Corneal biomechanical response following collagen cross-linking with Rose Bengal-green light and riboflavin-UVA

10 págs.; 9 figs. ; Open Access funded by Creative Commons Atribution Licence 4.0To compare the biomechanical corneal response of two different corneal cross-linking (CXL) treatments, rose bengal¿green light (RGX) and riboflavin-UVA (UVX), using noninvasive imaging.Supported by the European Research Council under the European Union’s Seventh Framework Program ERC Advanced Grant agreement no. 294099; Comunidad de Madrid and EU Marie Curie COFUND program (FP7/2007-2013/REA 291820); and the Spanish Government Grant FIS2014-56643-R.Peer Reviewe

Endogenous Skin Fluorescence Includes Bands that may Serve as Quantitative Markers of Aging and Photoaging

Aging and photoaging cause distinct changes in skin cells and extracellular matrix. Changes in hairless mouse skin as a function of age and chronic UVB exposure were investigated by fluorescence excitation spectroscopy. Fluorescence excitation spectra were measured in vivo, on heat-separated epidermis and dermis, and on extracts of mouse skin to characterize the absorption spectra of the emitting chromophores. Fluorescence excitation spectra obtained in vivo on 6 wk old mouse skin had maxima at 295, 340, and 360 nm; the 295 nm band was the dominant band. Using heat separated tissue, the 295 nm band predominantly originated in the epidermis and the bands at 340 and 360 nm originated in the dermis. The 295 nm band was assigned to tryptophan fluorescence, the 340 nm band to pepsin digestable collagen cross-links fluorescence and the 360 nm band to collagenase digestable collagen cross-links fluorescence. Fluorescence excitation maxima remained unchanged in chronologically aged mice (34–38 wk old), whereas the 295 nm band decreased in intensity with age and the 340 nm band increased in intensity with age. In contrast, fluorescence excitation spectra of chronically UVB exposed mice showed a large increase in the 295 nm band compared with age-matched controls and the bands at 340 and 350 nm were no longer distinct. Two new bands appeared in the chronically exposed mice at 270 nm and at 305 nm. These reproducible changes in skin autofluorescence suggest that aging causes predictable alterations in both epidermal and dermal fluorescence, whereas chronic UV exposure induces the appearance of new fluorphores

Mechanism of Tetracycline Phototoxicity

Studies were made to determine factors important in the phototoxicity mechanism of 7 clinically used tetracyclines (TC). The clinical phototoxicity, the rates of photochemical degradation, and the in vitro phototoxicity of the TCs were qualitatively but not quantitatively correlated. Phototoxicity in vitro was partially oxygen-dependent and possibly singlet oxygen is involved. The contribution of photoproducts to the phototoxic process may be the basis for the reported differences between the in vivo action spectrum and the absorption spectrum of demethylchlorotetracycline. A mechanistic model for in vivo phototoxicity is proposed where the absorption of UVA radiation by TC leads to at least two main processes: (i) photosensitization by the drug of biologic molecules to cause phototoxicity; (ii) production of one or more photoproducts which photosensitize by absorption of visible radiation

Contribution to the study of the factors influencing Maillard reaction with dihydroxyacetone in order to induce cutaneous pigmentation

PARIS-BIUP (751062107) / SudocSudocFranceF

Corneal Collagen Ordering After In Vivo Rose Bengal and Riboflavin Cross-Linking

Producción CientíficaPurpose: Photoactivated cornea collagen cross-linking (CXL) increases corneal stiffness by initiating formation of covalent bonds between stromal proteins. Because CXL depends on diffusion to distribute the photoinitiator, a gradient of CXL efficiency with depth is expected that may affect the degree of stromal collagen organization. We used second harmonic generation (SHG) microscopy to investigate the differences in stromal collagen organization in rabbit eyes after corneal CXL in vivo as a function of depth and time after surgery. Methods: Rabbit corneas were treated in vivo with either riboflavin/UV radiation (UVX) or Rose Bengal/green light (RGX) and evaluated 1 and 2 months after CXL. Collagen fibers were imaged with a custom-built SHG scanning microscope through the central cornea (350 µm depth, 225 × 225 µm en face images). The order coefficient (OC), a metric for collagen organization, and total SHG signal were computed for each depth and compared between treatments. Results: OC values of CXL-treated corneas were larger than untreated corneas by 27% and 20% after 1 month and 38% and 33% after 2 months for the RGX and UVX, respectively. RGX OC values were larger than UVX OC values by 3% and 5% at 1 and 2 months. The SHG signal was higher in CXL corneas than untreated corneas, both at 1 and 2 months after surgery, by 18% and 26% and 1% and 10% for RGX and UVX, respectively. Conclusions: Increased OC corresponded with increased collagen fiber organization in CXL corneas. Changes in collagen organization parallel reported temporal changes in cornea stiffness after CXL and also, surprisingly, are detected deeper in the stroma than the regions stiffened by collagen cross-links.European Research Council Advanced Grant ERC-2011-AdG Ref. 294099, Spanish Government Grants FIS2014-56643 and FIS2017-84753-R, H2020 Research and Innovation Action H2020-ICT-2017 Ref. 779960