Background & Aims-The ability to obtain unlimited numbers of human hepatocytes would improve development of cell-based therapies for liver diseases, facilitate the study of liver biology and improve the early stages of drug discovery. Embryonic stem cells are pluripotent, can potentially differentiate into any cell type and could therefore be developed as a source of human hepatocytes.

Severe acute liver failure, even when transient, must be treated by transplantation and lifelong immune suppression. Treatment could be improved by bioartificial liver (BAL) support, but this approach is hindered by a shortage of human hepatocytes. To generate an alternative source of cells for BAL support, we differentiated mouse embryonic stem (ES) cells into hepatocytes by coculture with a combination of human liver nonparenchymal cell lines and fibroblast growth factor-2, human activin-A and hepatocyte growth factor. Functional hepatocytes were isolated using albumin promoter-based cell sorting. ES cell-derived hepatocytes expressed liver-specific genes, secreted albumin and metabolized ammonia, lidocaine and diazepam. Treatment of 90% hepatectomized mice with a subcutaneously implanted BAL seeded with ES cell-derived hepatocytes or primary hepatocytes improved liver function and prolonged survival, whereas treatment with a BAL seeded with control cells did not. After functioning in the BAL, ES cell-derived hepatocytes developed characteristics nearly identical to those of primary hepatocytes.

Excessive systemic inflammation following trauma, sepsis, or burn could lead to distant organ damage. The transplantation of bone marrow stromal cells or mesenchymal stem cells (MSCs) has been reported to be an effective treatment for several immune disorders by modulating the inflammatory response to injury. We hypothesized that MSCs can dynamically secrete systemic factors that can neutralize the activity of inflammatory cytokines. In this study, we showed that cocultured MSCs are able to decrease nuclear factor κ-B (NFκB) activation in target epithelial cells incubated in inflammatory serum conditions. Proteomic screening revealed a responsive secretion of soluble tumor necrosis factor (TNF) receptor 1 (sTNFR1) when MSCs were exposed to lipopolysaccharide (LPS)-stimulated rat serum. The responsive effect was eliminated when NFκB activation was blocked in MSCs. Intramuscular transplantation of MSCs in LPS-endotoxic rats decreased a panel of inflammatory cytokines and inflammatory infiltration of macrophages and neutrophils in lung, kidney, and liver when compared to controls. These results suggest that improvements of inflammatory responses in animal models after local transplantation of MSCs are at least, in part, explained by the NFκB-dependent secretion of sTNFR1 by MSCs.

Since the first attempt in 1968, survival following pig-to-primate liver xenotransplantation (LXT) has been limited. We evaluated a model utilizing α-1,3-galactosyltransferase knockout donors, continuous post-transplant infusion of human prothrombin concentrate complex and immunosuppression including anti-thymocyte globulin, FK-506, methylprednisone and co-stimulation blockade (belatacept, n=3 or anti-CD40mAb, n=1) to extend survival. Baboon #1 remained well until POD25 when euthanasia was required due to cholestasis and plantar ulcers. Baboon #2 was euthanized following a seizure on POD5, despite normal LFTs and no apparent pathology. Baboon # 3 demonstrated initial stable liver function, but was euthanized on POD8 due to worsening LFTs. Pathology revealed C4d positivity, extensive hemorrhagic necrosis and a focal CMV inclusion. Baboon # 4 was clinically well with stable LFTs until POD29, when euthanasia was again necessitated by plantar ulcerations as well as rising LFTs. Final pathology was C4d negative and without evidence of rejection, inflammation or TMA. Thus, nearly one-month rejection-free survival has been achieved following LXT in 2 of 4 continuous recipients, demonstrating that the porcine liver can support life in primates for several weeks and is encouraging for potential clinical application of LXT as a bridge to allotransplantation for patients with acute-on-chronic or fulminant hepatic failure.

This protocol describes a co-culture system for the in vitro differentiation of mouse embryonic stem cells into hepatocyte-like cells. Differentiation involves four steps: (i) formation of embryoid bodies (EB), (ii) induction of definitive endoderm from 2-d-old EBs, (iii) induction of hepatic progenitor cells and (iv) maturation into hepatocyte-like cells. Differentiation is completed by 16 d of culture. EBs are formed, and cells can be induced to differentiate into definitive endoderm by culture in Activin A and fibroblast growth factor 2 (FGF-2). Hepatic differentiation and maturation of cells is accomplished by withdrawal of Activin A and FGF-2 and by exposure to liver nonparenchymal cell-derived growth factors, a deleted variant of hepatocyte growth factor (dHGF) and dexamethasone. Approximately 70% of differentiated embryonic stem (ES) cells express albumin and can be recovered by albumin promoter-based cell sorting. The sorted cells produce albumin in culture and metabolize ammonia, lidocaine and diazepam at approximately two-thirds the rate of primary mouse hepatocytes.

Artificial bones have often used for bone regeneration due to their strength, but they cannot provide an adequate environment for cell penetration and settlement. We therefore attempted to explore various materials that may allow the cells to penetrate and engraft in bone defects. PuraMatrix TM is a self-assembling peptide scaffold that produces a nanoscale environment allowing both cellular penetration and engraftment. The objective of this study was to investigate the effect of PuraMatrix TM on bone regeneration in a mouse bone defect model of the calvaria. Matrigel TM was used as a control. The expression of bone-related genes (alkaline phosphatase, Runx2, and Osterix) in the PuraMatrix TM -injected bone defects was stronger than that in the Matrigel TM -injected defects. Soft X-ray radiographs revealed that bony bridges were clearly observed in the defects treated with PuraMatrix TM , but not in the Matrigel TM -treated defects. Notably, PuraMatrix TM treatment induced mature bone tissue while showing cortical bone medullary cavities. The area of newly formed bones at the site of the bone defects was 1.38-fold larger for PuraMatrix TM than Matrigel TM . The strength of the regenerated bone was 1.72-fold higher for PuraMatrix TM (146.0 g) than for Matrigel TM (84.7 g). The present study demonstrated that PuraMatrix TM injection favorably induced functional bone regeneration.

A human pancreatic beta-cell line that is functionally equivalent to primary beta-cells has not been available. We established a reversibly immortalized human beta-cell clone (NAKT-15) by transfection of primary human beta-cells with a retroviral vector containing simian virus 40 large T-antigen (SV40T) and human telomerase reverse transcriptase (hTERT) cDNAs flanked by paired loxP recombination targets, which allow deletion of SV40T and TERT by Cre recombinase. Reverted NAKT-15 cells expressed beta-cell transcription factors (Isl-1, Pax 6, Nkx 6.1, Pdx-1), prohormone convertases 1/3 and 2, and secretory granule proteins, and secreted insulin in response to glucose, similar to normal human islets. Transplantation of NAKT-15 cells into streptozotocin-induced diabetic severe combined immunodeficiency mice resulted in perfect control of blood glucose within 2 weeks; mice remained normoglycemic for longer than 30 weeks. The establishment of this cell line is one step toward a potential cure of diabetes by transplantation.

We sought to determine the effects of exogenous administration of human coagulation factors following pig-to-baboon liver xenotransplantation (LXT) using GalT-KO donors. Post-LXT, baboons received either: no coagulation factors (historical control, n=1), bolus administration of a human prothrombin concentrate complex (hPCC) (2.5 mL/kg, n = 2), continuous infusion of hPCC (1.0 ml/hr, n=1) or a continuous infusion of human recombinant Factor VIIa (1 mcg/kg/hr, n=3). The historical control recipient demonstrated persistent thrombocytopenia despite platelet administration post-transplant along with widespread thrombotic microangiopathy (TMA). In contrast, platelet levels were maintained in bolus hPCC recipients, however these animals quickly developed large vessel thrombosis and TMA leading to graft failure with shortened survival. Recipients of continuous coagulation factor administration experienced either stabilization or an increase in their circulating platelets with escalating doses. Furthermore, transfusion requirements were decreased and hepatic TMA was noticeably absent in recipients of continuous coagulation factor infusions when compared to the historical control and bolus hPCC recipients. This effect was most profound with a continuous, escalating dose of Factor VIIa. Further studies are warranted as this regimen may allow for prolonged survival following LXT.