A new and reliable animal model for optic nerve injury

Application of Proteomics Analysis and Animal Models in Optic Nerve Injury Diseases

Optic nerve damage is a common cause of blindness. Optic nerve injury is often accompanied by fundus vascular disease, retinal ganglion cell apoptosis, and changes in retinal thickness. These changes can cause alterations in protein expression within neurons in the retina. Proteomics analysis offers conclusive evidence to decode a biological system. Furthermore, animal models of optic nerve injury made it possible to gain insight into pathological mechanisms, therapeutic targets, and effective treatment of such injuries. Proteomics takes the proteome as the research object and studies protein changes in cells and tissues. At present, a variety of proteomic analysis methods have been widely used in the research of optic nerve injury diseases. This review summarizes the application of proteomic research in optic nerve injury diseases and animal models of optic nerve injury. Additionally, differentially expressed proteins are summarized and analyzed. Various optic nerve injuries, including those associated with different etiologies, are discussed along with their potential therapeutic targets and future directions.

Long-Term Effects of a Photodisruptive Laser-Induced Traumatic Neuropathy Model

Purpose

To create a mouse traumatic optic neuropathy (TON) model that is reproducible, reliable, and easy to manipulate with high specificity to retinal ganglion cell (RGC) layer and no mortality. The model will be useful for understanding the pathophysiology of retinal ganglion cell death and for testing neuroprotective therapeutics.

Methods

An Nd:YAG laser was used to generate focal photodisruptive retinal damage. Noninvasive in vivo ophthalmologic imaging technologies such as optical coherence tomography (OCT) and confocal laser scanning ophthalmoscopy (CSLO) were used to longitudinally track the retinal nerve fiber layer (RNFL) thickness and RGC number change, respectively. Immunostaining and pattern electroretinography (PERG) were also used to evaluate structure and functional change after laser injury.

Results

Our ND:YAG laser generates a concussive photodisruptive laser shockwave force which induces focal RGC death in the targeted area. We observed a correlative decrease in RGCs number, RNFL, and PERG function of RGC in the laser zone. The pattern of RNFL thinning and RGC soma loss correlates with the pattern and amount of fluorescence loss on OCT and CSLO images, respectively. The ND:YAG laser does not cause any damage to other layers in the retina nor any side effects including changes in intraocular pressure, corneal edema, and calcification or mortality (which has been observed in other TON models).

Conclusions

We have created a new and novel RGC TON death model that confers no mortality and produces a quantifiable decrease in RGC number and function. The laser targeted regions of the retina correlate with both in vivo imaging by OCT and CSLO and histologically with regions of RGC loss without ophthalmic side effects.

Translational Relevance

This laser-based TON injury model is simple to implement, is reproducible, and is useful for determining the molecular and cellular pathophysiology of TON and RGC death and for testing neuroprotective therapeutics.

Effect of Mannitol Infusion on Optic Nerve Injury After Acute Traumatic Subarachnoid Hemorrhage and Brain Injury

The primary aim of this paper is to investigate the neuroprotective and antiinflammatory effects of mannitol on optic nerve injury after acute traumatic subarachnoid hemorrhage and brain injury in rat models. Traumatic brain injury (TBI) and traumatic subarachnoid hemorrhage (tSAH) were produced by a custom-made weight-drop impact acceleration device. Thirty male Wistar rats were divided into 3 groups. Group I (n = 10) was the sham group, group II (n = 10) received TBI, and group III (n = 10) received TBI + mannitol (1 mg/kg intravenously). Optic nerve tissue glutathione peroxidase (GPx) and interleukin 1 beta (IL-1β) levels were measured 4 hours after the trauma. The authors used Kruskal-Wallis variance analysis and Mann-Whitney U tests for statistical analysis. Optic nerve tissue GPx levels were significantly higher in group III than in groups I and II (P < 0.05). Optic nerve tissue IL-1β levels were significantly lower in group III than in group II (P < 0.05) and higher than in group I (P < 0.05).Mannitol increased the antioxidant GPx levels and decreased the IL-1β levels, which can protect the optic nerve from secondary injury after severe acute trauma. Mannitol plays an important role in the treatment of acute severe indirect optic nerve injury after TBI and tSAH.

Valproic acid attenuates inflammation of optic nerve and apoptosis of retinal ganglion cells in a rat model of optic neuritis

AIMS

Optic neuritis (ON) is an inflammatory disease of the optic nerve, which often occurs in patients with multiple sclerosis (MS) and leads to retinal ganglion cell (RGC) death and even severe visual loss. Valproic acid (VPA) is a short-chain branched fatty acid with anti-epileptic, neuro-protective and anti-inflammatory effects. Here, we examined the effects of VPA in experimental autoimmune encephalomyelitis (EAE) rats and explored the underlying mechanisms.

MAIN METHODS

EAE was induced by subcutaneous injection with myelin basic protein, emulsified with complete Freund's adjuvant and Mycobacterium tuberculosis H37Ra into the Lewis rats. Subsequently, animals in the VPA groups were treated orally with VPA (250 or 500 mg/kg) once a day for 13 days.

KEY FINDINGS

VPA treatment significantly attenuated inflammation and microgliosis in optic nerve in EAE-ON rats, as evidenced by the decrease in the mRNA levels of interferon (INF)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-17, and inducible nitric oxide synthase (iNOS), the suppression in nuclear factor (NF)-κB signal pathway as well as the down-regulation of CD11b expression in optic nerve. Additionally, the apoptotic RGCs were remarkably increased in the EAE retina, which was inhibited by VPA treatment. Consistent with the TUNEL staining, VPA administration also obviously suppressed the ratio of Bax: Bcl-2 and the expression of cleaved caspase-3 and PARP in optic nerve in EAE rats.

SIGNIFICANCE

Our findings demonstrated that VPA treatment could prevent inflammation responses and RGC apoptosis in optic nerve in EAE-ON rats, suggesting that VPA may be available for optic nerve protection during ON.

Development of medical treatment for eye injuries in the mainland of China over the past decade

In the article, the development of medical treatment for eye injuries in the mainland of China was reviewed. According to the data provided in Eye Injury Vitrectomy Study (EIVS), 27% of 72 eyes with no light perception (NLP) gained recovery in term of antomy and visual function. Vitrectomy initiated at more than 4 weeks after open eye injury is an independent risk factor for developing PVR. Prognosis of anatomy and visual function of the injured eye with PVR is markedly worse than that without PVR. Serious injuries of ciliary body, choroid and retina are three key parts of the eye with NLP. The concept that the treatment of the eye injury gradually focus on the whole globe is embodied. The data from 13575 in patients with traumatic eyes in 14 hospitals revealed that the rate of immediate enucleation was remarkable reduced with comparison of 20 years ago.

Morphological and functional changes of the optic nerve following traumatic optic nerve injuries in rabbits

The aim of the present study was to investigate the morphological changes of the optic nerve following traumatic injuries and decompression at different times after injury, and to observe the changes of the visually evoked potentials, to identify the relevant associations between surgical opportunity and the clinical effect of traumatic optic nerve injuries. Rabbits were chosen as the animal model for the study. All the rabbits were randomly divided into five groups (A-E), representing the normal control, decompression in 48 h, in 1 week, in 2 weeks and non-decompression groups, respectively. The pattern reversal visual evoked potentials (P-VEP) and morphological changes of the optic nerve were observed. The P-VEP of each healthy rabbit revealed typical NPN contours, while NPN waves in the injured rabbits were low and flat. The latent period of the P-wave was lengthened and the amplitude was reduced. The differences of the latent period and amplitude pre- and post-trauma were statistically significant. The morphological changes were also assessed. In the normal control group, the astrocytes of the optic nerve exhibited a cylindrical form and were arranged evenly on the vertical section. The neural fibers were arranged neatly, were even following application of a dye, and the cross section exhibited a normal configuration of the blood vessel. For the 48-h decompression group, the arrangement of the astrocytes was even on the vertical section, and vacuoles, slight swelling of the nerve, exudation around the blood vessel and a small amount of astrocytic hyperplasia were observed in the damaged area. In the non-decompression group there were large areas of necrosis, clear nerve demyelination, serious exudation around the blood vessel and astrocytic hyperplasia were observed. In conclusion, the optic nerve decompression is beneficial to protect the visual function in indirect optic nerve injuries. Visual function may be improved by decompression in 48 h compared to 2 weeks. In order to prevent secondary axon injury and to protect visual functions, the decompression should be performed as soon as possible.

Stability of rat models of fluid percussion-induced traumatic brain injury: comparison of three different impact forces

Fluid percussion-induced traumatic brain injury models have been widely used in experimental research for years. In an experiment, the stability of impaction is inevitably affected by factors such as the appearance of liquid spikes. Management of impact pressure is a crucial factor that determines the stability of these models, and direction of impact control is another basic element. To improve experimental stability, we calculated a pressure curve by generating repeated impacts using a fluid percussion device at different pendulum angles. A stereotactic frame was used to control the direction of impact. We produced stable and reproducible models, including mild, moderate, and severe traumatic brain injury, using the MODEL01-B device at pendulum angles of 6°, 11° and 13°, with corresponding impact force values of 1.0 ± 0.11 atm (101.32 ± 11.16 kPa), 2.6 ± 0.16 atm (263.44 ± 16.21 kPa), and 3.6 ± 0.16 atm (364.77 ± 16.21 kPa), respectively. Behavioral tests, hematoxylin-eosin staining, and magnetic resonance imaging revealed that models for different degrees of injury were consistent with the clinical properties of mild, moderate, and severe craniocerebral injuries. Using this method, we established fluid percussion models for different degrees of injury and stabilized pathological features based on precise power and direction control.

Increased Th17 cells and IL‑17 in rats with traumatic optic neuropathy

T helper 17 (Th17) cells are strong inducers of numerous autoimmune diseases and inflammation. However, the role of Th17 cells and interleukin (IL)‑17 in traumatic optic neuropathy (TON) are yet to be elucidated. In the present study, a rat model of TON was established using a fluid percussion brain injury device. Th17 cells were found to be upregulated in the spleens of rats in the TON group. In addition, the level of IL‑17 in the retina of rats in the TON group was observed to increase with the upregulation of the Th17 cells. Furthermore, the expression of IL‑17 in the optic nerve was found to be upregulated between one and seven days following injury in the rats in the TON group. These findings strongly suggest that the ratio of Th17 cells and the expression of IL‑17 are upregulated in rats with TON. These findings also provide a rationale for developing therapeutic agents to treat TON.