This year’s winning entry in the BPS Art of Sciences Image Contest was submitted by Chiara Peres, a postdoctoral student at the Istituto Italiano di Tecnologia in Genoa. The image shows collagen fibers in a radial section of an ex vivo bovine knee meniscus, which based on the votes, was a crowd pleaser among the BPS Meeting attendees. Peres took some time to provide some information about the image and the science it represents.
To produce this image, I used a custom made microscope for Second Harmonic Generation (SHG) Microscopy, a label free technique that exploits a second order nonlinear coherent optical process to image macromolecules with non-centrosymmetric structure, like collagen fibers. The picture is a mosaic of false colored images given by the overlay of the Backward and Forward SHG signal from the not-stained collagen fibers. In particular the image shows the big long branches of radial “tie” collagen fibers which pack together circumferential fibers, perpendicularly aligned with respect to the plane of the image.
I submitted this image because I love the hierarchical structure of the collagen and the harmonious branched, natural organization of the collagen fibers in this section of the meniscus that makes it to look like a big tree in a forest. I love also the fact that this image is “natural” and staining independent, being an image taken with a label-free technique, just collecting and false coloring the endogenous Second Harmonic Generation signal and the Two-Photon autofluorescence of the collagen, without any modification of the sample.
I also like this image because it is a good example of my research activity: I am working to improve and develop new microscopy techniques for biological applications. In particular I am using SHG microscopy as an imaging tool for morphological characterization. This image gives us an easy and immediate means to visualize at a glance the hierarchical structure, organization and orientation of collagen fibers in different areas of the bovine meniscus, the final aim of this study.
When others look at the image, I hope that this image reminds them of an expressionist painting of a forest, as if they were looking at a “micro Van Gogh” being, at the same time, an important method of tissue imaging which connects structures at the micro-scale to macroscopic properties.
Supporting Scientific Information
The cartilage meniscus regeneration after an injury is rarely successful, because the soft scaffolds used lack the mechanical properties to withstand immediate loading. For this reason a strong effort is being done in tissue engineering area to design and to develop a new scaffold that mimics the original tissue, selecting an appropriate material and paying close attention at its mechanical and structural properties. We are studying ex vivo bovine meniscus to realize a proper model for a meniscus scaffold. Our work provides insights on the link between microscopic organization of collagen in different areas of meniscus and its biomechanical macroscopic functions. These results offer, for example, precious guidance for tissue engineers to evaluate the good outcome of the artificial tissues.
In addition to tissue engineering applications, our work can be useful for medical applications. In fact collagen is essential for the biomechanical integrity and the physical properties of various biological tissues and organs. In this context SHG microscopy can be used for ex-vivo imaging of different kinds of collagenous tissues that have a crucial structural and mechanical role in organism. Not only collagen, but also the myosin presents in muscle sarcomeres is another biological macromolecules which generates second harmonic. So SHG microscopy can be used to visualize the organization of these macromolecules in tissue, giving a powerful tool to monitor tissue development and pathology diagnosis.