Figure 2
Raman spectroscopy of nodules within human aortic valve leaflet tissues in histology cryosections embedded in ultrapure water. (a) and (b), Paired high resolution BF (a) and CPOL (b) images showing the ___location (white dots) of Raman spot analyses (n = 9) of nodules that formed within original and altered collagen fibers and SMC myofilaments comprising the fibrosa tissue layer at the aortic margin of calcified aortic valve leaflets. Some nodules are beginning to exhibit geometric (euhedral) forms. Additional low magnification contextual images presented in SI Fig. 10. (c), A representative 300–1800 cm-1 Raman baseline spectrum from the nine spot analyses shown in (a). Expanded spectral regions are shown at 400–700 and 925–985 cm-1. Broad red and blue filled peak areas correspond to ACP and ACP transformation toward HAP Raman bands, respectively, resolved by performing peak fitting analyses [see experimental Sect. 42 for details]. Unfilled circles and solid black line represent raw data and their fit. These Raman analyses, in combination with the suite of other integrated analyses conducted in the present study, indicate that the nodules are composed of metastable ACP and ACP at the threshold of transforming toward HAP. ACP = amorphous calcium phosphate. HAP = hydroxyapatite. SMC = smooth muscle cell.BF = bright field. HCS = histology cryosection. CPOL = circular polarization.
