Enhanced generation of myeloid lineages in hematopoietic differentiation from embryonic stem cells by silencing transcriptional repressor Twist-2

An "unexpected" role for EMT transcription factors in hematological development and malignancy

The epithelial to mesenchymal transition (EMT) is a fundamental developmental process essential for normal embryonic development. It is also important during various pathogenic processes including fibrosis, wound healing and epithelial cancer cell metastasis and invasion. EMT is regulated by a variety of cell signalling pathways, cell-cell interactions and microenvironmental cues, however the key drivers of EMT are transcription factors of the ZEB, TWIST and SNAIL families. Recently, novel and unexpected roles for these EMT transcription factors (EMT-TFs) during normal blood cell development have emerged, which appear to be largely independent of classical EMT processes. Furthermore, EMT-TFs have also begun to be implicated in the development and pathogenesis of malignant hematological diseases such as leukemia and lymphoma, and now present themselves or the pathways they regulate as possible new therapeutic targets within these malignancies. In this review, we discuss the ZEB, TWIST and SNAIL families of EMT-TFs, focusing on what is known about their normal roles during hematopoiesis as well as the emerging and "unexpected" contribution they play during development and progression of blood cancers.

Regulators of pluripotency and their implications in regenerative medicine

The ultimate goal of regenerative medicine is to replace damaged tissues with new functioning ones. This can potentially be accomplished by stem cell transplantation. While stem cell transplantation for blood diseases has been increasingly successful, widespread application of stem cell therapy in the clinic has shown limited results. Despite successful efforts to refine existing methodologies and to develop better ones for reprogramming, clinical application of stem cell therapy suffers from issues related to the safety of the transplanted cells, as well as the low efficiency of reprogramming technology. Better understanding of the underlying mechanism(s) involved in pluripotency should accelerate the clinical application of stem cell transplantation for regenerative purposes. This review outlines the main decision-making factors involved in pluripotency, focusing on the role of microRNAs, epigenetic modification, signaling pathways, and toll-like receptors. Of special interest is the role of toll-like receptors in pluripotency, where emerging data indicate that the innate immune system plays a vital role in reprogramming. Based on these data, we propose that nongenetic mechanisms for reprogramming provide a novel and perhaps an essential strategy to accelerate application of regenerative medicine in the clinic.

Role of Kupffer cells in bacterial infectious diseases

Kupffer cells (KCs) are also known as liver inherent macrophages, which account for the largest part of human tissue macrophages and participate in the pathogenesis of various liver diseases. In vitro study using primary culture is a valuable tool for the exploration of specific immunological functions of KCs. Obtaining KCs with high purity and activity is the basis for research. A large number of phagocytosable particles and soluble substances can activate KCs by binding to specific receptors on the membrane. The most important molecule that activates KCs is lipopolysaccharide (LPS). A tiny quantity of LPS will drive a Toll-like receptor 4 (TLR4) -dependent proinflammatory response that alerts the host to the presence of infection. Higher quantities of LPS, which reach the cytoplasm, will trigger inflammasome activation, interleukin-1 beta (IL-1β) production and, ultimately, cell death. KCs play an important role in sepsis, endotoxin tolerance and acute pancreatitis. In this review, we describe the role of KCs in these diseases and the underlying molecular mechanisms.

Ablation of coactivator Med1 switches the cell fate of dental epithelia to that generating hair

Cell fates are determined by specific transcriptional programs. Here we provide evidence that the transcriptional coactivator, Mediator 1 (Med1), is essential for the cell fate determination of ectodermal epithelia. Conditional deletion of Med1 in vivo converted dental epithelia into epidermal epithelia, causing defects in enamel organ development while promoting hair formation in the incisors. We identified multiple processes by which hairs are generated in Med1 deficient incisors: 1) dental epithelial stem cells lacking Med 1 fail to commit to the dental lineage, 2) Sox2-expressing stem cells extend into the differentiation zone and remain multi-potent due to reduced Notch1 signaling, and 3) epidermal fate is induced by calcium as demonstrated in dental epithelial cell cultures. These results demonstrate that Med1 is a master regulator in adult stem cells to govern epithelial cell fate.

Directing stem cell fate by controlled RNA interference

Directing stem cell fate remains a major area of interest and also a hurdle to many, particularly in the field of regenerative medicine. Unfortunately, conventional methods of over-expressing inductive factors through the use of biochemical induction cocktails have led to sub-optimal outcomes. A potential alternative may be to adopt the opposite by selectively silencing genes or pathways that are pivotal to stem cell differentiation. Indeed, over recent years, there have been an increasing number of studies on directing stem cell fate through gene knockdown via RNA interference (RNAi). While the effectiveness of RNAi in controlling stem cell differentiation is evident from the myriad of studies, a chaotically vast collection of gene silencing targets have also been identified. Meanwhile, variations in methods of transfecting stem cells have also affected silencing efficiencies and the subsequent extent of stem cell differentiation. This review serves to unite the pioneers who have ventured into the emerging field of RNAi-enhanced stem cell differentiation by summarizing and evaluating the current approaches adopted in utilizing gene silencing to direct stem cell fate and their corresponding outcomes.