Proceedings of The Physiological Society
University College Dublin (2009) Proc Physiol Soc 15, C119
Growth Hormone is present in Human Retinal Ganglion Cells and Correlates with Cell Survival.
E. J. Sanders1, E. Parker1, S. Harvey1
1. Physiology, University of Alberta, Edmonton, Alberta, Canada.
Locally synthesized growth hormone (GH) may act as a survival factor in a number of tissues (Sanders & Harvey, 2008). Experimental studies with chick retinal ganglion cells (RGCs) suggest that GH, synthesized within the developing retina, may have autocrine/paracrine roles in the regulation of the waves of cell death characteristic of RGC differentiation (Sanders et al. 2008). There is also evidence that endogenous GH may have a similar neuroprotective function in the adult rat retina, however, there is no information concerning the possible presence or action of GH in the human retina. In this study we show, for the first time, that GH is present in the human retina and that the local expression of retinal GH correlates with RGC cell survival. GH-immunoreactivity, identical in size to that in the pituitary gland (22kDa), was detected by Western blotting as a single band in extracts of cadaver retinas (obtained with ethical approval). Using tissue sections from eyes collected post-mortem (with ethical approval), this immunoreactivity was largely confined to large, rounded cells in the GLC (ganglion cell layer) of the neural retina and co-localized in RGCs, labeled by a synuclein antibody. GH receptor (GHR) immunoreactivity was similarly located in the GCL and 35% of these cells were both GH- and GHR- positive. None of the cells that had GH immunoreactivity were apoptotic, as determined by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL). In summary, these results demonstrate the presence of GH and its receptor in RGCs of the human retina in which GH expression correlates with cell survival. These results are consistent with our earlier in vivo and in vitro experimental studies in chick embryos that show autocrine or paracrine actions of GH in RGCs that promote cell survival during development and suggest that GH is a novel neurotrophic factor for human RGCs.
Where applicable, experiments conform with Society ethical requirements