Two important goals in stem cell research are to control the cell proliferation without differentiation and to direct the differentiation into a specific cell lineage when desired. Here, we demonstrate such paths by controlling only the nanotopography of culture substrates. Altering the dimensions of nanotubular-shaped titanium oxide surface structures independently allowed either augmented human mesenchymal stem cell (hMSC) adhesion or a specific differentiation of hMSCs into osteoblasts by using only the geometric cues, absent of osteogenic inducing media. hMSC behavior in response to defined nanotube sizes revealed a very dramatic change in hMSC behavior in a relatively narrow range of nanotube dimensions. Small (Ϸ30-nm diameter) nanotubes promoted adhesion without noticeable differentiation, whereas larger (Ϸ70-to 100-nm diameter) nanotubes elicited a dramatic stem cell elongation (Ϸ10-fold increased), which induced cytoskeletal stress and selective differentiation into osteoblast-like cells, offering a promising nanotechnology-based route for unique orthopedics-related hMSC treatments.differentiation ͉ mesenchymal ͉ nanotopography ͉ osteogenesis ͉ proliferation N anostructures are of particular interest because they have the advantageous feature of a high surface-to-volume ratio, and they elicit a higher degree of biological plasticity compared with conventional micro-or macrostructures. In the field of biomaterial development and in vivo implant technology, the nanoscale structure and morphologenic factor of the surface have played a critical role in accelerating the rate of cell proliferation and enhancing tissue acceptance with a reduced immune response (1, 2). In terms of in vitro cell biology, there has also been much attention placed on cellular responses to their structural surroundings (3). In fact, it has been observed that macro-, micro-and nano-sized topographical factors stimulate behavioral changes in both cells and tissues. Recent studies related to the effect of nanotopography on cellular behavior indicated that osteoblast adhesion and functionality was enhanced by 30% when cultured on a nanograined Al 2 O 3 and TiO 2 substrate (4-6) compared with those cultured on a micrograined surface, and nanostructures such as TiO 2 nanotubes with Ͻ100-nm spacing showed superior characteristics in bone mineral synthesis (5). However, most of the previous studies on nanostructures and cell responses have mainly used oriented, patterned, or semiordered polymer arrays (7-9) and alumina/ polymer hybrid patterned arrays (10).The material and mechanical characteristics of titanium (Ti) metal, which has a thin native oxide layer of TiO 2 , make it an ideal orthopedic material that bonds directly to the adjacent bone surface (11,12). Fabrication of the nanostructured titanium dioxide (TiO 2 ) nanotube arrays has been a primary subject of investigation lately because of the wide range of TiO 2 applications in the fields of solar cells (13-16), photocatalysis (17-19), photoelectrolysis (20), sensors (21,22), and b...

Extracellular matrix (ECM) and growth factor signaling networks are known to interact in a complex manner. Therefore, reductionist approaches that test the cellular response to individual ECM components and growth factors cannot be used to predict the response to more complex mixtures without knowledge of the underlying signaling network. To address this challenge, we have developed a technology platform to experimentally probe the interactions of ECM components and soluble growth factors on stem cell fate. We present a multiwell microarray platform that allows 1200 simultaneous experiments on 240 unique signaling environments. Mixtures of extracellular matrix (fibronectin, laminin, collagen I, collagen III, collagen IV) are arrayed using a robotic spotter and arranged in a multiwell format. Embryonic stem (ES) cells adhere to ECM spots and are cultured in mixtures of soluble factors [wnt3a, activin A, bone morphogenetic protein-4 (BMP-4), and fibroblast growth factor-4 (FGF-4)]. Differentiation along the cardiac lineage is monitored by myosin heavy chain-alpha-green fluorescent protein (MHC alpha-GFP) reporter expression as compared to growth by monitoring nuclear DNA, and both signals are quantified using a confocal microarray scanner. In developing the platform, we characterized the amount of deposited protein, the fluorescent readout of GFP expression and DNA content, and the use of a laser-based scanner as compared to fluorescent microscopy for data acquisition. The effects of growth factors on growth and differentiation are consistent with previously reported literature, and preliminary evidence of interactive signaling is illuminated. This versatile technique is compatible with virtually any set of insoluble and soluble cues, leverages existing software and hardware, and represents a step toward developing the 'systems biology' of stem cells.

Background:The increasing usage of statins (the 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors) has revealed a number of unexpected beneficial effects, including a reduction in cancer risk.Methods:We investigated the direct anticancer effects of different statins approved for clinical use on human breast and brain cancer cells. We also explored the effects of statins on cancer cells using in silico simulations.Results:In vitro studies showed that cerivastatin, pitavastatin, and fluvastatin were the most potent anti-proliferative, autophagy inducing agents in human cancer cells including stem cell-like primary glioblastoma cell lines. Consistently, pitavastatin was more effective than fluvastatin in inhibiting U87 tumour growth in vivo. Intraperitoneal injection was much better than oral administration in delaying glioblastoma growth. Following statin treatment, tumour cells were rescued by adding mevalonate and geranylgeranyl pyrophosphate. Knockdown of geranylgeranyl pyrophosphate synthetase-1 also induced strong cell autophagy and cell death in vitro and reduced U87 tumour growth in vivo. These data demonstrate that statins main effect is via targeting the mevalonate synthesis pathway in tumour cells.Conclusions:Our study demonstrates the potent anticancer effects of statins. These safe and well-tolerated drugs need to be further investigated as cancer chemotherapeutics in comprehensive clinical studies.

We use a novel 3D inter-/intracellular force microscopy technique based on 3D traction force microscopy to measure the cell-cell junctional and intracellular tensions in subconfluent and confluent vascular endothelial cell (EC) monolayers under static and shear flow conditions. We found that z-direction cell-cell junctional tensions are higher in confluent EC monolayers than those in subconfluent ECs, which cannot be revealed in the previous 2D methods. Under static conditions, subconfluent cells are under spatially nonuniform tensions, whereas cells in confluent monolayers are under uniform tensions. The shear modulations of EC cytoskeletal remodeling, extracellular matrix (ECM) adhesions, and cell-cell junctions lead to significant changes in intracellular tensions. When a confluent monolayer is subjected to flow shear stresses with a high forward component comparable to that seen in the straight part of the arterial system, the intracellular and junction tensions preferentially increase along the flow direction over time, which may be related to the relocation of adherens junction proteins. The increases in intracellular tensions are shown to be a result of chemomechanical responses of the ECs under flow shear rather than a direct result of mechanical loading. In contrast, the intracellular tensions do not show a preferential orientation under oscillatory flow with a very low mean shear. These differences in the directionality and magnitude of intracellular tensions may modulate translation and transcription of ECs under different flow patterns, thus affecting their susceptibility for atherogenesis.cell alignment | endothelial monolayer | finite element method | fluid shear stress | junctional force B lood vessels are constantly exposed to hemodynamic forces imposed by the blood flow and pressure. Vascular endothelial cells (ECs), which line the inner blood vessel wall, bear the shear stress resulting from the blood flow. Responses of ECs to hemodynamic forces play significant roles in vascular homeostasis in health and disease. Atherosclerotic lesions are preferentially localized in regions, such as arterial branch points, where the ECs are subjected to disturbed flow consisting of flow separation, reversal, and reattachment (1-3). The reattachment area, which is exposed to a low shear stress magnitude and significant oscillatory reversal (i.e., the flow oscillates back and forth with little net direction), has random EC morphology and cytoskeletal organization, incomplete intercellular junctions, and pro-inflammatory and pro-atherogenic phenotypes (1). In contrast, ECs in the straight part of the arterial tree, which is generally spared from atherosclerosis, are exposed to high shear flow with a large net mean direction and have parallel cell orientation, aligned cytoskeletal fibers, and intact junctions. Studies on cultured ECs have advanced the knowledge of how different flow conditions regulate EC functions (1, 4, 5) and provided evidence for the biomedical importance of EC responses to flow shear. The b...