Protective Effects of Human iPS-Derived Retinal Pigment Epithelium Cell Transplantation in the Retinal Dystrophic Rat

Transformation of somatic cells with a set of embryonic transcription factors produces cells with the pluripotent properties of embryonic stem cells (ESCs). These induced pluripotent stem (iPS) cells have the potential to differentiate into any cell type, making them a potential source from which to produce cells as a therapeutic platform for the treatment of a wide range of diseases. In many forms of human retinal disease, including age-related macular degeneration (AMD), the underlying pathogenesis resides within the support cells of the retina, the retinal pigment epithelium (RPE). As a monolayer of cells critical to photoreceptor function and survival, the RPE is an ideally accessible target for cellular therapy. Here we report the differentiation of human iPS cells into RPE. We found that differentiated iPS-RPE cells were morphologically similar to, and expressed numerous markers of developing and mature RPE cells. iPS-RPE are capable of phagocytosing photoreceptor material, in vitro and in vivo following transplantation into the Royal College of Surgeons (RCS) dystrophic rat. Our results demonstrate that iPS cells can be differentiated into functional iPS-RPE and that transplantation of these cells can facilitate the short-term maintenance of photoreceptors through phagocytosis of photoreceptor outer segments. Long-term visual function is maintained in this model of retinal disease even though the xenografted cells are eventually lost, suggesting a secondary protective host cellular response. These findings have identified an alternative source of replacement tissue for use in human retinal cellular therapies, and provide a new in vitro cellular model system in which to study RPE diseases affecting human patients

MUC1* mediates the growth of human pluripotent stem cells.

The MUC1 protein is aberrantly expressed on an estimated 75% of all human solid tumor cancers. We recently reported that a transmembrane cleavage product, MUC1*, is the predominant form of the protein on cancer cells [1]. Further, our evidence indicated that MUC1* functions as a growth factor receptor on tumor cells, while the full-length protein appeared to have no growth promoting activity. Here, we report that MUC1* acts as a growth factor receptor on undifferentiated human embryonic stem cells (hESCs). Cleavage of the full-length ectodomain to form MUC1*, a membrane receptor, appears to make binding to its ligand, NM23, possible. Unexpectedly, we found that newly differentiated cells no longer express the cleaved form, MUC1*, or its ligand, NM23. Newly differentiated stem cells exclusively present full-length MUC1. Antibody-induced dimerization of the MUC1* receptor on hESCs stimulated cell growth to a far greater degree than currently used methods that require the addition of exogenous basic fibroblast growth factor (bFGF) as well as factors secreted by fibroblast "feeder cells". Further, MUC1* mediated growth was shown to be independent of growth stimulated by bFGF or the milieu of factors secreted by feeder cells. Stimulating the MUC1* receptor with either the cognate antibody or its ligand NM23 enabled hESC growth in a feeder cell-free system and produced pluripotent colonies that resisted spontaneous differentiation. These findings suggest that this primal growth mechanism could be utilized to propagate large numbers of pluripotent stem cells for therapeutic interventions

Integrins in the development, function and dysfunction of the nervous system.

Integrin receptors mediate cell-cell and cell-extracellular matrix (ECM) interactions in many different cell types, including neuronal cells. Earlier studies have shown a clear role for integrins in axon extension and cell adhesion/migration in CNS inflammation. Here we summarize more recent work that shows integrin functions in many phases of neural development, from neuroblast migration to synapse formation. Integrins of the beta-1 and alpha-v family are widely expressed on neurons at many stages of development, and their activity is regulated. Integrins are also important in the adult nervous system, since they have been implicated in synaptic plasticity involved in memory and learning. In addition, several diseases of the nervous system appear to involve beta-1, beta-2, and alpha-v integrins on leukocytes and glial cells. Research challenges for the future include understanding functions of specific integrin heterodimers and identifying the relevant integrin ligands that function in the nervous system

Defined culture of human embryonic stem cells and xeno-free derivation of retinal pigmented epithelial cells on a novel, synthetic substrate.

Age-related macular degeneration (AMD), a leading cause of blindness, is characterized by the death of the retinal pigmented epithelium (RPE), which is a monolayer posterior to the retina that supports the photoreceptors. Human embryonic stem cells (hESCs) can generate an unlimited source of RPE for cellular therapies, and clinical trials have been initiated. However, protocols for RPE derivation using defined conditions free of nonhuman derivatives (xeno-free) are preferred for clinical translation. This avoids exposing AMD patients to animal-derived products, which could incite an immune response. In this study, we investigated the maintenance of hESCs and their differentiation into RPE using Synthemax II-SC, which is a novel, synthetic animal-derived component-free, RGD peptide-containing copolymer compliant with good manufacturing practices designed for xeno-free stem cell culture. Cells on Synthemax II-SC were compared with cultures grown with xenogeneic and xeno-free control substrates. This report demonstrates that Synthemax II-SC supports long-term culture of H9 and H14 hESC lines and permits efficient differentiation of hESCs into functional RPE. Expression of RPE-specific markers was assessed by flow cytometry, quantitative polymerase chain reaction, and immunocytochemistry, and RPE function was determined by phagocytosis of rod outer segments and secretion of pigment epithelium-derived factor. Both hESCs and hESC-RPE maintained normal karyotypes after long-term culture on Synthemax II-SC. Furthermore, RPE generated on Synthemax II-SC are functional when seeded onto parylene-C scaffolds designed for clinical use. These experiments suggest that Synthemax II-SC is a suitable, defined substrate for hESC culture and the xeno-free derivation of RPE for cellular therapies

Integrins in the development, function and dysfunction of the nervous system.

Integrin receptors mediate cell-cell and cell-extracellular matrix (ECM) interactions in many different cell types, including neuronal cells. Earlier studies have shown a clear role for integrins in axon extension and cell adhesion/migration in CNS inflammation. Here we summarize more recent work that shows integrin functions in many phases of neural development, from neuroblast migration to synapse formation. Integrins of the beta-1 and alpha-v family are widely expressed on neurons at many stages of development, and their activity is regulated. Integrins are also important in the adult nervous system, since they have been implicated in synaptic plasticity involved in memory and learning. In addition, several diseases of the nervous system appear to involve beta-1, beta-2, and alpha-v integrins on leukocytes and glial cells. Research challenges for the future include understanding functions of specific integrin heterodimers and identifying the relevant integrin ligands that function in the nervous system

Defined culture of human embryonic stem cells and xeno-free derivation of retinal pigmented epithelial cells on a novel, synthetic substrate.

Age-related macular degeneration (AMD), a leading cause of blindness, is characterized by the death of the retinal pigmented epithelium (RPE), which is a monolayer posterior to the retina that supports the photoreceptors. Human embryonic stem cells (hESCs) can generate an unlimited source of RPE for cellular therapies, and clinical trials have been initiated. However, protocols for RPE derivation using defined conditions free of nonhuman derivatives (xeno-free) are preferred for clinical translation. This avoids exposing AMD patients to animal-derived products, which could incite an immune response. In this study, we investigated the maintenance of hESCs and their differentiation into RPE using Synthemax II-SC, which is a novel, synthetic animal-derived component-free, RGD peptide-containing copolymer compliant with good manufacturing practices designed for xeno-free stem cell culture. Cells on Synthemax II-SC were compared with cultures grown with xenogeneic and xeno-free control substrates. This report demonstrates that Synthemax II-SC supports long-term culture of H9 and H14 hESC lines and permits efficient differentiation of hESCs into functional RPE. Expression of RPE-specific markers was assessed by flow cytometry, quantitative polymerase chain reaction, and immunocytochemistry, and RPE function was determined by phagocytosis of rod outer segments and secretion of pigment epithelium-derived factor. Both hESCs and hESC-RPE maintained normal karyotypes after long-term culture on Synthemax II-SC. Furthermore, RPE generated on Synthemax II-SC are functional when seeded onto parylene-C scaffolds designed for clinical use. These experiments suggest that Synthemax II-SC is a suitable, defined substrate for hESC culture and the xeno-free derivation of RPE for cellular therapies

Osteopontin Is Proinflammatory in Experimental Autoimmune Uveitis

PURPOSE. Osteopontin (OPN) has been implicated in inflammatory and wound-healing processes. Increased OPN mRNA levels have been reported in experimental autoimmune uveitis (EAU), but the function of OPN in the inflamed eye is unknown. The purpose of this study was to investigate the role of OPN in the pathogenesis of EAU. METHODS. EAU was induced in OPN-null and wild-type (WT) mice by immunization with interphotoreceptor retinoid-binding protein (IRBP). Immunofluorescence experiments were performed to identify OPN-positive cells in WT mice. Disease incidence, serum IRBP antibody levels, vitreous infiltrates, retinal granulomas, and lymphocyte proliferation were assessed in OPN-null and WT mice. To determine whether OPN could induce an EAU-like condition, purified OPN and OPN fragments were injected intraocularly into WT mice and vitreous infiltrates were characterized and quantified. RESULTS. In WT EAU-positive eyes, cell types with increased OPN immunoreactivity were identified as F4/80-positive macrophages/microglia and CD4-positive T cells. OPN-null mice manifested attenuated disease with decreased vitreous infiltrates, fewer granulomas, less lymphocyte proliferation, and lower serum IRBP antibody levels. Exogenous full-length OPN, as well as N-and C-terminal fragments, induced leukocyte infiltration and retinal folding, with some similarities to EAU. CONCLUSIONS. The results demonstrate that OPN is proinflammatory in EAU and may be important for recruitment and activation of leukocytes in retinal inflammation. (Invest Ophthalmol Vis Sci. 2006;47:4435-4443