Tissue Reactivity to, and Stability of, Glaucoma Drainage Device Materials Placed Under Rabbit Conjunctiva.

Purpose: To evaluate tissue reactivity to, and the stability of, glaucoma drainage device materials placed under rabbit conjunctiva in vivo. Methods: Disks (diameter, 3 mm; thickness, ∼0.3 mm) fabricated from poly(styrene-block-isobutylene-block-styrene) (SIBS), silicone, stainless-steel, or glutaraldehyde cross-linked collagen (GACLC) were inserted under rabbit conjunctiva. Conjunctival and scleral sections obtained at 4, 8, and 12 weeks after surgery were immunostained for α-smooth muscle actin (SMA). The ratio of the maximum thickness of the α-SMA-positive conjunctiva to the scleral thickness (α-SMA/S ratio) was calculated. The in vivo stability of the drainage devices at 12 weeks after insertion was evaluated. Results: The mean α-SMA/S ratios of the SIBS and silicone groups were lower than that of the stainless-steel group at 4 weeks after surgery (P < 0.05), and that of the SIBS group was lower than that of the GACLC group (P < 0.05). The ratios at 8 weeks after surgery were lower in the SIBS and silicone groups than in the GACLC group (P < 0.01). The ratios at 12 weeks after surgery were lower in the SIBS and silicone groups than in the GACLC group (P < 0.05). The surface areas of GACLC disks explanted from conjunctivae were significantly lower than that of intact disks (P < 0.01). Conclusions: SIBS and silicon were highly biostable and exhibited less tissue reactivity than GACLC in vivo. Translational Relevance: Comparisons of materials using animal models can predict the clinical stability and safety of such materials in humans.

Intraocular Pressure-Lowering Effects of Trabeculectomy Versus MicroShunt Insertion in Rabbit Eyes.

Purpose: To compare the surgical results of PRESERFLO MicroShunt (MicroShunt) insertion and trabeculectomy in rabbit eyes. Methods: Trabeculectomy or MicroShunt insertion was performed on the eyes of Japanese white rabbits. Intraocular pressure (IOP) was measured on conscious rabbits using a rebound tonometer for up to 12 weeks after surgery. Filtering bleb appearance was evaluated. Scarring in the filtering bleb was assessed by immunohistochemical analyses. The change in mRNA expression in the conjunctiva was evaluated using RNA sequence analyses. Results: The preoperative IOP of the operative eye did not differ significantly between trabeculectomy (11.6 ± 1.0 mmHg, n = 10) and MicroShunt insertion (12.6 ± 1.3 mmHg, n = 10). In both groups, the IOP of the operative eye was significantly lower than that of the contralateral eye at one day postoperatively, which continued until 12 weeks after surgery. The peak differences in IOP were -8.4 ± 3.0 (trabeculectomy) and -8.1 ± 2.1 mmHg (MicroShunt) at two weeks after surgery; no significant differences were observed in IOP reduction between the groups. Appearance and immunohistochemical analyses of the filtering bleb showed no significant difference between the groups. Moreover, RNA sequence analysis results showed no difference between the groups in mRNA expression fluctuations. Conclusions: Postoperative IOP, bleb appearance, and immunohistochemical analysis results were similar in the trabeculectomy and MicroShunt groups, indicating that MicroShunt insertion is as effective as trabeculectomy in lowering IOP. Translational Relevance: Comparison of surgical procedures using animal models has made it possible to predict clinical efficacy and safety.

The DNA topoisomerase II inhibitor amsacrine as a novel candidate adjuvant in a model of glaucoma filtration surgery.

Treatments for refractory glaucoma include trabeculectomy, in which a filtering bleb is created to reduce aqueous pressure. Mitomycin C (MMC) is often used as an adjuvant to reduce post-trabeculectomy bleb scarring and consequent failure. However, scarring sometimes still occurs. Thus, we searched for more effective trabeculectomy adjuvants with high-throughput screening (HTS) of a library of 1,165 off-patent drug compounds. This revealed that amsacrine (AMSA), a DNA topoisomerase II (TOP2) inhibitor, was the top candidate. Compared to MMC, rabbits that underwent trabeculectomy with 10% AMSA had lower IOP at 42, 56, and 70 days (P < 0.01 at all measurement points) and a higher bleb score at 28, 42, 56, and 70 days (P = < 0.01, 0.04, 0.04, and < 0.01, respectively). Compared to saline, rabbits that received 1% AMSA also had lower IOP and better bleb score at all time points, without a sharp drop in IOP just after surgery (all P < 0.01). Both effects were milder than MMC at 7 days (P = 0.02 and <0.01, respectively). Thus, this study showed that HTS may help identify new, promising uses for off-patent drugs. Furthermore, trabeculectomy with AMSA at a suitable concentration may improve the prognosis after trabeculectomy compared to MMC.

Eyedrops containing SA9000 prodrugs result in sustained reductions in intraocular pressure in rabbits.

AIM: Poor topical bioavailability and ocular irritation have impeded the development of the diuretic, ethacrynic acid (ECA) as a clinically useful ocular hypotensive for the treatment of glaucoma. Thus, the development of analogs and prodrugs of analogs with improved ocular penetration, potency, and tolerability is required. The aim of this work is to evaluate the corneal penetration and ocular distribution of SA9000, an ECA analog. Novel SA9000 prodrugs intended to further improve ocular pharmacodynamic effect were also evaluated. RESULTS: SA9000 penetrated porcine corneas more effectively than ECA in corneal diffusion studies. In vivo studies in Dutch-belted (DB) rabbits indicated that topical application of a single dose (0.3%) of SA9000 could significantly reduce intraocular pressure (IOP) (approximately 25% vs. fellow untreated eye) but caused significant conjunctival hyperemia. Since this hyperemia was likely the result of its inherent thiol reactivity, SA9000 was formulated with equimolar cysteine, an exogenous thiol donor. The administration of increasing SA9000-cysteine adduct concentrations (0.3%, 0.6%, 0.9%) demonstrated that they cause less ocular irritation than unadducted SA9000 but could still significantly reduce IOP (0.3%: 8.7 +/- 2%; 0.6%: 14.4 +/- 5%; 0.9%: 23.3 +/- 4.4%) versus untreated contralateral control eyes. CONCLUSIONS: These data suggest that novel thiol donor adduction can improve the ocular bioavailability and tolerability of SA9000. SA9000-cysteine prodrugs may represent a new option for the topical treatment of glaucoma.

Pharmacological characteristics of AFP-168 (tafluprost), a new prostanoid FP receptor agonist, as an ocular hypotensive drug.

To evaluate the pharmacological characteristics of AFP-168 (tafluprost), a new prostaglandin (PG) F(2alpha) derivative, we examined its receptor-binding affinities, intraocular pressure (IOP)-lowering effect, effects on aqueous humor dynamics, and stimulating effect on melanogenesis. The receptor-binding profile for AFP-172, a carboxylic acid of AFP-168, was determined by measuring muscle contractions in an organ bath, inhibition of platelet aggregation, and competitive binding of a radio-labelled ligand. For the IOP-measurement study, ocular normotensive and laser-induced ocular hypertensive cynomolgus monkeys were used, and IOP was measured using a pneumatonograph. For the studies of aqueous humor dynamics, IOP (Goldmann applanation tonometry), fluorophotometry, two-level constant pressure perfusion, and isotope dilution and accumulation techniques were used in ocular normotensive monkeys. The melanin contents in the medium and in the cell bodies of cultured B16-F0 melanoma cells were measured. The affinity for the FP receptor shown by AFP-172 (Ki : 0.4 nm) was 12 times that of PhXA85 ( Ki : 4.7 nm), a carboxylic acid of latanoprost. A single application of AFP-168 at 0.0025% significantly lowered IOP in both ocular normotensive and hypertensive monkeys (3.1 and 11.8 mmHg, respectively, p < 0.01) and latanoprost at 0.005% significantly lowered IOP (2.1 mmHg, p < 0.01 and 9.5 mmHg, p = 0.059 respectively). Once daily instillation of AFP-168 at 0.001, 0.0025, or 0.005% for 5 days in normotensive monkeys significantly reduced IOP not only for a few hours, but also at the drug-trough time 24hr after application. Latanoprost at 0.005% also reduced IOP, but not at the drug-trough time. AFP-168 decreased IOP mainly by increasing uveoscleral outflow by 65% (p < 0.05) and, as sometimes seen with other prostanoids, also increased total outflow facility (33% increase, p < 0.05). In cultured B16-F0 melanoma cells, AFP-172 (100 microM) did not stimulate melanogenesis, but PhXA85 (100 microM) did. These findings indicate that AFP-168 has a high affinity for the prostanoid FP receptor, has potent IOP-lowering effects in both ocular normotensive and hypertensive monkeys that exceed those of latanoprost, and has less stimulating effect on melanogenesis in melanoma cells.