Aflibercept monotherapy versus aflibercept with targeted retinal laser to peripheral retinal ischemia for diabetic macular oedema (LADAMO)

OBJECTIVE

We tested the hypothesis that targeted retinal laser photocoagulation (TPRP) to peripheral retinal ischaemia reduces the overall burden of aflibercept injections when treating diabetic macular oedema (DMO) over a 24-month period.

METHODS

Prospective, double-masked, multicentre, randomised controlled trial in Australia comparing aflibercept monotherapy, following a treat-and-extend protocol, or combination therapy of aflibercept and TPRP for DMO. The aflibercept monotherapy group received placebo laser. The primary outcome measure was the mean number of intravitreal aflibercept injections for each group at 24 months. Secondary outcome included: mean change in central macular thickness (CMT) and vision at trial completion, the proportion of eyes whose DMO resolved and the mean injection treatment interval. Ocular and systemic adverse events were recorded.

RESULTS

We enrolled 48 eyes of 47 patients; 27 eyes were randomised to combination therapy (aflibercept and TPRP) and 21 to aflibercept monotherapy. Thirty-two eyes (67%) completed the 2-year study. The number of intravitreal treatments given were similar for combination therapy (10.5 (SD 5.8) and monotherapy (11.8 (SD5.6)) (P = 0.44). The mean visual improvement (+4.0 (-1.8, 9.8) and +7.8 (2.6, 12.9) letters, P = 0.32), mean decrease in CMT (-154 (-222,-87) µm and -152 (-218,-86) µm, P = 0.96), proportion of eyes with CMT < 300 µm (48% and 67%; P = 0.50) and safety outcomes were similar in both the combination and monotherapy treatment groups (respectively).

CONCLUSIONS

Laser to areas of ischaemic peripheral retina does not reduce the burden of intravitreal aflibercept injections when treating diabetic macular oedema.

Optogenetic approaches to vision restoration

Inherited retinal disease (IRD) affects about 1 in 3000 to 1 in 5000 individuals and is now believed to be the most common cause of blindness registration in developed countries. Until recently, the management of such conditions had been exclusively supportive. However, advances in molecular biology and medical engineering have now seen the rise of a variety of approaches to restore vision in patients with IRDs. Optogenetic approaches are primarily aimed at rendering secondary and tertiary neurons of the retina light-sensitive in order to replace degenerate or dysfunctional photoreceptors. Such approaches are attractive because they provide a "causative gene-independent" strategy, which may prove suitable for a variety of patients with IRD. We discuss theoretical and practical considerations in the selection of optogenetic molecules, vectors, surgical approaches and review previous trials of optogenetics for vision restoration. Optogenetic approaches to vision restoration have yielded promising results in pre-clinical trials and a phase I/II clinical trial is currently underway (ClinicalTrials.gov NCT02556736). Despite the significant inroads made in recent years, the ideal optogenetic molecule, vector and surgical approach have yet to be established.

Diabetes impairs mobilization of mouse bone marrow-derived Lin(-)/VEGF-R2(+) progenitor cells

Endothelial progenitor cells circulating in the peripheral blood (PB) contribute to vascular repair. This study aimed to evaluate the potential of a 'cocktail' consisting of erythropoietin, granulocyte colony-stimulating factor and tetrahydrobiopterin to mobilize hematopoietic lineage negative/vascular endothelial growth factor receptor 2 positive (Lin(-)/VEGF-R2(+)) cells from the bone marrow (BM) to PB in non-diabetic and diabetic mice. Diabetes was induced in mice by intraperitoneal injection of streptozotocin. Diabetic mice were studied after 16weeks of hyperglycemia. Half the mice in each group (non-diabetic and diabetic) received daily intraperitoneal injections of the cocktail for 6 consecutive days while the other half received vehicle buffer. Mobilization of Lin(-)/VEGF-R2(+) cells, which were expanded in MCP301 medium, was evaluated after isolating them from BM and PB and their phenotypic and morphological properties were studied. We found that 16weeks of diabetes affected neither the total number of BM mononucleated cells nor the number of Lin(-)/VEGF-R2(+) cells in BM compared with non-diabetic controls. In non-diabetic mice, cocktail treatment resulted in a significant decrease in BM Lin(-)/VEGF-R2(+) cells, paralleled by a significant increase of these cells in PB. Such changes in the number of Lin(-)/VEGF-R2(+) cells in BM and PB after the cocktail treatment were less marked in diabetic mice. In vitro studies of BM Lin(-)/VEGF-R2(+) cells from diabetic and non-diabetic mice did not reveal any differences in either phenotypes or colony forming potential. These findings indicate that diabetes impairs the mobilization of Lin(-)/VEGF-R2(+) cells from BM to PB. Impaired mobilization of BM Lin(-)/VEGF-R2(+) cells soon after the onset of diabetes may contribute to complications such as diabetic retinopathy.

Bruch's membrane and choroidal macrophages in early and advanced age-related macular degeneration

AIM

To determine the sub-macular Bruch's membrane (BrM) macrophage count and the choroidal and BrM macrophage immunophenotype in normal eyes and in eyes with early and advanced age-related macular degeneration (AMD).

METHODS

BrM macrophages were counted in 125 human eyes (normal, normal aged, early AMD and geographical atrophy), and CD68 and inducible nitric oxide synthase (iNOS) immunohistochemistry was performed on 16 human eyes (normal, normal aged, early AMD, geographical atrophy and disciform scarring). All eyes were examined clinically ante mortem. Results were correlated with histopathological features, including basal laminar deposit and membranous debris, and with clinical fundus appearance.

RESULTS

CD68(+) macrophages were found in the choroid of normal human eyes, and did not express iNOS. Expression of iNOS by choroidal macrophages (as well as endothelial cells and pericytes) was associated with: (1) recruitment of macrophages to BrM in early AMD eyes with soft drusen or thick continuous basal laminar deposit, corresponding to clinically detectable soft drusen or pigment changes; and (2) active disciform scarring. iNOS expression was absent in BrM macrophages, suggesting immunomodulatory differences between the choroid and BrM. The highest BrM macrophage counts were found in eyes with subclinical choroidal neovascularisation.

CONCLUSION

The presence of extracellular deposits (soft drusen and thick continuous basal laminar deposit) is associated with macrophage recruitment to BrM and alteration in the immunophenotype of resident choroidal macrophages.

Conditioned medium from mixed retinal pigmented epithelium and Müller cell cultures reduces in vitro permeability of retinal vascular endothelial cells

AIM

To investigate the in vitro effect of laser photocoagulation on blood-retinal barrier permeability.

METHODS

Retinal capillary endothelial cells were exposed to supernatants from long term co-cultured cells that were argon laser treated. Endothelial cell permeability was analysed by (1) measurement of transendothelial electrical resistance and (2) equilibration of [(3)H] inulin and [(14)C] albumin across the cell monolayer.

RESULTS

Laser photocoagulation of various retinal cells and control ECV304 cells in the lower chamber did not appreciably improve permeability of the endothelial cell monolayer compared with that of unlasered cells. However, medium that was conditioned by mixed retinal pigmented epithelium and Müller cells significantly reduced both inulin (43.2% (SD 6.5%) equilibration in mixed cultures v 59.8% (SD 7.0%) control cells, p<0.05) and albumin (15.1% (SD 3.8%) v 31.1% (SD 6.7%), p<0.05) permeability of the endothelial cell monolayers. A fourfold increase in transendothelial electrical resistance was also seen.

CONCLUSIONS

These results are consistent with the hypothesis that interaction of Müller cells with retinal pigmented epithelium induced by laser treatment results in secretion of soluble factor(s), which reduces permeability of retinal vascular endothelium. Identification of these factor(s) may have implications for the clinical treatment of macular oedema secondary to diabetic retinopathy and other diseases.

Pseudo-endophthalmitis after intravitreal injection of triamcinolone

AIMS

To describe an unusual endophthalmitis-like reaction after an intravitreal injection of triamcinolone acetonide in four patients.

METHODS

Retrospective case series.

RESULTS

Four patients are reported with an endophthalmitis-like reaction following an intravitreal injection of triamcinolone acetonide. There was a dense vitreous haze with severe reduction of fundus view in all cases. One case was treated as an infectious endophthalmitis but the vitreous tap showed no evidence of an endophthalmitis and no bacterial or fungal growth in culture. In all four cases, the vitreous haze cleared without specific treatment. The anterior chamber remained quiet in all cases but one, which was examined 30 minutes after the injection, and there was no periorbital inflammation or pain.

CONCLUSION

Pseudo-endophthalmitis after an intravitreal injection of triamcinolone acetonide seems to be a distinct clinical entity that may resolve without specific treatment.

Immunological and aetiological aspects of macular degeneration

Aetiological and immunological aspects of AMD, a leading cause of blindness in Western countries, have been reviewed. Developmental studies suggest that anatomical features unique to the fovea result in a critical relationship between metabolic demand and blood supply at the macula, which is maintained throughout life. Recent studies show a sufficient degree of consistency in the link between smoking and both dry and wet AMD to regard it as causative. Dry AMD is considered to be the natural endstage of the disease; epidemiological and morphological studies point to choroidal vascular atrophy as the causative event and it is suggested that signals associated with acute vascular compromise lead to the development of subretinal neovascularisation. The relationship between sub-pigment epithelial deposits, including basal laminar deposit, and the pathogenesis of AMD is examined. Much of the literature is consistent with a choroidal origin for the constituents of drusen. The blood-retinal barrier preserves the physiological environment of the neural retina and limits inflammatory responses. The factors, including cytokines, adhesion molecules and the presence of resident immunocompetent cells (microglia), which determine the immune status of the retina are considered. Historical descriptions of the involvement of inflammatory cells are provided, evidence implicating inflammation in the pathogenesis of AMD involving macrophages, giant cells and microglia has been derived from observations of human and animal subretinal neovascular lesions. The role of humoral factors such as anti-retinal autoantibodies and acute phase proteins together with clinical observations has been surveyed. Taken together these data demonstrate the involvement of both cellular and humoral immunity in the pathogenesis of AMD. It remains to be determined to what degree the influence of immunity is causative or contributory in both wet and dry AMD, however, the use of anti-inflammatory agents to ameliorate the condition further indicates the existence of an inflammatory component.

Triamcinolone acetonide modulates permeability and intercellular adhesion molecule-1 (ICAM-1) expression of the ECV304 cell line: implications for macular degeneration

Whilst animal studies and a pilot clinical trial suggest that intravitreal triamcinolone acetonide (TA) may be useful in the treatment of age-related macular degeneration (AMD), its mode of action remains to be fully elucidated. The present study has investigated the capacity of TA to modulate the expression of adhesion molecules and permeability using a human epithelial cell line (ECV304) as a model of the outer blood-retinal barrier (BRB). The influence of TA on the expression of ICAM-1 and MHC-I was studied on resting and phorbol myristate acetate (PMA)- or interferon-gamma (IFN-gamma)- and/or tumour necrosis factor-alpha (TNF-alpha)-activated cells using flow cytometry and immunocytochemistry. Additionally, ECV304 cells were grown to confluence in uncoated Transwell chambers; transepithelial resistance (TER) across resting and PMA-activated cells was monitored. TA significantly decreased the paracellular permeability of ECV304 cells and down-regulated ICAM-1 expression, consistent with immunocytochemical observations. PMA-induced permeability changes were dose-dependent and TA decreased permeability of both resting and PMA-activated monolayers. MHC-I expression by ECV304 cells however, was not significantly affected by TA treatment. The modulation of TER and ICAM-1 expression in vitro correlate with clinical observations, suggesting re-establishment of the BRB and down-regulation of inflammatory markers are the principal effects of intravitreal TA in vivo. The results further indicate that TA has the potential to influence cellular permeability, including the barrier function of the retinal pigment epithelium (RPE) in AMD-affected retinae.

Regulators of vascular permeability: potential sites for intervention in the treatment of macular edema

Rather than being a non-specific reaction to a noxious stimulus, breakdown of the capillary blood-retinal barrier causing macular edema appears to be dependent on a number of active processes which may be open to pharmacological manipulation. Extracellular influences which may affect barrier function include serum and neighboring cell types, which act though cytokines, such as vascular endothelial growth factor and transforming growth factor-beta, and other factors. A number of intracellular pathways acting on the cytoskeleton and components of the intercellular junctional complexes have been identified which mediate agonist-induced leak of the vascular endothelium. The further elucidation of these processes may be useful in the development of better treatments for breakdown of the inner blood-retinal barrier.

A randomized phase II trial of interferon-alpha2b versus 5-fluorouracil after trabeculectomy

PURPOSE

The aim of the present study was to investigate the safety and potential efficacy of subconjunctival interferon-alpha2b (IFN-alpha), either alone or in combination with 5-fluorouracil (5-FU), in reducing the risk of failure of glaucoma surgery

METHODS

A prospective, masked randomized phase II study was undertaken in which patients received three subconjunctival injections per week for 3-4 weeks postoperatively. Three treatments were compared: (i) IFN-alpha (1 x 10(6)IU per dose); (ii) 5-FU (5 mg per dose); and (iii) alternating IFN-alpha and 5-FU (BOTH). The primary outcome measures were: (i) rate of successful control of intra-ocular pressure without further surgery; and (ii) the incidence of side effects.

RESULTS

Fifty-seven patients undergoing glaucoma surgery with an increased risk of failure were evaluated, including 23 patients (40%) undergoing trabeculectomy combined with extracapsular cataract extraction as well as other conventional high-risk groups. With 53 patients (93%) completing 2 years follow up,there was no significant difference in success rates among the three groups. Intra-ocular pressure was controlled without further surgery in 79% of patients (95% confidence interval (CI): 61, 97%) receiving IFN-alpha, in 89% of patients (76, 100%) receiving 5-FU and in 89% of patients (76, 100% receiving BOTH. Side effects were similar among the three groups.

CONCLUSIONS

These results are consistent with a beneficial effect of IFN-alpha2b given either alone or in combination with 5-FU after glaucoma filtering surgery. However, the lack of a clear and substantial benefit over conventional anti-fibrotic therapy does not support the further clinical evaluation of these treatments.

Exudative macular degeneration and intravitreal triamcinolone: 18 month follow up

PURPOSE

To evaluate the safety and efficacy of intravitreal triamcinolone after 18 months of follow up in patients with age-related macular degeneration and subfoveal or juxtafoveal choroidal neovascularization considered unsuitable for laser photocoagulation.

METHODS

Thirty eyes of 28 patients, referred from general eye clinics as well as the private clinic of one of the authors to a hospital-based retinal out-patient clinic, were treated with an intravitreal injection of triamcinolone (4 mg). The primary outcome measure was the proportion of eyes with loss of six or more lines on a Bailey-Lovie Chart. The incidence of adverse events associated with treatment was also observed.

RESULTS

Of the 20 eyes with initial visual acuity (VA) of 6/60 or better, the vision was maintained (+/-1 Bailey-Lovie lines) in 11 eyes (55%), while six eyes (30%) suffered severe visual loss (six or more lines). The VA improved by five to six lines in three of 10 eyes with initial vision of 3/60 or worse. Three of four eyes receiving a second injection suffered either progressive cataract or elevated intra-ocular pressure (IOP) requiring cataract surgery and/or filtering surgery. One of 26 eyes (3%) receiving a single injection showed progression of cataract and elevation of IOP within 6 weeks of treatment and required anti-glaucoma medication for 6 weeks. Progression of nuclear sclerosis 8-12 months after treatment was observed in six of 26 eyes (23%) receiving a single injection.

CONCLUSIONS

The results of the present study suggest that a single intravitreal injection of 4 mg triamcinolone is reasonably well tolerated by the human eye. The rate of development of severe visual loss was less than reported for historical controls. Because the results are preliminary and uncontrolled, the treatment should not be used routinely until its benefit to patients is established by a prospective, randomized controlled study.

Effect of high glucose on permeability of retinal capillary endothelium in vitro

PURPOSE

To study the effect of high glucose on the permeability of bovine retinal capillary endothelial cell (BRCEC) monolayers.

METHODS

The paracellular permeability of second-passage BRCEC cultured on millipore filters in two chamber transwell inserts was assayed by measuring the peak trans-monolayer electrical resistance and percent equilibration of 14C-inulin 48 hours after it had been added to the luminal chamber.

RESULTS

High glucose increased the paracellular permeability of BRCEC monolayers independently of its hypertonic action (5 mM glucose: 154.2 +/- 21.2 and 19.5 +/- 2.4; 30 mM glucose: 134.2 +/- 5.1 [P = 0.01] and 23.5 +/- 2.1 [P = 0.01]; 5 mM glucose + 25 mM mannitol: 168.7 +/- 13.7 ohm.cm2 [P = 0.04] and 19.3% +/- 1.2% 48-hour equilibration of inulin [P = 0.008]). In a separate series of experiments, the authors were unable to show that either aminoguanidine or ponalrestat prevented the effect of high glucose on permeability (30 mM glucose 95.1 +/- 16.7 and 45.4 +/- 5.6; 5 mM glucose: 122.9 +/- 14.2 [P = 0.02] and 36.6 +/- 5.6 [P = 0.001]; 30 mM glucose + aminoguanidine 87.9 +/- 17.5 [P = 0.04] and 75.3 +/- 14.9 [P = 0.6]; 30 mM glucose + ponalrestat 79.9 +/- 12.7 ohm.cm2 [P = 0.1] and 48.2 +/- 2.5% 48-hour equilibration of inulin [P = 0.15]). Ponalrestat did not abrogate the effect of high glucose despite its ability to reduce a high glucose-induced increase in BRCEC intracellular sorbitol levels.

CONCLUSIONS

The data are consistent with a role for increased paracellular permeability in breakdown of the blood-retinal barrier in diabetic retinopathy, which appears to be independent of both nonenzymatic glycosylation and the polyol pathway.

Topical interferon alpha 2b for corneal haze after excimer laser photorefractive keratectomy. The Melbourne Excimer Laser Group

PURPOSE

To determine whether topical interferon alpha 2b (IFN-alpha) prevents corneal haze after excimer laser photorefractive keratectomy (PRK).

SETTING

Tertiary referral ophthalmic hospital.

METHOD

A prospective, double-blind, placebo-controlled, randomized study of 31 patients was undertaken. After surgery in a single institution, patients received a drop of either a placebo or IFN-alpha (5 x 10(6) IU/ml) four times daily for 4 weeks. The main outcome measures were corneal haze, refraction, and visual acuity.

RESULTS

The major side effect of interferon alpha treatment was a significant delay in epithelial healing by a mean of 2 days. The means of the average post-treatment clinical scores for haze in all patients up to 12 months after surgery were 0.46 +/- 0.25 for the IFN-alpha group and 0.64 +/- 0.43 for the placebo group (P = .20). Of patients with a correction of greater than 5.00 diopters (D), the IFN-alpha group had significantly less haze over the course of the study (0.39 +/- 0.23 versus 0.98 +/- 0.50; P = .03). After 12 months, the mean absolute spherical equivalent in the two groups was not significantly different (1.02 +/- 1.13 D versus 1.44 +/- 2.64 D). There was a tendency toward better uncorrected visual acuity in the INF-alpha group (P < .10, Kolmogorov-Smirnov).

CONCLUSION

Topical IFN-alpha may merit further investigation as a treatment to reduce corneal haze after excimer laser PRK for corrections greater than 5.00 D.

Electrical resistance and macromolecular permeability of retinal capillary endothelial cells in vitro

This study was undertaken to examine the ability of retinal capillary endothelial cells to retain blood-retinal barrier properties in vitro. Second passage bovine retinal capillary endothelial cells were grown to confluence on polycarbonate filters in two chamber systems coated with laminin, fibronectin and type IV collagen. The electrical resistances, permeability of 3H-insulin and expression of blood-brain barrier related enzymes by retinal cells was observed and compared with bovine aortic endothelial cells and bovine fibroblasts. The electrical resistance of retinal cells rose over the first week of culture, peaking after 5-9 days in culture. In eleven separate experiments (n = 5 for each experiment) the average peak resistance of retinal endothelial cells ranged from 89.3-186.6 with a mean average of 129.0 ohm.cm2. In one of these experiments, the peak electrical resistance of retinal cells was 149.0 +/- 10.3 compared with 34.8 +/- 6.8 for aortic cells and 37.8 +/- 3.8 ohm.cm2 for fibroblasts. The permeability coefficients of inulin were: retinal cells 0.17 +/- 0.09, aortic cells 3.47 +/- 1.58 (p = 0.015), fibroblasts 3.93 +/- 0.78 (p = 0.002) x 10(-6) cm/sec. Retinal cells expressed significantly higher activities of gamma-glutamyl transpeptidase and alkaline phosphatase than the other cell types. Treatment of the monolayers with the calcium ionophore, A23187, resulted in a reversible increase in permeability as has been described for peripheral vascular endothelium. We conclude that BRCEC retain at least some of their specialised barrier properties in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)

Interferon-alpha 2b enhances barrier function of bovine retinal microvascular endothelium in vitro

Increased permeability of the vascular endothelium is a critical part of pathological processes such as inflammation and wound healing. While several cytokines have been shown to increase endothelial permeability, none has been shown to reduce it. We studied the effect of interferon-alpha 2b on the barrier function of bovine retinal capillary endothelial cells in vitro and found that it increased the electrical resistance of the monolayers (treated cells 211 +/- 6 ohm.cm2, untreated 109 +/- 14 ohm.cm2), decreased their permeability to inulin (Pc inulin of untreated cells 0.73 +/- 0.21 x 10(-6) cm/sec, treated 0.31 +/- 0.23 x 10(-6) cm/sec, P = 0.015), and enhanced their morphological differentiation. Interferon-gamma had no effect. No effect of interferon-alpha treatment on the permeability of bovine aortic endothelial cells was found. We conclude that interferon-alpha 2b can enhance the barrier function of retinal microvascular endothelium in vitro. This is consistent with the hypothesis that interferon-alpha is an effector of a mechanism which actively promotes tissue homeostasis and suggests that it might have therapeutic potential in diseases characterized by leakage of the vascular endothelium.

Treatment of choroidal neovascularisation in age-related macular degeneration with interferon alfa-2a and alfa-2b

Forty eight eyes of 42 patients with choroidal neovascular membranes and age-related macular degeneration who received three different dose regimens of systemic interferon alfa-2 were studied retrospectively. The response to treatment of 41 eyes of the 37 patients who received at least 4 weeks' treatment was analysed with respect to the change in size of the choroidal neovascular membrane and the visual acuity compared with pretreatment levels. The size of the membrane at the end of the course of treatment had decreased in seven (17%) eyes overall, not changed in 16 (39%), and increased in 18 (44%). At the end of treatment, the visual acuity had improved in seven (17%) eyes, not changed in 27 (66%), and deteriorated in seven (17%). With an average follow up of 10 months after treatment, the visual acuity had deteriorated compared with the pretreatment value in 21 out of 41 (51%) eyes. Vision improved in some fellow eyes with disciform scars. Side effects were common and often severe. The data suggest that one of the major effects of interferon alfa may be to decrease vascular permeability. While further research may identify a place for interferon alfa in the treatment of choroidal neovascularisation, we were unable to demonstrate that the treatment regimens of systemic interferon alfa we used caused a dramatic benefit to patients with exudative age-related macular degeneration.

Effect of topical interferon-alpha 2b on corneal haze after excimer laser photorefractive keratectomy in rabbits

BACKGROUND

Anterior corneal stromal keratocytes are activated by excimer laser photorefractive keratectomy resulting in haze with healing of the ablated area. In some eyes, this causes a visible haze or scar on the cornea, and an unpredictable regression of the myopic correction following refractive ablations.

METHODS

Following a 6.00-diopter excimer laser photorefractive keratectomy to both eyes, 16 rabbits were treated for 5 weeks with interferon-alpha 2b drops four times a day to one eye only. Eight of these rabbits were treated with dexamethasone drops four times a day to both eyes. Using a standard grading scale for haze, the corneas were examined and the haze graded weekly.

RESULTS

The observed corneal haze was significantly reduced in the treated eyes by the application of topical interferon-alpha 2b drops (p = .004), and topical dexamethasone drops (p < .001). Topical dexamethasone also produced less haze in combination with interferon-alpha 2b than when used alone (p = .035). There was continuing resolution of the corneal haze in those rabbits observed for 7 weeks after the cessation of the drops. Topical interferon-alpha therapy was not toxic to the rabbit eye and was not associated with delayed reepithelialization after the laser procedure.

CONCLUSION

Topical interferon-alpha 2b appears to reduce the corneal haze produced by excimer laser photorefractive keratectomy in rabbits.

High glucose inhibits retinal capillary pericyte contractility in vitro

PURPOSE

To study the effect of high glucose concentrations on pericyte contractility.

METHODS

Bovine retinal capillary pericytes were cultured on silicone rubber sheets, which could be seen to wrinkle when a cell contracted. Cells were grown in glucose, or mannitol, in concentrations ranging from 5 to 40 mMol. Pericyte contractility was expressed as the percentage of cells wrinkling the silicone substratum. Observations were made fortnightly for 8 weeks.

RESULTS

Cells grown in glucose exhibited a dose-dependent inhibition of contractility that was significantly greater than that seen with cells grown in mannitol, which were affected to a lesser extent. After returning to normoglycemic conditions for a further 4 weeks, the contractility of cells grown in lower glucose concentrations recovered partially, but cells grown in 40 mMol glucose did not recover at all. Pericyte proliferation was also impaired by the high-glucose growth medium.

CONCLUSIONS

Pericyte contractility is inhibited by high glucose concentrations. This is consistent with the hypothesis that increased retinal blood flow may be a factor in the early pathogenesis of diabetic retinopathy.

Glaucoma Filtering Surgery With Interferon-alpha-2b

The effect of subconjunctival interferon-alpha-2b treatment on success rates after glaucoma filtering surgery was compared with that of 5-fluorouracil in a pilot study. Surgery was defined as successful if it reduced the intraocular pressure to less than 21 mm Hg without medication. Initially, doses of 2 x 10 IU of interferon-alpha were given. By 6 months postoperatively, 6 of 16 interferon-treated patients had had to resume medication to control their glaucoma, compared with only 2 of 16 patients treated with 5-fluorouracil (p = 0.08). When the dose of interferon was increased to 1 x 10 IU, 2 of 13 interferon-treated patients had to resume by 6 months (p = 0.14 when compared with the patients receiving the lower dose). Corneal epithelial defects were less common in the 1 x 10 IU interferon-alpha group compared with the 5-fluorouracil group (1 of 13 vs. 11 of 16; p = 0.0002) while other side effects, both local and systemic, were similar between the two groups. This study shows that (a) interferon-alpha-2b, in the doses used, is well-tolerated by the human eye, and (b) interferon-alpha-2b may reduce the risk of failure of glaucoma filtration surgery with fewer corneal complications than are seen with 5-fluorouracil.

A simple method for the in vitro culture of human retinal capillary endothelial cells

A simple method for the culture of human retinal capillary endothelial cells in vitro is described in this report. Through a process of gentle mechanical disruption and sieving, a sufficient yield of retinal microvessels was obtained from one or two human eyes to allow the culture of endothelial cells in abundance. The cells were factor VIII-positive and demonstrated typical vascular endothelial morphology. Pericyte contamination was prevented by using human platelet-poor serum in primary culture and passaging cells with a low concentration of trypsin. Proliferation assays revealed that the cells grew best in Iscove's modified Dulbecco's modified Eagle's medium with 15% fetal calf serum (FCS). There was no difference in induced proliferation when FCS was compared to human platelet-poor serum. The method seemed to be as good as and much simpler than other recently described techniques. The study of human retinal capillary endothelial cells cultured in this way may shed light on the earliest stages of diabetic retinopathy and other diseases of the retinal microvasculature, particularly AIDS-related retinopathy and radiation retinopathy.

Cytokines, fibrosis and the failure of glaucoma filtration surgery

Current therapies for the prevention of fibrosis after glaucoma filtering surgery can be effective but often produce unwanted side effects. An understanding of the cellular basis of the fibrotic reaction may lead to better treatments. Wound repair revolves around angiogenesis and the activation of fibroblasts by cytokines. These peptides, a number of which have been described, act together in intricately complicated networks to encourage fibroblast chemotaxis, proliferation and contractility, as well as to stimulate the production of glycosaminoglycans and collagen. Since interferons seem to inhibit many of these responses, they deserve further evaluation in the treatment of ocular fibrosis.

The evolution of function and response to arginine challenge and pregnancy of portally and systemically placed islet cell grafts in streptozotocin diabetic mice

Mice made diabetic with streptozotocin received organ cultured fetal islet cell grafts in the portal (PG) or systemic (SG) vascular beds in order to determine whether portal delivery of insulin is an important consideration in graft placement. Grafts were established more quickly in SG mice as shown by body weight and blood glucose estimations. Intraperitoneal arginine was found to be a stronger insulin secretagogue than intravenous glucose with the doses used when serum insulin was measured 5 minutes after injection. Glucose response to an arginine challenge was initially abnormal in both groups of mice, but was identical to normal controls 4 months after transplantation, showing that engraftment is a gradual process. Mice were then mated and their response to the chronic glycemic stress of pregnancy was noted. PG and SG mice had normal fertility rates in contrast to untreated diabetics, none of which became pregnant. Offspring were normal with respect to litter size, body weight, malformation rate, and pancreatic insulin content compared with historical controls. PG and SG mothers behaved normally during pregnancy, with the exception of a raised glycosylated hemoglobin level at day 19.5 gestation (5.5% and 5.5% v 3.7%, P less than .01). We were, therefore, unable to detect any difference between portally and systemically placed islet grafts.

The prevention of diabetic retinal and renal basement membrane thickening in mice by islet cell allografts

The effect of fetal islet cell allografts on retinal capillary (RCBMT) and glomerular (GBMT) basement membrane thickening in diabetic mice was studied, as well as the effect of diabetes on the anterior lens capsule and the inner lamina of Descemet's membrane. CBA mice rendered diabetic with streptozotocin received fetal pancreatic islet cell grafts from C3H and BALB/c donors four weeks after induction of diabetes with an additional late transplant group receiving C3H grafts after six months of diabetes. After 12 months animals with successful grafts were examined for RCBMT along with untreated diabetics (UD, n = 4) and normals (N, n = 9). Untreated diabetics had significantly increased RCBMT (167.1 +/- 12.1 vs 129.2 +/- 24.3 nm, p = 0.05) and GBMT (278 +/- 11 vs 248 +/- 6 nm, p = 0.004) compared to normals. All graft recipients had RCBMT similar to normal and significantly less than untreated diabetics: BALB/c (n = 7), 123.8 +/- 21.0, p = 0.02; C3h early (n = 5), 126.6 +/- 21.7, p = 0.05; C3H late (n = 4), 134.4 +/- 16.9, p = 0.03. The same was true for GBMT; 250 +/- 10 nm, p = 0.02 for BALB/c recipients, 250 +/- 8 nm, p = 0.04 for early and 255 +/- 9 nm, p = 0.02 for late C3H recipients. GMBT in six month biopsies of normals and prospective late graft recipients were well below these levels.(ABSTRACT TRUNCATED AT 250 WORDS)