Hepatocytes derived from human embryonic stem cells (hESCs) may be a useful source for the treatment of diseased or injured liver. However, a low survival rate of grafted hepatocytes and immune rejection are still major obstacles to be overcome. We previously showed that secreted proteins (secretome) from hESC-derived hepatocytes had a potential therapeutic power in the tissue repair of injured liver without cell transplantation. The purpose of the present study was to discover key protein(s) in the secretome of hESC-derived hepatocytes using proteomic analysis and to study the tissue repair mechanism which may be operated by the secretomes. Purified indocyanine green+ hepatocytes derived from hESCs displayed multiple hepatic features, including expression of hepatic genes, production of albumin, and glycogen accumulation. The nano-LC/ESI-QTOF-MS analysis identified 365 proteins in the secretome of hESC-derived hepatocytes and the protein functional network analysis was conducted using the MetaCore TM from GeneGO. In addition, 20 tissue regeneration-related transcription factors (TFs) were extrapolated through further proteomic analysis. After intraperitoneal injection, the secretome significantly promoted the liver regeneration in a mouse model of acute liver injury. Protein functional network analysis on the secretome-induced regenerating liver confirmed 20 transcription factors (TFs) which were identified in the ICGhigh cells. The upreguation of these tissue repair-related TFs were validated by qPCR and western blotting on the regenerating liver tissues. These results demonstrate that application of the secretome analysis in combination with the protein functional network mapping would provide a reliable tool to discover new tissue-regenerating proteins as well as to expand our knowledge of the mechanisms of tissue regeneration.

Here, we first demonstrate that identification of rice brown spot disease fungus (Cochliobolus miyabeanus, C. miyabeanus) proteins is possible in infected tissues using in planta apoplastic proteome with non-destructive tissues. In planta apoplastic proteins from rice leaves inoculated with C. miyabeanus, CM2 (compatible race), were isolated by vacuum infiltration with CaCl2/Na-acetateextractionbuffer, separated by SDS-PAGE, and identified by MudPIT. Of the 529 proteins that were identified by MudPIT, a large proportion (490) was from the rice. Numerous carbohydrate metabolic process (48), oxidation and reduction (44), response to oxidative stress (20%) were identified and confirmed their expression at RNA levels using microarray. Bioinformatic analysis showed that 176 and 39 of these proteins have a signal peptide in rice and rice brown spot fungus, respectively, using Signal P. The large proportion of proteins interestingly identified from the in planta apoplast were involved inprotease, hydrophobin, and host cell wall hydrolysis (Xylanase, beta-glucosidase) derived from pathogen. Thus, we suggest that in planta rice apoplastic secretome will be an important clue to understand the rice-rice brown spot fungus interactions.

We previously reported that purified hepatocyte-like cells derived from human embryonic stem cell (hESC) promoted the liver tissue recovery not only by cell replacement, but also by delivering proteins (secretome) that enhance endogenous host liver regeneration. In this study, we investigated possible therapeutic effects of secretomes obtained from undifferentiated hESC and mesenchymal stem cell (hMSC), and explored the underlying mechanism in a mouse model of chronic liver injury. Mice pre-intoxicated with dimethylnitrosamine (DMN) were treated with single intraperitoneal injection of secretome or medium used to support the growth of hESCs or hMSCs. Both hESC- and MSC-secretomes induced robust host liver regeneration, as determined by biochemical and histological analyses. The expression of MMP2 was significantly increased in the liver that received hESC- or hMSC-secretome, compared to control groups. In contrast, expression of α-SMA, a hallmark of activated hepatic stellate cells, was profoundly decreased after administration of both secretomes. These results suggest that hESCs and MSCs may release soluble factors that support the host tissue regeneration of chronically injured liver.

The remarkable regenerative capacity of the adult liver provides a setting to test the functional consequences of grafting human cells generated from pluripotent stem cells. This presentation describes a procedure to differentiate hepatocytes from human embryonic stem and induced pluripotent stem cells using only defined factors. Two cell populations generated in vitro were grafted into the spleen of mice treated with the hepato-toxin carbon tetra-chloride. The population containing few hepatocytes generated few surviving cells that produced low levels of albumin and did not support regeneration of the host liver. The cells enriched in donor hepatocytes efficiently engrafted around the branches of the portal vein, expressed hepatic features for at least 5 weeks. These cells also contributed to the endogenous tissue regeneration and function of the host liver. These results show that the controlled differentiation of hepatocytes from human pluripotent cells provides new approaches to define the mechanisms of tissue regeneration and restore liver function.