Changes in human skin after topical PDT with hexyl aminolevulinate.
BACKGROUND
Photodynamic therapy (PDT) induces physiological changes in human skin, but details and kinetics are not known.


METHODS
Changes in human skin induced by PDT with red light in the presence of topically applied cream with the hexyl aminolevulinate (HAL) were investigated in the skin of five healthy volunteers. In addition to testing the effects of HAL-PDT three control studies were performed on the volunteers: (A) the HAL containing cream was applied to the skin without light exposure; (B) the cream without HAL was applied to the skin; (C) the skin was exposed to light in the absence of the cream. Reflectance spectra of the skin were measured in the wavelength region 300-600 nm before and after treatment. An advanced and new inverse radiative transfer model was used to determine changes induced in a number of skin parameters.


RESULTS
The main discoveries were that the dermal blood concentration increased immediately after PDT, reached a maximum after 1-2 days, and then decreased. The blood oxygenation increased significantly immediately after PDT and then decreased. After PDT the melanosome concentration in the upper epidermis increased steadily. No such changes were observed in the control sites.


CONCLUSIONS
Our results imply that HAL-PDT leads to increased vascularisation, oxygenation and melanin formation.
Department of Radiation Biology, Institute for Cancer Research, The Norwegian Radium Hospital, Rikshospitalet University Hospital, Montebello, 0310 Oslo, Norway. asta.juzeniene@rr-research.no
Asta
A
Juzeniene
Kristian Pagh
KP
Nielsen
Lu
L
Zhao
Gennady A
GA
Ryzhikov
Marina S
MS
Biryulina
Jakob J
JJ
Stamnes
Knut
K
Stamnes
Johan
J
Moan
D000287:Administration, Topical; D000328:Adult; D000622:Aminolevulinic Acid / Q000008:administration & dosage / Q000494:pharmacology*; D006801:Humans; D020460:Melanosomes / Q000737:chemistry; D008875:Middle Aged; D010778:Photochemotherapy; D017319:Photosensitizing Agents / Q000008:administration & dosage / Q000494:pharmacology*; D012015:Reference Standards; D012867:Skin / Q000737:chemistry / Q000187:drug effects*
D017319:Photosensitizing Agents; D000622:Aminolevulinic Acid