Turbid polarimetry for tissue characterization

We have developed a novel turbid polarimetry platform for characterization of biological tissues. Currently, we are exploring the use of this platform for characterization of the extracellular matrix particularly for use in monitoring regenerative treatments of myocardial infarctions. Collagen is a fibrous protein and exhibits birefringence due to different refractive indices parallel and perpendicular to the direction of the fibers. As a result, changes in the collagen content and organization in the tissue lead to changes in birefringence. We demonstrate our ability to measure these extracellular changes in vivo using a mouse dorsal window chamber model. Collagenase was injected into a region of the chamber to denature the extracellular matrix. Birefringence measurements show a large decrease in birefringence associated with the destruction of collagen fibers. Birefringence measurements were also made through ex vivo myocardial tissues from rats with induced myocardial infarctions including a number that had undergone regenerative treatment with mesenchymal stem cells. Results show a decrease in birefringence from normal to infracted myocardium, indicating a decrease in tissue organization associated with scar formation, however, an increase in birefringence was seen in those myocardial tissues that had undergone regenerative treatment indicating reorganization of tissue structure.