In vivo TPEF-SHG microscopy for detecting collagen remodeling after laser micro-ablative fractional resurfacing treatment

Second-harmonic generation and two-photon excited fluorescence microscopy were used in combination in the same optical system for in vivo imaging. This work aimed at detecting collagen remodeling and reorganization in living subjects following laser micro-ablative fractional resurfacing treatment. Treated regions in the forearm of volunteers covering a wide age range were imaged with two-photon microscopy before and forty days after the treatment. A strong age-dependence of the treatment effectiveness was found, demonstrating a negligible effect in very young subjects (age < 35 years) face to a mild effect on mid-age subjects (35 years < age < 60 years) and a significant synthesis of new collagen in the most aged subjects (age > 60 years). The amount of newly synthesized collagen as well as its organization were evaluated by means of both visual examination of two-photon images and an image analysis methods, based on second-harmonic to autofluorescence ageing index of dermis (SAAID) scoring. The obtained results demonstrate the performance of laser fractional micro ablative resurfacing without the need for an invasive biopsy.