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J.B. Sheffield, M. He, M.W. Davidson; Visualization of Cell Migration During Histogenesis in Living Chick Retina Slices . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2037.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Indirect studies of retinal development using fixed tissues have suggested that retinal precursor cells migrate between the apical and basal portions of the tissue until they reach appropriate positions, and then stop. In the present study, we wished to examine the migration patterns of cells in living tissues using optical sectioning and time-lapse microscopy. Methods: Chick retinas of embryonic ages from 5 to 14 days of incubation were dissected into cold Tyrode's solution, and embedded in 8% Ultra-low-gellation temperature agarose (Sigma, type IX-A) in Tyrode's solution. After gellation, the tissue was sliced with a Smith-Farquhar Tissue Slicer into sections of approximately 135 microns. The slices were transferred to a thermally regulated chamber (Bioptechs) containing 1 ml of Ham's F-12 medium supplemented with fetal calf serum. The apparatus was placed on an inverted microscope equipped with DIC or Hoffman optics, and a Nikon digital camera (DXM1200). Images were taken every 15 seconds with a 40x lens at a resolution of 1280x1024 pixels per image. The images were combined into video streams of 15 frames per second using the RAD video tool set, and the Divx 5.02 codec. Results: Cell migration was easily visualized in the preparations. Individual cells could be seen to contract, extend, and move between the apical and basal borders. Cells were most active in retinas of 5-7 days of incubation. Migration was limited to the apical-basal axis. There was no significant lateral movement beyond approximately one cell diameter. The cells often migrated within the tissue in an alternating pattern. They would move in a certain direction, reverse, and then resume their original direction. Having reached the opposite surface of the tissue, they would frequently reverse and continue to migrate. The cells achieved maximum speeds of 10 microns/minute, although there was considerable variation in rate of movement even for any one cell. In older retinas, 8-15 days, cellular migration was progressively reduced, although there was continuing intercellular activity. Individual small structures (either cells or nuclei within cell bodies) migrated from the apical portion of the tissue to positions within the growing inner nuclear layer, and stopped. Conclusions: This study provides dynamic confirmation of many aspects of the pattern of retinal histogenesis that have been proposed on the basis of static images. At all ages examined, migration was restricted to the apical-basal axis. The complexity of cellular movement in early embryonic ages was unexpected.
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