Upregulation of NT4 and downregulation of TrkB in human retina from eyes with proliferative vitreoretinopathy

Abstract

Abstract: : Purpose:To examine the expression and localisation of NT4 and its receptor, TrkB, in normal human retina and to identify changes in their expression in eyes with proliferative vitreoretinopathy (PVR) Methods:Normal human retina from donor eyes and retinectomy specimens from patients with PVR were fixed in 4% PFA. Specimens were embedded in agarose gel and 100 µm retinal sections were cut using a vibratome. Sections were immunostained with either mouse monoclonal antibodies to rhodopsin (Rho4D2) or glial fibrillary acidic protein (GFAP), and rabbit polyclonal antibodies to NT4 or TrkB. Donkey anti–mouse antibodies (Alexa Fluor 488) and goat anti–rabbit antibodies (Alexa Fluor 546) were used as secondary antibodies. T0–pro3–iodide was used for nuclear staining. Sections were examined using laser scanning confocal microscopy (BioRad Radiance 2000 AGR–3 (Q)). Results:We observed minimal intensity staining for NT4 and TrkB at the ganglion cell layer in the normal human retina. Staining for NT4 was greatly increased in retinal sections from eyes with PVR, with the NT4 localisation being prominent throughout the entire retinal thickness and localising to Müller cells as identified with GFAP immunostaining. TrkB immunostaining was not detectable in PVR retinectomy sections. Conclusions:NT4 and TrkB are detectable by immunostaining at the ganglion cell layer in the normal human retina. Increased expression of NT4 localised to Müller cells in PVR retinectomy sections may be indicative of a positive regulatory role that these supporting cells may play in retinal regeneration. Down–regulation of TrkB receptor may be a direct consequence of excess NT4 expression. Reduced receptor availability in retinal disorders may be related to the neuro–degeneration seen in such pathologies and also may explain the short term effect of some exogenous neurotrophic factors on neuronal survival observed in other studies.

Keywords: neuropeptides • proliferative vitreoretinopathy • Muller cells