Non‐invasive Raman spectroscopy of cardiovascular matrix

The non‐invasive monitoring of extracellular matrix (ECM) remodeling and degradation processes is a great challenge for biomedical research. Although multiphoton imaging is suitable for ECM state identification in various tissues and organs, multiphoton‐based imaging modalities are associated with very high costs. Raman spectroscopy provides a less expensive, non‐contact, real‐time method for in situ applications. Here, we employed Raman spectroscopy for the detection of heart valve ECM. We obtained porcine hearts (n=6) from a local slaughterhouse and dissected the aortic valves. Valve leaflets were measured either directly as non‐treated controls or the tissues were enzymatically treated with collagenase for 15 and 30 minutes at 37°C as well as 17 hours at room temperature before analysis (each n=30). In our experiments, we focused on the collagen‐rich layer of the leaflets (=fibrosa). Comparing the fingerprint region (400–1800 cm‐1) of the Raman spectra of control and treated valve leaflets, we detected no significant differences based on Raman shifts. However, interestingly and similar to multiphoton microscopy, we identified significant changes in the signal intensities based on the stage of ECM remodeling. Increasing collagen degradation translated into decreasing Raman signal intensities. Our data demonstrate that Raman microscopy is a promising non‐invasive tool to probe ECM state in situ. Grant Funding Source : Fraunhofer Gesellschaft