Biomedical subjects

Sascha Fauser

Publications and source records attributed to Sascha Fauser.

13 recordsLinked to original sources

PubMed2006

Overexpression of FasL in retinal pigment epithelial cells reduces choroidal neovascularization.

Choroidal neovascularization (CNV) is responsible for the severe visual loss in age-related macular degeneration. CNV formation is considered to be due to an imbalance between pro- and antiangiogenic factors that lead to neovascular growth from the choriocapillaris into the subretinal space. To define whether FasL overexpression in retinal pigment epithelial cells (RPE) can inhibit choroidal neovascularization through Fas-FasL-mediated apoptosis, we examined the role of this pathway in a mouse model of laser-induced choroidal neovascularization. FasL was expressed in the retinal pigment epithelium of transgenic mice. Polymerase chain reaction (PCR), immunoblot, and immunohistochemistry confirmed that the transgene FasL was specifically expressed in RPE. The established laser model was used to induce choroidal neovascularization (CNV) in wild-type (WT) and transgenic mice. CNV formation was compared with respect to fluorescein angiographic leakage (at days 0 and 14 after laser injury) and histological appearance. The lesions were assessed on RPE-choroidal flatmounts after CD31-labeling and with confocal microscopy after perfusion with rhodamine-labeled concanavalin A (Con A). Apoptosis was quantified by TUNEL positivity and caspase activation. FasL mRNA and protein were highly expressed in the RPE of the transgenic mice before and after laser photocoagulation. In contrast, FasL was only weakly expressed in the RPE layer of WT C57BL/6J mice. While ruptures of Bruch's membrane and CNV formation were observed histologically two weeks after laser photocoagulation in transgenic as well as control eyes, the shape and size of CNV lesions were reduced in the transgenic mice. The area of leakage was decreased by 70% in FasL transgenic mice compared with WT mice (P<0.005). The number of TUNEL-positive cells was greater in FasL-overexpressing mice and correlated with the expression of activated caspases. Th expression of other antiangiogenic factors such as PEDF remained unchanged. The specific overexpression of FasL in RPE layer reduced CNV formation in our laser model. Our results strongly point to the FasL-Fas pathway as a potential therapeutic target in controlling pathological choroidal neovascularization.

Animals↗

PubMed2004

Developmental plasticity of NMDA receptor function in the retina and the influence of light.

Despite the early expression of NMDA receptors (NMDARs) in the retina, not much is known about their regulation and involvement in plasticity processes during retinal development and synapse formation. Here we report that NMDAR function in the inner retina is developmentally regulated and controlled by ambient light condition. A prominent down-regulation after eye opening of NMDAR function was observed in rat retinal ganglion cells (RGCs), which was prevented by dark rearing the animals for 1 month but was again induced by subsequent light exposure. As shown by molecular analysis of single RGCs, alterations in the subunit composition of NMDAR did not account for the light-dependent regulation of NMDAR function. Immunocytochemistry showed no differences in the NMDAR protein expression pattern between normal and dark-reared animals. In conclusion, our data clearly demonstrate that NMDAR function is modulated during periods of retinal plasticity independent of structural alterations in its subunit composition and thus different from mechanisms observed in higher visual centers.

Electric Conductivity↗

PubMed2004

A central role for inflammation in the pathogenesis of diabetic retinopathy.

Diabetic retinopathy is a leading cause of adult vision loss and blindness. Much of the retinal damage that characterizes the disease results from retinal vascular leakage and nonperfusion. Diabetic retinal vascular leakage, capillary nonperfusion, and endothelial cell damage are temporary and spatially associated with retinal leukocyte stasis in early experimental diabetes. Retinal leukostasis increases within days of developing diabetes and correlates with the increased expression of retinal intercellular adhesion molecule-1 (ICAM-1) and CD18. Mice deficient in the genes encoding for the leukocyte adhesion molecules CD18 and ICAM-1 were studied in two models of diabetic retinopathy with respect to the long-term development of retinal vascular lesions. CD18-/- and ICAM-1-/- mice demonstrate significantly fewer adherent leukocytes in the retinal vasculature at 11 and 15 months after induction of diabetes with STZ. This condition is associated with fewer damaged endothelial cells and lesser vascular leakage. Galactosemia of up to 24 months causes pericyte and endothelial cell loss and formation of acellular capillaries. These changes are significantly reduced in CD18- and ICAM-1-deficient mice. Basement membrane thickening of the retinal vessels is increased in long-term galactosemic animals independent of the genetic strain. Here we show that chronic, low-grade subclinical inflammation is responsible for many of the signature vascular lesions of diabetic retinopathy. These data highlight the central and causal role of adherent leukocytes in the pathogenesis of diabetic retinopathy. They also underscore the potential utility of anti-inflammatory treatment in diabetic retinopathy.

Animals↗

PubMed2004

Visual outcome of patients with macular edema after pars plana vitrectomy and indocyanine green-assisted peeling of the internal limiting membrane.

PURPOSE: To evaluate the efficacy of inner limiting membrane (ILM) peeling in persistent macular edema. METHODS: This retrospective review analyzed a series of 23 eyes from 23 patients with persistent macular edema treated by pars plana vitrectomy (PPV) with indocyanine green (ICG)-assisted peeling of the ILM. Thirteen female and 10 male patients with a mean age of 57.2+/-15.6 (24-77) years underwent operation between May 2000 and October 2001. The main diagnoses were uveitis (anterior, intermediate, posterior and panuveitis) ( n=9), central retinal vein occlusion (CRVO) (n=4), diabetic retinopathy (DR) ( n=5), vitreoretinal traction syndrome ( n=2), and Irvine-Gass syndrome ( n=3). Nine eyes had undergone phacoemulsification (PE) previously and two eyes had been subjected to combined PE and ILM peeling. The eyes were tamponaded with gas (3), silicone oil (5) or air (11). In four cases no endotamponade was used. Improvement in visual acuity of 2 lines or more was regarded as significant. RESULTS: Visual acuity improved after 3 months in 9 of the 23 patients. After 6 months and at the follow-up, a significant improvement was found in 6/21 and 7/21 patients. This improvement was predominantly seen in patients with uveitis (5/9), or diabetic maculopathy (3/5); One patient with Irvine-Gass syndrome showed a significant reduction, one with vitreoretinal traction an improvement in visual acuity. The group of patients with CRVO showed no significant change during the follow-up. The choice of endotamponade did not alter the visual acuity outcome. CONCLUSIONS: Different patient groups respond differently to ILM peeling. Although overall significant visual acuity improvement was observed in only one third of all cases 12 months after ILM peeling for persistent macular edema, patients with uveitis and nonproliferative diabetic maculopathy demonstrated a benefit. The lack of long-term improvement in the majority of cases is in accordance with the hypothesis that ILM peeling may reduce the intraretinal edema, but does not affect the underlying mechanism causing macular edema. So far, only diabetics have shown improvement (still unproven) from ILM peeling, and this study provides no justification for extending the treatment to macular edema of other causes. Large-scale investigations are needed to evaluate the efficacy in certain diagnosis groups.

Adult↗

PubMed2004

Pharmacokinetics and safety of intravitreally delivered etanercept.

BACKGROUND: The anti-inflammatory drug etanercept may be an effective therapeutic agent in diabetic retinopathy. In order to further evaluate its potential, the pharmacokinetics and safety of this drug after intravitreal delivery were investigated. METHODS: After intravitreal administration of etanercept in rabbits, clinical examination, electroretinography (ERG), visually evoked potentials (VEP) and histology were evaluated. The pharmacokinetics and distribution of etanercept were analyzed using fluorescence-coupled protein at 0, 2, 4, and 8 weeks after injection in vitreous, retina, and choroid. RESULTS: No adverse effects and signs of toxicity were found. Etanercept showed peak concentrations after 4 weeks in the retina and choroid. CONCLUSIONS: Intravitreally delivered etanercept is safe and results in high concentrations in the retina and choroid over a long period of time.

Animals↗

PubMed2003

[Diabetic maculopathy - classification and therapy].

The current clinical classification into focal, diffuse, and ischaemic maculopathy is useful with respect to pathomechanism and therapy. This review discusses the value of standard therapeutical options as well as the recent surgical and pharmacological approaches.

Clinical Trials as Topic↗

PubMed2003

[Pathogenesis of diabetic macular oedema].

Hyperglycaemia causes breakdown of the blood retina barrier leading to formation of macular oedema and consecutive visual loss. Three major mechanisms are involved in barrier breakdown: increased paracellular permeability of vascular endothelium due to disruption of cell junctions, loss of endothelial cell layer integrity due to cell destruction, and increased transcellular transport through the endothelium. This review focuses on the molecular basis of these mechanisms and discusses the role of cytokines and cellular interactions in blood retina barrier breakdown.

Animals↗

PubMed2003

N-methyl-D-aspartate receptor subunit NR3A in the retina: developmental expression, cellular localization, and functional aspects.

PURPOSE: Recently, a novel N-methyl-D-aspartate receptor (NMDAR) subunit, NR3A, has been discovered in the brain and shown to decrease NMDAR activity by modulating the calcium permeability of the receptor channel. The insertion of NR3A within the NMDAR complex may thus alter NMDAR properties and play a crucial role during processes of neuronal development and degeneration. The present study is the first to investigate the expression and cellular localization of NR3A on the protein level in the retina and to elucidate its putative functional roles within the retinal circuitry. METHODS: The expression of NR3A in the retina was analyzed by reverse transcription-polymerase chain reaction (RT-PCR), immunohistochemistry, and Western blot analysis. Functional aspects of NR3A in the retina were addressed by measuring the NMDA-induced increase in intracellular calcium, [Ca(2+)](i), in retinal cells prepared from wild-type (NR3A(+/+)) and NR3A knockout (NR3A(+/-), and NR3A(-/-)) mice. RESULTS: NR3A protein expression was initially observed in the first postnatal week and was predominantly localized to cell bodies in the ganglion cell layer. In older animals, two bands of NR3A immunoreactivity were additionally observed in the inner plexiform layer. NMDA-evoked [Ca(2+)](i) responses were found to be significantly greater in retinal cells in NR3A(-/-) mice than in wild-type retinas. CONCLUSIONS: The data indicate that NR3A is specifically expressed in the inner retina and may modulate NMDAR-mediated calcium influx and thus [Ca(2+)](i) levels in retinal ganglion cells and amacrine cells.

Animals↗

PubMed2002

Leber's hereditary optic neuropathy: clinical and molecular genetic results in a patient with a point mutation at np T11253C (isoleucine to threonine) in the ND4 gene and spontaneous recovery.

BACKGROUND: Mitochondrial DNA mutations at nucleotide position (np) 3460 in the ND1 gene, np 11778 in the ND4 gene, and np 14484 in the ND6 gene are commonly considered to be associated with the clinical features of LHON and account for the majority of LHON cases. Here we report the clinical and molecular genetic findings of a LHON patient with a new mitochondrial DNA mutation at np 11253 in the ND4 gene and spontaneous recovery. METHODS: The clinical examination consisted of visual acuity measurements, visual field testing, and ophthalmoscopy over a period of 14 years. Total lymphocyte DNA was analyzed for all common LHON mutations. Because the LHON patient did not harbor any of the common or recently described rare LHON mutations, we performed a sequence analysis of the whole mitochondrial genome. RESULTS: The patient exhibited typical clinical features of LHON. Molecular genetic analysis did not reveal any of the common LHON mutations. Sequence analysis of the mtDNA of the patient and his unaffected sister and niece was performed and showed a T to C missense mutation at np 11253 in the ND4 gene, leading to a replacement of an evolutionary highly conserved isoleucine by a threonine residue. This mutation introduces a polar group into a hydrophobic domain of the protein and induces a significant change in hydrophobicity of the peptide sequence. The mutation was not found among 100 controls. CONCLUSION: The fact that the new mutation at np 11253 is found within a highly conserved region and was not present in any controls implies that this mutation is responsible for LHON in this patient. Interestingly, this point mutation has formerly been reported in the mitochondria of the substantia nigra in an unrelated patient with proven Parkinson's disease.

Adult↗

PubMed2002

Sequence analysis of the complete mitochondrial genome in patients with Leber's hereditary optic neuropathy lacking the three most common pathogenic DNA mutations.

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disorder characterized by central vision loss in young adults. The majority of LHON cases around the world are associated with mutations in the mitochondrial genome at nucleotide positions (np) 3460, 11,778, and 14,484. Usually, these three mutations are screened in suspected LHON patients. The result is important not only in respect to the diagnosis but also as different LHON mutations lead to variations in expression, severity, and recovery of the disease. There are, however, a significant number of patients without any of these primary mutations. In these situations, genetic counselling of a patient and his family can be difficult. We sequenced the complete mitochondrial DNA (mtDNA) in 14 LHON patients with the typical clinical features but without a primary mtDNA mutation to evaluate the potential of extensive mutation screening for clinical purposes. Our results suggest to include the mutation at np 15,257 in a routine screening as well as the ND6 gene, a hot spot for LHON mutations. Screening for the secondary LHON mutations at np 4216 and np 13,708 may also help in making the diagnosis of LHON as these seem to modify the expression of LHON mutations. Although they do not allow to prove the clinical diagnosis, their presence increases the probability of LHON. Sequencing the complete mitochondrial genome can reveal novel and known rare disease causing mutations. However, considering the effort it adds little value for routine screening.

Adolescent↗

PubMed2002

A mutational hot spot in the mitochondrial ND6 gene in patients with Leber's hereditary optic neuropathy.

BACKGROUND: Leber's hereditary optic neuropathy (LHON) is a maternally inherited disorder characterized by rapid bilateral loss of central vision. Most patients harbor one of three mutations in the mitochondrial DNA. In order to identify the genetic cause of the disease in one LHON patient without any of the three primary mutations, we sequenced the mitochondrial genome. METHODS: Ophthalmological examination was performed in the affected person and his unaffected relatives. The complete mitochondrial protein coding region was sequenced in the patient. RESULTS: Clinical examination of the affected 10-year-old Turkish boy showed typical features of LHON. Peripapillary microangiopathy was also seen in relatives of the maternal line. Sequence analysis revealed a point mutation at position 14482 in the mitochondrial ND6 gene that changes a conserved methionine residue to isoleucine. A mutation at this nucleotide position has been previously suggested to be of pathogenic significance and has not been detected in any controls. CONCLUSIONS: We have identified that the mutation at nucleotide position 14482 which is the eight mutation in the ND6 gene that causes LHON, making this gene a hot spot for the disease. All eight identified mutations in the ND6 gene lie within the evolutionarily most conserved region of the ND6 gene in a hydrophobic pocket. This may help in understanding the pathomechanism of LHON.

Child↗

PubMed2002

Confirmation of the 14568 mutation in the mitochondrial ND6 gene as causative in Leber's hereditary optic neuropathy.

Leber's hereditary optic neuropathy (LHON) is a maternally inherited disorder characterized by a rapid bilateral loss of central vision. The majority of patients have one of three mutations in the mitochondrial DNA. In order to identify the genetic cause of the disease in a family with two affected individuals without any of the three primary LHON mutations, we have sequenced the complete mitochondrial genome. Sequence analysis revealed a point mutation at position 14568 in the mitochondrial ND6 gene that changes a conserved methionine residue to isoleucine. This mutation has been previously suggested to be of pathogenic significance and has not been detected in any controls. This case confirms the pathogenicity of this mutation. It is the seventh mutation in the ND6 gene leading to LHON. All seven identified mutations in the ND6 gene lie within the evolutionarily most conserved region of the ND6 gene in a hydrophobic pocket making it a hot spot for the disease. This clustering of mutations may help to understand the disease mechanism of LHON.

Adult↗

PubMedDate not supplied

Genetic animal models for retinal degeneration.

Inherited retinal degenerations are a common cause of blindness in Western countries. A mechanism for most retinal degenerations is still unknown; hence, a suitable treatment for most of these diseases has yet to be found. Before one can rationally design a treatment, it is necessary to understand the pathway from a gene mutation to the phenotype in patients. Animal models are crucial to understand this process and to develop a treatment. Some naturally occurring animal models are known. However, over the past few years, transgenic engineering has allowed the generation of a rapidly growing number of animal models. In this review, we give an overview of the broad variety of genetic animal models for retinal degeneration.

Animals↗