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Updated: Jun 27, 2026
Intravital Imaging of Axonal Interactions with Microglia and Macrophages in a Mouse Dorsal Column Crush Injury
Published on: November 23, 2014
Peripheral formalin injection induces unique spinal cord microglial phenotypic changes
Kai-Yuan Fu1, Yong-Hui Tan, Backil Sung
1Center for TMD & Orofacial Pain, Peking University School & Hospital of Stomatology, Beijing 100081, People's Republic of China. kqkyfu@bjmu.edu.cn
Insights
Peripheral tissue injury activates brain microglia. Formalin injection in rats showed specific upregulation of leukocyte common antigen (CD45) and MHC class I on activated microglia, indicating distinct phenotypic changes.
Area of Science:
- Neuroimmunology
- Cellular Biology
- Immunology
Background:
- Microglia are the primary immune cells residing in the central nervous system.
- Peripheral tissue injury is known to trigger microglial activation.
- Understanding microglial responses is crucial for neuroinflammatory research.
Purpose of the Study:
- To investigate microglial surface immunomolecule expression in the spinal cord after peripheral formalin injection.
- To identify phenotypic changes in microglia following acute tissue injury.
Main Methods:
- Rats received formalin injections in their hind paws.
- Spinal cord tissue was analyzed for microglial surface markers.
- Immunohistochemistry and flow cytometry were employed to assess marker expression.
Main Results:
- Leukocyte common antigen (CD45) and MHC class I antigen showed significant upregulation on activated microglia.
- Peak expression of CD45 and MHC class I was observed on day 7 post-injection.
- MHC class II antigen, CD11c, and Fc receptor expression remained low and unchanged.
Conclusions:
- Peripheral formalin injection induces specific phenotypic alterations in microglia.
- Upregulation of CD45 and MHC class I represents a distinct microglial response to peripheral injury.
- These findings highlight a unique pattern of central nervous system changes following peripheral tissue damage.
Abstract:
Microglia are resident immune cells of brain and activated by peripheral tissue injury. In the present study, we investigated the possible induction of several microglial surface immunomolecules in the spinal cord, including leukocyte common antigen (LCA/CD45), MHC class I antigen, MHC class II antigen, Fc receptor, and CD11c following formalin injection into the rat's hind paw. CD45 and MHC class I were upregulated in the activated microglia, which was evident on day 3 with the peak expression on day 7 following peripheral formalin injection. There was a very low basal expression of MHC class II, CD11c, and the Fc receptor, which did not change after the formalin injection. These results, for the first time, indicate that peripheral formalin injection can induce phenotypic changes of microglia with distinct upregulation of CD45 and MHC class I antigen. The data suggest that phenotypic changes of the activated microglia may be a unique pattern of central changes following peripheral tissue injury.
