In-vivo observation of cells with a combined high-resolution multiphoton–acoustic scanning microscope

High-resolution multiphoton tomography and fluorescence lifetime imaging of UVB-induced cellular damage on cultured fibroblasts producing fibres

BACKGROUND

Multiphoton tomography (MPT) is suitable to perform both ex vivo and in vivo investigations of living skin and cell cultures with submicron resolution. Fluorescence lifetime imaging (FLIM) generates image contrast between different states of tissue characterized by various fluorescence decay rates. Our purpose was to combine MPT and FLIM to evaluate fibroblasts and collagen fibres produced in vitro.

METHODS

Fibroblast cultures, 2-4 days old, at a subconfluent stage, were evaluated before and after irradiation with a single UVB dose. One month old cultures stimulated with ascorbic acid were also assessed.

RESULTS

After UVB radiation, fibroblasts appear irregular in size, lose their alignment and show a decrease in fluorescence lifetime. One month-old fibroblasts, producing collagen fibres after stimulation with ascorbic acid, appear as small roundish structures intermingled by filaments showing a granular arrangement.

CONCLUSION

The combination of MPT and FLIM may be useful for the in vitro study of cell modifications induced by injurious or protective agents and drugs.

Clinical application of multiphoton tomography in combination with high-frequency ultrasound for evaluation of skin diseases

The first-ever application of high-frequency ultrasound combined with multiphoton tomography (MPT) and dermoscopy in a clinical trial is reported. 47 patients with different dermatoses such as benign and malign skin cancers, connective tissue diseases, inflammatory skin diseases, and autoimmune bullous skin diseases have been investigated with (i) state-of-the-art and highly sophisticated ultrasound systems for dermatology, (ii) the femtosecond laser multiphoton tomograph and (iii) dermoscopes. Dermoscopy provides two-dimensional color images of the skin surface with a magnification up to 70 x. Depending on the ultrasonic frequencies from 7.5 MHz to 100 MHz, the signal depth varies from about 1 mm to 80 mm. Vertical ultrasound wide-field images provide fast information on depth and volume of the lesion. The 100 MHz ultrasound allows imaging with resolutions down to 16 μm (axial) and 32 μm (lateral). Multiphoton tomography provides 0.36 x 0.36 x 0.001 mm³ horizontal optical sections of a particular region of interest with submicron resolution down to 200 μm tissue depth. The autofluorescence of mitochondrial coenzymes, keratin, melanin, and elastin as well as the network of collagen structures can be imaged. The combination of ultrasound and MPT opens novel synergistic possibilities in diagnostics of skin diseases with a special focus on the early detection of skin cancer as well as the evaluation of treatments.