Hepatitis C 
virus replication at extrahepatic sites has been suggested; however, complete 
viral replication has only been confirmed in hepatocytes. Here we show that human adipogenic DLK-1+ stem cells (hADSC) freshly isolated from HCV-infected individuals contained viral transcripts, replication intermediates and 
viral antigens in vivo, and viral transcripts increased in supernatants upon prolonged 
ex vivo culture. Furthermore, naive hADSC isolated from HCV (−) individuals support complete replication of clinical isolates 
in vitro, and the infection is donor-nonspecific for cells and cross-genotypic for viruses. 
Viral infection / replication is mediated through CD81, LDL-R, SR-B1, EGFR, Apolipoprotein E, 
occludin, 
claudin-1, NPC1L1 and diacylglycerol 
acetyltransferase-1, and can be inhibited by anti-viral drugs. In addition, the physical properties of hADSC-propagated viral particles resemble clinical isolates more than JFH1 / HCVcc, and viruses propagated by 
in vitro infected hADSC are infectious to primary human hepatocytes. Therefore, hADSC are an 
in vivo HCV reservoir and represent a novel venue of clinical 
virus-host interaction. hADSC can also be exploited as a physiologically relevant 
primary cell culture 
system to propagate clinical isolates.