Other research has shown that MCs have acted as a funnel to provide light to rod and cone photoreceptors in the mammalian eye, similar to fiber optic plates ( 12). The characteristics of MCs contrast with the rest of the retina, which has a surprisingly high light scattering effect. The cytoplasm of MCs contains several mitochondria that help to reduce light scattering and are enriched with long, thin filaments that form the dielectric anisotropy. The unique funnel shape of MCs, the radial alignment in the retina, and more suitable physical properties allow light to be transmitted from the vitreous to the photoreceptors behind the retina ( 3, 4). The progenitor cell may be divided and differentiated into a number of retinal cell types, including photoreceptor cells that may have been damaged during injury ( 9– 11). In the zebrafish genus, MCs have been shown to differentiate into multipotent progenitor cells. The result of the response depends on the damage and the organism in which damage occurs. It is known that the destruction of MCs can lead to the development of a macular hole or pseudohole. Damage to retinal cells causes MCs to undergo gliosis. Studies in human models have shown that MCs have the potential to serve as stem cells in the adult retina and are rod photoreceptor progenitors. Research continues to examine their role in neural regeneration in humans ( 7, 8). Furthermore, MCs may differentiate into neural progenitors or stem cells that reproduce lost photoreceptors and neurons under pathological conditions ( 5, 6). MCs serve as a soft substrate for neurons to protect them in case of mechanical trauma and also for neuronal development and neuronal plasticity. MCs interconnect the neural elements of the retina with synapses and dendrites. They work in a symbiotic relationship with neurons. MCs contribute important structural and metabolic functions to ensure the viability and stability of retinal cells. Schematic drawing of the relationship between a Müller cell and other retinal neurons.Ī: Amacrine cell B: Bipolar cell C: Cone cell G: Ganglion cell GCL: Ganglion cell layer H: Horizontal cell ILM: Inner limiting membrane INL: Inner nuclear layer IPL: Inner plexiform layer M: Müller cell MMV: Müller micro-villi OLM: Outer limiting membrane ONL: Outer nuclear layer OPL: Outer plexiform layer PROS: Photoreceptor outer segments R: Rod cell RPE: Retinal pigmented epithelium. MCs contribute to the internal blood-retinal barrier formed by endothelial cells by inducing the synthesis of tight junction and tight junction proteins ( 4). As all glial cells do, they serve as support cells for neurons. MCs fill gaps in the retina that the neuron cells do not fill. MCs contain blood vessels in the plexiform and nerve fiber layers ( Fig. The apical portion extends to the rear to form the outer limiting membrane and separates the internal and external parts of the photoreceptors. The cell bodies sit on the inner nuclear layer. The uppermost portion of the MCs creates the internal limiting membrane, which separates the retina from the vitreous. MCs cover the entire thickness of the retina and have interactions with every type of neuronal cell body. The early phase of neurons born at the apical border of neuroepithelium adjacent to the pigment epithelium produces cone cells, horizontal cells, and ganglion cells, while the second phase of cells produces MCs, rod photoreceptors, bipolar cells, and amacrine cells ( 2– 3). MCs have been shown to originate from neural crest cells ( 2).Ī single progenitor cell forms both MCs and retinal neurons. The MC is the only retinal glial cell sharing a common cell line with retinal neurons. Retinal gliocytes were first described by Heinrich Müller ( 1). Müller cells (MCs) (retinal gliocytes, Müller glia) are the most common of the 3 glial cells found in the human retina, followed by astroglia and microglia.
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