The generation of large numbers of functional human hepatocytes for cell-based approaches to liver disease is an important and unmet goal. Direct reprogramming of fibroblasts to hepatic lineages could offer a solution to this problem but so far has only been achieved with mouse cells. Here, we generated human induced hepatocytes (hiHeps) from fibroblasts by lentiviral expression of FOXA3, HNF1A, and HNF4A. hiHeps express hepatic gene programs, can be expanded in vitro, and display functions characteristic of mature hepatocytes, including cytochrome P450 enzyme activity and biliary drug clearance. Upon transplantation into mice with concanavalin-A-induced acute liver failure and fatal metabolic liver disease due to fumarylacetoacetate dehydrolase (Fah) deficiency, hiHeps restore the liver function and prolong survival. Collectively, our results demonstrate successful lineage conversion of nonhepatic human cells into mature hepatocytes with potential for biomedical and pharmaceutical applications.

Recent studies have shown that defined factors could lead to the direct conversion of fibroblasts into induced hepatocyte-like cells (iHeps). However, reported conversion efficiencies are very low, and the underlying mechanism of the direct hepatic reprogramming is largely unknown. Here, we report that direct conversion into iHeps is a stepwise transition involving the erasure of somatic memory, mesenchymal-to-epithelial transition, and induction of hepatic cell fate in a sequential manner. Through screening for additional factors that could potentially enhance the conversion kinetics, we have found that c-Myc and Klf4 (CK) dramatically accelerate conversion kinetics, resulting in remarkably improved iHep generation. Furthermore, we identified small molecules that could lead to the robust generation of iHeps without CK. Finally, we show that Hnf1α supported by small molecules is sufficient to efficiently induce direct hepatic reprogramming. This approach might help to fully elucidate the direct conversion process and also facilitate the translation of iHep into the clinic.

Highlights d Loss of METTL3 inhibits proliferation and differentiation of hematopoietic stem cells d Depletion of m 6 A results in aberrant dsRNA formation of long m 6 A-modified transcripts d Loss of METTL3 induces deleterious innate immune responses in hematopoiesis d Mavs and Rnasel depletion partially rescue defects in Vav-Cre + -Mettl3 fl/

Acute liver failure (ALF) is a life-threatening illness. The extracorporeal cell-based bioartificial liver (BAL) system could bridge liver transplantation and facilitate liver regeneration for ALF patients by providing metabolic detoxification and synthetic functions. Previous BAL systems, based on hepatoma cells and non-human hepatocytes, achieved limited clinical advances, largely due to poor hepatic functions, cumbersome preparation or safety concerns of these cells. We previously generated human functional hepatocytes by lineage conversion (hiHeps). Here, by improving functional maturity of hiHeps and producing hiHeps at clinical scales (3 billion cells), we developed a hiHep-based BAL system (hiHep-BAL). In a porcine ALF model, hiHep-BAL treatment restored liver functions, corrected blood levels of ammonia and bilirubin, and prolonged survival. Importantly, human albumin and α-1-antitrypsin were detectable in hiHep-BAL-treated ALF pigs. Moreover, hiHep-BAL treatment led to attenuated liver damage, resolved inflammation and enhanced liver regeneration. Our findings indicate a promising clinical application of the hiHep-BAL system.

Surface-enhanced Raman spectroscopy (SERS), a sensitive analytical technique that has single molecular sensitivity, has attracted continuous attention for both application and academic research. Semiconductor-based substrates with SERS activity present more practical applications, ranging from surface science to biological detection because of their lower cost and better biocompatibility compared with noble metals. However, the SERS performance of most semiconductor-based substrates is not significant. Herein, we propose the concept of semiconductor heterojunction-enhanced Raman scattering and design a vertical nanothickness heterojunction of W18O49/monolayer MoS2. As a result, the Raman signals of analyte Rhodamine 6G are detectable even with an ultralow concentration of 10–9 M on W18O49/monolayer MoS2 substrates. The enhancement factor is around 3.45 × 107. We confirmed from experiments and theory that the coupling of these two semiconductor materials could lead to dramatic enhancement of photoinduced charge-transfer processes, which enables giant heterojunction-enhanced Raman scattering.

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