Abstract
Purpose: :
To study the time-dependent expression of a set of heat shock proteins and the stress-regulated chemokine, stromal cell-derived factor-1 (SDF-1) in the RPE layer following 810 nm laser application to the mouse eye.
Methods: :
Utilizing the micropulse mode of an 810 nm solid state laser system , 40-50 laser spots, either 50 or 100 µm, were applied to the retina and RPE of one eye of C57/B6 mice. The other eye served as a control. Both eyes of lasered mice were harvested at fixed times post-laser and the RNA was isolated. Separate control eyes from mice that received no laser treatment in either eye were also harvested. RT-PCR was performed using primers for hsp70, hsp90, αA-crystallin, αB-crystallin and SDF-1. Separately, and to complement the in vivo studies, ARPE-19 cells were heat shocked, and the same RT-PCR analysis was performed.
Results: :
There is time-dependent increase in the mRNA of the heat shock proteins and SDF-1 from the posterior eyecups of lasered eyes when compared to the contralateral eye as well as non-lasered controls. Hsp90 mRNA levels rise most rapidly, peaking at 2 hrs (5X greater than controls) while hsp70 peaks at 4 hrs post-laser (2.5X greater than controls). Both returned to baseline levels by 12 hrs. In addition, SDF-1 increased by 25% which was statistically significant. Increasing lengths of heat shock exposure to ARPE-19 (the equivalent of longer duration laser applications to the retina), led to the increased levels of hsp70, hsp90, the crystallins and SDF-1, with a time-course similar to that seen in the mouse retina.
Conclusions: :
810 nm laser application to the retina results in the induction of the heat shock response and a time-dependent increase in SDF-1 in the RPE layer. This response is recapitulated in RPE cell culture experiments. These experiments link the heat shock response with SDF-1 expression. Both the cell culture and laser mouse model can provide insights into the cellular events triggered by the laser systems used in managing retinal disease.
Keywords: laser • retinal pigment epithelium • stress response