Analysis of focal adhesions and cytoskeleton by custom microarray

Towards modular engineering of cell signalling: Topographically-textured microparticles induce osteogenesis via activation of canonical hedgehog signalling

Polymer microparticles possess great potential as functional building blocks for advanced bottom-up engineering of complex tissues. Tailoring the three-dimensional architectural features of culture substrates has been shown to induce osteogenesis in mesenchymal stem cells in vitro, but the molecular mechanisms underpinning this remain unclear. This study proposes a mechanism linking the activation of Hedgehog signalling to the osteoinductive effect of surface-engineered, topographically-textured polymeric microparticles. In this study, mesenchymal progenitor C3H10T1/2 cells were cultured on smooth and dimpled poly(D,l-lactide) microparticles to assess differences in viability, cellular morphology, proliferation, and expression of a range of Hedgehog signalling components and osteogenesis-related genes. Dimpled microparticles induced osteogenesis and activated the Hedgehog signalling pathway relative to smooth microparticles and 2D-cultured controls without the addition of exogenous biochemical factors. We observed upregulation of the osteogenesis markers Runt-related transcription factor2 (Runx2) and bone gamma-carboxyglutamate protein 2 (Bglap2), as well as the Hedgehog signalling components, glioma associated oncogene homolog 1 (Gli1), Patched1 (Ptch1), and Smoothened (Smo). Treatment with the Smo antagonist KAAD-cyclopamine confirmed the involvement of Smo in Gli1 target gene activation, with a significant reduction in the expression of Gli1, Runx2 and Bglap2 (p ≤ 0.001) following KAAD-cyclopamine treatment. Overall, our study demonstrates the role of the topographical microenvironment in the modulation of Hedgehog signalling, highlighting the potential for tailoring substrate topographical design to offer cell-instructive 3D microenvironments. Topographically-textured microparticles allow the modulation of Hedgehog signalling in vitro without adding exogenous biochemical agonists, thereby eliminating potential confounding artefacts in high-throughput drug screening applications.

Overexpression of the QKI Gene Promotes Differentiation of Goat Myoblasts into Myotubes

The QKI genes encode RNA-binding proteins regulating cell proliferation, differentiation, and apoptosis. The Goat QKI has six isoforms, but their roles in myogenesis are unclear. In this study, the six isoforms of the QKI gene were overexpressed in goat myoblast. Immunofluorescence, qPCR and Western blot were used to evaluate the effect of QKI on the differentiation of goat myoblast. An RNA-Seq was performed on the cells with the gain of the function from the major isoforms to screen differentially expressed genes (DEGs). The results show that six isoforms had different degrees of deletion in exons 6 and 7, and caused the appearance of different types of encoded amino acids. The expression levels of the QKI-1 and QKI-5 groups were upregulated in the biceps femoris and latissimus dorsi muscle tissues compared with those of the QKI-4, QKI-7, QKI-3 and QKI-6 groups. After 6 d of myoblast differentiation, QKI-5 and the myogenic differentiators MyoG, MyoD, and MyHC were upregulated. Compared to the negative control group, QKI promoted myotube differentiation and the myoblasts overexpressing QKI-5 formed large, abundant myotubes. In summary, we identified that the overexpression of the QKI gene promotes goat-myoblast differentiation and that QKI-5 is the major isoform, with a key role. The RNA-Seq screened 76 upregulated and 123 downregulated DEGs between the negative control and the QKI-5-overexpressing goat myoblasts after d 6 of differentiation. The GO and KEGG analyses associated the downregulated DEGs with muscle-related biological functions. Only the pathways related to muscle growth and development were enriched. This study provides a theoretical basis for further exploring the regulatory mechanism of QKI in skeletal-muscle development in goats.

Nischarin regulates focal adhesion and Invadopodia formation in breast cancer cells

Background

During metastasis, tumor cells move through the tracks of extracellular matrix (ECM). Focal adhesions (FAs) are the protein complexes that link the cell cytoskeleton to the ECM and their presence is necessary for cell attachment. The tumor suppressor Nischarin interacts with a number of signaling proteins such as Integrin α5, PAK1, LIMK1, LKB1, and Rac1 to prevent cancer cell migration. Although previous findings have shown that Nischarin exerts this migratory inhibition by interacting with other proteins, the effects of these interactions on the entire FA machinery are unknown.

Methods

RT-PCR, Western Blotting, invadopodia assays, and immunofluorescence were used to examine FA gene expression and determine whether Nischarin affects cell attachment, as well as the proteins that regulate it.

Results

Our data show that Nischarin prevents cell migration and invasion by altering the expression of key focal adhesion proteins. Furthermore, we have found that Nischarin-expressing cells have reduced ability to attach the ECM, which in turn leads to a decrease in invadopodia-mediated matrix degradation.

Conclusions

These experiments demonstrate an important role of Nischarin in regulating cell attachment, which adds to our understanding of the early events of the metastatic process in breast cancer.

Electronic supplementary material

The online version of this article (10.1186/s12943-018-0764-6) contains supplementary material, which is available to authorized users.

Adult Stem Cell Responses to Nanostimuli

Adult or mesenchymal stem cells (MSCs) have been found in different tissues in the body, residing in stem cell microenvironments called "stem cell niches". They play different roles but their main activity is to maintain tissue homeostasis and repair throughout the lifetime of an organism. Their ability to differentiate into different cell types makes them an ideal tool to study tissue development and to use them in cell-based therapies. This differentiation process is subject to both internal and external forces at the nanoscale level and this response of stem cells to nanostimuli is the focus of this review.

The interaction between nanoscale surface features and mechanical loading and its effect on osteoblast-like cells behavior

Osteoblasts respond to mechanical stimulation by changing morphology, gene expression and matrix mineralization. Introducing surface topography on biomaterials, independently of mechanical loading, has been reported to give similar effects. In the current study, using a nanotextured surface, and mechanical loading, we aimed to develop a multi-factorial model in which both parameters interact. Mechanical stimulation to osteoblast-like cells was applied by longitudinal stretch in parallel direction to the nanotexture (300 nm wide and 60 nm deep grooves), with frequency of 1 Hz and stretch magnitude varying from 1% to 8%. Scanning electron microscopy showed that osteoblast-like cells subjected to mechanical loading oriented perpendicularly to the stretch direction. When cultured on nanotextured surfaces, cells aligned parallel to the texture. However, the parallel cell direction to the nanotextured surface was lost and turned to perpendicular when parallel stretch to the nanotexture, greater than 3% was applied to the cells. This phenomenon could not be achieved when a texture with micro-sized dimensions was used. Moreover, a significant synergistic effect on upregulation of fibronectin and Cfba was observed when dual stimulation was used. These findings can lead to a development of new biomimetic materials that can guide morphogenesis in tissue repair and bone remodeling.

Differential in-gel electrophoresis (DIGE) analysis of human bone marrow osteoprogenitor cell contact guidance

We have used a recent comparative proteomics technique, differential in-gel electrophoresis (DIGE), to study osteoprogenitor cell response to contact guidance in grooves. In order to increase protein output from small sample sizes, we used bioreactor culture before protein extraction and gel electrophoresis. Mass spectroscopy was used for protein identification. A number of distinct proteins were observed to exhibit significant changes in expression. These changes in protein expression suggest that the cells respond to tailored grooved topographies, with alterations in their proteome concurrent with changes in osteoprogenitor phenotype.

The beta integrins and cytoskeletal nanoimprinting

"Nanoimprinting", whereby topographical features are directly imprinted on or in cells, has recently been documented. The mechanism(s) underlying this may explain the cause of cell behavioural alterations as a result of contact with nanotopography. Integrin-mediated cell-substrate adhesions are likely to play a key role in this phenomenon due to their involvement in bidirectional signalling between extra- and intracellular environments. We describe the effects of blocking beta1 and beta3 integrin subunits on the ability of the cytoskeleton to conform to colloidal-derived nanotopography. Scanning electron and atomic force microscopy were used to characterise substrate nanofeatures. Nanofeature circularity was calculated relative to substrate topography and the cytoskeleton of cells cultured on patterned and planar surfaces in the presence/absence of beta1/beta3 integrin antibody. Cross-correlation investigations were similarly conducted by producing a target image relative to individual topographical nanofeatures. This was then compared with cytoskeletal patterning in the presence/absence of beta integrin antibodies. Inhibiting the beta1 subunits increased the ability of fibroblasts to nanoimprint, while inhibiting the beta3 subunit reduced nanoimprinting of the topography to the cell. Fibroblasts cultured on planar substrates also expressed some features sharing similarities with those observed in cells on the nanotopography, indicating an inherent cytoskeletal nanopatterning at high resolution.