A preliminary study on the effect of photothermal laser therapy on the vascularization and innervation of psoriatic lesions*

Vascular laser therapy for psoriasis seems to achieve a remarkably long
treatment-free duration of remission. But why would sub-second heating of the
blood vessels of the skin result in a year-long resolution of an infamously
stubborn condition? The only other situation in which such long term clearance
is observed is in patients that experience significant damage to the
innervation, such as paraplegia. Even then the duration of remission is
correlated with the persistence of the injury. Fortunately laser therapy is not
associated with permanent nerve damage, but it does raise the question if it is
through an effect on the local innvervation that laser therapy results in a
cessation of the inflammation.

Unraveling the mechanism of action of laser therapy would not only allow for
the improvement of existing laser therapy protocols but also, could open the
door to a whole new range of interventions offering quasi-permanent solutions
for patients. There is a high need for such enduring therapies: Psoriasis is
both, a common and a costly skin condition. It affects between 1% and 9% of the
population and has a very severe impact on the quality of life of the patient.
It's chronic character implies lifelong treatment, and the associated risks and
effort.

This project aims to assess the effect of laser therapy on the blood vessels
and (peripheral) innervation of psoriasis plaques. The primary objective is to
quantify the regression and recovery of nerves compared to blood vessels. We
hypothesize that the recovery of nerves after SPT is decreased compared to the
recovery of blood vessels.

Randomized single blinded intra patient comparative study.

Patients undergo regular 595 nm pulsed dye laser therapy for psoriasis. Tissue
samples will be collected from the patients using a total of two 3 mm
punch-biopsies under local anesthesia. These samples are used to determine the
nerve density and blood vessel density in the treated and non-treated lesions.

During standard laser treatment for psoriasis, two tissue samples will be
acquired using 3 mm punch biopsies. As a consequence, two small permanent scars
(2x 7mm^2) are infliced upon the patients. The study is not expected to involve
significant risks or benefits compared to standard dermatological treatments
for psoriasis.