Masato Nagaoka

UNLABELLED: There exists a worldwide shortage of donor livers available for orthotropic liver transplantation and hepatocyte transplantation therapies. In addition to their therapeutic potential, primary human hepatocytes facilitate the study of molecular and genetic aspects of human hepatic disease and development and provide a platform for drug toxicity screens and identification of novel pharmaceuticals with potential to treat a wide array of metabolic diseases. The demand for human hepatocytes, therefore, heavily outweighs their availability. As an alternative to using donor livers as a source of primary hepatocytes, we explored the possibility of generating patient-specific human hepatocytes from induced pluripotent stem (iPS) cells. CONCLUSION: We demonstrate that mouse iPS cells retain full potential for fetal liver development and describe a procedure that facilitates the efficient generation of highly differentiated human hepatocyte-like cells from iPS cells that display key liver functions and can integrate into the hepatic parenchyma in vivo.

Lactobacilli are nonpathogenic gram-positive inhabitants of microflora. At least some Lactobacillus strains have been postulated to have health beneficial effects, such as the stimulation of the immune system. Here we examined the stimulatory effects of lactobacilli on mouse immune cells. All six heat-killed Lactobacillus strains examined induced the secretion of tumor necrosis factor alpha (TNF-alpha) from mouse splenic mononuclear cells, albeit to various degrees. When fractionated subcellular fractions of Lactobacillus casei were tested for NF-kappaB activation and TNF-alpha production in RAW264.7, a mouse macrophage cell line, the activity was found to be as follows: protoplast > cell wall >> polysaccharide-peptidoglycan complex. Both crude extracts and purified lipoteichoic acids (LTAs) from two Lactobacillus strains, L. casei and L. fermentum, significantly induced TNF-alpha secretion from RAW264.7 cells and splenocytes of C57BL/6, C3H/HeN, and C3H/HeJ mice but not from splenocytes of C57BL/6 TLR2(-/-) mice. Lactobacillus LTA induced activation of c-Jun N-terminal kinase activation in RAW264.7 cells. Furthermore, in HEK293T cells transected with a combination of CD14 and Toll-like receptor 2 (TLR2), NF-kappaB was activated in response to Lactobacillus LTA. Taken together, these data suggest that LTAs from lactobacilli elicit proinflammatory activities through TLR2.

IL-6/STAT-3 signals play key roles in inflammatory bowel disease (IBD). It is known that Lactobacillus casei strain Shirota (LcS) improves inflammatory disorders. This study aimed to elucidate the effect of LcS on murine chronic IBD and to clarify the mechanism. We focused the inhibitory effect of LcS on the production of IL-6 in lipopolysaccharide (LPS)-stimulated large intestinal lamina propria mononuclear cells (LI-LPMC) isolated from mice with chronic colitis and in RAW264.7 cells in vitro. We also determined in vivo the effect of LcS on murine chronic IBD models induced with dextran sodium sulphate and SAMP1/Yit mice. Finally, we examined the cellular determinants of LcS for the down-regulation of IL-6 secretion by LI-LPMC, RAW264.7 cells and peripheral blood mononuclear cells (PBMC) derived from patients with ulcerative colitis (UC). LcS, but not other strains of Lactobacillus, inhibited the production of IL-6 in LPS-stimulated LI-LPMC and RAW264.7 cells, down-regulating the nuclear translocation of NF-kappaB. The LcS-diet-improved murine chronic colitis is associated with the reduction of IL-6 synthesis by LI-LPMC. LcS also improved chronic ileitis in SAMP1/Yit mice. The release of IL-6 in vitro in LPS-stimulated LI-LPMC, RAW 264.7 cells and UC-PBMC was inhibited by a polysaccharide-peptidoglycan complex (PSPG) derived from LcS. This probiotic-induced improvement in murine chronic inflammatory bowel disease is associated with the down-regulation of pro-inflammatory cytokines such as IL-6 and IFN-gamma production in LPMC. Therefore, LcS may be a useful probiotic for the treatment of human inflammatory bowel disease.

The availability of pluripotent stem cells offers the possibility of using such cells to model hepatic disease and development. With this in mind, we previously established a protocol that facilitates the differentiation of both human embryonic stem cells and induced pluripotent stem cells into cells that share many characteristics with hepatocytes. The use of highly defined culture conditions and the avoidance of feeder cells or embryoid bodies allowed synchronous and reproducible differentiation to occur. The differentiation towards a hepatocyte-like fate appeared to recapitulate many of the developmental stages normally associated with the formation of hepatocytes in vivo. In the current study, we addressed the feasibility of using human pluripotent stem cells to probe the molecular mechanisms underlying human hepatocyte differentiation. We demonstrate (1) that human embryonic stem cells express a number of mRNAs that characterize each stage in the differentiation process, (2) that gene expression can be efficiently depleted throughout the differentiation time course using shRNAs expressed from lentiviruses and (3) that the nuclear hormone receptor HNF4A is essential for specification of human hepatic progenitor cells by establishing the expression of the network of transcription factors that controls the onset of hepatocyte cell fate.