Transpupillary thermotherapy (TTT) with short duration laser exposures induce heat shock protein (HSP) hyperexpression on choroidoretinal layers.
OBJECTIVE
To assess a choroidal heat shock protein hyperexpression after transpupillary thermotherapy (TTT) performed with exposures shorter than 60 seconds.


METHODS
Nine male pigmented rabbits were anesthetized and TTT was performed on their right eye with a 810 nm diode laser (Iridis, Quantel-Medical (France)) (spot size: 1.3 mm). Three exposure durations (60, 30, or 15 seconds) were used with three ranges of power for each duration ("high," "mild," or "low"). A series of laser impacts was delivered to the posterior pole of the retina. Left eyes were used as controls. Twenty-four hours after laser irradiation, the animals were killed and histological study was performed on chorioretinal layers. Tissue samples were fixed in formalin and embedded in paraffin. A monoclonal antibody was used to detect Hsp70 immunoreactivity (mouse IgGl, SPA-810, Stress Gen, Victoria, BC, Canada), followed by a biotinylated goat anti-mouse antibody (Dako, Glostrup, Denmark), revealed by the avidin-biotin complex (Vectastain kit, Vector Laboratries, Burlingame, CA, USA) and the AEC chromogen. Retinal structures were further identified by HES coloration.


RESULTS
During the experiments, the laser spots were not visible except for the strongest "high" powers for each exposure duration, where a whitening was discernable at the end of the laser exposures. A strong HSP70 immunoreactivity was detected in choroidal, non-pigmented cells for laser exposures lasting 60, 30, or 15 seconds with "mild" laser powers. On the contrary, rare HSP hyperexpression was detected with "high" or "low" laser powers lasting 60, 30, or 15 seconds. No HSP-70 immunoreactivity was detected on control eyes nor outside of the irradiated zones of treated eyes.


CONCLUSIONS
Transpupillary laser irradiation lasting 15, 30, or 60 seconds induces an hyperexpression of HSP on choroidal layers. This could be a basis for the use of TTT with "short" laser exposures.
Desmettre
Thomas
T
UPRES-EA2689 INSERM IFR 114, University Hospital, 59037 Lille, France.
Maurage
Claude-Alain
CA
Mordon
Serge
S
D000818:Animals; D002829:Choroid / Q000378:metabolism / Q000473:pathology / Q000601:surgery*; D006360:Heat-Shock Proteins / Q000096:biosynthesis*; D006979:Hyperthermia, Induced / Q000379:methods*; D053685:Laser Therapy / Q000379:methods*; D008297:Male; D023421:Models, Animal; D011817:Rabbits; D012160:Retina / Q000378:metabolism / Q000473:pathology / Q000601:surgery*; D013997:Time Factors
D006360:Heat-Shock Proteins