Optically characterizing vascular tissue constructs made with soluble vs. homogenized collagen

The ability of optical imaging techniques such as optical coherence tomography (OCT) to non-destructively characterize tissue-engineered constructs has generated enormous interest recently. We are testing the hypothesis that OCT data can be used to characterize the cellularity of collagen-based vascular constructs made from 2 types of collagen scaffold matrix: soluble collagen and homogenized collagen. Smooth muscle cells were seeded in these 2 scaffold matrices at a seeding density of 1×10⁶ cells/ml. The disk-shaped constructs were allowed to remodel and compact in the incubator for 96 hours. OCT imaging of the constructs occurred at 24 hour intervals. From the OCT data, the attenuation and reflectivity were evaluated by fitting the data to a theoretical model that relates the tissue optical properties (scattering coefficient and anisotropy factor) and imaging conditions to the OCT signal. The fitted optical properties were compared to the construct volume. Representative H&E histological sections of the constructs were used to assess cell proliferation. Our data showed that the optical properties of the solubilized constructs changed over time while those of the homogenized constructs did not, in agreement with the histology and compaction observations.