Background and Objectives: Keratoconus is a disease characterized by progressive steepening and thinning of the cornea, altering visual acuity and sometimes potentiating the need for corneal transplant if the disease progresses.1–3 Corneal crosslinking, a procedure that uses topical riboflavin and UV light to increase the stiffness of the cornea through the creation of collagen crosslinks was recently approved by the FDA for use in the U.S. The objective of the present study was to investigate whether endogenous collagen fluorescence changes following treatment can be correlated to alterations in the stiffness of the cornea, thereby guiding treatment parameters. Study Design and Results: 78 ex-vivo rabbit eyes divided into three groups: riboflavin solution plus UV irradiation, dextran solution plus UV irradiation, and riboflavin solution only. An additional group of eyes received no treatment. The epithelium was removed from each sample and topical riboflavin was applied. Eyes were irradiated with a 365 nm black ray UV lamp for various treatment times, ranging from half the clinical treatment time to three times the length. Mechanical testing was performed to determine the force/displacement relationship for the various treatment times. Fluorescence spectral changes following treatment corresponded with changes in stiffness. In particular, a decrease in the value of fluorescence intensity at 290/340 nm excitation/emission wavelengths corresponded to an increase in corneal stiffness following treatment. It may be possible to use fluorescence spectral changes of endogenous corneal crosslinks to evaluate mechanical stiffness changes non-invasively.
The aim of our study was to identify fluorescence excitation-emission pairs correlated with atherosclerotic
pathology in ex-vivo human aorta. Wide-field images of atherosclerotic human aorta were captured using UV and
visible excitation and emission wavelength pairs of several known fluorophores to investigate correspondence with
gross pathologic features. Fluorescence spectroscopy and histology were performed on 21 aortic samples. A matrix
of Pearson correlation coefficients were determined for the relationship between relevant histologic features and the
intensity of emission for 427 wavelength pairs. A multiple linear regression analysis indicated that elastin (370/460
nm) and tryptophan (290/340 nm) fluorescence predicted 58% of the variance in intima thickness (R-squared =
0.588, F(2,18) = 12.8, p=.0003), and 48% of the variance in media thickness (R-squared = 0.483, F(2,18) = 8.42,
p=.002), suggesting that endogenous fluorescence intensity at these wavelengths can be utilized for improved
pathologic characterization of atherosclerotic plaques.
Background and Objectives: We have previously demonstrated the efficacy of a non-invasive, non-contact, fast and
simple but robust fluorescence imaging (u-FEI) method to monitor the healing of skin wounds in vitro. This system can
image highly-proliferating cellular processes (295/340 nm excitation/emission wavelengths) to study epithelialization in
a cultured wound model. The objective of the current work is to evaluate the suitability of u-FEI for monitoring wound
re-epithelialization in vivo.
Study Design: Full-thickness wounds were created in the tail of rats and imaged weekly using u-FEI at 295/340nm
excitation/emission wavelengths. Histology was used to investigate the correlation between the spatial distribution and
intensity of fluorescence and the extent of wound epithelialization. In addition, the expression of the nuclear protein
Ki67 was used to confirm the association between the proliferation of keratinocyte cells and the intensity of
fluorescence.
Results: Keratinocytes forming neo-epidermis exhibited higher fluorescence intensity than the keratinocytes not
involved in re-epithelialization. In full-thickness wounds the fluorescence first appeared at the wound edge where
keratinocytes initiated the epithelialization process. Fluorescence intensity increased towards the center as the
keratinocytes partially covered the wound. As the wound healed, fluorescence decreased at the edges and was present
only at the center as the keratinocytes completely covered the wound at day 21. Histology demonstrated that changes in
fluorescence intensity from the 295/340nm band corresponded to newly formed epidermis.
Conclusions: u-FEI at 295/340nm allows visualization of proliferating keratinocyte cells during re-epithelialization of
wounds in vivo, potentially providing a quantitative, objective and simple method for evaluating wound closure in the
clinic.
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