Worth a Thousand Words
Cells need to be able to stick to each other in order to form tissues and organs of multicellular organisms. Without the process of cell adhesion, multicellular life would be impossible. When cells that are supposed to stick with each other don’t, or when cells that are not supposed to stick to each other do so, we are facing serious diseases and disorders. Understanding the mechanism of cell adhesion is thus necessary for improving treatments of such disorders.
The term ‘cellular adhesion’ is used not just for the phenomenon of cells binding to each other, but also for the binding of a cell to a natural of artfiicial surface or an extracellular matrix. This has been used in organ transplantation and, more recently, in biotechnology – production of artificial tissues for transplantation.
A number of natural and artificial materials have been tested as potential scaffolding for such bioengineered tissues. Silk from the silkworm is good, but tends to trigger an immune response. Silk from spiders, on the other hand, is readily accepted by the host and its mechanical properties make it a potentially superior material. Data to date are equivocal as to the ability of the cells to adhere to the spider silk and to further divide and spread.
In Interactions between Spider Silk and Cells – NIH/3T3 Fibroblasts Seeded on Miniature Weaving Frames by Joern W. Kuhbier, Christina Allmeling, Kerstin Reimers, Anja Hillmer, Cornelia Kasper, Bjoern Menger, Gudrun Brandes, Merlin Guggenheim and Peter M. Vogt raised some spiders and then milked them for silk, placing the silk in regular, geometrically simple patterns on a frame. They then photographed the cells (and controls, on other substrates) with several different microscopy and photography methods over a period of several days. What they discovered is that cells immediatelly and readily stick to the spider silk and further proliferate.
But this post is about the images, right? So here are some of the beautiful pictures of the cells (fibroblasts) adhering to the spider silk, as seen under various kinds of microscopes:
Several materials have been used for tissue engineering purposes, since the ideal matrix depends on the desired tissue. Silk biomaterials have come to focus due to their great mechanical properties. As untreated silkworm silk has been found to be quite immunogenic, an alternative could be spider silk. Not only does it own unique mechanical properties, its biocompatibility has been shown already in vivo. In our study, we used native spider dragline silk which is known as the strongest fibre in nature.
Steel frames were originally designed and manufactured and woven with spider silk, harvesting dragline silk directly out of the animal. After sterilization, scaffolds were seeded with fibroblasts to analyse cell proliferation and adhesion. Analysis of cell morphology and actin filament alignment clearly revealed adherence. Proliferation was measured by cell count as well as determination of relative fluorescence each after 1, 2, 3, and 5 days. Cell counts for native spider silk were also compared with those for trypsin-digested spider silk. Spider silk specimens displayed less proliferation than collagen- and fibronectin-coated cover slips, enzymatic treatment reduced adhesion and proliferation rates tendentially though not significantly. Nevertheless, proliferation could be proven with high significance (p<0.01).
Native spider silk does not require any modification to its application as a biomaterial that can rival any artificial material in terms of cell growth promoting properties. We could show adhesion mechanics on intracellular level. Additionally, proliferation kinetics were higher than in enzymatically digested controls, indicating that spider silk does not require modification. Recent findings concerning reduction of cell proliferation after exposure could not be met. As biotechnological production of the hierarchical composition of native spider silk fibres is still a challenge, our study has a pioneer role in researching cellular mechanics on native spider silk fibres.