Histological and clinical studies on the effects of low to medium level infrared light therapy on human and mouse skin.
OBJECTIVE
Deep heating or denaturation of collagen has been reported to be necessary for nonablative skin rejuvenation. The purpose of this study was to examine whether thermally damaged collagen is an indispensable factor to increase the amount of collagen in vivo. Epidermal and dermal responses to infrared light therapy using a Titan source were examined with the aim of correlating histological and clinical responses in human and amelanotic mouse skin.


METHODS
Ten, 20, or 30 J/cm2 infrared light were irradiated on the human subject's skin (thigh), while 5, 10, 20, or 30 J/cm2 were used on amelanotic mouse skin. Biopsies were taken and analyzed using hematoxylin and eosin (H&E) and Elastica von Gieson stain.


RESULTS
Ten or 20 J/cm2 infrared light increased the amount of both collagen and elastin in all layers of the dermis without denaturing the collagen in human skin. A higher dose of 30 J/cm2 also increased the amount of collagen and elastin, but denatured the collagen in human skin. (In addition to the thigh, 2 treatments of 10 J/cm2 infrared light improved skin toning and texture on the subject's face). In mouse skin, 5 or 10 J/cm2 remarkably increased the amount of both collagen and elastin, and of epidermal cells. Twenty or 30 J/cm increased the amount of collagen and elastin and the number of keratinocytes, but caused some vacuolated degeneration of keratinocytes. The presence of denatured collagen was not evident due to the high density of collagen.


CONCLUSIONS
This study shows that the denaturation of collagen is not required to increase the amounts of collagen or elastin in vivo in human skin. The activation of the mitochondria as well as the denaturation of collagen may play important roles in infrared phototherapy.
Kameyama
Koichiro
K
Aoyama Dermatology Clinic, Tokyo, Japan. dr@aoyamahihuka.com
D000818:Animals; D003094:Collagen / Q000378:metabolism / Q000528:radiation effects*; D004549:Elastin / Q000378:metabolism / Q000528:radiation effects*; D006801:Humans; D007259:Infrared Rays; D015603:Keratinocytes / Q000528:radiation effects; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008875:Middle Aged; D010789:Phototherapy / Q000379:methods; D011829:Radiation Dosage; D012867:Skin / Q000378:metabolism / Q000473:pathology / Q000528:radiation effects*
D003094:Collagen; D004549:Elastin