Animal Models of Diabetic Retinopathy: Summary and Comparison

Diabetic retinopathy (DR) is a microvascular complication associated with chronic exposure to hyperglycemia and is a major cause of blindness worldwide. Although clinical assessment and retinal autopsy of diabetic patients provide information on the features and progression of DR, its underlying pathophysiological mechanism cannot be deduced. In order to have a better understanding of the development of DR at the molecular and cellular levels, a variety of animal models have been developed. They include pharmacological induction of hyperglycemia and spontaneous diabetic rodents as well as models of angiogenesis without diabetes (to compensate for the absence of proliferative DR symptoms). In this review, we summarize the existing protocols to induce diabetes using STZ. We also describe and compare the pathological presentations, in both morphological and functional aspects, of the currently available DR animal models. The advantages and disadvantages of using different animals, ranging from zebrafish, rodents to other higher-order mammals, are also discussed. Until now, there is no single model that displays all the clinical features of DR as seen in human. Yet, with the understanding of the pathological findings in these animal models, researchers can select the most suitable models for mechanistic studies or drug screening.published_or_final_versio

Stem Cell Therapy for Retinopathy of Prematurity

Retinopathy of Prematurity (ROP) is a leading cause of childhood blindness that severely affecting the quality of life of these children. Few treatment options are available but without favorable outcomes. Stem cell therapy, through its proven potential in tissue regeneration, provides an attractive therapeutic approach in treating ROP and thereby restoring vision.published_or_final_versio

Histological Evaluation of Diabetic Neurodegeneration in the Retina of Zucker Diabetic Fatty (ZDF) Rats

In diabetes, retinal dysfunctions exist prior to clinically detectable vasculopathy, however the pathology behind these functional deficits is still not fully established. Previously, our group published a detailed study on the retinal histopathology of type 1 diabetic (T1D) rat model, where specific alterations were detected. Although the majority of human diabetic patients have type 2 diabetes (T2D), similar studies on T2D models are practically absent. To fill this gap, we examined Zucker Diabetic Fatty (ZDF) rats - a model for T2D - by immunohistochemistry at the age of 32 weeks. Glial reactivity was observed in all diabetic specimens, accompanied by an increase in the number of microglia cells. Prominent outer segment degeneration was detectable with changes in cone opsin expression pattern, without a decrease in the number of labelled elements. The immunoreactivity of AII amacrine cells was markedly decreased and changes were detectable in the number and staining of some other amacrine cell subtypes, while most other cells examined did not show any major alterations. Overall, the retinal histology of ZDF rats shows a surprising similarity to T1D rats indicating that despite the different evolution of the disease, the neuroretinal cells affected are the same in both subtypes of diabetes

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A

On 2017 August 17, the gravitational-wave event GW170817 was observed by the Advanced LIGO and Virgo detectors, and the gamma-ray burst (GRB) GRB 170817A was observed independently by the Fermi Gamma-ray Burst Monitor, and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory. The probability of the near-simultaneous temporal and spatial observation of GRB 170817A and GW170817 occurring by chance is $5.0\times {10}^{-8}$. We therefore confirm binary neutron star mergers as a progenitor of short GRBs. The association of GW170817 and GRB 170817A provides new insight into fundamental physics and the origin of short GRBs. We use the observed time delay of $(+1.74\pm 0.05)\,{\rm{s}}$ between GRB 170817A and GW170817 to: (i) constrain the difference between the speed of gravity and the speed of light to be between $-3\times {10}^{-15}$ and $+7\times {10}^{-16}$ times the speed of light, (ii) place new bounds on the violation of Lorentz invariance, (iii) present a new test of the equivalence principle by constraining the Shapiro delay between gravitational and electromagnetic radiation. We also use the time delay to constrain the size and bulk Lorentz factor of the region emitting the gamma-rays. GRB 170817A is the closest short GRB with a known distance, but is between 2 and 6 orders of magnitude less energetic than other bursts with measured redshift. A new generation of gamma-ray detectors, and subthreshold searches in existing detectors, will be essential to detect similar short bursts at greater distances. Finally, we predict a joint detection rate for the Fermi Gamma-ray Burst Monitor and the Advanced LIGO and Virgo detectors of 0.1-1.4 per year during the 2018-2019 observing run and 0.3-1.7 per year at design sensitivity

Vulnerable vasculature and increased inflammation contribute to earlier death and higher mortality after transient focal ischemia in type 1 diabetic mice

Type 1 diabetic patients are found to be more prone to cerebrovascular mortality from stroke in epidemiological studies, with half median survival when compared with those in the general population. It has been suggested that type 1 diabetes is a risk factor for stroke, but with unclear underlying mechanisms. In this study, we aim to elucidate the potential mechanisms contributing to the exacerbation. Ins2Akita/+ mice, a type 1 diabetic murine model, and their wildtype(Ins2+/+) littermates at 12 weeks of age were challenged with experimental stroke induced by middle cerebral artery occlusion(MCAO)(2h ischemia and 2h or 22 h reperfusion). Survival was recorded at selected intervals and neurological deficits were accessed at the end of reperfusion. Two mm-thick brain slices were stained with 2, 3, 5-triphenyltetrazolium chloride for estimation of the infarct volume, hemispheric swelling and hemorrhagic area. Western blot analyses were performed to compare blood vessel integrity(ZO-1, VEGF, MMP,-2 and MMP-9) and inflammatory response(p Erk and p-p38) in the infarct core and penumbra region. Our results showed that after 2h of reperfusion, the neurological deficit and infarct volume were significantly increased in the Ins2Akita/+ mice. A higher mortality rate and a shorter survival were also observed. Hemorrhage was significantly increased and further advanced with longer reperfusion. VEGF and p Erk were remarkably up-regulated and ZO-1 was down-regulated in the Ins2Akita/+ mice. A trend of increase in MMP-2, MMP-9 and p-p38 were also observed. At 22 h after reperfusion, the expressions of p-Erk and p-p38 still persisted at a significant level. Here, we showed that induction of transient focal ischemia in Ins2Akita/+ mice could mimic the clinical observations of high mortality and shortened survival in type 1 diabetic patients upon stroke. The increased hemorrhage together with VEGF up-regulation and ZO-1 down-regulation indicated that blood vessels were more vulnerable in the Ins2Akita/+ mice. The effect of hemorrhagic transformation was observed as early as 2 h after reperfusion and was further provoked with longer reperfusion. Inflammatory response may also play an important role in the exacerbation of the ischemic injury in Ins2Akita/+ mice

Vulnerable vasculature and increased inflammation contribute to the exacerbation of transient focal ischemia in a genetic mouse model of type 1 diabetes

PURPOSE: Epidemiological studies showed that type 1 diabetic patients are much more prone to cerebrovascular mortality from stroke and the median survival is only half when compared with those in the general population. It has been suggested that type 1 diabetes is a risk factor for stroke; however, the underlying mechanisms are still unclear. In the current study, we aim to elucidate the potential mechanisms contributing to the exacerbation. METHOD: Ins2Akita/+ mice, a type 1 diabetic murine model, and their wildtype (Ins2+/+) littermates at 12 weeks of age were challenged with experimental stroke by middle cerebral artery occlusion (MCAO) for 2h followed by 2h of reperfusion. Survival rate and neurological deficits were accessed at the end of reperfusion. Brain slices were prepared and stained with 2, 3, 5-triphenyltetrazolium chloride for estimating the infarction, hemispheric swelling, and hemorrhagic area. Blood vessel integrity (ZO-1) and inflammatory response (VEGF and pErk) were compared between Ins2Akita/+ and Ins2+/+ ipsilateral brains using Western blot analysis. ER-stress (ATF6, BiP, CHOP, PERK and IRE-1α) and autophagy (Atg12, Bcn1, LC3-a, LC3-b and p62) response were also compared using real-time PCR. RESULTS: Ins2Akita/+ mice showed a decreased survival rate and increased neurological deficits after MCAO, together with a significant increase in infarction and hemorrhage size. Down-regulation of ZO-1 protein and remarkable up-regulation of VEGF and pErk protein were observed in Ins2Akita/+ mice when compared with Ins2+/+ mice. mRNA expression of CHOP was significantly increased in both mice after MCAO challenge and was further augmented in Ins2Aktia/+ mice. Atg12, Bcn1 and LC3-b mRNA expressions were significantly lower in the Ins2+/+ mice after MCAO when compared with the sham-operated controls but there was no difference between the post-MCAO Ins2Akita/+ and Ins2+/+ groups. CONCLUSION: We showed that induction of MCAO in Ins2Akita/+ mice could mimic the clinical observations of high mortality in type 1 diabetic patients upon stroke. Decrease in ZO-1 expression and augmented hemorrhage indicated that blood vessel integrity was more vulnerable in the Ins2Akita/+ mice. Provoked inflammatory response and ER-stress may play important roles in the exacerbation of the ischemic brain, which was evidenced in increased infarction in Ins2Akita/+ mice

Inflammation and vulnerable blood vessels aggravate ischemic injuries in a mouse model of Type 1 diabetes

Poster Presentation - Session 793 - Ischemia: Human - paper no. 793.20 / R17PURPOSE: Patients with type 1 diabetes are more prone to cerebrovascular mortality after stroke and display a more severe post-ischemic outcome. Their median survival is only half when compared with those in the general population. In the current study, we aim to elucidate the potential mechanisms contributing to the exacerbation. METHOD: Ins2Akita/+ mice, a type 1 diabetic mouse model, and their wildtype (Ins2+/+) littermates at 12 weeks of age were challenged with experimental stroke by middle cerebral artery occlusion (MCAO) for 2h followed by 2h of reperfusion. Survival rate and neurological deficits were assessed at the end of reperfusion. Their brain slices were stained with 2, 3, 5-triphenyltetrazolium chloride for estimation of the infarction, hemispheric swelling and hemorrhagic area. Western blot analysis was used to compare levels of ZO-1, VEGF and pErk for assessment of blood vessel integrity and inflammation. ER-stress (ATF6, BiP, CHOP, PERK and IRE-1α) and autophagy (Atg12, Bcn1, LC3-a, LC3-b and p62) response were also assayed using real-time PCR. RESULTS: Decreased survival rate, increased neurological deficits as well as increased infarct and hemorrhage after MCAO were observed in Ins2Akita/+ mice. There were also significant down-regulation of ZO-1 protein and remarkable up-regulation of VEGF and pErk protein. mRNA expression of CHOP was further augmented in Ins2Aktia/+ mice. CONCLUSION: Ins2Akita/+ mice displayed high mortality after MCAO, similar to that in type 1 diabetic patients upon stroke. Augmented cerebral hemorrhage and decreased ZO-1 expression indicated a lower blood vessel integrity in Ins2Akita/+ mice. Provoked inflammatory response and ER-stress may play important roles in the exacerbation of the ischemic brain, which was evidenced in increased infarction in Ins2Akita/+ mice

Over-expression of endothelin-1 in astrocytes lead to chronic cognitive deficit and brain edema after transient middle cerebral artery occlusion

Program / Poster no. 748.11 / Y15Previously, we demonstrated that transgenic mice with the overexpression of endothelin-1 (ET-1) in astrocyte (GET-1) displayed more severe sensorimotor deficits, larger infarct volume and edema after 2 hours of middle cerebral artery occlusion (MCAO) and 22 hours of reperfusion. However, it is not clear whether astrocytic ET-1 has chronic functional deficit after transient MCAO. Here, GET-1 and non-transgenic mice were challenged with 30 minutes of ischemia followed by 1, 3, 7 days and 1, 3 or 5 months of reperfusion. Cognitive deficit was determined by testing their spatial reference memory as well as evaluating their brain lesion and edema by T2-weighted MRI (T2WI). T2WI results indicated that severe brain infarct and edema occurred 3 days after injury in GET-1 mice in the cortex and hippocampus. In addition, glial fibillary acidic protein (GFAP) staining revealed that the number of reactivated astrocytes was increased dramatically in the similar areas with T2WI positive signal. Progressive tissue loss was subsequently observed in the same areas when assessed 3 months after injury. In line with the imaging and histological data, GET-1 mice exhibited severe spatial reference memory impairment when assessed 7 days and 3 months after injury. Taken together, astrocytic ET-1 contributed to cognitive function deficit associated with brain edema and infarct induced by short duration of ischemia.The 38th Annual Meeting of the Society for Neuroscience (Neuroscience 2008), Washington, DC., 15-19 November 2008