. Levels of C-reactive protein and interleukin-1 beta were significantly elevated in groups A and E at day 14. CONCLUSION: Components of pathological tissues from granulomatous mastitis patient combined with CK suspension, can successfully induce CNGM in rat models.