Abstract
Purpose: :
To characterize the temporal loss of mice retinal ganglion cells (RGC) identified by hydroxystilbamidine methanesulfonate (OHSt) tracing and Brn3a expression, induced by complete intraorbital optic nerve transection (IONT).
Methods: :
RGCs were labelled with OHSt applied to both superior colliculi one week before surgery or processing. For IONT, the left optic nerve was cut close to the optic disc. As controls, naïve and the right untouched retinas of the experimental groups were used. At several survival intervals after IONT, retinas were dissected and prepared as whole mounts (2, 5, 7, 9, 14 or 21 days, n=8 per time point) or cryoprotected for radial sectioning (2, 7 or 14 days, n=3 per time point). Immunodetection of Brn3a was performed in all whole mounts and radial sections. The proportion of RGCs doubly labelled with OHSt and Brn3a was determined in naïve sections (n=6). Sections from experimental retinas were analyzed to assess whether Brn3a expression pattern was affected by IONT. To estimate RGC survival the entire population of OHSt-labelled and Brn3a+RGCs was quantified in the same wholemounted retinas at the abovementioned times after IONT.
Results: :
In radial sections from naïve retinas, 71.2% of RGCs are OHSt and Brn3a positive, while 22.4% are OHSt+ and Brn3a- and 6.3% are Brn3a+ and OHSt-. The expression pattern of Brn3a is not affected by IONT. In naïve whole mount retinas (n=5), the mean number±SD of OHSt+ RGCs is 40,016±2,854 and of Brn3a+ RGCs is 33,853±1,028. The number of OHSt+ and Brn3a+ RGCs, decreases along time post-lesion with a similar trend although the loss of Brn3a expression is observed earlier than the loss of OHSt.
Conclusions: :
The temporal course of axotomy-induced RGC degeneration in mice is similar to that described in rat (Peinado-Ramón et al., 1996; IOVS, 37:489, Nadal-Nicolás et al., 2009; IOVS, 50:3860). Both, OHSt and Brn3a are good markers to evaluate RGC fate after axonal injury.
Keywords: ganglion cells • retina • lesion study