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 (SiO2) 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-alpha (TNF-alpha) and lentivirus-mediated expression of epidermal growth factor (EGF) and hepatocyte growth factor (HGF). Results SiO2 stimulation tripled the number of activated fibroblasts. Foxa3, Gata4 and Hnf1a converted SiO2-remodelled spleen fibroblasts into 2x10(6) functional iHeps in one spleen. TNF-alpha protein and lentivirus-mediated expression of EGF and HGF further enabled the total hepatocytes to expand to 8x10(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.