Protective effect of ultrasound microbubble combined with gross saponins of tribulus terrestris on glaucomatous optic nerve damage

BACKGROUND: To investigate the protective effect of ultrasound microbubble combined with gross saponins of tribulus terrestris (GSTT) (a Chinese herb) on glaucomatous optic nerve damage. METHODS: Rabbits were randomly divided into five groups. Normal (Group A), high intraocular pressure (IOP, Group B), GSTT (Group C), GSTT + ultrasound (Group D), and GSTT + ultrasound + microbubble destruction (Group E). The high intraocular pressure eye (model eye) was compared to the normal eye (control eye) at 1, 2, and 4 weeks after model establishment. Rabbits were sacrificed 4 weeks later to measure the retina thickness using Cirrus OCT, slit lamp photograph, and fundus photography. The retina and optic nerve of rabbits in each group were collected and the stretched retina were prepared for retinal ganglion cell (RGC) counting, the optic nerve axon was measured, and a transmission electron microscopy was used. RESULTS: Retina thickness based on Cirrus OCT: mean retinal thickness in Group E was significantly greater than that in Group B, but still thinner than that in Group A. RGCs counts: RGCs counts in Group E were significantly higher than those in Groups B, C, and D but still lower than those in Group A. Quantitative analysis of optic nerve axons: In Group E, the number of optic nerves was increased, diameters of optic nerve axons were decreased, the percentage of optic nerve area occupied by axons was increased, and there were statistically significant differences compared to Groups B, C, and D. Content of GSTT in retina: The content of GSTT in Group E was significantly higher than that in other groups. Observation of the rabbit optic nerves: In Group E, the structure of the myelin sheath of the optic nerve was still intact but less ordered, and the microtubule and microfilament structures in the axons were clear. CONCLUSIONS: Combination of the ultrasound microbubble and GSTT can improve the protective effect of GSTT on optic nerve damage in rabbits with ocular hypertension.