Recent progress in studies on direct cell-fate conversion of differentiated somatic cells into other cell types, which is known as “direct reprogramming”, is expected to lead to innovations in health care. In our previous study, we found that three specific combinations of two transcription factors, comprising Hnf4α plus Foxa1, Foxa2, or Foxa3, were able to induce conversion of mouse fibroblasts into functional hepatocyte-like cells. These induced hepatocyte-like (iHep) cells will be useful for developing regenerative therapies for liver diseases and examining the pharmacological effects of drugs. However, to evaluate the potential utility of iHep cells, the phenomena involved in the direct conversion of fibroblasts into iHep cells should be examined in detail. Thus, in this study, we sequentially analyzed the early stage of fibroblast conversion into iHep cells after infection with retroviruses expressing Hnf4α and Foxa3. Our data demonstrated that the conversion into iHep cells began within 2 days after introduction of the transgenes into fibroblasts, and the number of iHep cells increased gradually as the culture progressed. The rapid cell-fate conversion of fibroblasts into iHep cells and stable expansion of iHep cells are two pieces of evidence suggesting the utility of iHep cells for cell transplantation therapy, bioartificial liver development, and screening of drugs for patients with liver diseases, which require many hepatocytes within a short period of time.

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Adult cardiomyocytes have little regenerative capacity following injury, and damaged myocardium heals via fibroblast proliferation and scar formation, leading to cardiac remodeling and heart failure. We and other reported that functional cardiomyocytes can be directly generated from fibroblasts using several combinations of cardiac-specific defined factors. Mouse fibroblasts can be directly converted into cardiomyocyte-like cells by overexpression of cardiac-specific transcription factors, Gata4, Mef2c, and Tbx5 (GMT), GMT plus Hand2 (GHMT), or Mef2c, Myocd, and Tbx5 in vitro. More recently, we and others reported that human fibroblasts can be reprogrammed into differentiated cardiomyocyte-like cells by overexpressing GMT plus Myocd and Mesp1 or Gata4, Hand2, Tbx5, Myocd, miR-1, and miR-133. We found that miR-133 promoted cardiac reprogramming by directly suppressing Snai1, a master gene of fibroblasts, and silencing fibroblast signature. In vivo cardiac reprogramming by GMT or GHMT also converted endogenous CFs into cardiomyocyte-like cells in situ, and improved cardiac function after acute myocardial infarction in mouse. These studies demonstrate that direct cardiac reprogramming technology may be a potential approach that could regenerate diseased hearts. The present article reviews the recent studies in cardiac reprogramming, and discusses the hopes and challenges of direct cardiac reprogramming towards regenerative therapy.

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Trans-differentiation of cells through direct reprogramming offers significant potential for regenerative medicine and drug screen, but currently it requires exhaustive trials and errors before the desired target cells can be created. Based on the comprehensive transcriptome analyses by the FANTOM consortium, in particular the recently published transcriptional regulatory network analysis, we have developed a systematic method for direct reprogramming and succeeded in creating monocyte-like cells with several monocyte-specific functions. Further analysis of the created cells reveals that the transcriptional regulatory networks and the epigenomes of the original terminally differentiated cells act as strong barriers that prevent easy reprogramming by extra stimuli. These biological insights should be carefully considered for efficient and complete direct reprogramming.

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For many decades, tools for cell-cell communication were of great concern in various research fields, not only in basic research, but also in medical research. Although a large number of humoral factors, such as cytokines, chemokines, growth factors, hormones, and so on, have been identified and characterized, few molecular mechanisms of cell-cell communication have been clarified. Recently, small membrane vesicles, called exosomes (also known as extracellular vesicles), have been at the center of attention again. Current vigorous worldwide research found that exosomes play multiple important roles in physiological and pathological phenomena. In this review, we will summarize our current reports showing the essential roles of exosomes in cancer development, the novel utility of exosomes to know the status of the patient, and the potential novel treatment choice for neurological disease.

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Phosphorylation and dephosphorylation of intracellular enzymes, such as the T-cell-specific Tec family protein kinase Txk, are critically involved in the regulation of a number of cellular functions. Although PTPs located in the nucleus are limited, TCPTP is known to be one such nuclear phosphatase, due to its nuclear localization signal sequences. Here, we investigate the role of TCPTP in the regulation of Txk phosphorylation/dephosphorylation in Txk-transfected Cos7 and Jurkat cells.
Nuclear-type TCPTP (TC45) was present in both the nuclear and cytoplasmic compartments of Cos7 cells transfected with TC45. Cytoplasmic-type TCPTP (TC48) was localized in the cytoplasmic compartment of Cos7 cells transfected with TC48. We observed that expression of TC45 dephosphorylated Txk in the nuclei of Cos7 cells. TC48 expression did not dephosphorylate Txk; rather, it enhanced and sustained Txk phosphorylation in the nuclei of Cos7 cells.
Phosphorylation of Txk increased 60 minutes after lectin stimulation in Jurkat cells transfected with TCPTP-specific small interfering RNA (siRNA), which efficiently knocked down endogenous TCPTP.
TCPTP may play a crucial role in the regulation of Txk phosphorylation status in T-cells after stimulation.

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