Quantitative characterization of developing collagen gels using optical coherence tomography

Abstract

Nondestructive optical imaging methods such as optical coherence tomography (OCT) have been proposed for characterizing engineered tissues such as collagen gels. In our study, OCT was used to image collagen gels with different seeding densities of smooth muscle cells (SMCs), including acellular gels, over a five-day period during which the gels contracted and became turbid with increased optical scattering. The gels were characterized quantitatively by their optical properties, specified by analysis of OCT data using a theoretical model. At 6 h, seeded cell density and scattering coefficient (mu(s)) were correlated, with mu(s) equal to 10.8 cm(-1)(10(6) cells mL). Seeded cell density and the scattering anisotropy (g) were uncorrelated. Over five days, the reflectivity in SMC gels gradually doubled with little change in optical attenuation, which indicated a decrease in g that increased backscatter, but only a small drop in mu(s). At five days, a subpopulation of sites on the gel showed substantially higher reflectivity (approximately a tenfold increase from the first 24 h). In summary, the increased turbidity of SMC gels that develops over time is due to a change in the structure of collagen, which affects g, and not simply due to a change in number density of collagen fibers due to contraction.

Ex Vivo Assessment of Vascular Response to Coronary Stents by Optical Frequency Domain Imaging

“…Stent-related hypersensitivity, although of rare occurrence, is also associated with a thrombogenic milieu that can lead to stent thrombosis (21 attenuation rate in the areas adjacent to the stent struts, as demonstrated in the OFDI signal analysis of this study, may help confirm hypersensitivity and future risk of thrombosis though prospective data is obviously needed to validate this claim. Using collagen-SMC gels studied in vitro, Levitz et al (25,26) recently showed that OCT signal reflection was potentially regulated by modifications of ECM through active matrix metalloproteinases, rather than cell or collagen density. Moreover, other studies involving animals, human atherectomy, and autopsy specimens of coronary stents also demonstrated changes in neointimal ECM over time (27)(28)(29).…”

Dynamic measurement of the optical properties of bovine enamel demineralization models using four-dimensional optical coherence tomography

“…These expressions have facilitated the use of OCT for quantitative evaluation of the optical properties of collagen gel tissue scaffolds 35 and biological tissues, 36 such as atherosclerotic plaques, 25,37,38 epithelial precancer, 39,40 dental caries, 11,14,41,42 and enamel structure. 43 These methods have been extended to the spatial mapping of μ OCT , a technique termed both parametric OCT 44 and scattering attenuation microscopy.…”

Polarized light imaging specifies the anisotropy of light scattering in the superficial layer of a tissue

“…from cultured cells causes g to drop as fiber bundles are broken down to small fibrils. 15,16 The effect of a gene mutation, osteogenesis imperfecta, in mouse skin is to drop g, as collagen fibrils fail to aggregate properly into fiber bundles. 17 Optical clearing of dermis using glycerol causes a drop in g, 18 which is tentatively thought to be due to increased fibril packing and order as the glycerol dessicates the collagen fiber bundles.…”