Protective effect of high concentration of BN52021 on retinal contusion in cat eyes

Abstract

Background: Blunt injuries/contusion on eyes might cause retina blunt trauma. This study is to evaluate the protective function of BN52021 against retinal trauma.

Methods: A total of 70 cats, 6 months old, were divided into six groups: Group A to E (n = 12) and normal control (N) group (n = 10). The right eyes in Group A to E were contused. All experiments were performed under general anesthetization. Retrobulbar injections of medication in right eyes were performed. Cats were administrated with 0.5 mL of normal saline (NS), dimethyl sulphoxide, 0.2 g/L BN52021, 1 g/L BN52021 and 5 g/L BN52021, respectively. Cats in Group N were administrated with 0.5 mL of NS. Intraocular pressure (IOP), flash electroretinogram (ERG), and retinal nerve fiber layer (RNFL) thickness were measured. Hematoxylin and eosin (HE) staining and transmission electron microscope (TEM) were detected.

Results: No significant difference was observed in IOP levels among groups. Comparing with cats in Group N, those in Group A to E showed significant lower amplitudes of rod a- and b-waves (P < 0.05). Amplitudes of rod a- and b-waves were increased by administration of high concentration of BN52021 (≥ 1 g/L). Moreover, high concentration of BN52021 decreased the RNFL thickness increased by contusion. Axons in RNFL in Group E arranged neatly at 7 days after modeling.

Conclusions: The degenerated axons caused by contusion were repaired by BN52021. The administration of high concentration of (≥ 1 g/L) BN52021 could partially repair retinal function in contused cat eyes.

Figure 1

Mean intraocular pressure. * indicates P < 0.05 compared with other groups at 1 day, 3 days and 7 days after modeling.

Figure 2

The electroretinogram (ERG) amplitudes and latency periods of a- and b-waves. A, ERG amplitude of a-wave; B, ERG amplitude of b-wave; C, ERG latency period of a-wave; D, ERG latency period of b-wave. * and ** indicates P < 0.05 and P < 0.01 compared with the other groups at the same treatment time point, respectively.

Figure 3

Tracings of oscillograhic records of cat retinas after dark adaptation. A - D, represent 4 inspection time points: 4 h, 1 day, 3 days and 7 days after modeling. From up to down, oscillograms for cats in Group E, D, C, B, and A, respectively. The stimulus duration is 250 ms.

Figure 4

Optical coherence tomography (OCT) results of the retinal nerve fiber layer (RNFL) during the experimental periods. A, OCT result of the normal RNFL; B and C, OCT results of the RNFL in Group A at 1 day and 7 days after modeling with 0.5 mL of normal saline administration. An obvious swelling was observed in RNFL; D and E, OCT results of the RNFL in Group B at 1 day and 7 days after modeling, with 0.5 mL of DMSO administration; F and G, OCT results of the RNFL in Group D at 1 day and 7 days after modeling, with 0.5 mL of 1 g/L BN52021 administration; H and I, OCT results of the RNFL in Group E at 1 day and 7 days after modeling, with 0.5 mL of 5 g/L BN52021 administration. Comparing with the normal RNFL, all RNFLs in the experimental groups were swelling to some extent. For A, D and G, bar = 150 μm, for B, C, E, F, H and I, bar = 175 μm.

Figure 5

Results of retinal nerve fiber layer (RNFL) thickness examination. Significant differences could be seen among the groups. The administrations of middle concentration (1 g/L, 0.5 mL) and high concentration (5 g/L, 0.5 mL) of BN52021 significantly and very significantly decreased the RNFL thickness. * and ** represents significant level at P < 0.05 and P < 0.01, respectively.

Figure 6

Hematoxylin and eosin (HE) staining results of the cell layers in retina and anterior optic nerves. A, HE staining result of the cell layers in normal retina; B and C, HE staining results of retina in Group A and B administrated with normal saline and DMSO at 1 day after modeling, respectively; D, HE staining result of retina in Group E administrated with high concentration (5 g/L, 0.5 mL) of BN52021 at 7 days after modeling. E to G, HE staining results of anterior optic nerves in normal retina (E) and contusion retina at 4 h (F) and 7 days (G) after modeling. The arrows in Figure A-D indicate the ganglionic layers in the RNFL. A to D, original magnification × 400. E to G, original magnification × 100.

Figure 7

Transmission electron microscope (TEM) results of the anterior optic nerves in cat eyes. A, anterior optic nerves in normal cat eyes; B, anterior optic nerves in contused cat eyes; C, anterior optic nerves in cat eyes administrated with high concentration (5 g/L, 0.5 mL) of BN52021. Black arrows indicate the space between axons. A, original magnification × 10000. B and C, original magnification × 4000.