Engineering High-fidelity Preclinical Mouse Model for Brain Metastasis using Interlock Pulsatile Injection Technique and Microsurgical Vascular Repair

Brain metastasis remains a devastating clinical problem. A major challenge in brain metastasis research is the lack of high-quality models that accurately recapitulate the metastatic process, thereby enabling mechanistic insights into how cancer cells colonize in the brain. Traditional intracarotid artery injection models of brain metastasis often require permanent ligation of the common carotid artery (CCA), which alters cerebral hemodynamics and compromises the integrity of the blood-brain barrier (BBB). The protocol presents a refined method for establishing a high-fidelity mouse model of brain metastasis. The core innovation involves the Interlock Pulsatile Injection (IPI) technique for tumor cell delivery, followed by microsurgical arterial reconstruction at the puncture site to restore physiological blood flow in the CCA. Compared with the conventional CCA ligation model, the IPI-microsurgical repair approach significantly reduced perioperative mortality (2.86% vs. 25.71%) and increased the rate of brain metastasis establishment (94.12% vs. 65.38%). The IPI technique utilizes a tandem syringe configuration to minimize cell regurgitation during intracarotid injection. After tumor cell infusion, the CCA is meticulously repaired using microsurgical sutures under a stereomicroscope, thereby avoiding permanent occlusion. This preserves the native cerebral hemodynamics and the integrity of the BBB at the time of tumor cell entry, while significantly improving surgical success rates and reducing mortality. The metastatic intracranial lesions are validated by serial bioluminescence imaging and histopathology. The method provides a superior platform for studying the pathophysiology of brain metastasis and for preclinical therapeutic evaluation, thereby recapitulating the metastatic process.