Skin and subcutaneous fat morphology alterations under the LED or laser treatment in rats in vivo

The main objective of this work is to quantify the impact of photodynamic/photothermal treatment by using visible LED and NIR laser irradiation through the skin of subcutaneous fat in vivo followed up by tissue sampling and histology. The optical method may provide reduction of regional or site‐specific accumulations of abdominal or subcutaneous adipose tissue precisely and least‐invasively by inducing cell apoptosis and controlled necrosis of fat tissue. As photodynamic/photothermal adipose tissue sensitizers Brilliant Green (BG) or Indocyanine Green (ICG) dyes were injected subcutaneously in rats. The CW LED device (625 nm) or CW diode laser (808 nm) were used as light sources, respectively. Biopsies of skin together with subcutaneous tissues were taken for histology. The combined action BG‐staining and LED‐irradiation (BG + LED) or ICG‐staining and NIR‐laser irradiation (ICG + NIR) causes pronounced signs of damage of adipose tissue characterized by a strong stretching, thinning, folding and undulating of cell membranes and appearance of necrotic areas. As a posttreatment after 14 days only connective tissue was observed at the site of necrotic areas. The data obtained are important for safe light treatment of site‐specific fat accumulations, including cellulite. This work provides a basis for the development of fat lipolysis technologies and to move them to clinical applications. Schematics of animal experiment. The combined photodynamic/photothermal in vivo treatment of subcutaneous adipose tissue (AT) is proposed. The effects of transcutaneous irradiation of photosensitized AT with visible LED or NIR laser (DL) are compared. Pronounced signs of selective damage to subcutaneous AT were obtained for such photosensitizers as Brilliant Green (BG) or Indocyanine Green (ICG) delivered by subcutaneous injection. The results obtained open up the prospect for introducing new minimally invasive optical liposuction methods into the clinic.