RAGE and its ligand amyloid beta promote retinal ganglion cell loss following ischemia-reperfusion injury.

Introduction: Glaucoma is a progressive neurodegenerative disease associated with age. Accumulation of amyloid-beta (Aß) proteins in the ganglion cell layer (GCL) and subsequent retinal ganglion cell (RGC) loss is an established pathological hallmark of the disease. The mechanism through which Aß provokes RGC loss remains unclear. The receptor for the advanced glycation end product (RAGE), and its ligand Aß, have been shown to mediate neuronal loss via internalizing Aß within the neurons. In this study, we investigated whether the RAGE-Aß axis plays a role in RGC loss in experimental glaucoma. Methods: Retinal ischemia was induced by an acute elevation of intraocular pressure in RAGE-/- and wild-type (WT) control mice. In a subset of animals, oligomeric Aß was injected directly into the vitreous of both strains. RGC loss was assessed using histology and biochemical assays. Baseline and terminal positive scotopic threshold (pSTR) were also recorded. Results: Retinal ischemia resulted in 1.9-fold higher RGC loss in WT mice compared to RAGE-/- mice (36 ± 3% p < 0.0001 vs. 19 ± 2%, p = 0.004). Intravitreal injection of oligomeric Aß resulted in 2.3-fold greater RGC loss in WT mice compared to RAGE-/- mice, 7-days post-injection (55 ± 4% p = 0.008 vs. 24 ± 2%, p = 0.02). We also found a significant decline in the positive scotopic threshold response (pSTR) amplitude of WT mice compared to RAGE-/- (36 ± 3% vs. 16 ± 6%). Discussion: RAGE-/- mice are protected against RGC loss following retinal ischemia. Intravitreal injection of oligomeric Aß accelerated RGC loss in WT mice but not RAGE-/-. A co-localization of RAGE and Aß, suggests that RAGE-Aß binding may contribute to RGC loss.

First uterine transplant case at the Royal Prince Alfred Hospital.

Uterine transplantation (UT) is an emerging medical treatment for women affected by absolute uterine factor infertility (AUFI). To date there have been over 90 documented cases of UT performed worldwide, with over 50 live births. UT allows women affected by AUFI the opportunity to carry and deliver a childd. The Royal Prince Alfred Hospital (RPAH) introduced a UT study in 2019; however, due to the impacts of the COVID pandemic the study was placed on hold for two years. In February 2023, RPAH performed the centre's first UT from a living unrelated donor to a 25-year-old woman with Mayer-Rokitansky-Küster-Hauser syndrome. The donor and recipient surgeries were uncomplicated and both are recovering well in the early post-operative period.

Uterus transplantation and pregnancy induction: Approved protocol at the Royal Prince Alfred Hospital.

Absolute uterine factor infertility (AUFI) is defined as the absence of a uterus or the presence of a non-functional uterus. Before the first live birth from a uterus transplant in 2014, the only fertility options for women with AUFI were surrogacy and adoption. In November 2019, our team was granted approval for the first uterus transplant trial in Australia using known living donors. Our program is based on that of our overseas collaborators in Dallas, Texas; this team will also be proctoring us for our first two cases.

Heart rate and blood pressure dependence of aortic distensibility in rats: comparison of measured and calculated pulse wave velocity.

OBJECTIVES: When assessing arterial stiffness, heart rate (HR) and blood pressure (BP) are potential confounders. It appears that the HR/BP dependences of pulse wave velocity (PWV) and distensibility are different, even though both assess arterial stiffness. This study aims to compare aortic PWV as measured using pulse transit time (PWVTT) and as calculated from distensibility (PWVdist) at the same measurement site and propose a solution to the disparity in dependences of PWVTT and PWVdist. METHODS: Adult anaesthetized rats (n = 24) were randomly paced at HRs 300-500 bpm, at 50 bpm steps. At each step, aortic PWVTT (two pressure-tip catheters) and PWVdist (pressure-tip catheter and ultrasound wall-tracking; abdominal aorta) were measured simultaneously while BP was varied pharmacologically. RESULTS: HR dependence of PWVdist paradoxically decreased at higher levels of BP. In addition, BP dependence of PWVdist was much larger than that of PWVTT. These discrepancies are explained in that standard PWVdist uses an approximate derivative of pressure to diameter, which overestimates PWV with increasing pulse pressure (PP). In vivo, PP decreases as HR increases, potentially causing a PWVdist decrease with HR. Estimating the full pressure-diameter curve for each HR corrected for this effect by enabling calculation of the true derivative at diastolic BP. This correction yielded a PWVdist that shows HR and BP dependences similar to those of PWVTT. As expected, BP dependence of all PWV metrics was much larger than HR dependence. CONCLUSION: Measured and calculated PWV have different dependences on HR and BP. These differences are, at least in part, because of approximations made in using systolic and diastolic values to calculate distensibility.

A longitudinal assessment of retinal function and structure in the APP/PS1 transgenic mouse model of Alzheimer's disease.

BACKGROUND: A great body of evidence suggests that there are retinal functional and structural changes that occur in Alzheimer's disease (AD). However, whether such changes are primary or secondary remains to be elucidated. We studied a range of retinal functional and structural parameters in association with AD- specific pathophysiological markers in the double transgenic APP/PS1 and control mice across age. METHODS: Electroretinogram (ERG) and optical coherence tomography (OCT) was performed in APP/PS1 and wild type (WT) control mice every 3 months from 3 to 12 months of age. For functional assessment, the a- and b-wave of the ERG, amplitude of oscillatory potentials (OP) and the positive scotopic threshold response (pSTR) were quantified at each time point. For structural assessment, the inner and outer retinal thickness was segmented and measured from OCT scans. Episodic memory was evaluated at 6, 9 and 12 months of age using the novel object recognition test. Amyloid beta (Aß) distribution in the hippocampus and the retina were visualised at 3, 6 and 12 months of age. Inter- and intra- group analysis was performed to study rate of change for each parameter between the two groups. RESULTS: Inter-group analysis revealed a significant difference in b-wave and OPs of APP/PS1 compared to WT controls starting from 3 months (p < 0.001). There was also a significant difference in the amplitude of pSTR between the two groups starting from 6 months (p < 0.001). Furthermore, a significant difference in the inner retinal thickness, between the two groups, was observed starting from 9 months (p < 0.001). CONCLUSIONS: We observed an age-related decline in retinal functional and structural parameters in both APP/PS1 and WT controls, however, inter-group analysis revealed that inner retinal functional and structural decline is exacerbated in APP/PS1 mice, and that retinal functional changes precede structural changes in this strain. Further studies are required to confirm whether such phenomenon occurs in humans and if studying retinal functional changes can aid-in early assessment of AD.

Postural effects on spontaneous retinal venous pulsations in healthy individuals.

PURPOSE: To assess amplitudes of spontaneous retinal venous pulsations (SVP) in three various postures (sitting, supine and lateral decubitus) in healthy individuals. METHODS: Thirty participants (28 ± 8 years, 25 females) were included in the study. Intraocular pressure (IOP), blood pressure (BP) and SVP's were measured at three different postures using a calibrated Tono-Pen applanation tonometer, a digital sphygmomanometer, and a custom-built handheld video ophthalmoscope, respectively. Retinal venous pulsations (SVP) amplitudes were extracted from the retinal videos using a custom written MATLAB algorithm. Mean arterial pressure (MAP = (systolic + 2diastolic)/3) and mean ocular perfusion pressure (MOPP = (2/3 MAP)-IOP) were also calculated at each posture. A one-way ANOVA was applied to each parameter to determine any significant difference for the various postural changes. RESULTS: Mean IOP increased (p < 0.0001) and mean SVP decreased (p < 0.0001) from sitting to supine. The mean IOP (mmHg) and SVP (MU; measuring units) in sitting, supine and lateral decubitus were 16.2 ± 2, 19.4 ± 4, 19.8 ± 2 mmHg and 5.8 ± 2, 4.5 ± 2, and 4.7 ± 2 MU, respectively. Mean arterial pressure (MAP) and MOPP also decreased significantly from sitting to supine (p < 0.001, p < 0.001) and sitting to lateral decubitus (p < 0.05, p < 0.01). There were no significant differences between IOP, SVP, MAP or MOPP during a postural modification from supine to lateral decubitus. CONCLUSIONS: In this study, we showed a significant reduction in SVP amplitudes and a significant increase in IOP from sitting to supine position in a healthy young cohort. This supports the rationale to further study such phenomenon in ocular conditions such as glaucoma to determine whether relative SVP change, for a similar postural change, can reveal early signs of vascular dysfunction.

Quantitative Retinal Vascular Changes in Obstructive Sleep Apnea.

PURPOSE: To examine the relationship between both static and dynamic retinal vascular caliber and the severity of obstructive sleep apnea (OSA). DESIGN: Prospective cross-sectional study. METHODS: Adult patients undergoing diagnostic polysomnography studies at a private Australian university teaching hospital were recruited. OSA severity was defined by the apnea-hypopnea index (AHI): severe >30, moderate >15-30, mild 5-15, and controls <5. Of 115 patients recruited (73 male; mean age 58 ± 13 years), there were 41 severe, 35 moderate, and 25 mild OSA patients and 14 controls. Static retinal vascular caliber was measured as the average diameter of retinal arterioles (CRAE) and venules (CRVE), and summarized as the arteriovenous ratio (AVR). Dynamic retinal vascular caliber was evaluated as the average pulsation amplitude of retinal arterioles (SRAP) and venules (SRVP). Comparisons across groups were performed using multivariate linear regression analysis. All results were adjusted for age, body mass index, and mean arterial pressure. RESULTS: Increasing AHI was significantly associated with decreasing AVR (P = .008) and CRAE (P = .016). A significant relationship was demonstrated between increasing AHI and attenuated retinal vascular pulsation amplitude (arterioles P = .028; venules P < .0001). CONCLUSIONS: Increasing OSA severity is independently associated with retinal arteriolar narrowing and attenuated vascular pulsation amplitude. The retinal vasculature is easily imaged, and may be a surrogate biomarker of cerebral and systemic vascular risk in patients with OSA requiring further comprehensive investigation.

Diagnostic and Prognostic Potential of Retinal Biomarkers in Early On-Set Alzheimer's Disease.

OBJECTIVE: Accumulating evidence suggests that the eye can be used in the assessment of early on-set Alzheimer's disease (AD). The eye offers a natural window to the brain through the retina. The retina and brain share common developmental origins and patho-physiological origins and mechanisms, having been sequestered from it during early development, but retaining its connections with the brain via the optic nerve. Therefore, it is well understood that neurological abnormalities have a direct profound impact on the retina. Recent studies suggest an array of physiological and pathological changes in the retina in dementia and specifically in AD. There are also reports on imaging the two hallmark proteins of the disease, extracellular amyloid beta peptides and intracellular hyper phosphorylated tau protein, as a proxy to neuroimaging. RESULTS: In this review, we summarise retinal structural, functional and vascular changes reported to be associated with AD. We also review techniques employed to image these two major hall mark proteins of AD and their relevance for early detection of AD.

Retinal vascular and structural changes are associated with amyloid burden in the elderly: ophthalmic biomarkers of preclinical Alzheimer's disease.

BACKGROUND: Retinal imaging may serve as an alternative approach to monitor brain pathology in Alzheimer's disease (AD). In this study, we investigated the association between retinal vascular and structural changes and cerebral amyloid-ß (Aß) plaque load in an elderly cohort. METHODS: We studied a total of 101 participants, including 73 elderly subjects (79 ± 5 years, 22 male) with no clinical diagnosis of AD but reporting some subjective memory change and an additional 28 subjects (70 ± 9 years, 16 male) with clinically established AD. Following a complete dilated ocular examination, the amplitude of retinal vascular pulsations and dynamic response, retinal nerve fibre layer thickness and retinal ganglion cell layer (RGCL) thickness were determined in all patients. Systemic blood pressure and carotid-to-femoral pulse wave velocity were measured. The elderly cohort also underwent magnetic resonance imaging and 18F-florbetaben (FBB)-positron emission tomographic amyloid imaging to measure neocortical Aß standardised uptake value ratio (SUVR), and this was used to characterise a 'preclinical' group (SUVR >1.4). RESULTS: The mean FBB neocortical SUVR was 1.35 ± 0.3. The amplitude of retinal venous pulsations correlated negatively with the neocortical Aß scores (p < 0.001), whereas the amplitude of retinal arterial pulsations correlated positively with neocortical Aß scores (p < 0.01). RGCL thickness was significantly lower in the clinical AD group (p < 0.05). CONCLUSIONS: The correlation between retinal vascular changes and Aß plaque load supports the possibility of a vascular component to AD. Dynamic retinal vascular parameters may provide an additional inexpensive tool to aid in the preclinical assessment of AD.

Amyloid ß accumulation and inner retinal degenerative changes in Alzheimer's disease transgenic mouse.

The APP-PS1ΔE9 mouse model of Alzheimer's disease (AD) exhibits age dependent amyloid ß (Aß) plaque formation in their central nervous system due to high expression of mutated human APP and PSEN1 transgenes. Here we evaluated Aß deposition and changes in soluble Aß accumulation in the retinas of aged APP-PS1 mice using a combination of immunofluorescence, retinal flat mounts and western blotting techniques. Aß accumulation in the retina has previously been shown to be associated with retinal ganglion cell apoptosis in animal models of glaucoma. This study investigated changes in the inner retinal function and structure in APP-PS1 mice using electrophysiology and histological approaches respectively. We report for the first time a significant decline in scotopic threshold response (STR) amplitudes which represents inner retinal function in transgenic animals compared to the wild type counterparts (p<0.0001). Thinning of the retina particularly involving inner retinal layers and reduction in axonal density in the optic nerve was also observed. TUNEL staining was performed to examine neuronal apoptosis in the inner retina. Intraocular pressure (IOP) measurements showed that APP-PS1ΔE9 mice had a slightly elevated IOP, but the significance of this finding is not yet known. Together, these results substantiate previous observations and highlight that APP-PS1ΔE9 mice show evidence of molecular, functional and morphological degenerative changes in the inner retina.

High speed in-vivo imaging of retinal hemodynamics in a rodent model of hypertension.

The eye is the only organ through which microcirculation can be visualized non-invasively. This unique feature makes the eye and specifically retinal vasculature an excellent target area to monitor and study micro-vascular damage in systemic diseases. Dynamic (real-time) changes of retinal vessels have been shown to be more specific to the disease in comparison with static measurements. In this study we utilize high speed imaging (i.e. 125 fps) to study and derive dynamic changes of retinal vessels in a rat model of hypertension. A Eulerian video magnification algorithm was used to extract retinal arterial and venous pulse amplitude from five Spontaneously Hypertensive Rats (SHR) and five Wister Kyoto (WKY) rats were used as the control group. Results showed that retinal arterial diameter and pulse amplitude are significantly lower in the SHRs compared with WKYs. Dynamic biomarkers of retinal micro-vasculature may be used as a diagnostic tool for systemic diseases.

Correlation of retinal nerve fibre layer thickness and spontaneous retinal venous pulsations in glaucoma and normal controls.

PURPOSE: To study the relationship between amplitude of spontaneous retinal venous pulsatility (SRVP) and retinal nerve fibre layer (RNFL) thickness in glaucomatous eyes, and to determine if this parameter may be a potential marker for glaucoma severity. METHOD: 85 subjects including 50 glaucoma (21 males, 67±10 yrs) and 35 normals (16 males, 62±11 yrs) were studied. SRVP amplitude was measured using the Dynamic Vessel Analyser (DVA, Imedos, Germany) at four regions of the retina simultaneously within one disc diameter from the optic disc--temporal-superior (TS), nasal-superior (NS), temporal-inferior (TI) and nasal-inferior (NI)). This was followed by RNFL thickness measurement using spectral domain optical coherence tomography (Spectralis OCT). The correlation between SRVP amplitude and corresponding sectoral RNFL thickness was assessed by means of non-linear regression (i.e. logarithmic). Linear regression was also applied and slopes were compared using analysis of covariance (ANCOVA). RESULTS: Greater SRVP amplitude was associated with thicker RNFL. Global SRVP amplitude was significantly lower in glaucoma eyes compared with normals (p<0.0001). The correlation coefficient of the linear regression between RNFL and SRVP at TS, NS, TI and NI quadrants in the glaucoma group were r = 0.5, 0.5, 0.48, 0.62. Mean SRVP amplitude and RNFL thickness for TS, NS, TI and NI quadrants were 4.3±1.5, 3.5±1.3, 4.7±1.6, 3.1±1 µm and 96±30, 75±22, 89±35 and 88±30 µm, respectively. The ANCOVA test showed that the slope of linear regression between the four quadrants was not significant (p>0.05). Since the slopes are not significantly different, it is possible to calculate one slope for all the data. The pooled slope equals 10.8 (i.e. RNFL = 10.8SRVP+41). CONCLUSION: While SRVP was present and measurable in all individuals, the amplitude of SRVP is reduced in glaucoma with increasing RNFL loss. Our findings suggest the degree of SRVP may be an additional marker for glaucoma severity. Further studies are needed to determine the mechanism of reduction in SRVP, and whether changes can predict increased risk of progression.

Dog behavior co-varies with height, bodyweight and skull shape.

Dogs offer unique opportunities to study correlations between morphology and behavior because skull shapes and body shape are so diverse among breeds. Several studies have shown relationships between canine cephalic index (CI: the ratio of skull width to skull length) and neural architecture. Data on the CI of adult, show-quality dogs (six males and six females) were sourced in Australia along with existing data on the breeds' height, bodyweight and related to data on 36 behavioral traits of companion dogs (n = 8,301) of various common breeds (n = 49) collected internationally using the Canine Behavioral Assessment and Research Questionnaire (C-BARQ). Stepwise backward elimination regressions revealed that, across the breeds, 33 behavioral traits all but one of which are undesirable in companion animals correlated with either height alone (n = 14), bodyweight alone (n = 5), CI alone (n = 3), bodyweight-and-skull shape combined (n = 2), height-and-skull shape combined (n = 3) or height-and-bodyweight combined (n = 6). For example, breed average height showed strongly significant inverse relationships (p<0.001) with mounting persons or objects, touch sensitivity, urination when left alone, dog-directed fear, separation-related problems, non-social fear, defecation when left alone, owner-directed aggression, begging for food, urine marking and attachment/attention-seeking, while bodyweight showed strongly significant inverse relationships (p<0.001) with excitability and being reported as hyperactive. Apart from trainability, all regression coefficients with height were negative indicating that, across the breeds, behavior becomes more problematic as height decreases. Allogrooming increased strongly (p<0.001) with CI and inversely with height. CI alone showed a strong significant positive relationship with self-grooming (p<0.001) but a negative relationship with chasing (p = 0.020). The current study demonstrates how aspects of CI (and therefore brain shape), bodyweight and height co-vary with behavior. The biological basis for, and significance of, these associations remain to be determined.