O12 The safety and efficacy of ultrasound histotripsy and human hepatocyte stem cell spheroid implantation as a potential therapy for treating liver failure: assessment in an immunocompetent rodent model

<h3>Background</h3> Paediatric liver failure can arise from inborn metabolic disorders, often necessitating liver transplantation with significant long-term risks. While cell therapy presents a hopeful alternative, current methods of hepatocyte transplant through the portal vein have shown limited effectiveness. Histotripsy, a non-invasive mechanical ablation technique utilizing high-frequency ultrasonic waves, offers a promising solution. Unlike thermal ablation methods, histotripsy selectively targets soft tissue without causing coagulative necrosis, preserving essential structures like hepatic vasculature and significant biliary network. With, recent FDA approval for the treatment of liver cancer, histotripsy-induced cavitations present a niche for the engraftment of stem cell-derived 3D hepatocyte-like cells (3D Heps) as a novel approach for enhancing stem cell therapy in liver failure reversal. <h3>Aim</h3> To investigate the feasibility and safety of US Histotripsy application in conjunction with hepatocyte stem cell therapy (3D Heps) for reversing liver failure caused by metabolic errors. <h3>Methods</h3> Under general anaesthesia, rats (n=12) underwent laparotomy and focal US histotripsy to the exposed liver. 7×106 3D Heps were injected into the histotripsy cavity under direct vision. On completion haemostasis was secured, laparotomy closed, and the animals recovered. Animals were terminated immediately (n=2; histotripsy only control), immediately (n=2), 4 hrs (n=2), 18 hrs (n=2), 24 hrs (n=2), 4 days (n=1) and 7 days (n=1) post-3D Heps transplantation. The endpoints were the safety of histotripsy, local complications, and evidence of cell engraftment and function. <h3>Results</h3> Histology identified cavitations in 5 of the 10 animals injected with 3D Heps and 1 of the 2 histotripsy-only control group. Histology and immunohistochemical analysis using anti-human nuclei antibody demonstrated 3D Heps suspended in cavities. Both human albumin and alpha-fetoprotein were detected in the plasma of n=1 and n=5 of ten injected rats, respectively. <h3>Conclusion</h3> We report the successful delivery of functioning 3D Heps into liver parenchyma post-US histotripsy. Further, planned studies in immunocompromised rodents with chronic liver disease aim to evaluate efficacy, with a strategy to prevent rejection. Additional research is underway to explore more minimally invasive approaches to leverage histotripsy for cell therapy purposes.