FIGURE 7 - uploaded by Randy H Kardon
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Laser cauterization of ICG-filled episcleral veins caused almost complete obstruction of the venous lumen. (A) Control. Arrows: borderlines of an episcleral vein that is positioned in proximity to the conjunctiva of the limbal region. (B) Treated eye. Open arrows: borderlines of an episcleral vein. A fibrous proliferation was evident that almost completely obstructed the venous lumen . C, conjunctival epithelium; CB, ciliary body; S, sclera; EV, episcleral vein lumen. Bar, 50 m.
Source publication
To develop an inducible mouse model of glaucoma.
An obstruction of aqueous humor outflow in adult C57BL6/J mice was induced by combined injection of indocyanine green (ICG) dye into the anterior chamber and diode laser treatment. To evaluate intraocular pressure (IOP), tonometry was performed with a modified Goldmann tonometer. The function of the...
Contexts in source publication
Context 1
... latency of flERG responses, b-waves, and OPs was significantly increased in surgical eyes 28 days after surgery (Fig. 7): a-wave latency control , 22.2 0.7 ms, and latency surgical , 23 0.7 ms (P 0.06, paired t-test); b-wave latency control , 19.6 0.4, and latency surgical , 22 0.9 ms (P 0.03, paired t-test); OPs latency control , 25.2 0.9 ms, and latency surgical , 26.5 0.8 ms (P 0.04, paired t-test); and flERG latency control , 50.6 1.5 ms, and latency ...
Context 2
... electrophysiological studies revealed a reduction of the function in all retinal layers. Histologic analysis was performed to determine whether functional defects were in agreement with the morphologic appearance of the surgical eyes. Light microscopy analysis revealed an obstruction of the episcleral veins (Fig. 7), trabecular meshwork destruction with partial or complete obstruction of Schlemm's canal (Fig. 8), and development of anterior synechia in nine surgical eyes (Fig. 10A). The thickness of all retinal layers appeared de- creased in surgical eyes compared with the control (Fig. 10E). Light microscopy analysis of optic nerves revealed ...
Similar publications
Introduction
Much interest has been addressed to antioxidant dietary supplements that are known to lower the risk of developing glaucoma or delay its progression. Among them, niacin and citicoline protect retinal ganglion cells (RGCs) from degeneration by targeting mitochondria, though at different levels. A well-established mouse model of RGC dege...
Citations
... Various methods have been used to increase the IOP in several species of animals. Cautery of episcleral vessels [17,18], episcleral vein sclerosis with hypertonic saline [19], injection of microbeads into the anterior chamber [20], and laser scarification of the trabecular meshwork [21,22] have been conducted in primates [23], rabbits [24], rats [25], and dogs [26]. The methods of inducible ocular hypertension can be categorized into three types of models: pretrabecular, trabecular, and post-trabecular. ...
Introduction:
The purpose of this study was to establish a novel and reversible experimental ocular hypertension primate model by blocking Schlemm's canal.
Methods:
A model was induced in adult cynomolgus monkeys (n=4) by blocking Schlemm's canal with an inserted microcatheter (200 μm diameter); it was removed 6 weeks later from one monkey to reverse the elevated intraocular hypertension. All animals were monitored for 11 months; weekly measurements of intraocular pressure and biweekly examinations with spectral domain optical coherence tomography and disc photography were performed. Histopathology of the eye and retinal ganglion cell counts were completed at the end of the study.
Results:
The intraocular pressure of the blocked eyes was significantly higher than that of the contralateral eyes at 1 month after the blockage (P <0.001); the mean intraocular pressure was similar to the contralateral eye from 1 week to 11 months after the microcatheter was removed in monkey A (P=0.170). The mean intraocular pressure of the blocked eyes of the remaining monkeys was significantly higher than that of the contralateral eyes throughout the follow-up period (P <0.001). The fundus imaging showed decreases in the retinal nerve fibre layer thickness, and localised defects were observed in two blocked eyes. A histological examination demonstrated that the number of retinal ganglion cells in blocked eyes of monkeys A, B, and C was significantly decreased compared with the control.
Conclusion:
Schlemm's canal blockage alone in the monkey model produces sustained elevation of intraocular pressure, which present a novel animal model for studying the pathogenesis of glaucoma.
... Among them, rodent glaucoma models are frequently used due to the ease and low cost of implementation. Most currently available rodent models are accomplished by laser treatment of the outflow area, [13][14][15] cautery or affliction of osmotic damage to the episcleral and vortex veins, 16,17 external ocular compression using circumlimbal suture, [18][19][20] or injection of beads [21][22][23][24][25][26][27][28] or hydrogel [33][34][35][36][37][38] into the anterior chamber. Each rodent glaucoma model, however, is established based on a different rat strain, 28 and strains are reported to have different IOP and RGC death profiles. ...
Purpose:
To compare the inter-strain differences of three rodent glaucoma models as induced by magnetic bead injection, hydrogel injection, and circumlimbal suture.
Methods:
In Brown Norway (BN) and Sprague Dawley (SD) rat strains, intraocular pressure (IOP) was elevated by injection of magnetic beads or hydrogel to obstruct the aqueous humor outflow or by external compression of circumlimbal suture. Maximum and average IOP values were compared according to both procedure and rat strain over 1 month postoperatively. Retinal ganglion cell (RGC) density loss was evaluated using confocal microscopic images of the flat-mounted retina obtained at postoperative days 14 and 30.
Results:
The maximum IOPs were higher in the hydrogel injection or circumlimbal injection models than in the magnetic bead injection model (P < 0.001), whereas average IOP showed no difference between the two strains (both P ≥ 0.05). A generalized estimating equation regression model showed that the IOP increase was maintained better in the BN rats than in the SD rats (P < 0.001). Such inter-strain difference was smaller in the circumlimbal suture model. A significant decrease in RGC density was observed in all of the models for the BN rats and in the circumlimbal suture model for the SD rats at postoperative day 30.
Conclusions:
BN rats were advantageous for the magnetic bead or hydrogel injection model, but either rat strain could be used for the circumlimbal suture model. Strains should be considered cautiously when establishing rodent glaucoma models with different IOP profiles.
Translational relevance:
This comparison offers the best strain for each rodent glaucoma model for assessment of glaucoma-relevant therapeutics.
... One week after intracameral injection of fibroblasts, pupil atresia occurred, which might be the primary cause of the elevated IOP that lasted for approximately 2 months. In contrast with other methods to maintain elevated IOP [20,21,28,29], this model may have some advantages, including being simple to carry out, only requiring a single operation, and meeting the standards of low cost and moderately high IOP with a long duration and stability. Nevertheless, due to pupil occlusion, the visual axis was obstructed during in vivo observation of the retina or optic disc with a fundoscope or fundus-imaging instru-ment. ...
Glaucoma is the leading cause of irreversible blindness worldwide, and pathologically elevated intraocular pressure (IOP) is the major risk factor. Neuroprotection is one of the potential therapies for glaucomatous retinal damage. Intravitreal mesenchymal stem cell (MSC) transplantation provides a viable therapeutic option, and human umbilical cord- (hUC-) MSCs are attractive candidates for cell-based neuroprotection. Here, we investigated the ability of transplanted hUC-MSCs to survive and migrate within the vitreous cavity and their neuroprotective effects on chronic glaucomatous retina. For this, we developed a chronic ocular hypertension (COH) rat model through the intracameral injection of allogeneic Tenon’s fibroblasts. Green fluorescent protein-transduced hUC-MSCs were then injected into the vitreous cavity one week after COH induction. Results showed that a moderate IOP elevation lasted for two months. Transplanted hUC-MSCs migrated toward the area of damaged retina, but did not penetrate into the retina. The hUC-MSCs survived for at least eight weeks in the vitreous cavity. Moreover, the hUC-MSCs were efficient at decreasing the loss of retinal ganglion cells; retinal damage was attenuated through the inhibition of apoptosis. In this study, we have developed a novel COH rat model and demonstrated the prolonged neuroprotective potential of intravitreal hUC-MSCs in chronic glaucoma.
... Anatomically, conventional rodent models, such as rats and mice, do not have the lamination of the LGN and the numbers of the LGN lamina in these models differ from those in carnivores and primates [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Therefore, an experimental monkey model of glaucoma has been anticipated to be an ideal model for the evaluation of central visual system changes in glaucoma. ...
We investigated structural changes and astrocyte responses of the lateral geniculate nucleus (LGN) in a ferret model of ocular hypertension (OH). In 10 ferrets, OH was induced via the injection of cultured conjunctival cells into the anterior chamber of the right eye; six normal ferrets were used as controls. Anterograde axonal tracing with cholera toxin B revealed that atrophic damage was evident in the LGN layers receiving projections from OH eyes. Immunohistochemical analysis with antibodies against NeuN, glial fibrillary acidic protein (GFAP), and Iba-1 was performed to specifically label neurons, astrocytes, and microglia in the LGN. Significantly decreased NeuN immunoreactivity and increased GFAP and Iba-1 immunoreactivities were observed in the LGN layers receiving projections from OH eyes. Interestingly, the changes in the immunoreactivities were significantly different among the LGN layers. The C layers showed more severe damage than the A and A1 layers. Secondary degenerative changes in the LGN were also observed, including neuronal damage and astrocyte reactions in each LGN layer. These results suggest that our ferret model of OH is valuable for investigating damages during the retina–brain transmission of the visual pathway in glaucoma. The vulnerability of the C layers was revealed for the first time.
... Thus, the altered flicker responses that we observe represents a change in cone pathway activity at the level of the inner retina. Retinal Ganglion Cell dysfunction and degeneration in a model of glaucoma greatly alters the flicker response (Grozdanic et al., 2003) The copyright holder for this preprint (which was not peer-reviewed) is the . https://doi.org/10.1101/2020.02.12.945584 doi: bioRxiv preprint inhibitory PV cells in V1 cortex and interference with its non-cell autonomous activity perturbs the normal opening and closing of the critical period for ocular dominance plasticity by altering the balance of excitation and inhibition (Sugiyama et al., 2008;Bernard et al., 2016). ...
OTX2 is a homeoprotein transcription factor expressed in photoreceptors and bipolar cells in the retina. OTX2, like many other homeoproteins, transfers between cells and exerts non-cell autonomous effects such as promoting survival of retinal ganglion cells that do not express the protein. Here we used a genetic approach to target extracellular OTX2 in the retina by conditional expression of a secreted single chain anti-OTX2 antibody. Compared to control mice, the expression of this antibody by Parvalbumin-expressing neurons in the retina is followed by a reduction in visual acuity in one-month-old mice with no alteration of the retinal structure or cell type number or aspect. A- and b-waves measured by electroretinogram were also indistinguishable from control mice, suggesting no functional deficit of photoreceptors and bipolar cells. Mice expressing the OTX2-neutralizing antibody did show a significant doubling in the flicker amplitude, consistent with a change in inner retinal function. Our results show that interfering in vivo with OTX2 non-cell autonomous activity in the postnatal retina leads to an alteration in inner retinal cell functions and causes a deficit in visual acuity.
Significance statement
OTX2 is a homeoprotein transcription factor expressed in retinal photoreceptors and bipolar cells. Although the Otx2 locus is silent in the inner retina, the protein is detected in cells of the ganglion cell layer consistent with the ability of this class of proteins to transfer between cells. We expressed a secreted single chain antibody (scFv) against OTX2 in the retina to neutralize extracellular OTX2. Antibody expression leads to reduced visual acuity with no change in retinal structure, or photoreceptor or bipolar physiology; however, activity in the inner retina was altered. Thus, interfering with OTX2 non-cell autonomous activity in postnatal retina alters inner retinal function and causes vision loss, highlighting the physiological value of homeoprotein direct non-cell autonomous signaling.
... While nonhuman primates represent the most ideal animal model for certain types of glaucoma research due to their complex load-bearing collagenous lamina cribrosa resembling humans, [10][11][12][13] these models are costly and, thus, not applicable to larger studies required to evaluate new treatments. Alternatively, many researchers have chosen to use rat [14][15][16][17][18][19][20] or mouse [21][22][23][24] models of glaucoma in their research. Murine models have the advantage of allowing unparalleled study of the genetic and molecular pathobiology underlying glaucoma. ...
Purpose
Primates and rodents are used widely as animal models of glaucoma, but each has significant limitations. Researchers need additional animal models that closely resemble the relevant anatomy and pathologic features of the human disease to more quickly advance research. We validate a novel glaucoma animal model in tree shrews (Tupaia belangeri).
Methods
Experimental glaucoma was induced in adult tree shrews (n = 8) by injecting 50 μL of a 25 mg/mL ferromagnetic bead solution into the anterior chamber. Beads were directed into the iridocorneal angle with a magnet to impede aqueous outflow. Animals were followed for 3 months with weekly IOP measurements and biweekly spectral domain optical coherence tomography (SD-OCT) images of the optic nerve head. Histopathology of the optic nerve and optic nerve axon counts were completed at the end of the study.
Results
The 12-week average mean IOP was 22.7 ± 3.6 and 8.6 ± 2.9 mm Hg in the treated and control eyes, respectively. Longitudinal analysis showed significant retinal nerve fiber layer (RNFL) thinning throughout the study. Axon counts were significantly reduced (59.7%) in treated versus control eyes. SD-OCT imaging showed cupping and posterior displacement of the lamina cribrosa in glaucomatous eyes. RNFL thickness and optic nerve axon counts were reduced consistent with IOP elevation. Optic nerves demonstrated histopathology consistent with glaucomatous optic neuropathy.
Conclusions
Tree shrews with experimental glaucoma show key pathologic characteristics of the human disease. The tree shrew model of glaucoma has the potential to help researchers accelerate our understanding of glaucoma pathophysiology.
... In order to increase the local photocoagulative effect of diode laser (810 nm) treatment, Grozdanic et al. 77 injected 10 mL of photosensitive dye (10 mg/mL indocyanine green) into the AC of C57/BL6 mice 20 min prior to laser exposure and induction of COH. A significant, sustained increase in IOP was detected in the first 6 wk in 88% of the laser-treated eyes, which subsequently returned to normal levels after 8 wk. ...
Glaucoma, a form of progressive optic neuropathy, is the second leading cause of blindness worldwide. Being a prominent disease affecting vision, substantial efforts are being made to better understand glaucoma pathogenesis and to develop novel treatment options including neuroprotective and neuroregenerative approaches. Cell transplantation has the potential to play a neuroprotective and/or neuroregenerative role for various ocular cell types (e.g., retinal cells, trabecular meshwork). Notably, glaucoma is often associated with elevated intraocular pressure, and over the past 2 decades, several rodent models of chronic ocular hypertension (COH) have been developed that reflect these changes in pressure. However, the underlying pathophysiology of glaucoma in these models and how they compare to the human condition remains unclear. This limitation is the primary barrier for using rodent models to develop novel therapies to manage glaucoma and glaucoma-related blindness. Here, we review the current techniques used to induce COH-related glaucoma in various rodent models, focusing on the strengths and weaknesses of the each, in order to provide a more complete understanding of how these models can be best utilized. To so do, we have separated them based on the target tissue (pre-trabecular, trabecular, and post-trabecular) in order to provide the reader with an encompassing reference describing the most appropriate rodent COH models for their research. We begin with an initial overview of the current use of these models in the evaluation of cell transplantation therapies.
... 14 It was later reported that chronic hypertension can also be achieved in mice using laser photocoagulation by targeting both the limbus and the episcleral veins, 15 by targeting the limbus following anterior chamber cannulation, 16 by targeting the trabecular meshwork through the limbus, 17 or by targeting the trabecular meshwork and the episcleral veins. 18 Fu et al. 19 reported a mouse model of acute ocular hypertension by laser photocoagulation of both limbal and episcleral vessels, and with this model, IOP elevation returns to normal within 1 week post-procedure. All these models, whether of the acute or chronic type, cause damage to the anterior chamber angles and are thus not ideal for our research purpose. ...
... In this study, we also observed pupil dilation upon IOP elevation, as reported previously. 18 This may be due to compromised pupil sphincter upon IOP elevation because iris blood vessels are not autoregulated. 34,35 This phenomenon is also seen in patients of acute glaucoma. ...
PURPOSE. This study was designed to develop and characterize a laser-induced model of acute
intraocular hypertension that permits the study of the anterior segment of the eye.
METHODS. CD1 mice aged 5 and 8 weeks were examined for elevation of IOP induced by laser
photocoagulation. We compared between occlusion of episcleral veins alone and when
combined with 2708 limbal vessel occlusion. Anterior chamber angle, corneal thickness, and
retinal nerve fiber layer (RNFL) thickness were evaluated by anterior- and posterior-segment
optical coherence tomography (OCT). Additionally, at day 7 post-procedure, the anterior
segment was evaluated for inflammatory cellular presentation by histologic analysis and OCT,
and limbal vessels and whole-mount retina were immunostained for CD31 and Brn3a,
respectively. Brn3a-positive retinal ganglion cells (RGCs) were quantified with ImageJ
software.
RESULTS. After single or combined laser treatment in mice aged 5 or 8 weeks, IOP was
significantly elevated for 5 to 6 days before returning to the baseline by day 7 post-procedure.
Anterior segment assessment indicated less synechiae in the anterior chamber angle and
better preserved limbal vessels with single versus combined laser treatment. Corneal
thickness was significantly increased after single or combined treatment. No inflammatory
cells were detected in the anterior chamber. The thickness of the RNFL and the density of
RGCs were both significantly reduced after single or combined treatment.
CONCLUSIONS. Laser photocoagulation of episcleral veins alone in CD1 mice aged 5 to 8 weeks
may be used to induce ocular hypertension resulting in RNFL thinning and ganglion cell loss.
This model permits the study of the anterior as well as the posterior segment of the eye.
... Mice are also amenable to induction of ocular hypertension by translimbal laser photocoagulation. Pigmentary pretreatment with indocyanine green followed by diode photocoagulation leads to IOP elevation for at least 30 days with subsequent loss of RGC structure and function (Grozdanic et al. 2003). Flattening of the anterior chamber via paracentesis appears to be more critical in this species, and leads to longer periods of IOP elevation, with one report suggesting that IOP remains above 20 mmHg for 4 months following photocoagulation (Feng et al. 2013a). ...
Glaucoma is a major cause of vision impairment worldwide. It is characterized by progressive retinal ganglion cell degeneration that can be attenuated by adequate reduction of intraocular pressure. Animal models of glaucoma have contributed significantly to our understanding of the pathogenesis of glaucoma and the development of treatments for the disease. The most commonly used experimental models are derived from rodents, which have important advantages over larger animal models, and several new rodent models have been developed and characterized in recent years. Here, we review the most important mouse and rat models of glaucoma, highlight recent progress in the development of new glaucoma models, and explore the strengths and weaknesses of these models for studying human disease.
... Many kinds of rodent models that simulate glaucoma pathology by blocking the outflow of aqueous humor to initiate chronic IOP elevation have been explored in recent decades (Johnson and Tomarev, 2010;Morrison et al., 2011). Among the commonly applied COH models, laser photocoagulation of the trabecular meshwork at the limbus (Aihara et al., 2003;Grozdanic et al., 2003), occlusion of the episcleral veins by cauterization or suture ligation (Shareef et al., 1995;Yu et al., 2006) and injection of microbeads into the anterior chamber (Sappington et al., 2010;Yang et al., 2012;Feng et al., 2013) are the most frequently used ones. There are advantages and disadvantages in these models (Goldblum and Mittag, 2002). ...
Glaucoma is an irreversible and blinding neurodegenerative disease of the eye, and is characterized by progressive loss of retinal ganglion cells (RGCs). Since endogenous hydrogen sulfide (H2S) was reported to be involved in neurodegeneration in central nervous system, the authors aimed to develop a chronic ocular hypertension (COH) rat model simulating glaucoma and therein test the H2S level together with the retinal protein expressions of related synthases, and further investigated the effect of exogenous H2S supplement on RGCs survival. COH rat model was induced by cross-linking hydrogel injection into anterior chamber, and the performance of the model was assessed by intraocular pressure (IOP) measurement, RGCs counting and retinal morphological analysis. Endogenous H2S level was detected along with the retinal protein expressions of H2S-related synthases cystathionine β-synthase (CBS), cystathionine γ-lyase (CSE) and 3-mercaptopyruvate sulfurtransferase (3-MST) in the COH rats. Retinal H2S level and RGCs survival were evaluated again after NaHS (a H2S donor) treatment in the COH rats. The results showed that the COH model succeeded in simulating glaucoma features, and retinal H2S level decreased significantly when the retinal protein expressions of CBS, CSE and 3-MST were downregulated generally in the COH rats. Furthermore, the decrease of retinal H2S level and loss of RGCs were both improved by NaHS treatment in experimental glaucoma, without obvious variation of IOP. Our study revealed that the intracameral injection of cross-linking hydrogel worked efficiently in modeling glaucoma, and H2S had protective effect on RGCs and might be involved in the pathological mechanism of glaucomatous neuropathy.
