Abstract
Purpose: :
Our previous study showed that loss of cone outer segments (COS) is an early sign of cone degeneration. In this study, we examined the effects of OSM, a member of the IL-6 family of cytokines, on the secondary cone degeneration in the transgenic rats carrying the murine rhodopsin mutation S334ter.
Methods: :
The left eyes of S334ter rats were intravitreally injected with OSM (10 µg in 3 µl PBS) at postnatal day (PD) 20 and the right eyes with 3 µl PBS. Eyes were collected 10 days later. Retinas were stained with FITC-conjugated PNA (Peanut agglutinin) which specifically labels COS, flat-mounted on slides, and examined by confocal microscopy. Quantitative analyses were performed by counting PNA-positive cells with software MBF-ImageJ and then calculating the densities of PNA-positive cells.
Results: :
Many round and irregularly shaped small PNA-negative areas were found in PBS-treated controls, similar to what was found in untreated retinas, indicating loss of cone outer segments. In eyes treated with OSM, however, the PNA-negative areas were much smaller and in many cases completely disappeared. Quantitative analyses showed that PNA-positive cells are 20% more in the retinas treated with OSM than in the PBS-treated retinas (P=0.01 Student t-test).
Conclusions: :
Our results demonstrate that OSM significantly protects cone cells from degeneration, similar to what was found in CNTF-treated retinas we reported previously. Since OSM and CNTF are members of the IL-6 family of cytokines and they share the same receptor complex of LIFRβ and gp130, our data suggest that the protective effect of CNTF and OSM is mediated through the same mechanism.
Keywords: retinal degenerations: cell biology • growth factors/growth factor receptors • photoreceptors