No SHA was present 12 days after injection. situ, analyses are needed to show functional engraftment of human main or stem cell-derived hepatocytes. == Introduction == Hepatocyte infusion is an alternative to whole liver transplantation, but its potential is limited by a shortage of donor hepatocytes (Ito et al., 2009;Fisher and Strom, 2006). Improvements in the directed differentiation of stem cells into hepatocytes continue to bring cell therapy for liver diseases closer to large-scale clinical power (Cai et al., 2007;Hay et al., 2008;Basma et al., 2009;Si-Tayeb et al., 2010;Touboul et al., 2010;Duan et al., 2010). Immunodeficient animal models of liver diseases provide powerful experimental systems for evaluating the efficacy of liver cell therapies with hepatocyte-like cells L-Buthionine-(S,R)-sulfoximine derived from human embryonic and induced pluripotent stem cells (Tateno et al., 2004,Azuma et al., 2007). In addition, the therapeutic potential of hepatocytes derived from human adult or fetal stem cells can be evaluated in such models (Wang et al., 2003;Mahieu-Caputo et al., 2004; Aurich et al., 2003). Currently, analysis of the ability of all L-Buthionine-(S,R)-sulfoximine of these cell types PKCC to engraft in the liver, provide L-Buthionine-(S,R)-sulfoximine hepatocyte function, and potentially expand relies mainly on the measurement of serum human albumin (SHA) as a readout. Besides reflecting the level of hepatocyte differentiation and therapeutic potential of cells derived from stem cells, SHA is also useful as a marker for the function of bioartificial liver systems loaded with main human hepatocytes or cell lines (Wurm et al., 2010;Varo L-Buthionine-(S,R)-sulfoximine Perez and Castroagudin, 2010). While the half-life of SHA in humans is known to be approximately 20 days (Peters, 1970), the half-life of SHA in mice has not been reported. Albumin-producing cells that pass away during cell preparation or after transplantation could release this protein, potentially confounding serum analyses of the recipient. If that was true, prolonged detection of SHA in mice could falsely show that transplanted human stem cell-derived hepatocytes successfully engrafted in the liver and are providing normal liver function. To address this uncertainty, we injected nonviable human hepatocytes into the abdomen of mice and followed the levels of human albumin in their sera. == Results == Aliquots of either human or mouse hepatocytes were resuspended in distilled water to create a lysate of 100% nonviable cells that would be unable to engraft (Fig. 1A). The albumin concentration of the human hepatocyte lysate was 37,241 ng/ml, and as expected, the lysate of nonviable mouse hepatocytes contained no detectable human albumin (data not shown). The nonviable cell suspensions were injected intraperitoneally (ip) into individual wild-type mice and SHA levels were followed over time. The level of human albumin detected in the serum of mice injected with human hepatocyte lysate was 2096 ng/ml 2 h after injection (Fig. 1B). The L-Buthionine-(S,R)-sulfoximine SHA levels peaked 24 h after injection at 3117 ng/ml before beginning to decline. The amount of 78.9 ng/ml of SHA was still detectable 8 days after injection. No SHA was present 12 days after injection. Normal renal function parameters excluded that hepatocyte transplantation-induced acute renal failure was responsible for the prolonged persistence of SHA in mice (Supplementary Figs. 1AandB). As expected, no SHA was recognized at any time in mice injected with nonviable mouse hepatocytes, or mice injected only with PBS (data not shown). == Physique 1. == Human albumin levels released from nonviable human hepatocytes. (A) Failure to exclude trypan blue shows that no viable hepatocytes remain prior to ip injection. Size bar= 75 m. (B) Mean SHA detectable in 3 mice 0, 2, 24, 96, 192, and 288 h after ip injection of nonviable human hepatocytes. Error bars symbolize averageSD. == Conversation == Albumin is usually produced solely by hepatocytes. It serves as the major depot and carrier protein for hydrophobic substances in the blood such as bilirubin, long-chain fatty acids,.
