Establishment of an optimized orthotopic bladder cancer model in mice

Bladder cancer (BC) is one of the most common malignancies of the genitourinary system. Our orthotopic murine BC model provides a tool that is predictable, reproducible, and convenient for exploring tumour initiation, progression, and therapeutic mechanisms. Here, we constructed an optimized orthotopic BC model in male C57BL/6 mice utilizing microsyringes to inoculate them with a murine BC cell line (MB49). Anesthetised mice were inoculated with an MB49 cell suspension (10 µL) at approximately 5×10 6 /mL. The whole process of modelling was observed and monitored every 3 days for 21 days utilizing HE staining and transabdominal ultrasonography (TUS). In this study, the model showed excellent success rates for tumour formation (96.67%) and metastatic rate (89.66%). Compared to the control group (sham operation), mice in the modelling group had serous cachexia, visible haematuresis and weight loss (all P < 0.05). The lungs, liver, ureter and kidneys were found to have tumour metastasis. Moreover, the average survival time (19.73 ± 1.69 d) of modelling mice was significantly shorter than that of the control mice (P < 0.05), which remained alive. Our study established a method using microsyringes to inject murine BC cells into the bladder wall, creating a stable transplantable BC model in mice.