Reprogramming the spleen into a functioning ‘liver’ in vivo

Objective Liver regeneration remains one of the biggest clinical challenges. Here, we aim to transform the spleen into a liver-like organ via directly reprogramming the splenic fibroblasts into hepatocytes in vivo. Design In the mouse spleen, the number of fibroblasts was through silica particles (SiO 2 ) stimulation, the expanded fibroblasts were converted to hepatocytes (iHeps) by lentiviral transfection of three key transcriptional factors (Foxa3, Gata4 and Hnf1a), and the iHeps were further expanded with tumour necrosis factor-α (TNF-α) and lentivirus-mediated expression of epidermal growth factor (EGF) and hepatocyte growth factor (HGF). Results SiO 2 stimulation tripled the number of activated fibroblasts. Foxa3, Gata4 and Hnf1a converted SiO 2 -remodelled spleen fibroblasts into 2×10 6 functional iHeps in one spleen. TNF-α protein and lentivirus-mediated expression of EGF and HGF further enabled the total hepatocytes to expand to 8×10 6 per spleen. iHeps possessed hepatic functions—such as glycogen storage, lipid accumulation and drug metabolism—and performed fundamental liver functions to improve the survival rate of mice with 90% hepatectomy. Conclusion Direct conversion of the spleen into a liver-like organ, without cell or tissue transplantation, establishes fundamental hepatic functions in mice, suggesting its potential value for the treatment of end-stage liver diseases.