Related Experiment Video
Updated: Jul 5, 2026
Live Imaging and Characterization of Microglia Dynamics and Interactions with Synapses in Diseased Murine Retina
Published on: January 16, 2026
Characteristics of bone marrow-derived microglia in the normal and injured retina
Hiroki Kaneko1, Koji M Nishiguchi, Makoto Nakamura
1Department of Ophthalmology, Nagoya University School of Medicine, Nagoya, Japan.
Purpose:
To compare the distribution and immunologic characteristics of bone marrow (BM)-derived and resident microglia in the retina.
Methods:
Mice were irradiated and injected with enhanced green fluorescent protein-positive (EGFP(+)) BM cells. One month to 12 months after BM transplantation, eyes were analyzed histologically for the expression of EGFP and various monocyte/microglia/macrophage markers (Iba-1, F4/80, GS-1, major histocompatibility complex [MHC] class II). N-methyl-N-nitrosourea (MNU) was injected or retinal detachment was created to induce retinal damage.
Results:
Many BM-derived EGFP(+) cells were found in the ciliary body and choroid and around the optic nerve in the uninjured eyes. Within the retina, few such cells existed at the retinal margin and juxtapapillary area at 3 to 12 months after BM transplantation. However, after MNU injection, many EGFP(+) cells were found in the retina adjacent to the retinal vessels, optic nerve, and ciliary body that rapidly spread throughout the retina. Most of them showed morphologic and immunohistochemical features of microglia. By 7 days after MNU injection, EGFP(+) BM-derived cells occupied approximately 15% of the total Iba-1(+) retinal microglia. Meanwhile, the proportion of MHC class II(+) cells was larger among BM-derived (EGFP(+)/Iba-1(+)) than resident (EGFP(-)/Iba-1(+)) microglia. In the eyes with retinal detachment, EGFP(+)/F4/80(+) cells engrafted exclusively around the detached retina.
Conclusions:
In response to retinal damage, numerous BM-derived cells migrated to the retina from the ciliary body, optic nerve, and retinal vessels and differentiated into microglia. The higher rate of immunologic activation and the increased specificity to the damaged site appeared to be the characteristic features of BM-derived microglia.
Insights
Bone marrow-derived cells can become retinal microglia after injury, migrating from surrounding tissues. These cells show heightened immune activation and target damaged areas more specifically than resident microglia.
Area of Science:
- Ophthalmology
- Neuroscience
- Immunology
Background:
- Microglia are the primary immune cells of the retina.
- The origin and plasticity of retinal microglia, particularly their potential to be replenished by bone marrow-derived cells, are not fully understood.
Purpose of the Study:
- To compare the distribution and immunologic characteristics of bone marrow (BM)-derived cells versus resident microglia in the retina.
- To investigate the response of BM-derived cells to retinal injury.
Main Methods:
- Mice received enhanced green fluorescent protein-positive (EGFP(+)) bone marrow (BM) cells after irradiation.
- Eyes were analyzed for EGFP expression and microglial markers (Iba-1, F4/80, MHC class II) at various time points post-transplantation.
- Retinal damage was induced using N-methyl-N-nitrosourea (MNU) injection or retinal detachment.
Main Results:
- In uninjured eyes, BM-derived cells were mainly found in the ciliary body, choroid, and optic nerve, with few in the retina.
- Following MNU-induced injury, numerous EGFP(+) BM-derived cells infiltrated the retina, differentiating into microglia.
- BM-derived microglia exhibited higher expression of major histocompatibility complex (MHC) class II compared to resident microglia.
Conclusions:
- Bone marrow-derived cells migrate to the retina upon injury and differentiate into microglia.
- These BM-derived microglia display enhanced immune activation and site-specific engraftment, suggesting a distinct functional role in retinal repair.
