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Published on: July 23, 2012
Transient expression of osteopontin mRNA and protein in amoeboid microglia in developing rat brain
Jeong-Sun Choi1, Jung-Ho Cha, Hyun-Jung Park
1Department of Anatomy, College of Medicine, The Catholic University of Korea, 505 Banpo-dong, Socho-gu, 137-701 Seoul, Korea.
Abstract:
To investigate a potential role of osteopontin (OPN) in developing rat brain, the expression of OPN mRNA and protein in the developing rat brain relative to the distribution of brain macrophages was investigated using in situ hybridization and immunohistochemistry, and the phagocytic capability of OPN-expressing cells was accessed using rhodamine isothiocyanate (RhIc) as a tracer. OPN-expressing cells appeared from embryonic day 16. During the first week of postnatal life, OPN-labeled cells increased markedly, and peaked around P7, then declined and had completely disappeared by the end of the second postnatal week. The spatiotemporal distribution pattern of OPN mRNA closely matched that of OPN protein. Their morphology and localization were compared with those of cells expressing the established microglial marker OX-42 in adjacent sections, and double-labeling studies demonstrated that OPN was localized to the amoeboid microglia which stain with the lectin GSI-B4, another marker for microglia. Furthermore, OPN-labeled cells were confirmed to be active phagocytes emitting RhIc fluorescence indicating that the tracer into the brain tissues was engulfed by phagocytosis. Therefore, these results provide the first evidence that OPN is transiently expressed in active brain macrophages in the embryonic and early postnatal brain, and suggest that OPN may contribute to the migration and phagocytic function of brain macrophages in the developing brain.
Insights
Osteopontin (OPN) is transiently expressed in active brain macrophages during early rat brain development. This suggests OPN plays a role in the migration and phagocytic functions of these crucial immune cells.
Area of Science:
- Neuroscience
- Immunology
- Developmental Biology
Background:
- Osteopontin (OPN) is a cytokine implicated in various biological processes.
- The role of OPN in the developing brain, particularly in relation to immune cells, remains largely unexplored.
Purpose of the Study:
- To investigate the expression and function of osteopontin (OPN) in the developing rat brain.
- To determine if OPN is associated with brain macrophages and their phagocytic activity.
Main Methods:
- In situ hybridization and immunohistochemistry were used to examine OPN mRNA and protein expression.
- Rhodamine isothiocyanate (RhIc) tracer was employed to assess phagocytic capability.
- Double-labeling studies identified OPN-expressing cells in relation to microglial markers (OX-42, GSI-B4).
Main Results:
- OPN expression was detected in brain macrophages starting from embryonic day 16, peaking in the first postnatal week, and disappearing by the second postnatal week.
- OPN-expressing cells were identified as amoeboid microglia, known for their phagocytic activity.
- OPN-labeled cells actively engulfed the RhIc tracer, confirming their phagocytic function.
Conclusions:
- Osteopontin (OPN) is transiently expressed in active brain macrophages during embryonic and early postnatal development.
- OPN may play a significant role in the migration and phagocytic functions of brain macrophages in the developing brain.
