Linking the p53 tumour suppressor pathway to somatic cell reprogramming.

Reprogramming somatic cells to induced pluripotent stem (iPS) cells has been accomplished by expressing pluripotency factors and oncogenes, but the low frequency and tendency to induce malignant transformation compromise the clinical utility of this powerful approach. We address both issues by investigating the mechanisms limiting reprogramming efficiency in somatic cells. Here we show that reprogramming factors can activate the p53 (also known as Trp53 in mice, TP53 in humans) pathway. Reducing signalling to p53 by expressing a mutated version of one of its negative regulators, by deleting or knocking down p53 or its target gene, p21 (also known as Cdkn1a), or by antagonizing reprogramming-induced apoptosis in mouse fibroblasts increases reprogramming efficiency. Notably, decreasing p53 protein levels enabled fibroblasts to give rise to iPS cells capable of generating germline-transmitting chimaeric mice using only Oct4 (also known as Pou5f1) and Sox2. Furthermore, silencing of p53 significantly increased the reprogramming efficiency of human somatic cells. These results provide insights into reprogramming mechanisms and suggest new routes to more efficient reprogramming while minimizing the use of oncogenes.

Human and mouse adipose-derived cells support feeder-independent induction of pluripotent stem cells.

Although adipose tissue is an expandable and readily attainable source of proliferating, multipotent stem cells, its potential for use in regenerative medicine has not been extensively explored. Here we report that adult human and mouse adipose-derived stem cells can be reprogrammed to induced pluripotent stem (iPS) cells with substantially higher efficiencies than those reported for human and mouse fibroblasts. Unexpectedly, both human and mouse iPS cells can be obtained in feeder-free conditions. We discovered that adipose-derived stem cells intrinsically express high levels of pluripotency factors such as basic FGF, TGFbeta, fibronectin, and vitronectin and can serve as feeders for both autologous and heterologous pluripotent cells. These results demonstrate a great potential for adipose-derived cells in regenerative therapeutics and as a model for studying the molecular mechanisms of feeder-free iPS generation and maintenance.

Novel TLR2xTLR4 Bispecific Antibody Inhibits Bacterial Sepsis.

Toll-like receptors (TLRs) sense microbial infection through recognition of pathogen-associated molecular patterns. For example, TLR4 responds to the lipopolysaccharide of gram-negative bacteria, whereas TLR2 recognizes a broad range of microbial ligands. Both receptors are, therefore, compelling targets for treating sepsis. Here, we developed a TLR2xTLR4 tetravalent bispecific antibody designated ICU-1, which inhibits both receptors. The inhibitory activity of ICU-1 was comparable to that of the parental antibodies in neutralization assays using a human monocyte cell line. Moreover, ICU-1 completely blocked stimulation of human peripheral blood mononuclear cells by clinically relevant bacterial species. These findings provide convincing evidence that ICU-1 offers a novel approach for treating bacterial sepsis.

Generation and Characterization of a Novel Anti-Rat TLR4/MD2 Antibody with Potent Neutralizing Activity In Vivo.

Toll-like receptor 4 (TLR4) plays a critical role in the innate immune system and is involved in the pathogenesis of multiple diseases. Here, we report the antagonistic and ratized antibody, 52-1H4 e2 (e2), which completely inhibited lipopolysaccharide-induced interleukin-6 secretion in vitro. The average serum drug concentration was above 10 µg/mL for 28 days in rats injected with e2. The novel anti-rat TLR4/myeloid differentiation factor 2 antibody, e2, may be a useful tool for investigating the role of TLR4 in rat disease models.