Biomedical subjects

Kate Poole

Publications and source records attributed to Kate Poole.

4 recordsLinked to original sources

PubMed2006

A new technical approach to quantify cell-cell adhesion forces by AFM.

Cell-cell adhesion is a complex process that is involved in the tethering of cells, cell-cell communication, tissue formation, cell migration and the development and metastasis of tumors. Given the heterogeneous and complex nature of cell surfaces it has previously proved difficult to characterize individual cell-cell adhesion events. Force spectroscopy, using an atomic force microscope, is capable of resolving such individual cell-cell binding events, but has previously been limited in its application due to insufficient effective pulling distances. Extended pulling range is critical in studying cell-cell interactions due to the potential for large cell deformations. Here we describe an approach to such experiments, where the sample stage can be moved 100 microm in the z-direction, by closed loop, linearized piezo elements. Such an approach enables an increase in pulling distance sufficient for the observation of long-distance cell-unbinding events without reducing the imaging capabilities of the atomic force microscope. The atomic force microscope head and the piezo-driven sample stage are installed on an inverted optical microscope fitted with a piezo-driven objective, to allow the monitoring of cell morphology by conventional light microscopy, concomitant with force spectroscopy measurements. We have used the example of the WM115 melanoma cell line binding to human umbilical vein endothelial cells to demonstrate the capabilities of this system and the necessity for such an extended pulling range when quantifying cell-cell adhesion events.

Cell Adhesion↗

PubMed2005

Molecular-scale topographic cues induce the orientation and directional movement of fibroblasts on two-dimensional collagen surfaces.

Collagen fibres within the extracellular matrix lend tensile strength to tissues and form a functional scaffold for cells. Cells can move directionally along the axis of fibrous structures, in a process important in wound healing and cell migration. The precise nature of the structural cues within the collagen fibrils that can direct cell movement are not known. We have investigated the structural features of collagen that are required for directional motility of mouse dermal fibroblasts, by analysing cell movement on two-dimensional collagen surfaces. The surfaces were prepared with aligned fibrils of collagen type I, oriented in a predefined direction. These collagen-coated surfaces were generated with or without the characteristic 67 nm D-periodic banding. Quantitative analysis of cell morphodynamics showed a strong correlation of cell elongation and motional directionality with the orientation of D-periodic collagen microfibrils. Neither directed motility, nor cell body alignment, was observed on aligned collagen lacking D-periodicity, or on D-periodic collagen in the presence of peptide containing an RGD motif. The directional motility of fibroblast cells on aligned collagen type I fibrils cannot be attributed to contact guidance, but requires additional structural information. This allows us to postulate a physiological function for the 67 nm periodicity.

Animals↗

PubMed2004

The effect of raft lipid depletion on microvilli formation in MDCK cells, visualized by atomic force microscopy.

We have investigated whether raft lipids of Madin-Darby canine kidney (MDCK) cells play any role in microvilli maintenance using a combination of atomic force microscopy (AFM) and laser scanning confocal microscopy. MDCK cells were treated to reduce the amount of sphingolipids, cholesterol, or both and subsequently imaged, in buffer solution, using AFM. It was observed that inhibition of either sphingolipid or cholesterol biosynthesis led to a reduction in the number of microvilli on the surface of MDCK cells. However, this effect was not uniform across the monolayer, with some cells resembling those in untreated controls. The subsequent extraction of cholesterol from cells grown in the presence of inhibitors led to a further reduction in microvilli on the surface of the cells and, in some cases, resulted in monolayers devoid of full length microvilli. Significantly, smaller spikes were observed on the surface of the smoother cells.

Actins↗

PubMed2004

Creating nanoscopic collagen matrices using atomic force microscopy.

The atomic force microscope (AFM) is introduced as a biomolecular manipulation machine capable of assembling biological molecules into well-defined molecular structures. Native collagen molecules were mechanically directed into well-defined, two-dimensional templates exhibiting patterns with feature sizes ranging from a few nanometers to several hundreds of micrometers. The resulting nanostructured collagen matrices were only approximately 3-nm thick, exhibited an extreme mechanical stability, and maintained their properties over the time range of several months. Our results directly demonstrate the plasticity of biological assemblies and provide insight into the physical mechanisms by which biological structures may be organized by cells in vivo. These nanoscopic templates may serve as platforms on non-biological surfaces to direct molecular and cellular processes.

Animals↗