Relationship of aqueous outflow resistance to age and total volume perfused in rhesus and cynomolgus monkeys

NCX 470 Reduces Intraocular Pressure More Effectively Than Lumigan in Dogs and Enhances Conventional and Uveoscleral Outflow in Non-Human Primates and Human Trabecular Meshwork/Schlemm's Canal Constructs

Purpose: To determine NCX 470 (0.1%) and Lumigan® (bimatoprost ophthalmic solution, 0.01%-LUM) intraocular pressure (IOP)-lowering activity after single or repeated (5 days) dosing along with changes in aqueous humor (AH) dynamics. Methods: Ocular hypotensive activity of NCX 470 and LUM was compared with vehicle (VEH) in Beagle dogs using TonoVet®. Non-human primates (NHP) and bioengineered three-dimensional (3D) human Trabecular Meshwork/Schlemm's Canal (HTM/HSC™) constructs exposed to transforming growth factor-β2 (TGFβ2) were used to monitor NCX 470 and LUM-induced changes in AH dynamics. Results: NCX 470 (30 μL/eye) showed greater IOP reduction compared with LUM (30 μL/eye) following single AM dosing [maximum change from baseline (CFBmax) = -1.39 ± 0.52, -6.33 ± 0.73, and -3.89 ± 0.66 mmHg (mean ± standard error of the mean) for VEH, NCX 470, and LUM, respectively]. Likewise, repeated 5 days daily dosing of NCX 470 resulted in lower IOP than LUM across the duration of the study (average IOP decrease across tests was -0.45 ± 0.22, -6.06 ± 0.15, and -3.60 ± 0.22 mmHg for VEH, NCX 470, and LUM, respectively). NCX 470 increased outflow facility (Cfl) in vivo in NHP (CflVEH = 0.37 ± 0.09 μL/min/mmHg and CflNCX470 = 0.64 ± 0.17 μL/min/mmHg) as well as in vitro (CHTM/HSC) in HTM/HSC constructs (CHTM/HSC_VEH = 0.47 ± 0.02 μL/min/mm2/mmHg and CHTM/HSC_NCX470 = 0.76 ± 0.03 μL/min/mm2/mmHg). In addition, NCX 470 increased uveoscleral outflow (FuVEH = 0.62 ± 0.26 μL/min and FuNCX470 = 1.53 ± 0.39 μL/min with episcleral venous pressure of 15 mmHg) leaving unaltered aqueous flow (AHFVEH = 2.03 ± 0.22 μL/min and AHFNCX470 = 1.93 ± 0.31 μL/min) in NHP. Conclusions: NCX 470 elicits greater IOP reduction than LUM following single or repeated dosing. Data in NHP and 3D-HTM/HSC constructs suggest that changes in Cfl and Fu account for the robust IOP-lowering effect of NCX 470.

Association of NOTCH3 With Elastic Fiber Dispersion in the Infrarenal Abdominal Aorta of Cynomolgus Monkeys

BACKGROUND

The regional heterogeneity of vascular components and transcriptomes is an important determinant of aortic biology. This notion has been explored in multiple mouse studies. In the present study, we examined the regional heterogeneity of aortas in nonhuman primates.

METHODS

Aortic samples were harvested from the ascending, descending thoracic, suprarenal, and infrarenal regions of young control monkeys and adult monkeys with high fructose consumption for 3 years. The regional heterogeneity of aortic structure and transcriptomes was examined by histological and bulk RNA sequencing analyses, respectively.

RESULTS

Immunostaining of CD31 and αSMA (alpha-smooth muscle actin) revealed that endothelial and smooth muscle cells were distributed homogeneously across the aortic regions. In contrast, elastic fibers were less abundant and dispersed in the infrarenal aorta compared with other regions and associated with collagen deposition. Bulk RNA sequencing identified a distinct transcriptome related to the Notch signaling pathway in the infrarenal aorta with significantly increased NOTCH3 mRNA compared with other regions. Immunostaining revealed that NOTCH3 protein was increased in the media of the infrarenal aorta. The abundance of medial NOTCH3 was positively correlated with the dispersion of elastic fibers. Adult cynomolgus monkeys with high fructose consumption displayed vascular wall remodeling, such as smooth muscle cell loss and elastic fiber disruption, predominantly in the infrarenal region. The correlation between NOTCH3 and elastic fiber dispersion was enhanced in these monkeys.

CONCLUSIONS

Aortas of young cynomolgus monkeys display regional heterogeneity of their transcriptome and the structure of elastin and collagens. Elastic fibers in the infrarenal aorta are dispersed along with upregulation of medial NOTCH3.

First-Generation iStent Bypass Implantation versus ab Externo Canaloplasty Combined with Phacoemulsification in Patients with Primary Open Angle Glaucoma-12-Month Follow-Up

This prospective, non-randomized, interventional clinical study evaluated the efficacy and safety profile of first-generation iStent bypass implantation versus ab externo canaloplasty, both combined with phacoemulsification, in patients with primary open-angle glaucoma (POAG) after 12-month follow-up. A total of 138 patients with POAG and their 138 eyes (69 phaco-iStent and 69 phacocanaloplasty) were included. Postoperatively at 12 months, the mean intraocular pressure (IOP) decreased from 18.44 ± 3.88 to 15.51 ± 2.50 mmHg and from 17.20 ± 4.04 to 14.97 ± 2.37 mmHg in the phaco-iStent (PiS) and phacocanaloplasty (PC) groups, respectively (p = 0.480). In both groups, 35.7% achieved >20% IOP reduction from baseline. A total of 86% and 71.4% of the eyes were medication-free at 12 months in the PiS and PC groups, respectively. In both groups, all eyes showed improvement in best-corrected visual acuity compared with baseline and demonstrated similar safety profiles throughout the 12-month follow-up period. This study showed equal hypotensive effects of PiS and PC. Both procedures significantly reduced the IOP and the requirement for IOP-lowering medications for at least 12 months postoperatively, with no significant differences between the groups.

Association of NOTCH3 with Elastic Fiber Dispersion in the Infrarenal Abdominal Aorta of Cynomolgus Monkeys

Background

The regional heterogeneity of vascular components and transcriptomes is an important determinant of aortic biology. This notion has been explored in multiple mouse studies. In the present study, we examined the regional heterogeneity of aortas in non-human primates.

Methods

Aortic samples were harvested from the ascending, descending, suprarenal, and infrarenal regions of young control monkeys and adult monkeys provided with high fructose for 3 years. The regional heterogeneity of aortic structure and transcriptomes was examined by histological and bulk RNA sequencing analyses.

Results

Immunostaining of CD31 and αSMA revealed that endothelial and smooth muscle cells were distributed homogeneously across the aortic regions. In contrast, elastic fibers were less abundant and dispersed in the infrarenal aorta compared to other regions and associated with collagen deposition. Bulk RNA sequencing identified a distinct transcriptome related to the Notch signaling pathway in the infrarenal aorta with significantly increased NOTCH3 mRNA compared to other regions. Immunostaining revealed that NOTCH3 protein was increased in the media of the infrarenal aorta. The abundance of medial NOTCH3 was positively correlated with the dispersion of elastic fibers. Adult cynomolgus monkeys provided with high fructose displayed vascular wall remodeling, such as smooth muscle cell loss and elastic fiber disruption, predominantly in the infrarenal region. The correlation between NOTCH3 and elastic fiber dispersion was enhanced in these monkeys.

Conclusions

Aortas of young cynomolgus monkeys display regional heterogeneity of their transcriptome and the structure of elastin and collagens. Elastic fibers in the infrarenal aorta are dispersed along with upregulation of medial NOTCH3.

HIGHLIGHTS

- The present study determined the regional heterogeneity of aortas from cynomolgus monkeys.- Aortas of young cynomolgus monkeys displayed region-specific aortic structure and transcriptomes.- Elastic fibers were dispersed in the infrarenal aorta along with increased NOTCH3 abundance in the media.

GRAPHIC ABSTRACT

Schlemm's canal: the outflow 'vessel'

In a healthy eye, the aqueous humour (AH) flows via the ciliary body and trabecular meshwork into the collector channels, which carry it to the episcleral veins. In glaucoma, a heterogeneous group of eye disorders affecting approximately 60 million individuals worldwide, the juxtacanalicular meshwork offers greater resistance to the outflow of the AH, leading to an increase in outflow resistance that gradually results in elevated intraocular pressure (IOP). The present review comprehensively covers the morphology of Schlemm’s canal (SC) and AH pathways. The path of the AH from the anterior chamber through the trabeculum into suprascleral and conjunctival veins via collector channels is described, and the role of SC in the development of glaucoma and outflow resistance is discussed. Finally, channelography is presented as a precise method of assessing the conventional drainage pathway and facilitating localization of an uncollapsed collector and aqueous veins. Attention is also given to the relationship between aqueous and episcleral veins and heartbeat. Possible directions of future research are proposed.

Anterior Segment Anatomy and Conventional Outflow Physiology of the Tree Shrew (Tupaia belangeri)

Purpose

Rodent and primate models are commonly used in glaucoma research; however, both have their limitations. The tree shrew (Tupaia belangeri) is an emerging animal model for glaucoma research owing in part to having a human-like optic nerve head anatomy, specifically a collagenous load-bearing lamina. However, the anterior segment anatomy and function have not been extensively studied in the tree shrew. Thus, the purpose of this study was to provide the first detailed examination of the anterior segment anatomy and aqueous outflow facility in the tree shrew.

Methods

Aqueous outflow dynamics were measured in five ostensibly normal eyes from three tree shrews using the iPerfusion system over a range of pressures. Gross histological assessment and immunohistochemistry were performed to characterize anterior segment anatomy and to localize several key molecules related to aqueous outflow.

Results

Anterior segment anatomy in tree shrews is similar to humans, demonstrating a scleral spur, a multilayered trabecular meshwork and a circular Schlemm's canal with a single lumen. Average outflow facility was 0.193 µL/min/mm Hg (95% confidence interval, 0.153-0.244), and was stable over time. Outflow facility was more similar between contralateral eyes (approximately 5% average difference) than between eyes of different animals. No significant dependence of outflow facility on time or pressure was detected (pressure-flow nonlinearity parameter of 0.01 (95% % confidence interval, -0.29 to 0.31 CI µL/min/mm Hg).

Conclusions

These studies lend support to the usefulness of the tree shrew as a novel animal model in anterior segment glaucoma and pharmacology research. The tree shrew's cost, load-bearing collagenous lamina cribrosa, and lack of washout or anterior chamber deepening provides a distinct experimental and anatomic advantage over the current rodent and nonhuman primate models used for translational research.

Effect of Timolol on Aqueous Humor Outflow Facility in Healthy Human Eyes

PURPOSE

Hyposecretion of aqueous humor has been postulated to adversely affect the health of the trabecular meshwork and outflow resistance. However, the effect of medications that reduce aqueous humor production on outflow facility in living human eyes is unclear. This study evaluated the effect of timolol, an aqueous humor flow suppressant, on outflow facility in healthy eyes.

DESIGN

Prospective, before-and-after study.

METHODS

In a multicenter study, 113 healthy participants over 40 years of age were included. Intraocular pressure (IOP) was measured with the participant in the sitting position by using a pneumatonometer. The outflow facility was measured with the participant in the supine position by 2-minute pneumatonography. After participants self-administered drops of timolol 0.5% for 1 week, twice daily in each eye, both measurements were repeated.

RESULTS

Mean IOP decreased from 15.1 ± 3.0 mm Hg at baseline to 12.4 ± 2.4 mm Hg (P < 0.001) after 1 week of timolol use. Mean outflow facility decreased from 0.23 ± 0.08 μL/min/mm Hg at baseline to 0.18 ± 0.08 μL/min/mm Hg (P < 0.001) after timolol. The change in outflow facility was negatively correlated with baseline outflow facility (r = -0.51; P < 0.001).

CONCLUSIONS

Timolol reduces outflow facility in healthy human eyes, and this effect is greater in eyes with higher baseline outflow facility. This phenomenon may be related to reduced aqueous humor flow, but the precise mechanism remains to be determined.

Total Outflow Facility in Live C57BL/6 Mice of Different Age

Purpose

To characterize total outflow facility across the live adult mouse lifespan as a reference for mouse glaucoma studies and the common C57BL/6 background strain.

Methods

Microperfusion was performed by single-needle cannulation and feedback-controlled coupling of pressure and flow to maintain a constant pressure in the anterior chambers of live C57BL/6NCrl mice aged 3-4 months (n = 17), 6-9 months (n = 10), and 23-27 months (n = 12). This mouse age range represented an equivalent human age range of young adult to elderly. We characterized the following across age groups in vivo: (1) outflow facility based on constant pressure perfusion in a pressure range of 15-35 mm Hg, (2) perfusion flow rates, and (3) anterior segment tissue histology after perfusion. Thirty-nine live mice underwent perfusion.

Results

Pressure-flow rate functions were consistently linear for all age groups (all R ² > 0.96). Total outflow facility in mice aged 3-4, 6-9, and 23-27 months was 0.0066, 0.0064, and 0.0077 μL/min/mm Hg, respectively. Facility was not significantly different between age groups (all p > 0.4). The groups had closely overlapping frequency distribution profiles with right-sided tails. Post hoc estimates indicated that group facility differences of at least 50% would have been detectable, with this limit set mainly by inherent variability in the strain. A trend toward higher perfusion flow rates was seen in older mice aged 23-27 months, but this was not significantly different from that of mice aged 3-4 months or 6-9 months (p > 0.2). No histological disruption or difference in iridocorneal angle or drainage tissue structure was seen following perfusion in the different age groups.

Conclusion

We did not find a significant difference in total outflow facility between different age groups across the live C57BL/6 mouse adult lifespan, agreeing with some human studies. The possibility that more subtle differences might exist ought to be judged with respect to the heterogeneity in facility at different ages. Our findings provide reference data for live perfusion studies pertaining to glaucoma involving the C57BL/6 strain.