Photodynamic therapy (PDT) promotes skin improvement according to many practitioners, however the immediately in
vivo assessment of its response remains clinically inaccessible. As a non-invasive modality, optical coherence
tomography (OCT) has been shown a feasible optical diagnostic technique that provides images in real time, avoiding
tissue biopsies. For this reason, our investigation focused on evaluates the PDT effect on a rodent model by means of
OCT. Therefore, a normal hairless mouse skin has undergone a single-session PDT, which was performed with topical 5-
aminolevulinic acid (ALA) cream using a red (630 nm) light emitting diode (LED) which reached the light dose of 75
J/cm2. As the optical imaging tool, an OCT (930 nm) with axial resolution of 6.0 microns in air was used, generating
images with contact to the mouse skin before, immediately after, 24 hours, and 2 weeks after the correspondent
procedure. Our result demonstrates that, within 24 hours after ALA-PDT, the mouse skin from the PDT group has shown
epidermal thickness (ET), which has substantially increased after 2 weeks from the treatment day. Moreover, the skin
surface has become evener after ALA-PDT. Concluding, this investigation demonstrates that the OCT is a feasible and
reliable technique that allows real-time cross-sectional imaging of skin, which can quantify an outcome and predict
whether the PDT reaches its goal.
Chronic exposure to ultraviolet (UV) sunlight causes premature skin aging. In light of this fact, photodynamic therapy
(PDT) is an emerging modality for treating cancer and other skin conditions, however its response on photoaged skin has
not been fully illustrated by means of histopathology. For this reason, the aim of this study was analyze whether PDT can
play a role on a mouse model of photoaging. Hence, SKH-1 hairless mice were randomly allocated in two groups, UV
and UV/PDT. The mice were daily exposed to an UV light source (280-400 nm: peak at 350 nm) for 8 weeks followed
by a single PDT session using 20% 5-aminolevulinic acid (ALA) topically. After the proper photosensitizer
accumulation within the tissue, a non-coherent red (635 nm) light was performed and, after 14 days, skin samples were
excised and processed for light microscopy, and their sections were stained with hematoxylin-eosin (HE) and Masson’s
Trichrome. As a result, we observed a substantial epidermal thickening and an improvement in dermal collagen density
by deposition of new collagen fibers on UV/PDT group. These findings strongly indicate epidermal and dermal
restoration, and consequently skin restoration. In conclusion, this study provides suitable evidences that PDT improves
the UV-irradiated hairless mice skin, supporting this technique as an efficient treatment for photoaged skin.
The purpose of this study is the assembly and characterization of a custom-made non-linear microscope. The microscope allows the adjustment for in vitro, in vivo and ex vivo imaging of biological samples. Two galvanometer mirrors conjugated by two spherical mirrors are used for the lateral scan and for the axial scan a piezoeletric stage is utilized. The excitation is done using a tunable femtosecond Ti: Sapphire laser. The light is focused in tissue by an objective lens 20X, water immersion, numerical aperture of 1.0, and working distance of 2.0 mm. The detection system is composed by a cut off filter that eliminates laser light back reflections and diverse dichroic filters can be chosen to split the emitted signal for the two photomultiplier detector. The calibration and resolution of the microscope was done using a stage micrometer with 10 μm divisions and fluorescent particle slide, respectively. Fluorescence and second harmonic generation images were performed using epithelial and hepatic tissue, the images have a sub-cellular spatial resolution. Further characterization and differentiation of tissue layers can be obtained by performing axial scanning. By means of the microscope it is possible to have a three dimensional reconstruction of tissues with sub-cellular resolution.
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