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Dania Hamassaki, Priscilla Akamine, Cesar Fuziwara, Carolina Del Debbio, Cristiano Pessoa, Edna Kimura; Expression of let-7 MicroRNA Family in the Aging Rat Retina and Vitreous. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1188.
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MicroRNAs (miRNA) are small non-coding RNAs that regulate a wide range of cellular processes by translational repression and mRNA degradation. To date, several studies have described the roles of these miRNAs in the retina, but not in the vitreous. Remodeling of the vitreous matrix starts at early stages and continues into old age, with gradual formation of collagen lamellae and liquefied spaces, which eventually leads to posterior vitreous detachment. Considering that members of the let-7 microRNA family are important regulators during development, tumorigenesis and in cellular aging, and that some vitreous matrix components such as collagens V and IX, as well as the enzyme hyaluronan synthase are their predicted targets, we investigated the influence of let-7 miRNAs in the aging rat retina and vitreous.
Newborn (postnatal day 1-3, n = 4), adult (2 months, n = 6) and aging (12 months, n = 5) Wistar rats were sacrificed by anesthesia overdose, their eyes were enucleated and the retinas and vitreous collected. Total RNA was isolated using Trizol, and gene expression of let-7a/b/c/d/e/f and let-7i miRNAs was analyzed by real-time PCR using Taqman microRNA assay (Life Tech.). To investigate whether Müller cells express and release let-7 miRNAs into the vitreous, these cells were cultured, the exosomes were isolated from culture medium by ultracentrifugation, and the let-7 expression was analyzed.
All let-7 miRNAs investigated were expressed in both vitreous and retina of newborn, adult and aging rats, with relatively higher expression in the vitreous. In all cases, let-7 miRNA levels in the vitreous were higher in adults and aging animals than in newborns, suggesting their modulation during aging. Moreover, let-7e showed the highest expression in both retina and vitreous whereas let-7f, the lowest. In vitro, rat Müller glial cells and their exosomes isolated from the medium supernatant also expressed let-7 miRNAs.
let-7 miRNA family is expressed in the rat vitreous and retina, being upregulated during the normal aging process. We suggest that Müller cells may play an important role on producing and releasing these miRNA to the vitreous, especially let-7e, which could be involved in vitreous pathologies related to matrix components degradation.
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