Abstract
Purpose :
Heat shock protein 27 (HSP27) is a molecular chaperone and is most commonly involved in cellular stress. Glaucoma patients showed an increased HSP27 level and autoantibodies against HSP27. Moreover, systemic application of HSP27 in rats induced a degeneration that resembles glaucomatous damage. Here, the direct effects of intravitreal HSP27 application were investigated.
Methods :
HSP27 (0.4 µg) or PBS were injected intravitreally in one eye per rat. Intraocular pressure (IOP) was measured over 21 days. At day 21, retinal cross-sections and longitudinal optic nerve sections (n=6/group) were used for immunohistology to evaluate retinal ganglion cells (RGCs; Brn-3a), amacrine cells (calretinin), bipolar cells (PKC-α), neurofilament (SMI-32) and myelin (LFB). Both groups were compared using student’s t-test.
Results :
The IOP in HSP27 and PBS treated eyes was comparable. Significantly fewer RGCs (HSP27: 65.5%±28.0; PBS: 100±24.4%, p=0.046) and amacrine cells (HSP27: 85.1±13.0; PBS:100%±7.9%, p=0.038) were observed in the HSP27 group. The number of PKC-α+ bipolar cells in the HSP27 and PBS group were comparable (p>0.05). Additionally, a significant higher SMI-32 score was observed in HSP27 optic nerves (1.0±0.1), in comparison to the PBS group (0.7±0.2, p=0.049). While no changes were observed regarding the LFB score (p>0.05).
Conclusions :
Intravitreal HSP27 injection leads to a degeneration of retinal ganglion cells and their axons, but also of amacrine cells. This suggests that the HSP27 might have a direct damaging effect on retinal cells.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.