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Objectives: Epithelial stem cells of the eye surface, of the cornea and of the conjunctiva, have the ability to give rise to self renewal and progeny production of differentiated cells with no apparent limit. The two epithelia are separated from each other by the transition zone of the limbus. The mechanisms adopted by stem cells of the two epithelia to accomplish their different characteristics, and how their survival, replacement and unequal division that generates differentiated progeny formation are controlled, are complex and still poorly understood. They can be learned only by understanding how stem cells/progenitors are regulated by their neighbouring cells, that may themselves be differently unspecialised, forming particular microenvironments, known as ‘niches’. Stem cells operate by signals and a variety of intercellular interactions and extracellular substrates with adjacent cells in the niche. Technical advances are now making it possible to identify zones in the corneal limbus and conjunctiva that can house stem cells, to isolate and expand them ex vivo and to control their behaviour creating optimal niche conditions. With improvements in biotechnology, regenerative cornea and conjunctiva transplantation using adult epithelial stem cells becomes now a reality. Results and Conclusions: Here we review our current understanding of stem cell niches and illustrate recent significant progress for identification and characterization of adult epithelial stem cells/progenitors at cellular, molecular and mechanistic levels, improvement in cell culture techniques for their selective expansion ex vivo and prospects for a variety of therapeutic applications. [ABSTRACT FROM AUTHOR]

Rhesus monkey embryonic stem cells (ESCs) (R366.4), cultured on a three-dimensional (3D) collagen matrix with or without human neonatal foreskin fibroblasts (HPI.1) as feeder cells, or embedded in the collagen matrix, formed complex tubular or spherical gland-like structures and differentiated into phenotypes characteristic of neural, epithelial and endothelial lineages. Here, we analysed the production of endogenous extracellular matrix (ECM) proteins, cell–cell adhesion molecules, cell-surface receptors, lectins and their glycoligands, by differentiating ESCs, forming a micro-environment, a niche, able to positively influence cell behaviour. The expression of some of these molecules was modulated by HPI.1 cells while others were unaffected. We hypothesized that both soluble factors and the niche itself were critical in directing growth and/or differentiation of ESCs in this 3D environment. Creating such an appropriate experimental 3D micro-environment, further modified by ESCs and modulated by exogenous soluble factors, may constitute a template for adequate culture systems in developmental biology studies concerning differentiation of stem cells. [ABSTRACT FROM AUTHOR]

Interleukin-1 (IL-1) production by the human monocyte-like cloned cell line CM-SM has been investigated as a function of the state of cell differentiation. CM-SM cells were induced to differentiate along the monocyte-macrophage lineage by bacterial lipopolysaccharides (LPS) or by 12-O-tetradecanoyl-phorbol-13-acetate (TPA). Cell differentiation was studied by various morphological, functional, cytochemical, and immunological variables, whereas IL-1 activity in the supernatants was measured by the lectin-primed thymocyte proliferation assay. Unstimulated CM-SM cells constitutively produced cell differentiation, but the effect was reversible, and the cells, in general, did not acquire a capacity for phagocytosis. IL-1 levels were increased about 10-fold over the controls. TPA induced further cell differentiation to macrophage-like cells capable of phagocytosis. IL-1 activity could not be measured directly in the supernatants owing to the synergistic effect of TPA in the assay system. Unequivocal removal of the phorbol was not achieved, but the data indicated that the ‘real’ levels of IL-1 in the TPA-induced cultures were not significantly higher than those from LPS-induced cultures. [ABSTRACT FROM AUTHOR]

Monoclonal antibodies against human fetal haemoglobin (HbF) were obtained by fusion of mouse myeloma cells with spleen lymphocytes from mice immunized against HbF from human umbilical cord blood erythrocytes. Initial antibody screening was by indirect immunofluorescence assays on smeared cord blood and normal adult blood erythrocytes. The specificity of these antibodies was further studied by combined immunoprecipitation assays and direct or inhibition solid-phase enzyme immunoassays. The combined pattern enabled recognition of three types of antigenic determinants: (i) common to both HbF and HbA, by both immunofluorescence and enzyme immunoassays; (ii) common to both HbF and HbA by enzyme immunoassays, present on fixed cord blood erythrocytes and adult thalassaemic erythrocytes by immunofluorescence, but not found on fixed normal adult erythrocytes; and (iii) private HbF by both immunofluorescence and enzyme immunoassays. [ABSTRACT FROM AUTHOR]