Nuclear reprogramming and adult stem cell potential

Isolation, culture, and verification of human sweat gland epithelial cells

Human sweat gland epithelial cells (SGECs) have been isolated and grown in vitro, However, slow proliferation makes the culture of these cells extremely difficult. The present study was carried out to explore the modified culture medium for SGECs in vitro. Full-thickness skin samples were minced (1 mm(3)) and digested overnight with type II collagenase. The gland coils were removed under an inverted phase-contrast microscope. An adherent culture method was used to isolate and culture SGECs. Staining with hematoxylin and eosin was performed, followed by observation of the morphologic features of these cells. Immunofluorescence staining with antibodies to cytokeratins CK7, CK18, and CK19 and carcinoembryonic antigen (CEA) was performed to verify the presence of SGECs. Growth curves by MTT were created for cells grown in serum-free keratinocyte medium and in modified keratinocyte medium containing 2.5% fetal bovine serum (FBS). One week after culturing, the cells grew well and were polygonal or irregular in shape by inverted phase contrast microscopy. Cell fusion, with a characteristic paving-stone arrangement, reached 100% after approximately 3 weeks in culture. Immunofluorescence staining indicated expression of CK7, CK18, CK19, and CEA. Compared with SGECs grown in serum-free keratinocyte medium, the proliferation of SGECs grown in modified culture medium with low concentration of FBS at days 6, 9, and 12 was significantly accelerated (p < 0.05). This study suggests that keratinocyte medium supplemented with 2.5% FBS is effective and suitable for the culture of SGECs.

[New strategies for tissue replacement in the head and neck region]

In recent years there has been an increase in the need for tissue replacement in the head and neck region. The disadvantages of classical reconstructive procedures are donor site morbidity for autologous transplants and the immunogenity of allogenous transplants. Tissue engineering is a promising method for the generation of autologous cartilagenous transplants for plastic and reconstructive surgery for closure of large defects by the use of minimal amounts of material for reconstruction. For this purpose harvested material must be cultivated in suitable culture/carrier systems. One obstacle is the loss of phenotype and function once the cells are detached from their environment (dedifferentiation). Adult mesenchymal stem cells are a valuable cell source for tissue engineering. The underlying strategy of using stem cells is the replacement of functionally compromised cells either by in vitro expanded stem cells or activation of stem cells in the tissue. However, there are still problems regarding valuable markers for cellular differentiation and the controlled differentiation towards a specific phenotype.

Neural crest as the source of adult stem cells

Recent studies suggest that adult stem cells can cross germ layer boundaries. For example, bone marrow-derived stem cells appear to differentiate into neurons and glial cells, as well as other types of cells. How can stem cells from bone marrow, pancreas, skin, or fat become neurons and glia; in other words, what molecular and cellular events direct mesodermal cells to a neural fate? Transdifferentiation, dediffereniation, and fusion of donor adult stem cells with fully differentiated host cells have been proposed to explain the plasticity of adult stem cells. Here we review the origin of select adult stem cell populations and propose a unifying hypothesis to explain adult stem cell plasticity. In addition, we outline specific experiments to test our hypothesis. We propose that peripheral, tissue-derived, or adult stem cells are all progeny of the neural crest.