The majority of tissue related diseases are known to alter tissue structure. During the last 10 years, increasing efforts have been put into the development of new techniques that could provide in vivo information on tissue morphology. Optical coherence tomography (OCT) is known to provide structural information in situ. However, there is also a strong demand to evaluate the mechanical properties of biological tissues in vivo. To address this need, we combined microindentation with non-invasive OCT imaging to determine spatiotemporal distributions of mechanical properties of in vivo and formaldehyde fixed chicken embryos. The use of OCT allows us to quantify changes in tissue morphology and to localize indentation at specific regions. To measure viscoelastic properties of living tissue, indentation tests are simultaneously performed on in vivo HH8-HH12 chicken embryos using a cantilever based force transducer. After performing live tissue indentation, we probed the properties of formaldehyde fixed embryo. The same general contrasts of elasticity between different histological regions were found, but the average value was found to be higher for the fixed sample. Furthermore, with this technique it is possible to follow the remodeling of tissue elastic properties during embryonic development, measure viscoelastic properties of living tissue, and investigate correlations between local mechanical properties during cell migration and differentiation. This method is applicable to a wide variety of biological samples and can provide new insight to better understand the link between the mechanical response of tissue and its biological structure, and to compare diseased tissues with healthy one.
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