Nanoscale topography of artificial substrates can greatly influence the fate of stem cells including adhesion, proliferation, and differentiation. Thus the design and manipulation of nanoscale stem cell culture platforms or scaffolds are of great importance as a strategy in stem cell and tissue engineering applications. In this report, we propose that a graphene oxide (GO) film is an efficient platform for modulating structure and function of human adipose-derived stem cells (hASCs). Using a self-assembly method, we successfully coated GO on glass for fabricating GO films. The hASCs grown on the GO films showed increased adhesion, indicated by a large number of focal adhesions, and higher correlation between the orientations of actin filaments and vinculin bands compared to hASCs grown on the glass (uncoated GO substrate). It was also found that the GO films showed the stronger affinity for hASCs than the glass. In addition, the GO film proved to be a suitable environment for the time-dependent viability of hASCs. The enhanced differentiation of hASCs included osteogenesis, adipogenesis, and epithelial genesis, while chondrogenic differentiation of hASCs was decreased, compared to tissue culture polystyrene as a control substrate. The data obtained here collectively demonstrates that the GO film is an efficient substratum for the adhesion, proliferation, and differentiation of hASCs.

Inspired by ultrastructural analysis of ex vivo human tissues as well as the physiological importance of structural density, we fabricated nanogrooves with 151, 153, and 155 spacing ratio (width5spacing, width 5 550 nm). In response to the nanotopographical density, the adhesion, migration, and differentiation of human mesenchymal stem cells (hMSCs) were sensitively controlled, but the proliferation showed no significant difference. In particular, the osteo-or neurogenesis of hMSCs were enhanced at the 153 spacing ratio rather than 151 or 155 spacing ratio, implying an existence of potentially optimized nanotopographical density for stem cell function. Furthermore, such cellular behaviors were positively correlated with several cell morphological indexes as well as the expression of integrin b1 or N-cadherin. Our findings propose that nanotopographical density may be a key parameter for the design and manipulation of functional scaffolds for stem cell-based tissue engineering and regenerative medicine.S tem cells are characterized by their unique ability to differentiate into various types of cells, allowing for many alternatives and opportunities in tissue engineering and regenerative medicine 1-3 . It is therefore important to develop a platform to regulate or improve stem cell functions from an integrative aspect of biology and engineering [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] . Stem cells reside within instructive and tissue-specific niches in the body, such as complex and controlled biochemical mixtures of soluble and insoluble factors 7,19 . In particular, it is widely accepted that stem cells display high sensitivity to the extracellular matrix (ECM) composed of complex and well-defined nanostructures of protein fibers such as fibrillar collagens and elastins with feature sizes (diameter and spacing) ranging from tens to several hundreds of nanometers. In conjunction with these observations, previous ex vivo and in vitro studies suggest that the use of nanotopographical cues hold great potentials to control stem cell functions [1][2][3][4][5][6][7]19 .The structure of the natural ECM in various tissues including bone, tooth, nerve, skin, muscle, and heart usually reveals highly oriented grooved structures with various length scales in nanometers (Fig. 1A) 1,5 . For example, the concentric nanoscale-thick cylinders enhance mechanical properties of cortical bone, while the aligned collagen matrix in the dermis of skin layer presents anisotropic mechanical properties 1 . Inspired by such ultrastructural observations, the utilization of nanoengineering technology to develop a nanogrooved matrix has been greatly attractive to biologists and engineers in the fields of classical stem biology and regenerative medicine 1,5,[20][21][22][23][24] . According to previous studies, the controlled polarity and subsequent mechanical tension turned out to be crucial for the cell behaviors such as spreading 25,26 , migration 27,28 , proliferation 29 , cell division 30 , tissue function 31 and tiss...

The vertebrate neural crest is a multipotent cell population that gives rise to a variety of different cell types. We have discovered that postmigratory cranial neural crest cells (CNCCs) maintain mesenchymal stem cell characteristics and show potential utility for the regeneration of craniofacial structures. We are able to induce the osteogenic differentiation of postmigratory CNCCs, and this differentiation is regulated by bone morphogenetic protein (BMP) and transforming growth factor-b signaling pathways. After transplantation into a host animal, postmigratory CNCCs form bone matrix. CNCC-formed bones are distinct from bones regenerated by bone marrow mesenchymal stem cells. In addition, CNCCs support tooth germ survival via BMP signaling in our CNCC-tooth germ cotransplantation system. Thus, we conclude that postmigratory CNCCs preserve stem cell features, contribute to craniofacial bone formation, and play a fundamental role in supporting tooth organ development. These findings reveal a novel function for postmigratory CNCCs in organ development, and demonstrate the utility of these CNCCs in regenerating craniofacial structures.

Statement of problem.The use of the platelet concentration technique is widespread in dental implant surgery. However, its effect or mechanism is not clearly understood.Purpose. This study introduced an animal model for the platelet concentration technique and evaluated its effect on bone formation with natural cancellous bovine bone mineral.Material and methods. Adult New Zealand white rabbits were used as the animal model. A density gradient medium was used to obtain a constant platelet count for the preparation of platelet concentrates. In the experimental group, natural cancellous bovine bone mineral with added platelet concentrates was grafted onto critically sized bony defects of the rabbit calvarium. Bone formation in the tissue sections was evaluated with soft x-ray imaging and computer tomography.Results. The average platelet count of the rabbit platelet concentrates was 1487 × 10 3 /µL (287% concentrated). In all the tested parameters, greater bone densities were obtained in grafts that were combined with platelet concentrates. Conclusion.This study showed that the rabbit is a useful animal model for studying the platelet concentration technique. When combined with grafts of natural cancellous bovine bone mineral, the technique increased bone formation. (J Prosthet Dent 2001;86:428-33.)