Immunological problems of transplantation into the subretinal space

The objective of retinal transplantation is to substitute destroyed or degenerated retina to improve visual function. Photoreceptors and retinal pigment epithelium cells of embryonic and nonembryonic origin have been transplanted into the subretinal space in different animal models. Recently, retinal cells have also been used for transplantation in untreated or immunosuppressed patients with retinitis pigmentosa and age-related macular degeneration. Transplants performed in animals such as the RCS rat have maintained retinal function at the transplantation site for long periods of time, although such transplantations in humans have not proved conclusively, to date, whether there is a real effect or not. One reason for this phenomenon seems to be an immune response to transplanted retinal cells at the transplantation site. The detectable rejection process shows that the posterior part of the eye is not absolutely immunologically privileged and that rejection is a serious problem in human retinal transplantation. Many questions concerning transplantation technique, graft treatment and postoperative treatment will be answered through more intensive experiments and clinical trials regarding the immunology. However, rejection of transplanted material is one of the main reasons why retinal transplantation has not yet proved successful.

Down-regulation of MHC class II expression on bovine retinal pigment epithelial cells by cytokines

To determine the effect of interleukin-10 (IL-10) and transforming growth factor-beta (TGF-beta) on the down-regulation of MHC class II antigens, bovine retinal pigment epithelial (RPE) cells were incubated with interferon-gamma (IFN-gamma) in different concentrations. Subsequently, the IFN-gamma pretreated RPE cells were cultured with TGF-beta or IL-10 in distinct concentrations and treatment modi. About 10% of native (totally untreated) RPE cells were positive for MHC class II antigens detected with immunocytostaining. Under the influence of IFN-gamma (1,000 U/ml), the number of MHC class II-bearing cells increased to 49.9 +/- 4.5% positive cells after 8 days' incubation. Expression decreased under the most effective TGF-beta treatment (5 ng/ml) to 2.0 +/- 0.9% after 24 h incubation, and under similar IL-10 treatment (200 U/ml) to 3.8 +/- 1.4% after 72 h. This decreasing number of the MHC class II-positive cells may be useful for various eye research studies and, more especially, to RPE cell transplantation in the future.

P2X7 receptors in Müller glial cells from the human retina

ATP has been shown to be an important extracellular signaling molecule. There are two subgroups of receptors for ATP (and other purines and pyrimidines): the ionotropic P2X and the G-protein-coupled P2Y receptors. Different subtypes of these receptors have been identified by molecular biology, but little is known about their functional properties in the nervous system. Here we present data for the existence of P2 receptors in Müller (glial) cells of the human retina. The cells were studied by immunocytochemistry, electrophysiology, Ca(2+)-microfluorimetry, and molecular biology. They displayed both P2Y and P2X receptors. Freshly enzymatically isolated cells were used throughout the study. Although the [Ca(2+)](i) response to ATP was dominated by release from intracellular stores, there is multiple evidence that the ATP-induced membrane currents were caused by an activation of P2X(7) receptors. Immunocytochemistry and single-cell RT-PCR revealed the expression of P2X(7) receptors by Müller cells. In patch-clamp studies, we found that (1) benzoyl-benzoyl ATP (BzATP) was the most effective agonist to evoke large inward currents and (2) the currents were abolished by P2X antagonists; however, (3) long-lasting application of BzATP did not cause an opening of large pores in addition to the cationic channels. By microfluorimetry it was shown that the P2X receptors mediated a Ca(2+) influx that contributed a small component to the total [Ca(2+)](i) response. Activation of P2X receptors may modulate the uptake of neurotransmitters from the extracellular space by Müller cells in the retina.

The local and systemic secretion of the pro-inflammatory cytokine interleukin-6 after transplantation of retinal pigment epithelium cells in a rabbit model

The rejection of retinal pigment epithelium (RPE) allografts is one of the major problems for long-term success after retinal transplantation. However, the details of the immunological interactions in the subretinal space after transplantation are still unknown. The aim of our study was to investigate the role of IL-6 in the rejection process in the subretinal space and to use IL-6 monitoring for a possible early sign of rejection after transplantation of allogeneic RPE cells. For this we used a model of transplanting pigmented RPE cells, either activated in vitro with 1000 U/ml interferon-gamma (IFN-gamma) for 8 days or non-activated, into 30 albino rabbits. The IL-6 was investigated 3, 5, 7, 9 and 14 days after transplantation. Additionally, sham operated animals and the untreated eyes served as controls. At these time-points the animals were killed, the liquid in the vitreous cavity and serum was collected and the IL-6 present in these samples was quantified with an enzyme-linked immunosorbent assay. Under these conditions, IL-6 was detected in the liquid of the vitreous cavity and in the serum of all RPE-transplanted rabbits. In the group receiving activated RPE two cytokine peaks were measured, 3 and 7 days after transplantation in the vitreous cavity. In non-activated grafts, a maximum was detected on the 5th day after transplantation. Generally, the detected quantity of IL-6 depended on the host status and on the phase of rejection. No significant changes were seen in the sera from either group. Possibly, the host RPE cells are the main source of this interleukin in the transplantation area. The measuring of IL-6 in the rejection model suggests that it plays a role in the immune cascade in the subretinal space.

Changes in the mRNA expression of cytokines and chemokines by stimulated RPE cells in vitro

PURPOSE

The transplantation of retinal pigment epithelial (RPE) cells is a possible therapy for degenerative diseases of the retina. However, the immune response and the subsequent rejection of the allografts are major problems in this field. We investigated the effect of pro-inflammatory factors on the cytokine and chemokine mRNA expression of human RPE cells during long-term observations in vitro.

METHODS

Human RPE cells were cultured in the presence of tumor necrosis factor-alpha (TNF-alpha, 10 ng/ml), interferon-gamma (IFN-gamma, 1000 U/ml) or with a combination of both up to 96 hours. Cells were harvested and total RNA was isolated. The changes in expression of mRNA coding for RANTES, the interleukines (IL)-6, 8, 10, 15, IFN-gamma, monocyte chemotactic protein-1 (MCP-1) and transforming growth factor-beta1 (TGF-beta1) during the stimulation were investigated using the ribonuclease protection assay.

RESULTS

IL-10 and IFN-gamma mRNA were detected in neither unstimulated nor stimulated cells. Human RPE cells constitutively express the mRNA for IL-6, MCP-1, IL-8, IL-15, TGF-beta1 and, at very low levels, for RANTES. The TGF-beta1 mRNA expression was not influenced by either stimulation. The mRNA of the other factors was up-regulated for 24-48 h dependent on the stimulation.

CONCLUSIONS

Human RPE cells are able to increase their mRNA expression for the detected cytokines in response to the pro-inflammatory factors which are detectable in the rejection process. These up-regulated cytokines themselves are known to be involved in several inflammatory and immunological processes, suggesting their role in the rejection of transplanted RPE allografts.

R-(+)-verapamil, S-(-)-verapamil, and racemic verapamil inhibit human retinal pigment epithelial cell contraction

PURPOSE

To evaluate the effects of R-(+)-verapamil, S-(-)-verapamil, and the racemate on in vitro contraction of human retinal pigment epithelial cells.

METHODS

RPE cells from human donor eyes were enzymatically dissociated and cultured on collagen gels. Transdifferentiated RPE cells (seventh and eighth passage) were used for experiments. The contraction assays were treated with different concentrations (10-1000 microM) of R-(+)-verapamil, S-(-)-verapamil, and racemic verapamil.

RESULTS

Verapamil inhibited the gel contraction of human RPE cells. R-(+)-verapamil, S-(-)-verapamil, and racemic verapamil acted equally in a dose-dependent manner from 10-1000 microM.

CONCLUSION

The results indicate the effectiveness of verapamil to inhibit the contraction of RPE cells. R-(+)-verapamil is recommended because it is associated with fewer systemic and local side effects.

[Blue-yellow perimetry in rhegmatogenous retinal detachment. Studies before and after therapy in comparison with white-white perimetry]

INTRODUCTION

Disturbance of the blue light perceptance in rhegmatogenous retinal detachment was demonstrated by Köllner 1907 with the help of colour-perimetries. We examined the blue- and white-function after retinal reattachment by blue-on-yellow-perimetry compared with white-on-white-perimetry.

PATIENTS AND METHODS

10 Patients with rhegmatogenous retinal detachment and a visual acuity > or = 0.1 were examined preoperatively, 4 days and 6 weeks after successful buckling procedure. We performed a white-on-white-perimetry as also perimetries with blue stimuli on a yellow luminance background (program 30-2 of the Humphrey Field Analyzer 750).

RESULTS

Four days after surgery the increase in sensitivity was significantly less for the blue-function compared with the white-function. Preoperatively and 6 weeks postoperatively the sensitivities were not significantly different. Between these time-points function recovered in average for both methods from MD -15 dB to MD -5 dB.

CONCLUSION

After successful retinal detachment surgery the blue- and white-function increased. Blue-on-yellow-perimetry showed more retinal sensitivity loss than white-on-white-perimetry immediately after surgery. Blue-on-yellow-perimetry measured the same retinal sensitivity loss as white-on-white-perimetry preoperatively and 6 weeks postoperatively.

[Clinical anophthalmos. Cosmetic outcome after 2 years therapy with an orbital expander for stimulating orbital growth]

BACKGROUND

Congenital anophthalmos is a rare condition in which intervention in an early age can stimulate orbital expansion. The therapeutic goal was to allow retention of a suitable prosthesis and to maximise facial symmetry.

METHODS AND PATIENTS

We report on 3 anophthalmic newborn male patients, of which one presented with microphthalmos in the other eye as well as associated systemic disorders. Solid moulded shapes were adapted and manufactured out of methylmethacrylate to increase expansion of orbital soft tissue and bone. The moulding of the orbita was performed by silicone made of two components under general anaesthesia during the first two years of life. The following day the solid shapes were fitted in the outpatient department. They were increased in size when they started to rotate within the orbit or when the eyelids were relatively loose around the solid shape. The initial insertion of the orbital expander was performed in the first weeks after birth and was repeated every 3 to 6 weeks within the first year of life. The degree of orbital expansion was determined by measurements of the horizontal eyelid length, the volume of the solid shapes, by measuring the volume in cm3 of water displaced by the shape after submerging it in a cylinder of water and assessment of the cosmetic aspect.

RESULTS

Within 8 months of therapy a horizontal eyelid lengthening to 10 mm and an increase of the volume of the orbital expander from 1.5 cm3 to 6 cm3 was achieved in patient 1. After 20 months of therapy patient 2 showed symmetry of the face and the horizontal eyelid length. In patient 3 therapy started 3 years late and after 2 years only a horizontal eyelid lengthening of 3 mm and a suboptimal symmetry of the face was achieved.

CONCLUSION

Our own experience suggests that early prosthetic fittings are necessary for an ideal cosmetic outcome. Motivation and cooperation of the parents is an important factor to achieve optimal results.

Massive suprachoroidal hemorrhage: secondary treatment and outcome

PURPOSE

Massive suprachoroidal expulsive hemorrhage (SCH) is a dramatic and devastating intraocular complication of intraocular surgery and trauma that can result in total loss of vision. The aim of our study was to present the results of secondary surgical treatment of eyes following massive SCH.

PATIENTS AND METHODS

We treated 10 patients suffering from massive SCH by combined radial sclerotomies for suprachoroidal drainage and vitrectomy with use of perfluorocarbon and instillation of silicone oil. We analyzed the clinical characteristics, visual acuity and anatomical status before and after secondary treatment.

RESULTS

Visual acuity of all eyes suffering from SCH was light perception. Postoperatively five patients with SCH showed either no improvement of function or visual acuity of counting fingers. An increase in visual acuity to maximal 0.1 was seen in four eyes; one patient achieved 0.6. With a minimum of 6 months' follow-up, four eyes developed hypotony, two eyes became phthisical, and in two eyes recurrent traction retinal detachment occurred.

CONCLUSIONS

Secondary treatment by combined suprachoroidal drainage by sclerotomies and vitrectomy should be performed to minimize the damaging effect of choroidal hemorrhage.

Human Müller glial cells: altered potassium channel activity in proliferative vitreoretinopathy

PURPOSE

To determine differences of K+ channel activity between Müller glial cells obtained from retinas of healthy human donors and of patients with retinal detachment and proliferative vitreoretinopathy.

METHODS

Müller cells were enzymatically isolated from retinas of healthy donors and from excised retinal pieces of patients. The whole-cell and the cell-attached configurations of the patch-clamp technique were used to characterize the current densities of different K+ channel types and the activity of single Ca2+ -activated K+ channels of big conductance (BK).

RESULTS

Cells from patients displayed a less negative mean membrane potential (-52.8 mV) than cells from healthy donors (-80.6 mV). However, the membrane potentials in cells from patients scattered largely between -6 and -99 mV. The inwardly rectifying K+ permeability in cells from patients was strongly reduced (0.3 pA/pF) when compared with cells from healthy donors (6.0 pA/pF). At the resting membrane potential, single BK channels displayed a higher mean activity (open probability, Po, and channel current amplitude) in cells from patients (Po, 0.30) than in cells from healthy donors (Po: 0.03). The variations of BK current amplitudes were correlated with the variations of the membrane potential.

CONCLUSIONS

The dominant expression of inwardly rectifying channels in cells from healthy donors is thought to support important glial cell functions such as the spatial buffering of extracellular K+. The downregulation of these channels and the less negative mean membrane potential in cells from patients should impair spatial buffering currents and neurotransmitter clearance. The increased activity of BK channels may support the proliferative activity of gliotic cells via feedback regulation of Ca2+ entry and membrane potential.

From four-bed clinic to modern eye hospital: ophthalmology in Leipzig, 1820-1996

The opening of the "Heilanstalt für arme Augenkranke" by Friedrich Philipp Ritterich (1782-1866) in 1820 was an important landmark for ophthalmology in Leipzig and in all of Germany. The first chair of ophthalmology in Germany was taken by Christian Georg Theodor Ruete in 1852. In 1883 the clinic moved to a new domicile, a modern building in the Leipzig "medical quarter." In the ensuing years, the hospital developed into a well-known university center of ophthalmology with the scientific, clinical, and organizational work of ophthalmologists such as Hubert Sattler and Ernst Hertel. The extension of the old building in 1908-1911 and the rebuilding after the destruction in World War II created better opportunities for research, teaching, and patient treatment. Comprehensive expansion and reconstruction of the Eye Hospital since 1994 has created excellent conditions for both clinical and experimental ophthalmology as well as the training of students.

[Penetrating and perforating eye injuries with foreign bodies during motorized brush-cutting while wearing head protection gear]

BACKGROUND

Protective clothing is prescribed concerning gloves, shoes, protective trousers and a helmet for protection of hearing and the face during brush-cutter work.

PATIENTS AND METHODS

Seven patients were observed in a time period from 1994 to 1998. Mostly a nylon head protection had been used. The side of the helmet has no protection shield. The 1- to 4-mm large foreign bodies passed the head protection shield from the side or by entering through the holes of the nylon mesh which may be not small enough to stop the foreign body. A pars plana vitrectomy with foreign body removal was performed after primary wound repair.

RESULTS

An endophthalmitis was diagnosed in two patients after primary wound treatment. In these cases, a pars plana vitrectomy and antibiotic instillation was performed. In 5 patients visual acuity increased postoperatively. We measured a postoperative visual acuity from 1/50 to 1.6. The development of proliferative vitreoretinopathy with retinal detachment in 4 patients was the main complication observed after pars plana vitrectomy.

CONCLUSIONS

A cosmetically satisfactory appearance of the injured eye was reached by pars plana vitrectomy in all patients. Anatomic and functional success was reached in most of the patients. For prophylaxis, a head-protection seems not safe enough. The additional usage of eye protection glasses may be imperative for the prevention of these eye injuries.

[Management of submacular hemorrhage by tissue plasminogen activator and SF(6) gas injection]

The formation of platelet-fibrin clots causes degeneration of foveolar photoreceptors by subretinal hemorrhage.

PATIENTS

Twenty-two patients with submacular hemorrhages were treated by intravitreal injection of 50 microg tpa and 0.5 ml SF(6) gas within 1 h. Biomicroscopy, fundus photography and fluorescein angiography were performed pre- and postoperatively. Further multifocal electroretinograms were recorded.

RESULTS

The subfoveolar hemorrhages were dissoluted and displaced out of the macular region. The visual acuity increased in 18 cases and ranged from hand movement and 0.3 to values between 1/10 and 0.5.

CONCLUSIONS

Toxic and hypoxic damage of foveolar photoreceptors by subretinal hemorrhage can be prevented by early and minimal invasive fibrinolytic therapy. After localization of choroidal neovascularizations, treatment by focal laser coagulation is possible in some cases.

360 degrees retinectomy in severe anterior PVR and PDR

We reviewed 30 cases of 360 degrees retinectomy in advanced anterior PVR or PDR with anterior traction. The preoperative visual acuity was light perception or hand motions. In all cases, a 360 degrees retinectomy with silicone oil tamponade was performed. After a mean follow-up of 10 months, the retina was attached in 83% and the visual acuity had improved in 47% of the patients. The mean visual field in patients with a visual acuity of more than counting fingers extended to 29 degrees nasally and 38 degrees temporally. Hypotony was seen in 6 patients, of whom two developed keratopathy. In conclusion, eyes with severe PDR or PVR and a preoperative low visual acuity can be treated successfully with 360 degrees retinectomy when conventional methods have failed. The patients can regain an ambulatory visual acuity and a visual field.

[Gene transfer in ophthalmology]

BACKGROUND

Research into the molecular and genetic basis of disease is continually expanding. How does the increasing knowledge about the genetic basis of eye diseases contribute to the development of new therapeutic strategies?

MATERIALS AND METHODS

Gene therapy, here defined as the introduction of genetic material into human cells, offers great opportunities. Gene transfer strategies can be used for gene replacement in recessive disease, gene inactivation in dominant disease, expression of "rescue factors" and apoptosis modulators in degenerative disease, "suicide genes" for example in proliferative diseases and expression of immunmodulatory factors in immunological disorders. Viral vector systems have been developed to introduce the gene of interest into the target cell.

RESULTS

Most of the published strategies include the use of vectors for gene transfer. Adenovirus (AV), adenoassociated virus (AAV), encapsulated adenovirus mini-chromosomes (EAMs), herpes simplex virus (HSV) and lentiviruses are the most frequently used viral vector systems to date. Their advantages and disadvantages, the in vivo models used for gene transfer in retinal degeneration, and the results obtained to date by different research groups in the field will be reviewed.

CONCLUSIONS

Gene transfer into ocular tissues has been demonstrated with growing functional success and may develop into a new therapeutic tool for clinical ophthalmology.

[Activated protein C resistance in patients with central retinal vein occlusion in comparison to patients with a history of deep-vein thrombosis and a healthy control group]

BACKGROUND

The recently described "APC resistance" caused by a mutant form of factor V (factor V Leiden) is the most frequent cause of hereditary thrombosis. This study was carried out to investigate the association between activated protein C resistance and central retinal vein occlusion (CRVO). We evaluated the prevalence of APC resistance in patients with CRVO, patients with a history of deep-vein thrombosis, and a healthy control group.

PATIENTS AND METHODS

We examined 107 patients with CRVO, 112 patients with deep-vein thrombosis and 70 healthy individuals. The test performed was a modified APC-resistance assay using factor V-deficient plasma.

RESULTS

We identified APC resistance in 5.6 % of patients with CRVO and in 5.7 % of the control group. All carriers were heterozygous. In the deep-vein thrombosis group 23.2 % tested positive for APC resistance. Four patients were homozygous and 22 were heterozygous carriers.

CONCLUSION

These results indicate that APC resistance has no major role in the pathogenesis of CRVO. Routine testing for the presence of factor V Leiden mutant in CRVO is not necessary.

[A survey of clinically used drugs in PVR: a review]

Colchicine, corticosteroids, daunomycin, fluorouracil, heparin and retinoids have been used in man and show an effect in different stages of the development of PVR. In this survey the effect of each drug is described and the clinical studies are discussed. This survey shows that there are many drugs that in addition to surgery might influence the natural course of clinical PVR during different stages. However, the only drug for which a significant reduction in the number of reoperations has been demonstrated in a randomized prospective trial is daunomycin. Literature search by medline.