Background: Retinal ganglion cells (RGCs) are protected in rats with acute elevated intraocular pressure (IOP) by Erigeron breviscapus (vant.) hand-mazz (EBHM). However, it is unclear whether EBHM has neuroprotective effect on RGCs in animal with chronic elevated IOP.
Objective: Investigate the protective effect of EBHM extract on RGCs in rabbits with chronic elevated IOP.
Methods: Unilateral chronic elevated IOP was produced in rabbits by repeated injection of 2% methylcellulose into the anterior chamber. Secondary degeneration was measured with and without EBHM extract treatment for 60 days. At 60 days, the cells density of the RGCs layer, the thickness of retinal nerve fiber layer (RNFL), and the optic nerve axons were observed and analyzed using an image analysis system. The ultrastructural changes of RGCs and optic nerve axons were observed using transmission electron microscopy.
Results: Compared with their contralateral control eyes with normal IOP, in the retinas of 3-4 mm from the optic disc, the cells density of the RGCs layer in the eyes with chronic elevated IOP was 23.2±6.5 cells (n = 6) and 36.0±8.9 cells (n = 10) per three 400x fields at 60 days in untreated and EBHM-treated group, respectively. The RNFL thickness in eyes with chronic elevated IOP was 3.4±0.4 μm (n = 6) and 5.0±1.0 μm (n = 10) at 60 days in untreated and EBHM-treated group, respectively. The axons number per 15057.8 μm2 in eyes with chronic elevated IOP was 370.4±41.0 (n = 6) and 439.0±50.8 (n = 10) at 60 days in untreated and EBHM-treated group, respectively. The number of the organelles in RGCs plasm appeared decreased and mitochondrion vacuolated in the elevated IOP eyes of EBHM-treated group, while some dispersive mitochondrion and rough surfaced endoplasmic reticulum and ribosome still existed in the RGCs plasm. The myelin sheath plates condensed and degenerated, and the microfilaments and microtubules decreased or disappeared in the elevated IOP eyes, but the axons degeneration in the chronic elevated IOP with EBHM treatment was less than that in the chronic elevated IOP without treatment.
Conclusion: EBHM extract provided a neuroprotective effect on retinal ganglion cells in rabbits with chronic elevated IOP.