Michael R. R. Böhm

βB2-Crystallin Promotes Axonal Regeneration in the Injured Optic Nerve in Adult Rats:

The purpose of the study was to further scrutinize the potential of βB2-crystallin in supporting regeneration of injured retinal ganglion cell axons both in vitro and in vivo. Retinal explants obtained from animals after treatment either with lens injury (LI) alone or with combined LI 5 days or 3 days before or simultaneously with an optic nerve crush (ONC) were cultured for 96 h under regenerative conditions, and the regenerating axons were quantified and compared with untreated controls. These measurements were then repeated with LI replaced by intravitreal injections of γ-crystallin and β-crystallin at 5 days before ONC. Finally, bB2-crystallin-overexpressing transfected neural progenitor cells (bB2-crystallin-NPCs) in the eye were studied after crushing the optic nerve in vivo. Regeneration was monitored with the aid of immunoblotting of the retina and optic nerve both distal and proximal to the lesion site, and this was compared with controls that received injections of phosphate buffer only. LI performed 5 days or 3 days before ONC significantly promoted axonal outgrowth in vitro (p < 0.001), while LI performed alone before explantation did not. Intravitreal injections of β-crystallin and γ-crystallin mimicked the effects of LI and significantly increased axonal regeneration in culture at the same time intervals (p < 0.001). Western blot analysis revealed that crystallins were present in the proximal optic nerve stump at the lesion site in ONC, but were neither expressed in the undamaged distal optic nerve nor in uninjured tissue. bB2-crystallin-NPCs supported the regeneration of cut optic nerve axons within the distal optic nerve stump in vivo. The reported data suggest that bB2-crystallin-producing “cell factories” could be used to provide novel therapeutic drugs for central nervous system injuries.

Traumatology of the optic nerve and contribution of crystallins to axonal regeneration

Within a few decades, the repair of long neuronal pathways such as spinal cord tracts, the optic nerve or intracerebral tracts has gone from being strongly contested to being recognized as a potential clinical challenge. Cut axonal stumps within the optic nerve were originally thought to retract and become irreversibly necrotic within the injury zone. Optic nerve astrocytes were assumed to form a gliotic scar and remodelling of the extracellular matrix to result in a forbidden environment for re-growth of axons. Retrograde signals to the ganglion cell bodies were considered to prevent anabolism, thus also initiating apoptotic death and gliotic repair within the retina. However, increasing evidence suggests the reversibility of these regressive processes, as shown by the analysis of molecular events at the site of injury and within ganglion cells. We review optic nerve repair from the perspective of the proximal axon stump being a major player in determining the successful formation of a growth cone. The axonal stump and consequently the prospective growth cone, communicates with astrocytes, microglial cells and the extracellular matrix via a panoply of molecular tools. We initally highlight these aspects on the basis of recent data from numerous laboratories. Then, we examine the mechanisms by which an injury-induced growth cone can sense its surroundings within the area distal to the injury. Based on requirements for successful axonal elongation within the optic nerve, we explore the models employed to instigate successful growth cone formation by ganglion cell stimulation and optic nerve remodelling, which in turn accelerate growth. Ultimately, with regard to the proteomics of regenerating retinal tissue, we discuss the discovery of isoforms of crystallins, with crystallin beta-b2 (crybb2) being clearly upregulated in the regenerating retina. Crystallins are produced and used to promote the elongation of growth cones. In vivo and in vitro, crystallins beta and gamma additionally promote the growth of axons by enhancing the production of ciliary neurotrophic factor (CNTF), indicating that they also act on astrocytes to promote axonal regrowth synergistically. These are the first data showing that axonal regeneration is related to crybb2 movement within neurons and to additional stimulation of CNTF. We demonstrate that neuronal crystallins constitute a novel class of neurite-promoting factors that probably operate through an autocrine and paracrine mechanism and that they can be used in neurodegenerative diseases. Thus, the post-injury fate of neurons cannot be seen merely as inevitable but, instead, must be regarded as a challenge to shape conditions for initiating growth cone formation to repair the damaged optic nerve.

Macula-less rat and macula-bearing monkey retinas exhibit common lifelong proteomic changes

The visual consequences of age-related alterations in the neural retina have been well documented, but little is known about their molecular bases. We performed a comparative proteomic analysis of the retinas in marmosets and rats to identify proteins for which the expression profiles are altered with maturation and aging. Protein profiles were compared in the newborn, juvenile, middle-age, and aged retinas using 2-dimensional gel electrophoresis. Matrix-assisted desorption ionization-time-of-flight mass spectrometry revealed common proteins in rats and marmosets that exhibited changes in concentration throughout life. Western blot, quantitative reverse-transcriptase polymerase chain reaction, and immunohistochemistry analyses of selected proteins and their mRNA were used to determine whether the changes identified by proteomics were verifiable at the cellular and molecular levels. We found 4 proteins common to both species (Parkinson disease [autosomal recessive, early onset] 7/DJ-1, stathmin, peroxiredoxin, and β-synuclein) whose concentrations were regulated with age. These findings were confirmed by Western blot, immunohistochemistry, and quantitative reverse-transcriptase polymerase chain reaction analyses. The proteins were localized in certain layers and subsets of cells within the retinas of both species. The expression of these proteins in the adult human retina was confirmed with immunohistochemistry. The present study is the first to provide evidence that the retina is physiologically characterized by specific lifelong changes in its proteome. These changes are independent of whether the retina bears a macula, occur in key functional pathways during the processing of visual signals, and might be involved in the development of age-related pathologic entities.

Life-time expression of the proteins peroxiredoxin, beta-synuclein, PARK7/DJ-1, and stathmin in the primary visual and primary somatosensory cortices in rats.

Four distinct proteins are regulated in the aging neuroretina and may be regulated in the cerebral cortex, too: peroxiredoxin, beta-synuclein, PARK[Parkinson disease(autosomal recessive, early onset)]7/DJ-1, and Stathmin. Thus, we performed a comparative analysis of these proteins in the the primary somatosensory cortex (S1) and primary visual cortex (V1) in rats, in order to detect putative common development-, maturation- and age-related changes. The expressions of peroxiredoxin, beta-synuclein, PARK[Parkinson disease (autosomal recessive, early onset)]7/DJ-1, and Stathmin were compared in the newborn, juvenile, adult, and aged S1 and V1. Western blot (WB), quantitative reverse-transcription polymerase chain reaction (qRT-PCR), and immunohistochemistry (IHC) analyses were employed to determine whether the changes identified by proteomics were verifiable at the cellular and molecular levels. All of the proteins were detected in both of the investigated cortical areas. Changes in the expressions of the four proteins were found throughout the life-time of the rats. Peroxiredoxin expression remained unchanged over life-time. Beta-Synuclein expression was massively increased up to the adult stage of life in both the S1 and V1. PARK[Parkinson disease (autosomal recessive, early onset)]7/DJ-1 exhibited a massive up-regulation in both the S1 and V1 at all ages. Stathmin expression was massively down regulated after the neonatal period in both the S1 and V1. The detected protein alterations were analogous to their retinal profiles. This study is the first to provide evidence that peroxiredoxin, beta-synuclein, PARK[Parkinson disease (autosomal recessive, early onset)]7/DJ-1, and Stathmin are associated with postnatal maturation and aging in both the S1 and V1 of rats. These changes may indicate their involvement in key functional pathways and may account for the onset or progression of age-related pathologies.

The pro-inflammatory role of high-mobility group box 1 protein (HMGB-1) in photoreceptors and retinal explants exposed to elevated pressure.

To determine the role of high-mobility group box 1 protein (HMGB-1) in cellular and tissue models of elevated pressure-induced neurodegeneration, regeneration, and inflammation. Mouse retinal photoreceptor-derived cells (661W) and retinal explants were incubated either under elevated pressure or in the presence of recombinant HMGB-1 (rHMGB-1) to investigate the mechanisms of response of photoreceptors. Immunohistochemistry, western blotting, and the quantitative real-time PCR were used to examine the expression levels of immunological factors (eg, HMGB-1, receptor for advanced glycation end products (RAGE)), Toll-like receptors 2 and 4 (TLR-2, TLR-4), apoptosis-related factors (eg, B-cell lymphoma 2 (Bcl-2), Bcl-2-associated death promoter (Bad)) as well as cytokine expression (eg, tumor necrosis factor alpha (TNF-α), interleukin (IL)-4, IL-6, and vascular endothelial growth factor (VEGF)). The data revealed increased the expression of HMGB-1 and its receptors RAGE, TLR-2, and TLR-4, and TNF-α as well as pro-apoptotic factors (eg, Bad) as well as apoptosis in 661W cells exposed to elevated pressure. Co-cultivation of 661W cells with rHMGB-1 increased the expression levels of pro-apoptotic Bad and cleaved Caspase-3 resulting in apoptosis. Cytokine array studies revealed an increased release of TNF-α, IL-4, IL-6, and VEGF after incubation of 661W cells with rHMGB-1. Upregulation of HMGB-1, TLR-2, and RAGE as well as anti-apoptotic Bcl-2 expression levels was found in the retinal explants exposed to rHMGB-1 or elevated pressure. The results suggest that HMGB-1 promotes an inflammatory response and mediates apoptosis in the pathology of photoreceptors and retinal homeostasis. HMGB-1 may have a key role in ongoing damage of retinal cells under conditions of elevated intraocular pressure.

Is Angiostatin Involved in Physiological Foveal Avascularity

Purpose The primate central retina is characterized by an avascular fovea and well-defined perifoveal capillary plexus. Neither blood vessels nor their accompanying astrocytes enter the fovea during any stage of retinal development; a balance of angiogenic and angiostatic factors probably maintains foveal avascularity throughout life. The aim of this study was to identify potentially angiorepulsive factors involved in the development of the avascular primate retinal fovea. Methods Retinas of newborn, juvenile, and adult Callithrix jacchus and Macaca fascicularis monkeys and control human retinas were studied to determine the localization of angiostatin relative to III β-tubulin, glial fibrillary acidic protein, vascular endothelial growth factor (VEGF), platelet endothelial cell adhesion molecule-1 (PECAM), and the angiostatin receptor αvβ3-integrin in the foveal, macular, and peripheral retina. Expression studies were performed using immunohistochemistry (IHC) on retinal whole-mount and paraffin sections, and Western blotting on frozen material. The complex network of the main retinal cell types was identified by IHC of retinal whole mounts. Results In general, lifetime expression of angiostatin was found in all retinas. Colabeling with different markers revealed retinal ganglion cells as the main source of angiostatin expression in the primate retina, whereas PECAM-immunopositive blood capillaries expressed the angiostatin receptor αvβ3-integrin, and capillary-associated astrocytes expressed VEGF. Conclusions This study provides the first evidence of angiostatin expression in the primate retina; the expression of angiostatin in the avascular foveal region and the peripheral retina suggests that angiostatin may play a role in the regulation of retinal vascularization, providing a possible explanation for the development and persistence of an avascular fovea.

Retinal damage induced by mirror-reflected light from a laser pointer

The safety of laser pointers is a major public health issue since class I and II laser pointers are available worldwide and used as toys by children despite several reports cautioning such use. Here we present the first case of retinal injury caused by the laser beam of a toy laser pointer operated by a school boy and directed via the rear-view mirror of a bus into the eye of the driver. This case emphasises the great importance of cautious and appropriate use of low-energy laser pointers. Laser pointers of any class should not be made available to children because they are unlikely to understand the risks of such lasers when using them in play.

Bacterial Spectrum and Antimicrobial Susceptibility Patterns in Acquired and Connatal Lacrimal Duct Stenosis

Abstract Purpose: (1) To determine the current bacteriological spectrum in connatal and acquired lacrimal duct obstruction (cLDO and aLDO, respectively) and (2) to analyze the antimicrobial susceptibility patterns of the recovered isolates. Materials and Methods: In a prospective study, 463 samples (30% bilateral LDO) were obtained from the lacrimal ducts of 132 infants and 192 adult patients with symptomatic LDO between 2007 and 2012 at a tertiary eye-care center. The samples were cultured for aerobic and anaerobic bacteria, which were subsequently identified using standard microbiological techniques. Antimicrobial susceptibility testing was performed for each isolate using the disk diffusion method. Data were analyzed using SPSS and chi-square test for significance testing. Results: (1) Among 463 samples investigated, 333 samples were positive, i.e. at least one bacterial isolate was recovered. A total of 72% were recovered (97% of samples from children and 56% of samples from adults), yielding a total of 654 bacterial isolates. Co-colonization with up to five different bacterial species was observed in a large proportion of the samples from children (87%), but in only 20% of those from adults and with a maximum of three different bacteria. Gram-positive bacteria were identified in 72% of the positive samples in both aLDO and cLDO. The most common Gram-positive species in cLDO was Streptococcus pneumoniae (29%), while that in cLDO was Staphylococcus aureus (60%). The most prevalent Gram-negative species were Moraxella catarrhalis (8%) and Haemophilus influenzae (9%) in cLDO and Pseudomonas aeruginosa in aLDO (12%). (2) Susceptibility testing revealed chloramphenicol to be the most active antibiotic with resistance rates of 3% in cLDO and 6% in aLDO, followed by ciprofloxacin (1% and 6%). Erythromycin and gentamicin were the least active of all, with resistances of 41% and 22%, respectively, in cLDO, and 23% and 11% in aLDO. Conclusions: Bacterial colonization occurs regularly in LDO, with Gram-positive bacteria being found in 97% of cLDO samples and 56% of aLDO samples. A remarkable number of different species were found to co-colonize in cLDO. The most common bacteria in LDO are highly susceptible in vitro to chloramphenicol and ciprofloxacin.

Leukemic hypopyon in acute myeloid leukemia.

Purpose. Leukemic hypopyon uveitis in acute myeloid leukemia (AML) is a very rare condition. We report this case of an unusual finding in a 2½-year-old boy in second remission after chemotherapy for relapsed AML. Methods. A young patient with an AML FAB M5 in second remission developed pain, photophobia, and conjunctival injections in the right eye. Recent bone marrow aspiration showed no blast increase and recent peripheral blood sampling presented no evidence of relapse. Results. The patient showed a viscous hypopyon and a myotic pupil in the right eye that was refractory to corticosteroids. Anterior chamber aspiration revealed atypical blasts similar to the leukemic cells that were found in the bone marrow aspirate at the time of systemic relapse. Conclusions. Timely anterior chamber aspiration and subsequent cytology is useful in differentiating leukemic hypopyon from true intraocular inflammation in AML patients. This is the first report about a leukemic hypopyon uveitis in AML without systemic findings of malignant cells in a child.

Cyclosporine A-Loaded Nanocarriers for Topical Treatment of Murine Experimental Autoimmune Uveoretinitis

In the present study, tissue distribution and the therapeutic effect of topically applied cyclosporine A (CsA)-loaded methoxy-poly(ethylene-glycol)-hexyl substituted poly(lactic acid) (mPEGhexPLA) nanocarriers (ApidSOL) on experimental autoimmune uveitis (EAU) were investigated. The CsA-loaded mPEGhexPLA nanocarrier was tolerated well locally and showed no signs of immediate toxicity after repeated topical application in mice with EAU. Upon unilateral CsA treatment, CsA accumulated predominantly in the corneal and sclera-choroidal tissue of the treated eye and in lymph nodes (LN). This regimen reduced EAU severity in treated eyes compared to PBS-treated controls. This improvement was accompanied by reduced T-cell count, T-cell proliferation, and IL-2 secretion of cells from ipsilateral LN. In conclusion, topical treatment with CsA-loaded mPEGhexPLA nanocarriers significantly improves the outcome of EAU.