Therapeutic Effect of Traditional Chinese Medicine on a Rat Model of Branch Retinal Vein Occlusion

Abstract

Branch retinal vein occlusion (BRVO) is a common retinal vascular disorder leading to visual impairment. Currently, the general strategies for BRVO are symptomatic therapies. Cardiovascular aspects are essential risk factors for BRVO. The traditional Chinese medicine hexuemingmu (HXMM), consisting of tanshinol and baicalin, dilates the vasculature and accelerates microcirculation. Therefore, the aim of this study was to determine the efficacy and possible mechanism of HXMM in a BRVO rat model established by laser photocoagulation. Successful BRVO rat models were treated with different doses of HXMM. Fundus photography and fluorescein fundus angiography (FFA) of the animals were applied. The retinal layers were measured by optical coherence tomography (OCT). Full-field electroretinography (ffERG) was applied to evaluate the retinal function. The ear vein flow velocity was measured via a microcirculation detector. The expression of the vascular endothelial growth factor (VEGF-α) was measured via western blotting and immunofluorescent staining. Our study found that retinal edema predominantly occurred in the inner nuclear layer (INL) and outer nuclear layer (ONL). The retinal edema of the treated groups was significantly relieved in the early stage of BRVO as visualized via OCT detection and HE staining. The amplitudes of the b wave and oscillatory potentials (OPs) waves of ffERG in the treated groups were increased compared with those of the control group at several detection points (3, 5, 7, 10, 14, and 21 d postocclusion). The expression of VEGF-α was reduced in the treated groups at an early stage of BRVO. Furthermore, the ear vein flow velocity of the HXMM treatment groups was faster than that of the control group. Thus, our study indicates that the traditional Chinese medicine HXMM could ameliorate retinal edema and rescue the retinal structure and function in BRVO models through promoting occluded vein recanalization, improving microcirculation, and regulating the expression of VEGF-α.

Figure 1

HXMM decreased occlusive vein recanalization duration and had no influence on the recanalization onset time. (a) The typical FFA and fundus photograph. (b) Recanalization starting time. (c) Duration of recanalization time. The statistical significance was determined by one-way ANOVA. Data are presented as the mean ± SEM. All analyses were performed in duplicate. n = 12 rats per group. ^∗∗p < 0.01, HIGH, MOD, and LOW groups vs. CK group; ^∗∗∗p < 0.001, HIGH, MOD, and LOW groups vs. CK group.

Figure 2

HXMM alleviated BRVO rat retinal edema and protected BRVO rat retinal integrity. (a) The typical OCT pictures of injured BRVO rat retina treated with different doses of HXMM at 1, 3, 5, 7, 10, and 14d. (b, c) The thickness of the BRVO rat retina treated with different doses of HXMM at the injury site and 250 µm from the injury site measured by OCT. The statistical significance was determined by one-way ANOVA. Data are presented as the mean ± SEM. All analyses were performed in duplicate. n = 12 rats per group. ^∗p < 0.05, HIGH group vs. CK group; ^#p < 0.05, MOD group vs. CK group; ^&p < 0.05, LOW group vs. CK group.

Figure 3

HXMM alleviated BRVO rat retinal edema and protected BRVO rat retinal integrity. (a) The typical HE pictures of normal and BRVO rat retina treated with different doses of HXMM at 1 d and 21 d postocclusion. (b, c) The thickness of INL and ONL of normal and injured BRVO rat retina treated with different doses of HXMM at 1 d postocclusion. (d, e) The thickness of INL and ONL of normal and BRVO rat retina treated with different doses of HXMM at 21 d postocclusion. The red arrow denotes retina disorder; the black arrow denotes ONL edema; and the yellow arrow denotes a thinner ONL. The statistical significance was determined by one-way ANOVA. Data are presented as the mean ± SEM. n = 6 rats per group. ^∗p < 0.05, HIGH, MOD, LOW, and CK groups vs. NOR group; ^#p < 0.05, HIGH, MOD, and LOW groups vs. CK group; ^&p < 0.05, HIGH and MOD groups vs. LOW group.

Figure 4

HXMM improved BRVO rat retinal function. (a) The typical ERG (dark-adaptation response 3.0) performance. (b) BRVO rat amplification of the b (d3.0) wave after modeling 0, 1, 3, 5, 7, 10, 14, and 21 d postocclusion. (c) BRVO rats peak time of the b (d3.0) wave after modeling 0, 1, 3, 5, 7, 10, 14, and 21 d postocclusion. (d) BRVO rat amplitude of the OPsO₂ wave after modeling 0, 1, 3, 5, 7, 10, 14, and 21 d postocclusion. (e) BRVO rat amplitude of the ∑OPs_1–4 wave after modeling 0, 1, 3, 5, 7, 10, 14, and 21 d postocclusion. The statistical significance was determined by one-way ANOVA. Data are presented as the mean ± SEM. All analyses were performed in duplicate. n = 12 rats per group. ^∗p < 0.05, HIGH group vs. CK group; ^#p < 0.05, MOD group vs. CK group.

Figure 5

The effect of HXMM on BRVO rat microcirculation. BRVO rat ear vein blood flow velocity at 1 d (a) and 21 d (b). The statistical significance was determined by one-way ANOVA. Data are presented as the mean ± SEM. All analyses were performed in duplicate. n = 6 rats per group. ^∗∗p < 0.01, HIGH, MOD, and LOW groups vs. CK group; ^∗∗∗p < 0.001, HIGH, MOD, and LOW groups vs. CK group.

Figure 6

HXMM decreased the expression of VEGF-α at 1 d postocclusion. (a) The typical immunofluorescence staining pictures of the BRVO rat retina with or without HXMM treatment at 1 d postocclusion. (b) The expression of VEGF-α: CK group, HIGH group, MOD group, and LOW group. The statistical significance was determined by one-way ANOVA. Data are presented as the mean ± SEM. All analyses were performed in duplicate. n = 6 rats per group. ^∗p < 0.05, HIGH, MOD, and LOW groups vs. CK group; ^#p < 0.05, HIGH and MOD groups vs. LOW group.

Figure 7

HXMM slightly increased the expression of VEGF-α at 21 d postocclusion. (a) The typical immunofluorescence staining pictures of the BRVO rat retina with or without HXMM treatment at 21 d postocclusion. (b) The expression of VEGF-α: CK group, HIGH group, MOD group, and LOW group. The statistical significance was determined by one-way ANOVA. Data are presented as the mean ± SEM. All analyses were performed in duplicate. n = 6 rats per group. ^∗p < 0.05, HIGH, MOD, and LOW groups vs. CK group.

Figure 8

The expression of VEGF-α in BRVO retina at 1 d (a) and 21 d (b) postocclusion. n = 6 rats per group, mean ± SEM; ^∗p < 0.05, HIGH, MOD, and LOW groups vs. CK group; ^#p < 0.05, HIGH and MOD groups vs. LOW group.