Stromal cells and/or soluble factors such as growth factors have been considered until now as the main niche of corneal epithelial stem cells. We found that cultivated epithelial cells had epithelial clusters when cultured, maintaining the sheet structure. Therefore, we hypothesized that the epithelial cells themselves might be a niche of the stem cells, and the cell clusters could be maintained during the gentle enzymatic digestion of the limbal epithelial sheets. The main methods of generating cultivated limbal epithelial sheet for clinical application are, the cell suspension method (complete enzymatic digestion of limbal epithelia), and the explant method (cells grown from limbal explants). For cell suspension, it is good to expand cells and generating sheets quickly, but it is not clear wheather these sheets maintain the normal homeostatic levels of the progenitor cells. Explants maintain homeostatic levels more similar to in vivo homeostasis, but the low proliferative speed of epithelial expansion and reproducibility are the problem. In this review, we hypothesize that to generate cultivated epithelial sheets while maintaining a corneal epithelial stem cells' niche is a better way to proceed as it includes the advantages of both the cell suspension and explant methods. The growth potential, colony-forming efficiency of p63-positive cell clusters, and immunostaining by differentiation/ undifferentiation markers, demonstrated that progenitor cells could be maintained by these gentle enzymatic digestion maintaining cell clusters.

Chondrocyte differentiation process is composed of multiple steps. During the process, hypertrophy of chondrocyte is controlled by various factors including Indian hedgehog (Ihh) and parathyroid hormone related peptide (PTHrP) . PTHrP signals regulate HDAC4-MEF2C axis in chondrocyte. Recently, several co-factors have been found to interact with Sox9. Function of chondrocyte-specific microRNA has been determined. Several types of Cre transgenic mice are available to express Cre at various steps during chondrocyte differentiation. Using these mice, gene functions at specific steps of chondrocyte differentiation are analyzed by generating conditional knockout mice and conditional transgenic mice. It may be possible in future to induce chondrocytes from skin fibroblasts of patients with genetic cartilage diseases by using iPS cell technology, and to analyze molecular mechanism that control differentiation of human chondrocytes.

Myelosuppression is one of the most serious adverse effects induced by chemotherapy targeting solid tumors and hematological malignancies, and results in neutropenia, anemia and thrombocytopenia. In particular, prompt and appropriate treatments are required for febrile neutropenia, because that disease may be fatal.

A 57-year-old man had limited-disease small cell lung cancer in the left lower lobe of the lung. He was treated with chemotherapy with concurrent accelerated hyperfractionated thoracic radiation, followed by high-dose chemotherapy with autologous peripheral blood stem cell transplantation. He had obtained a complete response for 10 years until the tumor in the left lower lobe was detected by positron emission tomography. Bronchoscopic brushing cytology revealed small cell cancer, which was considered to be local relapse by staging work-up. He achieved a partial response with chemotherapy consisting of cisplatin and irinotecan. The progression-free survival rate at 5 years in limited-disease small cell lung cancer ranges from 10% to 25%. Although it was difficult to distinguish the relapse of lung cancer from second primary lung cancer, we considered this case as relapse because the tumor had the same cytology in the same lobe as the previous primary tumor. The residual cells refractory to concomitant chemoradiotherapy followed by high-dose chemotherapy with stem cell transplantation had survived and proliferated after 10 years.

No treatment to cure of chronic obstructive pulmonary disease (COPD) is available. Regenerative medicine is one of promising areas for this intractable disease. Several reagents and growth factors are known to promote lung regeneration in small animal models. However, regenerative medicines for human lungs are not achieved yet. Recent advances in stem cell biology and tissue engineering have expanded our understanding of lung endogenous stem cells, and this new knowledge provides us with new ideas for future regenerative therapy for lung diseases. Although lungs are the most challenging organ for regenerative medicine, our cumulative knowledge of lung regeneration and of endogenous progenitor cells makes clear the possibilities for regenerative approach to COPD.

Crow-Fukase syndrome, also called POEMS (polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes) syndrome, is a rare cause of demyelinating and axonal mixed neuropathy with multiorgan involvement. The pathogenesis of Crow-Fukase syndrome is not well understood, but overproduction of vascular endothelial growth factor (VEGF), probably mediated by monoclonal proliferation of plasma cells, is likely to be responsible for most of the characteristic symptoms. There is no established treatment regimen. In appropriate candidates, high-dose chemotherapies with autologous peripheral blood stem cell transplantation is highly recommended, because this treatment could result in obvious improvement in neuropathy as well as other symptoms, with a significant decrease in serum VEGF levels. Indication of this treatment has not yet been established, and long-term prognosis is unclear at present. Thalidomide should be considered for patients who are not indicated for transplantation therapy. Treatments that should be considered as future therapy include lenalidomide, bortezomib, and anti-VEGF monoclonal antibody (bevacizumab).

Because embryonic stem (ES) cells and induced pluripotent stem (iPS) cells can differentiate into various types of cells in vitro, they are considered as a valuable model to understand the processes involved in the differentiation into functional cells as well as an unlimited source of cells for therapeutic applications. Efficient gene transduction method is one of the powerful tools for the basic researches and for differentiating ES and iPS cells into lineage-committed cells. Recently, we have developed an adenovirus (Ad) vector for efficient transduction into ES and iPS cells. We showed that Ad vectors containing the cytomegalovirus enhancer/β-actin promoter with β-actin intron (CA) promoter or the elongation factor (EF)-1α promoter were the appropriate for the transduction into ES and iPS cells. We also found that enforced expression of a PPARγ gene or a Runx2 gene into mouse ES and iPS cells by an optimized Ad vector markedly augmented the differentiation of adipocytes or osteoblasts, respectively. Thus, a gene transfer technique using an Ad vector could be an advantage for the regulation of stem cell differentiation and could be applied to regenerative medicine based on ES and iPS cells.

Skeletal muscle has great regenerative potential that depends on muscle stem cells, called satellite cells. In uninjured muscle, satellite cells reside beneath the basal lamina and are maintained in quiescent and undifferentiated state. This state is considered a requisite for sustaining the satellite cell pool, but the molecular mechanism is still unknown. In our previous study, we developed a novel monoclonal antibody that specifically recognized muscle satellite cells in skeletal muscle. Using this monoclonal antibody, we purified satellite cells and performed genome-wide transcriptome analysis. In these analyses, we found that satellite cells expressed Hesr1/Hey1 and Hesr3/HeyL genes known as down stream target of Notch signaling. Although each single knock out mice did not indicate obvious phenotype in skeletal muscle, Hesr1/Hesr3 double knock out mice showed remarkably decreased number of satellite cells. Intriguingly, dKO satellite cells were not kept in quiescent and differentiated state in adult skeletal muscle. This dysregulated state of satellite cells lead to gradually decreased number of satellite cells and age-dependent regeneration defect. These results indicate that Hesr1/3 is essential for muscle stem cell biology and will facilitate this research field.

The cerebral cortex is organized into six cell layers, each of which contains neurons with similar morphology, functions, gene-expression profiles, and projection patterns. These layer-specific neuronal phenotypes are sequentially generated from common cortical progenitor cells in the ventricular zone of dorsal telencephalon. Although recent investigations have clarified important roles of intrinsic factors such as transcription factors and regulators of the cell cycle for the maturation of cortical progenitors, growth factors and neurotrophic factors environmentally supplied by the cerebral cortex are thought to regulate proliferation and neural development and determine neuronal differentiation in the cerebral cortex. In this review, I focus on the function of neurotrophin-family neurotrophic factor, including nerve growth factor, brain-derived neurotrophic factor (BDNF), neurotropin-3 (NT-3) and neurotrophin-4 in the formation of the neuronal layer of the cerebral cortex. Especially, BDNF and NT-3 are expressed in the proliferating cortical progenitors and influence the biological properties of cortical progenitors prior to neurogenesis and play distinct roles in generation of cortical neuronal subtypes.