GlyCAM1 negatively regulates monocyte entry into the optic nerve head and contributes to radiation-based protection in glaucoma

BACKGROUND

We previously reported a profound long-term neuroprotection subsequent to a single radiation-therapy in the DBA/2J mouse model of glaucoma. This neuroprotection prevents entry of monocyte-like immune cells into the optic nerve head during glaucoma. Gene expression studies in radiation-treated mice implicated Glycam1 in this protection. Glycam1 encodes a proteoglycan ligand for L-selectin and is an excellent candidate to modulate immune cell entry into the eye. Here, we experimentally test the hypothesis that radiation-induced over-expression of Glycam1 is a key component of the neuroprotection.

METHODS

We generated a null allele of Glycam1 on a DBA/2J background. Gene and protein expression of Glycam1, monocyte entry into the optic nerve head, retinal ganglion cell death, and axon loss in the optic nerve were assessed.

RESULTS

Radiation therapy potently inhibits monocyte entry into the optic nerve head and prevents retinal ganglion cell death and axon loss. DBA/2J mice carrying a null allele of Glycam1 show increased monocyte entry and increased retinal ganglion cell death and axon loss following radiation therapy, but the majority of optic nerves were still protected by radiation therapy.

CONCLUSIONS

Although GlyCAM1 is an L-selectin ligand, its roles in immunity are not yet fully defined. The current study demonstrates a partial role for GlyCAM1 in radiation-mediated protection. Furthermore, our results clearly show that GlyCAM1 levels modulate immune cell entry from the vasculature into neural tissues. As Glycam1 deficiency has a more profound effect on cell entry than on neurodegeneration, further experiments are needed to precisely define the role of monocyte entry in DBA/2J glaucoma. Nevertheless, GlyCAM1's function as a negative regulator of extravasation may lead to novel therapeutic strategies for an array of common conditions involving inflammation.

[Comparative hemodynamic characteristics of patients with the organ of vision subjected to low-intensity laser radiation of the green and red wavelengths]

This comparative study was designed to evaluate effect of low-intensity speckle laser radiation in the green and red wavelengths on intraocular hemodynamics in 202 patients (202 eyes) with retinal vascular problems and without them. Irradiation was performed using "Izumrud" and "Rubin" adapters for an AMO-ATOS unit. Peak systolic velocity and peripheral resistance index in posterior short ciliary arteries and central retinal artery were measured. It was shown for the first time that green speckle laser radiation (wavelength 535 nm) has more pronounced (compared with the red light) effect on intraocular hemodynamics; thereby, it makes a greater contribution to the improvement of the visual function (e.g. in the case of glaucoma) and to the widening of the fields of vision.

[Secondary glaucoma treatment by means of Leksell gamma knife]

The authors followed up 107 eyes of 103 patients with the diagnosis of painful secondary glaucoma treated by irradiation of the ciliary body by means of Leksell gama knife (LGK Elekta Instruments AB). The goal was to decrease patient's subjective problems in to the treatment resistant and painful stages using non-invasive stereo tactic neurosurgical procedure. The final version of the irradiation schedule uses 8 mm collimators and the irradiation dose in blind eyes is 40 Gy at the maximum and 20 Gy at the peripheral treating 50% isodose; in partly sighted eyes it is 30 Gy at the maximum and 15 Gy at the peripheral treating 50% isodose. The follow up period was 3-80 months, (average 26 months). The lowering of the intraocular pressure to the not painful level was achieved in 56 eyes (52.2%) during the period of 1-8 weeks (median 4 weeks). The total disappearing of the pain after the treatment was noticed in 71 eyes (66.4%), partial reduction of the pain in 31 eyes (29%), and no effect was observed in 5 eyes. In all cases of neovascularization at least some decrease was noticed. The antiglaucomatous therapy was reduced in 42 patients (39.3%) 2-3 months after the irradiation, unchanged remained in 51 patients (47.7%). The stereotactic radiosurgical destruction of the ciliary body by means of Leksell gama knife, may reduce the pain, the intraocular pressure, and extensive medicament treatment in secondary painful glaucoma.

High-dose radiation with bone marrow transfer prevents neurodegeneration in an inherited glaucoma

Here, we show that high-dose gamma-irradiation accompanied with syngeneic bone marrow transfer can confer complete protection against glaucoma in a mouse model. Because bone marrow genotype was unaltered by this procedure, it was not the causative agent. The neuroprotection is robust and highly reproducible. Glaucoma-prone DBA/2J mice received a single treatment at 5-8 weeks of age and were protected from glaucomatous retinal ganglion cell degeneration out to 14 months of age (oldest assessed). By 12-14 months, retinal ganglion cell degeneration is usually very severe and essentially complete in the majority of untreated DBA/2J mice. To assess reproducibility, three groups of mice were treated at different times, and the results were essentially the same each time. Considering all experiments, the vast majority of treated mice had no detectable glaucomatous neurodegeneration. A beneficial effect of treatment including high-dose radiation is unprecedented, and we are not aware of any other neuroprotective effects this substantial. Because of the robust protective effect, this treatment offers another tool for studying mechanisms of neuroprotection.

Femtosecond laser for glaucoma treatment: a study on ablation energy in pig iris

Safe and effective laser ophthalmic surgery requires a fine balance between the efficiency of laser delivered and the degree of collateral side damage. The laser-ocular tissue interaction process is reliant on three main variables, namely, wavelength, pulse duration, and deposited energy. A certain amount of energy is needed to achieve ablation, while too much energy can result in unwanted collateral thermal damage. In our work the relationship between energy deposition and ablation effect is studied by an in-vitro experiment using an 800 nm wavelength 150 fs-pulse-duration laser system. This experiment aims to validate the probability of decreasing the supplied energy during glaucoma surgery by femtosecond laser. Our results show that less energy is needed using femtosecond laser than that using a longer pulse laser.

Beta irradiation: new uses for an old treatment: a review

Beta radiation has a long history as a treatment modality in ophthalmology. It is a convenient and practical method of applying radiation and has the advantage of minimal tissue penetration. There has been a recent resurgence in the use of beta radiation in other areas in medicine, such as the prevention of restenosis after coronary artery stenting. Beta radiation has been shown in vitro and in vivo to inhibit proliferation of human Tenon's fibroblasts, which enter a period of growth arrest but do not die. Effects on the cell cycle controller p53 have been shown to be important in this process. In ophthalmology, beta radiation has been used widely for the treatment of pterygium and is under evaluation for treatment of age-related macular degeneration and for controlling wound healing after glaucoma drainage surgery. In this latter role, beta radiation may be particularly appropriate for use in developing countries to improve the results of trabeculectomy while potentially avoiding some of the side effects of other antimetabolites.

Telemedicine techniques can be used to facilitate the conduct of multicentre trials

A multicentre randomized controlled trial was established in Pretoria, Bloemfontein and Edendale in South Africa, and coordinated from London. The purpose of the trial was to determine the efficacy of low-dose beta irradiation of glaucoma. Five communication modalities (telephone, fax, e-mail, videoconferencing and face-to-face meetings) were examined in terms of their benefits in a multicentre trial. The eight stages of the multicentre trial examined were: set-up and training, recruitment, standardization, patient management, data transmission, update and data dissemination, clinical follow-up and monitoring, and publication. On four-point Likert scales for rating the usefulness of the communication modalities at each of the eight stages of the trial (from 0 = not useful to 3 = very useful; maximum score 24) the telephone was given a total score of 10, fax 9, e-mail 13, videoconferencing 15 and face-to-face meetings 9. Telemedicine techniques offer considerable benefits in the coordination of multicentre trials by improving data collection, maintaining the efficacy and monitoring of trials, while potentially offering reduced costs in terms of travel and time. The realtime scrutiny of patient records helps to ensure data uniformity and completeness of data collection. Videoconferencing was most useful when considered as one of several communication tools that can be used to improve the effectiveness of a service or process.

[Successful irradiation of ciliary processes with electrons in therapy refractory aphakic glaucoma]

BACKGROUND

Successful radiation was already reported by Genée and Weitzel (1968): Electrons from a Betatron were used for irradiation of the ciliary epithelium to lower aqueous humor secretion. To our knowledge, no other paper on this topic has been published so far.

PATIENT

A 26-year-old man had history of concussion trauma and cataract surgery in childhood. In adult age, cataract surgery and retinal operations were followed by numerous surgical procedures and maximal medical treatment because of a secondary glaucoma. The patient refused further surgical and medical treatment with the exception of the administered systemic carbo-anhydrase inhibitor. Because of severe side-effects caused by the acetozolamide, irradiation of the ciliary processes with electrons, emitted from a linear accelerator, was performed. The total amount of 12 Gy both on the nasal and on the temporal side of the ciliary body was fractionated in several sessions.

RESULTS

During a follow-up of 22 months without medication, the mean value of i.o. pressure was 22.1 mm Hg. The patient is doing well, corrected VA is 0.8.

CONCLUSION

Irradiation of the ciliary processes with electrons for lowering aqueous humor secretion was effective in an otherwise non treatable case of glaucoma.

Trabeculectomy combined with beta irradiation for congenital glaucoma

Sixty-six eyes with congenital glaucoma were subjected to trabeculectomy between July 1975 and June 1989 are presented. Thirty-one were treated with beta irradiation at the time of surgery with a strontium-90 applicator; 35 were not treated with beta irradiation. The usual dose was 750 rad. Analysis was limited to three years because of the shorter follow-up of the irradiated eyes. Failure in the two groups was compared statistically. When failure was categorised as IOP greater than 21 mm Hg, beta irradiation was found to be significantly protective with an adjusted risk ratio of 0.31 (95% confidence interval 0.11-0.90, p less than 0.05). Failure categorised as the need for additional medical treatment or further surgery showed significant protection with an adjusted risk ratio of 0.33 (confidence interval 0.12-0.94, p less than 0.05). Multiple regression models were used for the analysis of intraocular pressure; beta irradiation was associated with a significantly lower IOP at six months, one year, and three years (p less than 0.05). Other factors identified as being associated with a reduced failure rate or lower IOP were: no previous topical glaucoma medications: age over seven years; lack of previous surgery involving the conjunctiva. The results indicate that beta irradiation may have a beneficial effect on the prognosis of trabeculectomy in children with congenital glaucoma. However, because of the retrospective and observational nature of the study, the results must be regarded as tentative.

The effect of topical dexamethasone and preoperative beta irradiation on a model of glaucoma fistulizing surgery in the rabbit

We studied the effect of topical dexamethasone (1%) and preoperative beta irradiation on a model of glaucoma fistulizing surgery in the rabbit. Intraocular pressure and gross facility of aqueous outflow following surgery were not influenced by either treatment, although blebs persisted longer in the irradiated eyes. Steroids reduced clinically observable inflammation as well as the number of inflammatory cells identifiable by microscopy. Fibroblast production temporarily slowed, and ultra-structural examination demonstrated lipid-filled vacuoles and dilated mitochondria in these eyes. Also, the scar was thinner at 24 days. Beta irradiation delayed wound healing and the scar was thinner in the early postoperative stages, but the light microscopic appearance of the scar was unaltered at 59 days. Inflammation was more pronounced initially, with abundant fibrin in the wound. Recovery of the conjunctival epithelium was delayed. The delay in fibroblast recruitment and wound contraction, the thinner scar tissue, and the increased survival of the bleb are all factors that suggest that beta irradiation may be a useful adjunct to glaucoma surgery.

Cyclodestructive surgery for glaucoma: past, present, and future

When surgical attempts to control glaucoma by improving aqueous outflow are not successful, the alternative approach is usually to reduce aqueous inflow by a cyclodestructive procedure. Cyclodestructive elements that have been tried in the past include diathermy, electrolysis, and beta irradiation. Cyclocryotherapy is presently the most commonly used cyclodestructive procedure, although this operation has significant limitations, and newer techniques are being evaluated utilizing laser energy or ultrasonic radiation. Each of these procedures uses a transcleral approach, which has the disadvantages of (1) the inability to precisely quantitate the destruction of the ciliary processes, and (2) damage to adjacent tissue. Transpupillary cyclophotocoagulation minimizes these problems, but is limited to the small number of eyes in which adequate gonioscopic visualization of the ciliary processes can be achieved. An alternative approach for aphakic eyes is intraocular cyclophotocoagulation, utilizing an endophotocoagulator through a pars plana incision. Depending on the status of the eye, visualization for this technique can be accomplished either by the transpupillary route or with an endoscope.

Infiltration of the iris in chronic lymphatic leukaemia

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