Cryo-Electrospinning Generates Highly Porous Fiber Scaffolds Which Improves Trabecular Meshwork Cell Infiltration

Human trabecular meshwork is a sieve-like tissue with large pores, which plays a vital role in aqueous humor outflow. Dysfunction of this tissue can occur, which leads to glaucoma and permanent vision loss. Replacement of trabecular meshwork with a tissue-engineered device is the ultimate objective. This study aimed to create a biomimetic structure of trabecular meshwork using electrospinning. Conventional electrospinning was compared to cryogenic electrospinning, the latter being an adaptation of conventional electrospinning whereby dry ice is incorporated in the fiber collector system. The dry ice causes ice crystals to form in-between the fibers, increasing the inter-fiber spacing, which is retained following sublimation. Structural characterization demonstrated cryo-scaffolds to have closer recapitulation of the trabecular meshwork, in terms of pore size, porosity, and thickness. The attachment of a healthy, human trabecular meshwork cell line (NTM5) to the scaffold was not influenced by the fabrication method. The main objective was to assess cell infiltration. Cryo-scaffolds supported cell penetration deep within their structure after seven days, whereas cells remained on the outer surface for conventional scaffolds. This study demonstrates the suitability of cryogenic electrospinning for the close recapitulation of trabecular meshwork and its potential as a 3D in vitro model and, in time, a tissue-engineered device.

Morphological and biomechanical analyses of the human healthy and glaucomatous aqueous outflow pathway: Imaging-to-modeling

BACKGROUND AND OBJECTIVE

Intraocular pressure (IOP) is maintained via a dynamic balance between the production of aqueous humor and its drainage through the trabecular meshwork (TM), juxtacanalicular connective tissue (JCT), and Schlemm's canal (SC) endothelium of the conventional outflow pathway. Primary open angle glaucoma (POAG) is often associated with IOP elevation that occurs due to an abnormally high outflow resistance across the outflow pathway. Outflow tissues are viscoelastic and actively interact with aqueous humor dynamics through a two-way fluid-structure interaction coupling. While glaucoma affects the morphology and stiffness of the outflow tissues, their biomechanics and hydrodynamics in glaucoma eyes remain largely unknown. This research aims to develop an image-to-model method allowing the biomechanics and hydrodynamics of the conventional aqueous outflow pathway to be studied.

METHODS

We used a combination of X-ray computed tomography and scanning electron microscopy to reconstruct high-fidelity, eye-specific, 3D microstructural finite element models of the healthy and glaucoma outflow tissues in cellularized and decellularized conditions. The viscoelastic TM/JCT/SC complex finite element models with embedded viscoelastic beam elements were subjected to a physiological IOP load boundary; the stresses/strains and the flow state were calculated using fluid-structure interaction and computational fluid dynamics.

RESULTS

Based on the resultant hydrodynamics parameters across the outflow pathway, the primary site of outflow resistance in healthy eyes was in the JCT and immediate vicinity of the SC inner wall, while the majority of the outflow resistance in the glaucoma eyes occurred in the TM. The TM and JCT in the glaucoma eyes showed 1.32-fold and 1.13-fold larger beam thickness and smaller trabecular space size (2.24-fold and 1.50-fold) compared to the healthy eyes.

CONCLUSIONS

Characterizing the accurate morphology of the outflow tissues may significantly contribute to constructing more accurate, robust, and reliable models, that can eventually help to better understand the dynamic IOP regulation, hydrodynamics of the aqueous humor, and outflow resistance dynamic in the human eyes. This model demonstrates proof of concept for determining changes to outflow resistance in healthy and glaucomatous tissues and thus may be utilized in larger cohorts of donor tissues where disease specificity, race, age, and gender of the eye donors may be accounted for.

Non-Viral Gene Therapy in Trabecular Meshwork Cells to Prevent Fibrosis in Minimally Invasive Glaucoma Surgery

The primary cause of failure for minimally invasive glaucoma surgery (MIGS) is fibrosis in the trabecular meshwork (TM) that regulates the outflow of aqueous humour, and no anti-fibrotic drug is available for intraocular use in MIGS. The myocardin-related transcription factor/serum response factor (MRTF/SRF) pathway is a promising anti-fibrotic target. This study aims to utilise a novel lipid nanoparticle (LNP) to deliver MRTF-B siRNA into human TM cells and to compare its effects with those observed in human conjunctival fibroblasts (FF). Two LNP formulations were prepared with and without the targeting peptide cΥ, and with an siRNA concentration of 50 nM. We examined the biophysical properties and encapsulation efficiencies of the LNPs, and evaluated the effects of MRTF-B silencing on cell viability, key fibrotic genes expression and cell contractility. Both LNP formulations efficiently silenced MRTF-B gene and were non-cytotoxic in TM and FF cells. The presence of cΥ made the LNPs smaller and more cationic, but had no significant effect on encapsulation efficiency. Both TM and FF cells also showed significantly reduced contractibility after transfection with MRTF-B siRNA LNPs. In TM cells, LNPs with cΥ achieved a greater decrease in contractility compared to LNPs without cΥ. In conclusion, we demonstrate that the novel CL4H6-LNPs are able to safely and effectively deliver MRTF-B siRNA into human TM cells. LNPs can serve as a promising non-viral gene therapy to prevent fibrosis in MIGS.

1H NMR Metabolite Monitoring during the Differentiation of Human Induced Pluripotent Stem Cells Provides New Insights into the Molecular Events That Regulate Embryonic Chondrogenesis

The integration of cell metabolism with signalling pathways, transcription factor networks and epigenetic mediators is critical in coordinating molecular and cellular events during embryogenesis. Induced pluripotent stem cells (IPSCs) are an established model for embryogenesis, germ layer specification and cell lineage differentiation, advancing the study of human embryonic development and the translation of innovations in drug discovery, disease modelling and cell-based therapies. The metabolic regulation of IPSC pluripotency is mediated by balancing glycolysis and oxidative phosphorylation, but there is a paucity of data regarding the influence of individual metabolite changes during cell lineage differentiation. We used ¹H NMR metabolite fingerprinting and footprinting to monitor metabolite levels as IPSCs are directed in a three-stage protocol through primitive streak/mesendoderm, mesoderm and chondrogenic populations. Metabolite changes were associated with central metabolism, with aerobic glycolysis predominant in IPSC, elevated oxidative phosphorylation during differentiation and fatty acid oxidation and ketone body use in chondrogenic cells. Metabolites were also implicated in the epigenetic regulation of pluripotency, cell signalling and biosynthetic pathways. Our results show that ¹H NMR metabolomics is an effective tool for monitoring metabolite changes during the differentiation of pluripotent cells with implications on optimising media and environmental parameters for the study of embryogenesis and translational applications.

Performance intensification of constructed wetland technology: a sustainable solution for treatment of high-strength industrial wastewater

The objectives of this study were to: (1) assess the intensification of chemical oxygen demand (COD) and phosphate (PO₄-P) removal; and (2) generate a set of rate constants of COD degradation (k_COD) and phosphate (k_PO4-P) removal for the treatment of industrial wastewater (WW) using intensified adsorption beds. Two horizontal subsurface flow constructed wetlands (HSSFCWs) filled with coal ash and alum sludge and two conventional HSSFCWs packed with gravels were operated with different loadings of COD and PO₄-P at a hydraulic retention time (HRT) of 24 hrs at water depth of 0.40 m. The bed performance was analysed for COD and PO₄-P removal efficiency. The intensified HSSFCWs outperformed the control beds by a mean COD and PO₄-P removal efficiency of 43 and 49%, respectively. The progression of COD and PO₄-P removal along the system was fitted into the first-order plug flow model (K-C model). In this study the k_COD values ranged from 0.36 to 0.65 m/d with a mean of 0.46 ± 0.08 m/d (n = 30). The k_PO4-P values ranged from 0.74 to 1.76 m/d and averaged to 1.23 ± 0.37 m/d (n = 30), irrespective of the condition applied. Hence, these data can be used for future projects using HSSFCWs to treat industrial wastewater.

Biofabrication of Artificial Stem Cell Niches in the Anterior Ocular Segment

The anterior segment of the eye is a complex set of structures that collectively act to maintain the integrity of the globe and direct light towards the posteriorly located retina. The eye is exposed to numerous physical and environmental insults such as infection, UV radiation, physical or chemical injuries. Loss of transparency to the cornea or lens (cataract) and dysfunctional regulation of intra ocular pressure (glaucoma) are leading causes of worldwide blindness. Whilst traditional therapeutic approaches can improve vision, their effect often fails to control the multiple pathological events that lead to long-term vision loss. Regenerative medicine approaches in the eye have already had success with ocular stem cell therapy and ex vivo production of cornea and conjunctival tissue for transplant recovering patients' vision. However, advancements are required to increase the efficacy of these as well as develop other ocular cell therapies. One of the most important challenges that determines the success of regenerative approaches is the preservation of the stem cell properties during expansion culture in vitro. To achieve this, the environment must provide the physical, chemical and biological factors that ensure the maintenance of their undifferentiated state, as well as their proliferative capacity. This is likely to be accomplished by replicating the natural stem cell niche in vitro. Due to the complex nature of the cell microenvironment, the creation of such artificial niches requires the use of bioengineering techniques which can replicate the physico-chemical properties and the dynamic cell-extracellular matrix interactions that maintain the stem cell phenotype. This review discusses the progress made in the replication of stem cell niches from the anterior ocular segment by using bioengineering approaches and their therapeutic implications.

Replacement of the Trabecular Meshwork Cells-A Way Ahead in IOP Control?

Glaucoma is one of the leading causes of vision loss worldwide, characterised with irreversible optic nerve damage and progressive vision loss. Primary open-angle glaucoma (POAG) is a subset of glaucoma, characterised by normal anterior chamber angle and raised intraocular pressure (IOP). Reducing IOP is the main modifiable factor in the treatment of POAG, and the trabecular meshwork (TM) is the primary site of aqueous humour outflow (AH) and the resistance to outflow. The structure and the composition of the TM are key to its function in regulating AH outflow. Dysfunction and loss of the TM cells found in the natural ageing process and more so in POAG can cause abnormal extracellular matrix (ECM) accumulation, increased TM stiffness, and increased IOP. Therefore, repair or regeneration of TM's structure and function is considered as a potential treatment for POAG. Cell transplantation is an attractive option to repopulate the TM cells in POAG, but to develop a cell replacement approach, various challenges are still to be addressed. The choice of cell replacement covers autologous or allogenic approaches, which led to investigations into TM progenitor cells, induced pluripotent stem cells (iPSCs), and mesenchymal stem cells (MSCs) as potential stem cell source candidates. However, the potential plasticity and the lack of definitive cell markers for the progenitor and the TM cell population compound the biological challenge. Morphological and differential gene expression of TM cells located within different regions of the TM may give rise to different cell replacement or regenerative approaches. As such, this review describes the different approaches taken to date investigating different cell sources and their differing cell isolation and differentiation methodologies. In addition, we highlighted how these approaches were evaluated in different animal and ex vivo model systems and the potential of these methods in future POAG treatment.

Plasma polymer surface modified expanded polytetrafluoroethylene promotes epithelial monolayer formation in vitro and can be transplanted into the dystrophic rat subretinal space

The aim of this study was to evaluate whether the surface modification of expanded polytetrafluoroethylene (ePTFE) using an n-heptylamine (HA) plasma polymer would allow for functional epithelial monolayer formation suitable for subretinal transplant into a non-dystrophic rat model. Freshly isolated iris pigment epithelial (IPE) cells from two rat strains (Long Evans [LE] and Dark Agouti [DA]) were seeded onto HA, fibronectin-coated n-heptylamine modified (F-HA) and unmodified ePFTE and fibronectin-coated tissue culture (F-TCPS) substrates. Both F-HA ePTFE and F-TCPS substrates enabled functional monolayer formation with both strains of rat. Without fibronectin coating, only LE IPE formed a monolayer on HA-treated ePTFE. Functional assessment of both IPE strains on F-HA ePTFE demonstrated uptake of POS that increased significantly with time that was greater than control F-TCPS. Surgical optimization using Healon GV and mixtures of Healon GV: phosphate buffered saline (PBS) to induce retinal detachment demonstrated that only Healon GV:PBS allowed F-HA ePTFE substrates to be successfully transplanted into the subretinal space of Royal College of Surgeons rats, where they remained flat beneath the neural retina for up to 4 weeks. No apparent substrate-induced inflammatory response was observed by fundus microscopy or immunohistochemical analysis, indicating the potential of this substrate for future clinical applications.

Differential Distribution of Laminin N-Terminus α31 Across the Ocular Surface: Implications for Corneal Wound Repair

Purpose

Laminin N-terminus (LaNt) α31 is a relatively unstudied protein derived from the laminin α3 gene but structurally similar to netrins. LaNt α31 has, to date, been investigated only in two-dimensional (2D) keratinocyte culture where it influences cell migration and adhesion, processes integral to wound repair. Here we investigated LaNt α31 distribution in ocular surface epithelium, during limbal stem cell activation, and corneal wound healing.

Methods

Human, mouse, and pig eyes, ex vivo limbal explant cultures, and alkali burn wounds were processed for immunohistochemistry with antibodies against LaNt α31 along with progenitor cell-associated proteins. LaNt α31 expression was induced via adenoviral transduction into primary epithelial cells isolated from limbal explants, and cell spreading and migration were analyzed using live imaging.

Results

LaNt α31 localized to the basal layer of the conjunctival, limbal, and corneal epithelial cells. However, staining was nonuniform with apparent subpopulation enrichment, and some suprabasal reactivity was also noted. This LaNt α31 distribution largely matched that of keratin 15, epidermal growth factor receptor, and transformation-related protein 63α (p63α), and displayed similar increases in expression in activated limbal explants. During active alkali burn wound repair, LaNt α31 displayed increased expression in limbal regions and loss of basal restriction within the cornea. Distribution returned to predominately basal cell restricted once the wounded epithelium matured. Cultured corneal epithelial cells expressing LaNt α31 displayed increased 2D area and reduced migration, suggesting a functional link between this protein and key wound repair activities.

Conclusions

These data place LaNt α31 in position to influence laminin-dependent processes including wound repair and stem cell activation.

The formation of a functional retinal pigment epithelium occurs on porous polytetrafluoroethylene substrates independently of the surface chemistry

Subretinal transplantation of functioning retinal pigment epithelial (RPE) cells may have the potential to preserve or restore vision in patients affected by blinding diseases such as age-related macular degeneration (AMD). One of the critical steps in achieving this is the ability to grow a functioning retinal pigment epithelium, which may need a substrate on which to grow and to aid transplantation. Tailoring the physical and chemical properties of the substrate should help the engineered tissue to function in the long term. The purpose of the study was to determine whether a functioning monolayer of RPE cells could be produced on expanded polytetrafluoroethylene substrates modified by either an ammonia plasma treatment or an n-Heptylamine coating, and whether the difference in surface chemistries altered the extracellular matrix the cells produced. Primary human RPE cells were able to form a functional, cobblestone monolayer on both substrates, but the formation of an extracellular matrix to exhibit a network structure took months, whereas on non-porous substrates with the same surface chemistry, a similar appearance was observed after a few weeks. This study suggests that the surface chemistry of these materials may not be the most critical factor in the development of growth of a functional monolayer of RPE cells as long as the cells can attach and proliferate on the surface. This has important implications in the design of strategies to optimise the clinical outcomes of subretinal transplant procedures.

Yield and Viability of Human Limbal Stem Cells From Fresh and Stored Tissue

PURPOSE

We compared cell number, putative stem cell markers, and clonogenic ability in fresh uncultured human limbal epithelial cells to that obtained from stored organ-cultured tissue.

METHODS

Cell suspensions were formed from fresh and organ culture-stored human limbal epithelium. Expression of putative stem cell markers ΔNp63 and TrkA was performed using immunofluorescent staining before culture. Colony-forming efficiency (CFE) assays were performed at first passage. The effects of tissue storage, age, and postmortem/culture times were analyzed in a general linear model.

RESULTS

Limbal tissue from 94 donors (34 fresh and 60 stored) was compared. Three times more cells were obtained per eye from fresh (35.34 × 104; SD, 17.39) than stored (11.24 × 104; SD, 11.57; P < 0.01) tissue. A higher proportion of cells from fresh tissue were viable (91.9%; SD, 5.7 vs. 85%; SD, 10.8) P < 0.01. Higher total cell expression of ΔNp63 (20.19 × 104; SD, 15.5 vs. 3.28 104; SD, 4.33) and TrkA (59.24 × 104; SD, 13.21 vs. 7.65 × 104; SD, 1.05) was observed in fresh than stored tissue (P < 0.01). Colony-forming efficiency was higher for fresh (1.42; SD, 0.12) than stored (0.43; SD, 0.15; P < 0.01) cells. For stored tissue only, there was a significant inverse relationship between donor age and total number of cells isolated (R2 = 0.27, P < 0.001).

CONCLUSIONS

Storage of corneoscleral discs in organ culture medium leads to significant reduction in limbal epithelial cell number, expression of ΔNp63 and TrkA, and viability compared to fresh tissue. There is a smaller basal stem cell population in stored compared to fresh tissue.

Ocular epithelial transplantation: current uses and future potential

Visual loss may be caused by a variety of ocular diseases and places a significant burden on society. Replacing or regenerating epithelial structures in the eye has been demonstrated to recover visual loss in a number of such diseases. Several types of cells (e.g., embryonic stem cells, adult stem/progenitor/differentiated epithelial cells and induced pluripotent cells) have generated much interest and research into their potential in restoring vision in a variety of conditions: from ocular surface disease to age-related macular degeneration. While there has been some success in clinical transplantation of conjunctival and particularly corneal epithelium utilizing ocular stem cells, in particular, from the limbus, the replacement of the retinal pigment epithelium by utilizing stem cell sources has yet to reach the clinic. Advances in our understanding of all of these cell types, their differentiation and subsequent optimization of culture conditions and development of suitable substrates for their transplantation will enable us to overcome current clinical obstacles. This article addresses the current status of knowledge concerning the biology of stem cells, their progeny and the use of differentiated epithelial cells to replace ocular epithelial cells. It will highlight the clinical outcomes to date and their potential for future clinical use.

Localisation of opticin in human proliferative retinal disease

This study sought to determine the distribution of opticin, an extracellular matrix small leucine-rich repeat protein secreted by the non-pigmented ciliary body epithelium (CBE), in pathological eye tissues including posterior hyaloid membranes (PHM) and epiretinal membranes (ERM) from subjects with proliferative diabetic retinopathy (PDR), central retinal vein occlusion (CRVO) and proliferative vitreoretinopathy (PVR). Eight enucleated eyes and eleven surgically excised PHMs/ERMs from patients with PDR, CRVO or PVR were analysed by immunohistochemistry for the presence and distribution of opticin, vitreous (delineated by a type II collagen antibody) and blood vessels (using CD31 and CD34 antibodies as endothelial markers). Opticin was present at the basal surface of the non-pigmented CBE and, in a patchy distribution, within CBE cells in all 8 enucleated globes. It also co-localised with the type II collagen of vitreous, where present, in these eyes. Opticin was present in 16 of the 19 PHMs/ERMs, where it was arranged in layers (10 membranes), diffusely (4 membranes) or in foci (2 membranes). Where in a layered pattern, opticin co-localised with vitreous type II collagen incorporated into the membrane, whereas the other two patterns did not co-localise with type II collagen labelling. We concluded that even in advanced proliferative retinal disease, the CBE continues to express and secrete opticin. Opticin was co-distributed with vitreous type II collagen and was also present in the pre-retinal membranes of proliferative retinopathies, where it could play a role in their development.

Expression of hypoxia-inducible factor-1alpha and -2alpha in human choroidal neovascular membranes

PURPOSE

Up-regulation of pro-angiogenic cytokine expression occurring secondary to hypoxia in physiologic and pathophysiologic conditions is mediated by the family of transcription regulators know as hypoxia inducible factors (HIF). The present study was undertaken to investigate the expression of HIF occurring in human choroidal neovascularization (CNV) and the posterior segment of young and old eyes.

METHODS

Surgically excised CNV from patients with either age-related macular degeneration (AMD; n = 9), punctuate inner choroidopathy (PIC; n = 3) and young normal eyes were immunohistochemically probed with monoclonal antibodies against HIF-1alpha and -2alpha and compared to that for cell markers specific for vascular endothelial cells (CD34), macrophages (CD68), retinal pigment epithelial cells (RPE; panel cytokeratins/CK18) and VEGF. Following secondary antibody amplification, reactions were visualized with fast red chromogen.

RESULTS

Cellular immunoreactivity of membranes for HIF-2alpha was strong in eight out of nine AMD specimens but it was only weakly positive for HIF-1alpha in five specimens. In contrast, two out of three PIC specimens were weakly positive for HIF-1alpha but demonstrated no staining for HIF-2alpha. Immunohistochemical analysis revealed areas within the CNV membranes that were predominantly immunopositive for CD68 and cytokeratin indicating the presence of RPE and/or macrophages and that these cells strongly co-localized with the presence of HIF and VEGF. No immunochemical co-localization was observed with HIF and the endothelial cell marker CD34 in any membranes studied. Normal globes also demonstrated HIF-2 positivity to be predominantly localized to the central RPE rather than peripheral RPE irrespective of age of donor.

CONCLUSIONS

The localization of HIF expression supports the concept that hypoxia is a major stimulus for the development of submacular wound healing and within this context CNV is but one component of this process.

Labeling of stem cells with monocrystalline iron oxide for tracking and localization by magnetic resonance imaging

Precise localization of exogenously delivered stem cells is critical to our understanding of their reparative response. Our current inability to determine the exact location of small numbers of cells may hinder optimal development of these cells for clinical use. We describe a method using magnetic resonance imaging to track and localize small numbers of stem cells following transplantation. Endothelial progenitor cells (EPC) were labeled with monocrystalline iron oxide nanoparticles (MIONs) which neither adversely altered their viability nor their ability to migrate in vitro and allowed successful detection of limited numbers of these cells in muscle. MION-labeled stem cells were also injected into the vitreous cavity of mice undergoing the model of choroidal neovascularization, laser rupture of Bruch's membrane. Migration of the MION-labeled cells from the injection site towards the laser burns was visualized by MRI. In conclusion, MION labeling of EPC provides a non-invasive means to define the location of small numbers of these cells. Localization of these cells following injection is critical to their optimization for therapy.

Polydimethylsiloxane as a substrate for retinal pigment epithelial cell growth

Retinal pigment epithelial (RPE) cell transplantation represents potential treatment for age-related macular degeneration (AMD). Because delivery of isolated cells can cause serious complications, it is necessary to develop a suitable transplant membrane that could support an intact functioning RPE monolayer. Polydimethylsiloxane (PDMS) possesses the physical properties required for a transplanting device and is widely used clinically. We have investigated the use of PDMS as a potential surface for the growth of healthy RPE monolayers. PDMS discs were surface modified by air and ammonia gas plasma treatments. Dynamic contact angles were measured to determine the changes in wettability. Human ARPE-19 cells were seeded onto untreated and treated samples. Cell number, morphology and monolayer formation, cytotoxicity, and phagocytosis of photoreceptor outer segments (POS) were assessed at set time-points. Air plasma treatment increased the wettability of PDMS. This significantly enhanced cell growth, reaching confluence by day 7. Immunofluorescence revealed well-defined actin staining, monolayer formation, and high cell viability on air plasma treated and untreated surfaces, and to a lesser extent, on ammonia plasma treated. Furthermore, RPE monolayers were able to demonstrate phagocytosis of POS in a time-dependent manner similar to control. PDMS can support an intact functional monolayer of healthy differentiated RPE cells.

Neoplastic transformation of ciliary body epithelium is associated with loss of opticin expression

BACKGROUND

Opticin is a recently discovered glycoprotein present predominantly in the vitreous humour. It is synthesised and secreted by the ciliary body epithelium (CBE) from the initiation of CBE development in the embryo, and production continues throughout life.

AIM

To determine whether a variety of ciliary body tumours synthesise opticin to characterise further its role in ciliary body health and disease.

METHODS

Immunohistochemistry was used to determine the distribution of opticin in normal human CBE, and in hyperplastic and neoplastic CBE lesions.

RESULTS

Opticin was immunolocalised to the basal cell surface and basement membrane material of the non-pigmented CBE in nine donor eyes as well as four hyperplastic lesions of the CBE (Fuchs's adenoma). By contrast, none of eight neoplastic lesions (two adenoma and six adenocarcinoma) of CBE stained for opticin.

CONCLUSION

The present series supports the theory that opticin is produced by the non-pigmented CBE throughout adult life. Loss of opticin expression by this tissue is associated with and could contribute towards neoplastic transformation.

The presence of AC133-positive cells suggests a possible role of endothelial progenitor cells in the formation of choroidal neovascularization

PURPOSE

Recent evidence suggests that vasculogenesis as well as angiogenesis occurs throughout the body during neovascularization. The recruitment of circulating stem cells is a key feature of vasculogenesis. The purpose of the present study was to determine whether markers of endothelial progenitor cells (EPCs) are present in choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD).

METHODS

Surgically excised CNV (n = 9) membranes from patients with AMD were probed with immunohistochemical techniques using the following monoclonal antibodies: AC133 a putative marker of EPCs and hematopoietic stem cells (HSCs); the endothelial cells markers CD31, CD34, and von Willebrand factor (vWF); and cytokeratins and CD68, markers for retinal pigment epithelium (RPE) and macrophages, respectively. After secondary antibody amplification, reactions were visualized with fast red substrate.

RESULTS

Six of nine specimens demonstrated cells positive for AC133 that were all found within predominantly cellular regions of the specimens. In the avascular fibrous stromal core of all specimens, the predominant cells were RPE cells and macrophages. The peripheral component of all CNV membranes was highly vascular and showed varying immunoreactivity for all endothelial markers. The greatest immunoreactivity for endothelial markers was observed with CD34 and vWF and least for CD31.

CONCLUSIONS

These findings support animal studies that vasculogenesis, in addition to angiogenesis, may contribute to the neovascularization that occurs in AMD.

A critical process analysis of wine production to improve cost, quality and environmental performance

Abstract Wine production in South Africa is delocalised, with numerous small-to-medium sized producers within several regions within the Western Cape. Whilst adapting to new technological changes, producers have to respond to pressure from consumers and governments regarding the environmental consequences of winemaking, especially water usage and pollution. To date, no systematic analysis integrating the various aspects of winemaking in South Africa has been done. This study assessed both physical inputs and outputs. A detailed questionnaire was developed to broadly assess these parameters and was submitted to all cellars in South Africa. Case studies were performed at three cellars during the 2002 harvest season to validate the questionnaires and collect missing information. Based on this, and a cocurrent project, the following parameters were correlated to the tons of grapes presses per annum: effluent parameters which include chemical oxygen demand, suspended solids, total dissolved solids, sodium adsorption ratio, quantity of effluent; wine produced, water consumed, and electricity consumed. These parameters were used to develop an input/output model. This model may be used by wineries to predict their water and electrical consumption, wine produced and effluent characteristics provided they know the tonnage of grapes pressed per year.

Edible mushroom (Agaricus bisporus) lectin inhibits human retinal pigment epithelial cell proliferation in vitro

The retinal pigment epithelium (RPE) plays a major role in the development of the anomalous retinal scarring response termed proliferative vitreoretinopathy. The present study was undertaken to investigate whether agaricus bisporus lectin inhibited human RPE proliferation in vitro. Fluorescein isothiocyanate-labeled agaricus bisporus lectin was used to study binding of lectin to cultured human RPE. The effect of a 24-hour exposure of agaricus bisporus lectin on RPE proliferation was measured using (methyl-3H)-thymidine incorporation into DNA. Toxicity studies were assessed using morphologic evaluation, trypan blue exclusion, and a cell viability assay. Agaricus bisporus lectin bound to RPE cells and was inhibited by preincubation of lectin with asialomucin. Agaricus bisporus lectin caused a dose-dependent inhibition of RPE proliferation (one-way ANOVA, F = 94.470, p < 0.001) that was partially reversible on removal of the lectin. Compared with controls, cells remained viable and no morphological changes or trypan blue staining was noted in RPE exposed to agaricus bisporus lectin. Human RPE binds agaricus bisporus lectin and inhibits proliferation without apparent cytotoxicity. It therefore merits consideration as a potential antiproliferative agent in the prevention and treatment of proliferative vitreoretinopathy and other nonocular anomalous wound healing processes.

The role of matricellular proteins thrombospondin-1 and osteonectin during RPE cell migration in proliferative vitreoretinopathy

PURPOSE

To investigate the hypothesis that the Matricellular proteins thrombospondin 1 (TSP1), tenascin (TN) and Secreted Protein Acidic and Rich in Cysteine (SPARC) modulate the migration of RPE cells in the epiretinal membranes of proliferative vitreoretinopathy.

METHODS

Ten PVR epiretinal membranes were studied by immunohistochemical methods in which aggregates of RPE cells were identified by their expression of a broad range of cytokeratins. RPE subsets containing migratory RPE cells were detected by immunoreactivity for the monoclonal antibody RGE53 (which detects an epitope on cytokeratin-18 on motile RPE cells). Co-localisation of the RPE subsets with the glycoproteins TSP-1, SPARC and TN was evaluated.

RESULTS

Nineteen migratory RPE (RGE53 positive) subsets and 13 RPE (RGE53 negative) subsets were identified. All of the RGE53+ subsets colocalised with TSP1 and SPARC and 17 with TN. Ten of the RGE53- aggregates stained for TN, 6 for SPARC and 5 for TSP1. The association between the presence of RGE53+ cells in the RPE cell aggregates and TSP1 immunoreactivity in the aggregates was significant (p < 0.001), and there was a comparable significant association between RGE53+ cells and SPARC (p < 0.001). No such association was detected for RGE53+ cells and TN (p > 0.2).

CONCLUSIONS

The findings support the concept that the migration of retinal pigment cells in epiretinal membranes is modulated by TSP1 and SPARC and thus that these two proteins ultimately may represent therapeutic targets in the management of the membranes.

Pathobiology of epiretinal and subretinal membranes: possible roles for the matricellular proteins thrombospondin 1 and osteonectin (SPARC)

Epiretinal and subretinal membranes are fibrocellular proliferations which form on the surfaces of the neuroretina as a sequel to a variety of ocular diseases. When these proliferations complicate rhegmatogenous retinal detachment (a condition known as proliferative vitreoretinopathy or PVR), the membranes often contain numerous retinal pigment epithelial (RPE) cells and a variety of extracellular proteins. The extracellular proteins include adhesive proteins like collagen, laminin and fibronectin. In addition, several matricellular proteins with potential counter-adhesive functions are present in the membranes. Two such matricellular proteins, thrombospondin 1 and osteonectin (or SPARC: Secreted Protein Acidic and Rich in Cysteine), tend to be co-distributed with the RPE cells in PVR membranes. By virtue of their counter-adhesive properties, thrombospondin 1 and SPARC may reduce RPE cell-matrix adhesion and so permit key RPE cellular activities (for example, migration or shape change) in periretinal membrane development. Furthermore, within a 'cocktail' containing other proteins such as the metalloproteinases and growth factors like the scatter factor/hepatocyte growth factor family, matricellular proteins may play a role in the RPE cell dissociation from Bruch's membrane, which characterises early PVR.

Matrix metalloproteinases: a role in the contraction of vitreo-retinal scar tissue

The most common cause of failure of retinal reattachment surgery is formation of fibrocellular contractile membranes on both surfaces of the neuroretina. This intraocular fibrosis, known as proliferative vitreoretinopathy, results in a blinding tractional retinal detachment because of the contractile nature of the membrane. Contractility is a cell-mediated event that is thought to be dependent on locomotion and adhesion to the extracellular matrix. Interactions between cells and the extracellular matrix can be influenced by matrix metalloproteinases (MMPs) and we investigated the role of MMPs in two in vitro models (two- and three-dimensional) of human retinal pigment epithelial (RPE) cell-mediated contraction. MMP activity was detected using enzyme-linked immunosorbent assays and zymography techniques that revealed MMP-1, -2, -3, and -9 positivity during the collagen matrix contraction assays. RPE-populated collagen matrix contraction (three-dimensional) was inhibited using a cocktail of anti-MMP antibodies and with Galardin (a broad-spectrum MMP inhibitor). Galardin inhibition was dose-dependent, reversible, and dependent on cell number. MMP inhibitors had no effect on contraction when RPEs were seeded on two-dimensional collagen matrices or on cellular adhesion to collagen type I. Our results suggest that MMP activity may be required for three-dimensional but not two-dimensional RPE-collagen matrix contraction.

Cultured human retinal pigment epithelial cells differentially express thrombospondin-1, -2, -3, and -4

Thrombospondins are a family of at least five proteins (TSP-1 to -4 and cartilage oligomeric matrix protein or COMP) whose functions are indeterminate. Distribution differences between family members suggest each protein may have some distinct functions. The retinal pigment epithelium (RPE) has divers unusual roles for an epithelia and can produce TSP-1. However, the wide range of RPE activities suggests that, if different thrombospondin family members do have different functions, RPE may express thrombospondins additional to TSP-1. Therefore, we analysed expression of thrombospondin isoforms by RPE using reverse-transcription-linked polymerase chain reaction. Cultured cells exhibited differential expression of TSP-1 to -4; TSP-2 and TSP-4 appearing later in culture than TSP-1 and TSP-3. In situ RPE expressed mRNA for TSP-1 to -4. No COMP mRNA was detected in RPE. These observations suggest that thrombospondin isoforms are regulated differently by the cells and that these proteins may have different functions in the RPE.

Synthesis of osteonectin by human retinal pigment epithelial cells is modulated by cell density

PURPOSE

To determine whether human retinal pigment epithelial (HRPE) cells are able to synthesize the antiadhesive protein osteonectin, also known as secreted protein, acidic and rich in cysteine (SPARC). Additionally, because locally produced SPARC may modulate cellular behavior during tissue repair, to ascertain whether HRPE SPARC production and HRPE proliferation, migration, and/or differentiation are associated, in a simple HRPE wound-healing model.

METHODS

Immunohistochemical and Western blot analyses of SPARC protein expression by low- and high-density cultured HRPE cells were undertaken. Total RNA extracted from cultures was studied by reverse transcription-polymerase chain reaction (RT-PCR) and Northern blot analysis. Western and Northern blot analyses were evaluated by densitometry. Experiments were repeated with HRPE cells cultured in the presence of 1, 10, or 100 microM of the differentiating agents butyric acid (BA) and retinoic acid (RA).

RESULTS

HRPE cell cultures exhibited SPARC immunoreactivity. Western blot analysis of cell lysates and conditioned media showed a 43-kDa protein. RT-PCR and Northern blot analysis confirmed the presence of SPARC mRNA (with transcripts at 2.2 and 3.0 kb). Protein and mRNA transcript band densitometry revealed a higher proportion of SPARC protein and mRNA in high-density HRPE cell culture than in low-density culture. Neither BA nor RA (at the concentrations assessed) had a significant effect on SPARC production by HRPE cells in high- or low-density culture.

CONCLUSIONS

HRPE can synthesize SPARC. Although the findings do not support an invariable association between SPARC production by HRPE and HRPE proliferation, migration, or differentiation, they demonstrate that synthesis of SPARC by HRPE is modulated by cell density.

Modulation of retinal pigment epithelial cell behavior by Agaricus bisporus lectin

PURPOSE

To determine whether Agaricus bisporus lectin (ABL) binds retinal pigment epithelial cells (RPEs), to conduct a preliminary viability study of RPEs exposed to ABL, and to evaluate the effects of ABL on RPE proliferation and RPE-mediated matrix contraction in vitro.

METHODS

Using cultured bovine RPEs, immunohistochemistry was used to study ABL binding. Morphologic and trypan blue exclusion techniques were used for toxicity studies. The effect of ABL on RPE proliferation was investigated by [methyl-3H]-thymidine incorporation. The effect of ABL on RPE-mediated matrix contraction was evaluated with RPE-populated three-dimensional collagen matrices.

RESULTS

ABL bound to RPE cells. This binding was inhibited by asialomucin. No change in RPE morphology or trypan blue exclusion compared with controls was observed in RPEs incubated with 5 to 60 microg/ml ABL for 3 days. Twenty-four-hour incubations of RPEs with ABL significantly inhibited RPE proliferation in a dose-dependent way, 40 microg/ml ABL inhibited proliferation by 83% (SE 14, P<0.05). ABL showed a dose-dependent significant inhibition of RPE-mediated collagen matrix contraction over 3 days, with 93% inhibition compared with controls by 40 microg/ml lectin (P<0.05). The inhibitory effect of ABL on proliferation and gel contraction was partly reversible after eliminating ABL from the culture medium.

CONCLUSIONS

Bovine RPE cells bind ABL, and preliminary evaluations suggest that levels of ABL that are nontoxic to the cells potently inhibit RPE proliferation and RPE-mediated matrix contraction. ABL deserves further investigation as a potential inhibitor of RPE proliferation and cell-mediated matrix contraction in anomalous reparative processes such as proliferative vitreoretinopathy and as a laboratory tool for RPE behavioral studies.

Nuclear export of NF-ATc enhanced by glycogen synthase kinase-3

The transcription factor NF-AT responds to Ca2+-calcineurin signals by translocating to the nucleus, where it participates in the activation of early immune response genes. Calcineurin dephosphorylates conserved serine residues in the amino terminus of NF-AT, resulting in nuclear import. Purification of the NF-AT kinase revealed that it is composed of a priming kinase activity and glycogen synthase kinase-3 (GSK-3). GSK-3 phosphorylates conserved serines necessary for nuclear export, promotes nuclear exit, and thereby opposes Ca2+-calcineurin signaling. Because GSK-3 responds to signals initiated by Wnt and other ligands, NF-AT family members could be effectors of these pathways.

Macrophages during fibrosis following scleral fistulising surgery in a rat model

PURPOSE

Glaucoma filtration surgery can fail in a minority of patients as a result of fibrosis in the subconjunctival bleb space and closure of the scleral fistula. In this study, the rat eye has been used as an experimental model for fistulising surgery in order to evaluate the clinical manifestation of bleb failure with the morphological events of the wound healing process.

METHODS

A conjunctival bleb was successfully formed in 25 rats and was examined daily using slit lamp microscopy to evaluate postoperative inflammation and the presence of a bleb. At defined post-operative time points, serial frozen sections of eyes were stained immunohistochemically using a panel of monoclonal antibodies directed against known surface markers on rat immune/inflammatory cells. Positively stained cells were counted (a) in the bleb site, (b) at the sclerostomy and (c) at the suture site.

RESULTS

Following an initial post-operative inflammation, a surgically formed sclerostomy and conjunctival bleb underwent a granulation and scarring response so that by 7-19 days the bleb had disappeared. Using the monoclonal antibodies applied in this study, it was possible to show that macrophages most likely play a major and pivotal role throughout the sequence of events that lead to repair of the fistula and closure of the bleb. It was also noted that the presence of an otherwise inert nylon suture used to close the incised conjunctiva can serve as a focus for macrophages.

CONCLUSION

The rat has been successfully used as an experimental model of fistulising surgery and its subsequent failure. The use of a panel of monoclonal antibodies directed against specific surface markers on immune-inflammatory cells, highlighted macrophages to be prominent in all stages of this wound healing process.