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Updated: Aug 7, 2026
Whole Retinal Explants from Chicken Embryos for Electroporation and Chemical Reagent Treatments
Published on: September 30, 2015
Myeloid body development in the chick retinal pigment epithelium
1Department of Anatomy, Dalhousie University, Halifax, Canada.
Abstract:
Previous investigations have reported a correlation between outer segment disk phagocytosis by the retinal pigment epithelium (RPE), and the formation of myeloid bodies, which are lamellar specializations of the smooth endoplasmic reticulum of the RPE. To further test the hypotheses that MBs are directly related to the process of outer segment shedding, we have undertaken to study the development of the retinal pigment epithelium in the chick utilizing a morphometric ultrastructural approach with specific attention to the timing of outer segment disk shedding and the formation of myeloid bodies. This study has demonstrated a temporal relationship between the initiation of photoreceptor outer segment disk shedding in the chick embryo and the occurrence of myeloid bodies. We have shown that photoreceptor outer segment disk shedding and phagocytosis by the RPE has been initiated in a substantial proportion of the retina by day 18 of development. Myeloid body formation does not begin until two days later at embryonic day 20, and is preceded by the development within the RPE of flattened areas of the normally tubular SER (templates), which we believe represent the precursors of myeloid body formation. Temporal development of outer segment phagocytosis, lamellar SER (template) occurrence and myeloid body formation are all statistically significant at the 95% level.
Insights
Myeloid bodies in the retinal pigment epithelium (RPE) form after outer segment disk shedding begins. This study reveals a temporal link between RPE phagocytosis and myeloid body development in chick embryos.
Area of Science:
- Ophthalmology
- Developmental Biology
- Cell Biology
Background:
- Retinal pigment epithelium (RPE) phagocytosis of photoreceptor outer segments is crucial for retinal health.
- Myeloid bodies (MBs) are lamellar structures within RPE, previously correlated with phagocytosis.
Purpose of the Study:
- To investigate the temporal relationship between outer segment disk shedding and myeloid body formation in the developing chick retina.
- To test the hypothesis that MBs are a direct consequence of outer segment shedding.
Main Methods:
- Morphometric ultrastructural analysis of chick embryo RPE.
- Detailed observation of outer segment disk shedding and MB formation timing.
Main Results:
- Photoreceptor outer segment disk shedding and RPE phagocytosis initiate by embryonic day 18.
- Myeloid body formation begins at embryonic day 20, following the development of smooth endoplasmic reticulum (SER) 'templates'.
- A statistically significant temporal relationship exists between shedding, SER template occurrence, and MB formation.
Conclusions:
- Outer segment phagocytosis precedes myeloid body formation in the developing chick retina.
- Flattened SER areas ('templates') are identified as precursors to myeloid bodies.
- The findings support a direct developmental link between RPE phagocytosis and MBs.
