IntroductionLutein is a carotenoid whose protective effects in the retina have been reported in various studies. The effect of lutein has not been reported in the retina of the Ins2Akita/+ mouse, a well-characterized genetic model for diabetic retinopathy (DR) in which the etiology of diabetes is better defined than the chemically induced diabetes. The objective of the present study is to investigate the effect of long-term administration of lutein in early stages of DR using the Ins2Akita/+ mouse.Research design and methodsHeterozygous male Ins2Akita/+ and age-matched wild-type mice were used. Lutein was administered to the mice in drinking water starting 6 weeks old daily until analysis at 4.5, 6.5 or 9 months of age. Plain water served as non-treatment control. Microglia were immunostained with ionized calcium-binding adapter molecule 1 (Iba-1) and cluster of differentiation 68 (CD68) in retinal flat-mounts. Vascular endothelial growth factor (VEGF) level in the retina was assessed by enzyme-linked immunosorbent assay (ELISA). Vascular permeability was analyzed in retinal flat-mounts after fluorescein isothiocyanate (FITC)-dextran perfusion. Retinal occludin expression was assessed via Western blots. Retinal function was examined by electroretinography (ERG).ResultsIncreased microglial reactivity was detected in the Ins2Akita/+ mouse retina and was suppressed by lutein. Lutein administration also reduced the upregulation of VEGF in the Ins2Akita/+ mouse retina. Increased vascular leakage and decreased occludin expression were observed in the Ins2Akita/+ mouse retina, and these alterations were attenuated by lutein treatment. ERG recordings showed reduced a-wave and b-wave amplitudes in the Ins2Akita/+ mice. With lutein treatment, the ERG deficits were significantly alleviated.ConclusionsWe showed beneficial effects of long-term lutein administration in the Ins2Akita/+ mouse retina, including suppression of retinal inflammation, protection of retinal vasculature and preservation of retinal function. These results point to lutein’s potential as a long-term therapeutic intervention for prevention of inflammation and retinal degeneration in patients with early DR.

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Mircoglia are specialized mononuclear phagocytes within the central nervous system (CNS). Their embryonic origins and routes of entry to the CNS remain controversial. In this study, we used Iba1 as a specific marker for microglial progenitors in mouse embryos and employed multiple immunohistochemical localization and tissue transplantation to establish (1) their routes of entry to the CNS and (2) their origin. Iba1+ microglial progenitors were found in the mesenchyme at E9.5, and started to appear in the neural tube at E10.5. By E13.5, significant numbers of Iba1+ cells were observed in the mantle layer. Examination of sectioned tissues suggested that Iba1+ cells entered the neural tube through its basal surface, apical surface or blood vessels. When fragments of E11.5 liver tissues genetically labeled with eGFP were transplanted to the mesenchyme next to the unlabeled E10.5 neural tube, eGFP+Iba1+ cells were found within the neural tube one day after transplantation, implicating that Iba1+ cells from the embryonic liver were able to migrate through the mesenchyme to enter the neural tube. In conclusion, microglial progenitors expressing Iba1 enter the neural tube through multiple sites, and the embryonic liver could represent a source of origin.The work was supported by the General Research Fund from the Research Grants Committee of the Hong Kong Special Administrative Region, China (Project No. 461909).