1,721,125 research outputs found
Harnessing nanotopography and integrin–matrix interactions to influence stem cell fate
No full textStem cells respond to nanoscale surface features, with changes in cell growth and differentiation mediated by alterations in cell adhesion. The interaction of nanotopographical features with integrin receptors in the cells' focal adhesions alters how the cells adhere to materials surfaces, and defines cell fate through changes in both cell biochemistry and cell morphology. In this Review, we discuss how cell adhesions interact with nanotopography, and we provide insight as to how materials scientists can exploit these interactions to direct stem cell fate and to understand how the behaviour of stem cells in their niche can be controlled. We expect knowledge gained from the study of cell–nanotopography interactions to accelerate the development of next-generation stem cell culture materials and implant interfaces, and to fuel discovery of stem cell therapeutics to support regenerative therapies
A genomics approach in determining nanotopographical effects on MSC phenotype
Full text linkTopography and its effects on cell adhesion, morphology, growth and differentiation are well documented. Thus, current advances with the use of nanotopographies offer promising results in the field of regenerative medicine. Studies have also shown nanotopographies to have strong effects on stem cell self-renewal and differentiation. What is less clear however is what mechanotransductive mechanisms are employed by the cells to facilitate such changes. In fastidious cell types, it has been suggested that direct mechanotransduction producing morphological changes in the nucleus, nucleoskeleton and chromosomes themselves may be central to cell responses to topography. In this report we move these studies into human skeletal or mesenchymal stem cells and propose that direct (mechanical) signalling is important in the early stages of tuning stem cell fate to nanotopography. Using fluorescence in situ hybridization (FISH) and Affymetrix arrays we have evidence that nanotopography stimulates changes in nuclear organisation that can be linked to spatially regulated genes expression with a particular focus on phenotypical genes. For example, chromosome 1 was seen to display the largest numbers of gene deregulations and also a concomitant change in nuclear positioning in response to nanotopography. Plotting of deregulated genes in reference to band positioning showed that topographically related changes tend to happen towards the telomeric ends of the chromosomes, where bone related genes are generally clustered. Such an approach offers a better understanding of cell-surface interaction and, critically, provides new insights of how to control stem cell differentiation with future applications in areas including regenerative medicine
Proteomic analysis of human osteoprogenitor response to disordered nanotopography
No full textPrevious studies have shown that microgroove-initiated contact guidance can induce bone formation in osteoprogenitor cells (OPGs) and produce changes in the cell proteome. For proteomic analysis, differential in-gel electrophoresis (DIGE) can be used as a powerful diagnostic method to provide comparable data between the proteomic profiles of cells cultured in different conditions. This study focuses on the response of OPGs to a novel nanoscale pit topography with osteoinductive properties compared with planar controls. Disordered near-square nanopits with 120nm diameter and 100nm depth with an average 300nm centre-to-centre spacing (300nm spaced pits in square pattern, but with ±50nm disorder) were fabricated on 1+—1cm<sup>2</sup> polycaprolactone sheets. Human OPGs were seeded onto the test materials. DIGE analysis revealed changes in the expression of a number of distinct proteins, including upregulation of actin isoforms, beta-galectin1, vimentin and procollagen-proline, 2-oxoglutarate 4-dioxygenase and prolyl 4-hydroxylase. Downregulation of enolase, caldesmon, zyxin, GRASP55, Hsp70 (BiP/GRP78), RNH1, cathepsin D and Hsp27 was also observed. The differences in cell morphology and mineralization are also reported using histochemical technique
Superhydrophobicity and Superhydrophilicy of Regular Nanopatterns
No full textThe hydrophilicity, hydrophobicity, and sliding behaviour of water droplets on nanoasperities of controlled dimensions were investigated experimentally. We show that the "hemi-wicking"theory for hydrophilic SiO2 samples successfully predicts the experimental advancing angles and that the same patterns, after silanization, become superhydrophobic in agreement with the Cassie-Baxter and Wenzel theories. Our model tophographies have the same dimensional scale of some naturally occurring structures that exhibit similar wetting properties. Our results confirm that a forest of hydrophilic/hydrophobic slender pillars is the most effective superwettable/water-repellent configuration. It is shown that the shape and curvature of the edges of the aspertieis play an important role in determining the advancing angles
Osteoprogenitor response to low-adhesion nanotopographies originally fabricated by electron beam lithography
No full textIt is considered that cells can use filopodia, or microspikes, to locate sites suitable for adhesion. This has been investigated using a number of mature cell types, but, to our knowledge, not progenitor cells. Chemical and topographical cues on the underlying substrate are a useful tool for producing defined features for cells to respond to. In this study, arrays of nanopits with different symmetries (square or hexagonal arrays with 120 nm diameters, 300 nm center-centre spacings) and osteoprogenitor cells were considered. The pits were fabricated by ultra-high precision electron-beam lithography and then reproduced in polycarbonate by injection moulding with a nickel stamp. Using scanning electron and fluorescence microscopies, the initial interactions of the cells via filopodia have been observed, as have subsequent adhesion and cytoskeletal formation. The results showed increased filopodia interaction with the surrounding nanoarchitecture leading to a decrease in cell spreading, focal adhesion formation and cytoskeletal organisation
Air-trapping on biocompatible nanopatterns
No full textThe occurrence of air-trapping inside poly-eta-caprolactone nanopits was investigated by measuring the contact angles of water droplets on a set of defined nanotopographies. It is shown that the advancing angles follow the Cassie-Baxter theory, thus revealing the presence of air bubbles inside the biodegradable nanopatterns. The importance of these observations for the definition of hydrophilicity/hydrophobicity and in the context of in vitro cell behavior is discussed
Nanotopographical cues augment mesenchymal differentiation of human embryonic stem cells
Full text linkThe production of bone-forming osteogenic cells for research purposes or transplantation therapies remains a significant challenge. Using planar polycarbonate substrates lacking in topographical cues and substrates displaying a nanotopographical pattern, mesenchymal differentiation of human embryonic stem cells is directed in the absence of chemical factors and without induction of differentiation by embryoid body formation. Cells incubated on nanotopographical substrates show enhanced expression of mesenchymal or stromal markers and expression of early osteogenic progenitors at levels above those detected in cells on planar substrates in the same basal media. Evidence of epithelial-to-mesenchymal transition during substrate differentiation and DNA methylation changes akin to chemical induction are also observed. These studies provide a suitable approach to overcome regenerative medical challenges and describe a defined, reproducible platform for human embryonic stem cell differentiatio
The control of human mesenchymal cell differentiation using nanoscale symmetry and disorder
No full textA key tenet of bone tissue engineering is the development of scaffold materials that can stimulate stem cell differentiation in the absence of chemical treatment to become osteoblasts without compromising material properties. At present, conventional implant materials fail owing to encapsulation by soft tissue, rather than direct bone bonding. Here, we demonstrate the use of nanoscale disorder to stimulate human mesenchymal stem cells (MSCs) to produce bone mineral in vitro, in the absence of osteogenic supplements. This approach has similar efficiency to that of cells cultured with osteogenic media. In addition, the current studies show that topographically treated MSCs have a distinct differentiation profile compared with those treated with osteogenic media, which has implications for cell therapies.<br/
The use of nanoscale topography to modulate the dynamics of adhesion formation in primary osteoblasts and ERK/MAPK signalling in STRO-1+enriched skeletal stem cells
No full textThe physiochemical characteristics of a material with in vivo applications are critical for the clinical success of the implant and regulate both cellular adhesion and differentiated cellular function. Topographical modification of an orthopaedic implant may be a viable method to guide tissue integration and has been shown in vitro to dramatically influence osteogenesis, inhibit bone resorption and regulate integrin mediated cell adhesion. Integrins function as force dependant mechanotransducers, acting via the actin cytoskeleton to translate tension applied at the tissue level to changes in cellular function via intricate signalling pathways. In particular the ERK/MAPK signalling cascade is a known regulator of osteospecific differentiation and function. Here we investigate the effects of nanoscale pits and grooves on focal adhesion formation in human osteoblasts (HOBs) and the ERK/MAPK signalling pathway in mesenchymal populations. Nanopit arrays disrupted adhesion formation and cellular spreading in HOBs and impaired osteospecific differentiation in skeletal stem cells. HOBs cultured on 10 ?m wide groove/ridge arrays formed significantly less focal adhesions than cells cultured on planar substrates and displayed negligible differentiation along the osteospecific lineage, undergoing up-regulations in the expression of adipospecific genes. Conversely, osteospecific function was correlated to increased integrin mediated adhesion formation and cellular spreading as noted in HOBS cultured on 100 ?m wide groove arrays. Here osteospecific differentiation and function was linked to focal adhesion growth and FAK mediated activation of the ERK/MAPK signalling pathway in mesenchymal populations.<br/
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