Optical coherence elastography of developing biological tissues

Biomechanical elastic properties are among the many variables used to characterize in vivo and in vitro tissues. Since these properties depend highly on the micro- and macro- scopic structural organization of tissue, it is useful to understand the mechanical properties and the alterations that occur when tissues are given biomechanical stimuli by applying external forces under different circumstances. Recent advances in tissue engineering have explored and utilized the significant role that externally-applied forces play during the development of engineered tissues. However, current methods for investigating the microscopic biomechanical changes in complex three-dimensional engineered tissues have been limited. Using Optical Coherence Elastography (OCE), we map the spatially-distributed mechanical displacements and strains in a representative model of a developing engineered tissue as cells begin to proliferate and attach within a three-dimensional collagen matrix. OCE is also preformed in the complex developing tissue of the Xenopus laevis (African frog) tadpole. Displacements were quantified by a cross-correlation algorithm on pre- and post- compression images, which were acquired using Optical Coherence Tomography (OCT). The differences in strain were observed over a certain period of time in various regions. OCE was able to differentiate changes in strain over time, which correspond with cell proliferation and matrix deposition as confirmed with histological observations. By anatomically mapping the regional variation of stiffness with micron resolution, it may be possible to provide new insight into the complex process by which engineered and natural tissues develop complex structures.