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Carol Greene, Trevor Sherwin, Colin Green; Exploring cell plasticity: the corneal keratocyte and beyond. Invest. Ophthalmol. Vis. Sci. 2013;54(15):5250.
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© ARVO (1962-2015); The Authors (2016-present)
Corneal keratocytes have a remarkable ability to heal wounds in the cornea throughout life and also exhibit a high level of cell plasticity. However, their differentiative potential is not limited to repair phenotypes. It has been shown in our laboratory that it is possible to induce human and rat stromal keratocytes to express neuron specific proteins by adding specific growth factors to the culture medium. The purpose of this study was to carry out ex vivo and in vivo experiments in an effort to uncover the extent of corneal keratocyte plasticity. Furthermore, to explore and compare the potential of other cell types to exhibit similar cell plasticity.
Tissue and cell culture was used for in vitro experiments. Immunohistochemistry and RT PCR were used to investigate protein and gene expression respectively. Confocal laser scanning microscopy was used for imaging cells and tissue slices.
Keratocytes obtained from adult humans and rats expressed Nestin, NF-200, and MAP2 when cultured in a neuronal differentiation medium containing EGF, FGF and IGF-1. RT PCR revealed up regulation of GAD1, SYN1, SOX2, SOX10 and NOTCH1. Subsequent in vivo studies also confirmed the expression of Nestin, MASH1, and NF200. Adult rat xiphosternum derived chondrocytes cultured in the same neurogenic media expressed NF-200, MAP2, GAP43 and β-III-tubulin. Adult human corneal keratocytes when cultured for 3 weeks in a chondrogenic differentiation medium containing TGF-β3 and dexamethasone formed spheres that produced Collagen Type II.
Apart from producing neuron specific proteins such as NF-200 and MAP2, the genes SOX2, SOX10 and NOTCH1 which are associated with neurogenesis were upregulated in corneal slices cultured in the neurogenic medium. Also, the expression of genes such as GAD1 and SYN1 which are associated with neurotransmitter synthesis and synapse formation indicate that the neuronal cells produced might be functional. Similar to corneal stroma, cartilage from adult rats contained cells that acquire a neuronal phenotype and express neuron specific proteins. Corneal keratocytes also have the potential to produce the cartilage specific protein Collagen II in cell culture and ex vivo slice culture when exposed to conditions which favour chondrogenic differentiation. These findings will have an impact on aspects of tissue regeneration research as well as our current understanding of adult cell plasticity.
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