Novel microscope for heart disease


Rebecca Pool

Tuesday, July 11, 2017 - 14:00
Image: Nanonet force microscope measures forces felt by cells growing in a matrix. 
US-based researchers have developed 'nanonet force microscopy' to measure the nanoscale forces exerted by or felt by cells when growing within an extracellular matrix.
Pioneered by Professor Amrinder Nain from Virginia Tech University, the platform was used by researchers at Virginia Tech and the University of Pittsburgh to quantify the cell-matrix adhesive forces that healthy muscle cells experience under stress.
The researchers hope the method will shed new light on smooth muscle cell biology and how to better treat cardiovascular disease.
As Nain points out, nanonet force microscopy can measure cell-matrix adhesive forces of a single cell, attached to multiple fibres, as it grows.
"A number of innovative methods exist to measure cell–matrix adhesive forces, but they have yet to accurately describe and quantify the intricate interplay of a cell and its fibrous extracellular matrix," he points out. "In cardiovascular pathologies, such as aortic aneurysm, new knowledge on the involvement of cell–matrix forces could lead to elucidation of disease mechanisms." 
The basic design of the platform resembles a net of nanofibres, fused at each intersection to form the so-called nanonet.
To measure cell-matrix adhesive forces, the researchers first attached single cells of human aortic smooth muscle to the fibres using a coating of fibronectin.
They then loosely stacked several layers of the nanonets inside a growth media chamber.
According to Nain, as the cells grow along and between the fibres of the nanonet, they pull the fibres with intrinsic contractile forces.
The researchers were able to determine the contractile, inside-out forces of the cells by measuring the deflections of fibres as the cells grew along them.
Meanwhile, external perturbation - outside-in - forces were measured when fibres were stretched with a probe to simulate forces within the heart acting upon the cells. 
The researchers also used phase contrast light microscopy to image these processes.
Nanonet force microscopy: f-actin (red), paxillin (green), and the nucleus (blue), scale bar: 20 nm.
As Nain highlights, the assembly aims to mimic, in as physiologically relevant a way as possible, what cells endure within the collagen fibres of the extra cellular matrix that supports cell growth.
Crucially, altering the fibre diameter, density, and spacing in a controlled and repeatable manner will allow the researchers to simulate conditions experienced by cells in many realistic situations.
“Nanonet force microscopy makes it possible to conduct drug testing at single-cell resolution to see if forces come back to normal phenotypic levels or if they are deviating in another way," highlights Nain. "Controlling the fibre diameter, spacing, and orientation brings a much needed new level of control and repeatability to interrogate matrix driven crosstalk within cells.”
Eventually, Nain and colleagues hope to establish a database of baseline forces for many types of cells that could be used to diagnose and treat disease.
Research is published in Molecular Biology of the Cell.
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