Funktionelle Morphologie der Abflusswege des Kammerwassers und ihre Veränderungen beim Offenwinkelglaukom

Plant-derived angiogenin fusion protein's cytoprotective effect on trabecular meshwork damage induced by Benzalkonium chloride in mice

Background

Benzalkonium chloride (BAK), commonly used in glaucoma treatment, is an eye drop preservative with dose-dependent toxicity. Previous studies have observed the multi-functional benefits of angiogenin (ANG) against glaucoma. In our study, we evaluated ANG’s cytoprotective effect on the trabecular meshwork (TM) damage induced by BAK. Additionally, we developed a plant-derived ANG fusion protein and evaluated its effect on TM structure and function.

Methods

We synthesized plant-derived ANG (ANG-FcK) by fuzing immunoglobulin G’s Fc region and KDEL to conventional recombinant human ANG (Rh-ANG) purified from transgenic tobacco plants. We established a mouse model using BAK to look for degenerative changes in the TM, and to evaluate the protective effects of ANG-FcK and Rh-ANG. Intraocular pressure (IOP) was measured for 4 weeks and ultrastructural changes, deposition of fluorescent microbeads, type I and IV collagen, fibronectin, laminin and α-SMA expression were analyzed after the mice were euthanized.

Results

TM structural and functional degeneration were induced by 0.1% BAK instillation in mice. ANG co-treatment preserved TM outflow function, which we measured using IOP and a microbead tracer. ANG prevented phenotypic and ultrastructure changes, and that protective effect might be related to the anti-fibrosis mechanism. We observed a similar cytoprotective effect in the BAK-induced degenerative TM mouse model, suggesting that plant-derived ANG-FcK could be a promising glaucoma treatment.

Canaloplasty in the Treatment of Primary Open-Angle Glaucoma: Patient Selection and Perspectives

Canaloplasty is a surgical procedure that has undergone a number of developments since its introduction in 2005. Many thousands of canaloplasties have been performed around the world since then and is, by definition, a blebless procedure. It does not necessitate the use of any antifibrotic agents and results in safe and effective IOP reductions in patients with open-angle glaucoma (OAG) with minimal complications and no bleb-related adverse events. When considering the surgical management of patients with early and medium stages of the disease, canaloplasty can be considered as a first line option. This paper will overview the theoretical effectiveness of canal surgery, the fundamental aspects of aqueous outflow resistance with particular emphasis on the role of the trabecular meshwork, Schlemm's canal, and the collector channels, and the methods available for the clinical evaluation of the outflow pathways in relation to the ocular anatomy. Further, the paper will detail the surgical technique itself and how this has developed over time together with the clinical aspects that should be accounted for when selecting patients for this surgery.

The effect of canaloplasty with suprachoroidal drainage combined with cataract surgery - 1-year results

PURPOSE

The purpose of this study was to investigate the safety and efficacy of phacocanaloplasty with suprachoroidal drainage (PCscD) and to compare its intraocular pressure (IOP)-lowering and drug-sparing effect to canaloplasty with suprachoroidal drainage (CscD).

METHODS

The study retrospective interventional study included patients with open-angle glaucoma or secondary forms of glaucoma who underwent either CscD or PCscD between the year 2011 and 2014 in Knappschaft Eye Clinic Sulzbach. Primary end-points were IOP reduction and the number of IOP-lowering medication after 12 months. Secondary end-points were intraoperative and postoperative complications.

RESULTS

A total of 328 eyes were included, 193 were treated with CscD and 135 underwent PCscD. Canaloplasty with scD achieved an IOP reduction of 37.0% (from 20.9 ± 3.6 mmHg to 13.2 ± 2.6 mmHg) after 1 year, whereas PCscD showed a significant higher reduction of 47.4% (from 23.2 ± 5.1 mmHg to 12.2 ± 1.7 mmHg). Reduction in IOP-lowering medication was higher after PCscD (from 3.6 ± 0.6 to 0.2 ± 0.5) than after CscD (from 3.5 ± 0.8 to 0.7 ± 1.0). Twelve months after surgery 55.5% in the CscD group and 80.2% in the PCscD group were free of IOP-lowering medication. In both groups, no severe or sight-threatening complications occurred.

CONCLUSION

Combining cataract surgery and CscD achieves a higher IOP reduction, and patients postoperatively need less IOP-lowering medication than after CscD alone.

Life under pressure: The role of ocular cribriform cells in preventing glaucoma

Primary open-angle glaucoma is a multifactorial blinding disease often impacting the two pressure-sensitive regions of the eye: the conventional outflow pathway and the optic nerve head (ONH). The connective tissues that span these two openings in the globe are the trabecular meshwork of the conventional outflow pathway and the lamina cribrosa of the ONH. Resident cribiform cells of these two regions are responsible for actively remodeling and maintaining their connective tissues. In glaucoma, aberrant maintenance of the juxtacanalicular tissues (JCT) of the conventional outflow pathway results in ocular hypertension and pathological remodeling of the lamina cribrosa results in ONH cupping, damaging retinal ganglion cell axons. Interestingly, cells cultured from the lamina cribrosa and the JCT of the trabecular meshwork have similarities regarding gene expression, protein production, plus cellular responses to growth factors and mechanical stimuli. This review compares and contrasts the current knowledge of these two cell types, whose health is critical for protecting the eye from glaucomatous changes. In response to pressure gradients across their respective cribiform tissues, the goal is to better understand and differentiate healthy from pathological behavior of these two cell types.

YBR/EiJ mice: a new model of glaucoma caused by genes on chromosomes 4 and 17

A variety of inherited animal models with different genetic causes and distinct genetic backgrounds are needed to help dissect the complex genetic etiology of glaucoma. The scarcity of such animal models has hampered progress in glaucoma research. Here, we introduce a new inherited glaucoma model: the inbred mouse strain YBR/EiJ (YBR). YBR mice develop a form of pigmentary glaucoma. They exhibit a progressive age-related pigment-dispersing iris disease characterized by iris stromal atrophy. Subsequently, these mice develop elevated intraocular pressure (IOP) and glaucoma. Genetic mapping studies utilizing YBR as a glaucoma-susceptible strain and C57BL/6J as a glaucoma-resistant strain were performed to identify genetic loci responsible for the iris disease and high IOP. A recessive locus linked to Tyrp1^b on chromosome 4 contributes to iris stromal atrophy and high IOP. However, this is not the only important locus. A recessive locus on YBR chromosome 17 causes high IOP independent of the iris stromal atrophy. In specific eyes with high IOP caused by YBR chromosome 17, the drainage angle (through which ocular fluid leaves the eye) is largely open. The YBR alleles of genes on chromosomes 4 and 17 underlie the development of high IOP and glaucoma but do so through independent mechanisms. Together, these two loci act in an additive manner to increase the susceptibility of YBR mice to the development of high IOP. The chromosome 17 locus is important not only because it causes IOP elevation in mice with largely open drainage angles but also because it exacerbates IOP elevation and glaucoma induced by pigment dispersion. Therefore, YBR mice are a valuable resource for studying the genetic etiology of IOP elevation and glaucoma, as well as for testing new treatments.

Summary: We identify the YBR/EiJ mouse strain as a new model of high intraocular pressure and glaucoma, and also identify genetic loci that contribute to this glaucoma.

The aqueous humor outflow pathways in glaucoma: A unifying concept of disease mechanisms and causative treatment

Intraocular pressure (IOP) is the critical risk factor for glaucoma, a neurodegenerative disease and frequent cause of blindness worldwide. As of today, all effective strategies to treat glaucoma aim at lowering IOP. IOP is generated and maintained via the aqueous humor circulation system in the anterior eye. Aqueous humor is secreted by the ciliary processes and exits the eye through the trabecular meshwork (TM) or the uveoscleral outflow pathways. The TM outflow pathways provide resistance to aqueous humor outflow and IOP builds up in response to it. In the normal eye, the resistance is localized in the inner wall region, which comprises the juxtacanalicular connective tissue (JCT) and the inner wall endothelium of Schlemm's canal (SC). Outflow resistance in the inner wall region is lowered through the contraction of the ciliary muscle or the relaxation of contractile myofibroblasts in the posterior part of the TM and the adjacent scleral spur. Patients with primary open-angle glaucoma (POAG), the most frequent form of glaucoma, typically suffer from an abnormally high outflow resistance of the inner wall region. There is increasing evidence that the increase in TM outflow resistance in POAG is the result of a characteristic change in the biological properties of the resident cells in the JCT, which increasingly acquire the phenotype of contractile myofibroblasts. This scenario strengthens simultaneously both their actin cytoskeleton and their directly associated extracellular matrix fibrils, leads to overall stiffening of the tissue, and is modulated by transforming growth factor-β (TGF-β)/connective tissue growth factor (CTGF) signaling. Essentially comparable changes appear to occur in SC endothelial cells in glaucoma. Causative therapy concepts targeting the aqueous outflow pathways in glaucoma should aim at interfering with this process either by attenuating TM or SC stiffness, and/or by modulating TGF-β/CTGF signaling.

Discovery of novel inhibitors for the treatment of glaucoma

INTRODUCTION

Glaucoma is a neurodegenerative disease with heterogeneous causes that result in retinal ganglionic cell (RGC) death. The discovery of ocular antihypertensives has shifted glaucoma therapy, largely, from surgery to medical intervention. Indeed, several intraocular pressure (IOP)-lowering drugs, with different mechanisms of action and RGC protective property, have been developed.

AREAS COVERED

In this review, the authors discuss the main new class of kinase inhibitors used as glaucoma treatments, which lower IOP by enhancing drainage and/or lowering production of aqueous humor. The authors include novel inhibitors under preclinical evaluation and investigation for their anti-glaucoma treatment. Additionally, the authors look at treatments that are in clinics now and which may be available in the near future.

EXPERT OPINION

Treatment of glaucoma remains challenging because the exact cause is yet to be delineated. Neuroprotection to the optic nerve head is undisputable. The novel Rho-associated kinase inhibitors have the capacity to lower IOP and provide optic nerve and RGC protection. In particular, the S-isomer of roscovitine has the capacity to lower IOP and provide neuroprotection. Combinations of selected drugs, which can provide maximal and sustained IOP-lowering effects as well as neuroprotection, are paramount to the prevention of glaucoma progression. In the near future, microRNA intervention may be considered as a potential therapeutic target.