Bidirectional developmental potential in reprogrammed cells with acquired pluripotency.

We recently discovered an unexpected phenomenon of somatic cell reprogramming into pluripotent cells by exposure to sublethal stimuli, which we call stimulus-triggered acquisition of pluripotency (STAP). This reprogramming does not require nuclear transfer or genetic manipulation. Here we report that reprogrammed STAP cells, unlike embryonic stem (ES) cells, can contribute to both embryonic and placental tissues, as seen in a blastocyst injection assay.

Stimulus-triggered fate conversion of somatic cells into pluripotency.

Here we report a unique cellular reprogramming phenomenon, called stimulus-triggered acquisition of pluripotency (STAP), which requires neither nuclear transfer nor the introduction of transcription factors. In STAP, strong external stimuli such as a transient low-pH stressor reprogrammed mammalian somatic cells, resulting in the generation of pluripotent cells. Through real-time imaging of STAP cells derived from purified lymphocytes, as well as gene rearrangement analysis, we found that committed somatic cells give rise to STAP cells by reprogramming rather than selection.

Successful serial recloning in the mouse over multiple generations.

Previous studies of serial cloning in animals showed a decrease in efficiency over repeated iterations and a failure in all species after a few generations. This limitation led to the suggestion that repeated recloning might be inherently impossible because of the accumulation of lethal genetic or epigenetic abnormalities. However, we have now succeeded in carrying out repeated recloning in the mouse through a somatic cell nuclear transfer method that includes a histone deacetylase inhibitor.

Effect on ligament marker expression by direct-contact co-culture of mesenchymal stem cells and anterior cruciate ligament cells.

Ligament and tendon repair is an important topic in orthopedic tissue engineering; however, the cell source for tissue regeneration has been a controversial issue. Until now, scientists have been split between the use of primary ligament fibroblasts or marrow-derived mesenchymal stem cells (MSCs). The objective of this study was to show that a co-culture of anterior cruciate ligament (ACL) cells and MSCs has a beneficial effect on ligament regeneration that is not observed when utilizing either cell source independently.

Reproducible subcutaneous transplantation of cell sheets into recipient mice.

Perfecting tissue engineering and cell sheet transplantation is an important step toward realizing regenerative medicine and is a growing area of research. Before being applied to clinical settings, it is important that these approaches are evaluated in vivo. Here we provide a detailed protocol for handling thin cell sheets, for a simple and highly reproducible subcutaneous transplantation of cell sheets into mice, and for the histological examination of regenerated tissues.

Development of osteogenic cell sheets for bone tissue engineering applications.

The use of scaffolds in combination with osteogenic cells has been the gold standard in bone tissue engineering strategies. These strategies have, however, in many cases failed to produce the desired results due to issues such as the immunogenicity of the biomaterials used and cell necrosis at the bulk of the scaffold related to deficient oxygen and nutrients diffusion. Here, we originally propose the use of cell sheet (CS) engineering as a possible way to overcome some of these obstacles.

The potential of stem cells in adult tissues representative of the three germ layers.

Mature adult tissues contain stem cells that express many genes normally associated with the early stage of embryonic development, when maintained in appropriate environments. Cells procured from adult tissues representative of the three germ layers (spinal cord, muscle, and lung), each exhibiting the potential to mature into cells representative of all three germ layers. Cells isolated from adult tissues of different germ layer origin were propagated as nonadherent clusters or spheres that were composed of heterogeneous populations of cells.

Hollow-fiber membrane chamber as a device for in situ environmental cultivation.

A hollow-fiber membrane chamber (HFMC) was developed as an in situ cultivation device for environmental microorganisms. The HFMC system consists of 48 to 96 pieces of porous hollow-fiber membrane connected with injectors. The system allows rapid exchange of chemical compounds, thereby simulating a natural environment.

Subcutaneous transplantation of autologous oral mucosal epithelial cell sheets fabricated on temperature-responsive culture dishes.

The oral mucosa is an attractive cell source for autologous transplantation in human patients who require regenerative therapies of various epithelia. However, the time-course of cellular changes in transplanted oral mucosal epithelia at ectopic sites remains poorly understood. By applying a rat model, we analyzed phenotypic changes in oral mucosal epithelial cell sheets after harvest from temperature-responsive culture dishes and subsequent autologous subcutaneous transplantation.