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Updated: May 24, 2026
Microglia as a Surrogate Biosensor to Determine Nanoparticle Neurotoxicity
Published on: October 25, 2016
Microglial cell activation is a source of metalloproteinase generation during hemorrhagic transformation
Gregory J del Zoppo1, Harald Frankowski, Yu-Huan Gu
1Division of Hematology, Department of Medicine, University of Washington School of Medicine, Seattle, WA 98104, USA. grgdlzop@u.washington.edu
Abstract:
Hemorrhage and edema accompany evolving brain tissue injury after ischemic stroke. In patients, these events have been associated with metalloproteinase (MMP)-9 in plasma. Both the causes and cellular sources of MMP-9 generation in this setting have not been defined. MMP-2 and MMP-9 in nonhuman primate tissue in regions of plasma leakage, and primary murine microglia and astrocytes, were assayed by immunocytochemistry, zymography, and real-time RT-PCR. Ischemia-related hemorrhage was associated with microglial activation in vivo, and with the leakage of plasma fibronectin and vitronectin into the surrounding tissue. In strict serum-depleted primary cultures, by zymography, pro-MMP-9 was generated by primary murine microglia when exposed to vitronectin and fibronectin. Protease secretion was enhanced by experimental ischemia (oxygen-glucose deprivation, OGD). Primary astrocytes, on each matrix, generated only pro-MMP-2, which decreased during OGD. Microglia-astrocyte contact enhanced pro-MMP-9 generation in a cell density-dependent manner under normoxia and OGD. Compatible with observations in a high quality model of focal cerebral ischemia, microglia, but not astrocytes, respond to vitronectin and fibronectin, found when plasma extravasates into the injured region. Astrocytes alone do not generate pro-MMP-9. These events explain the appearance of MMP-9 antigen in association with ischemia-induced cerebral hemorrhage and edema.
Insights
Metalloproteinase-9 (MMP-9) in ischemic stroke is generated by microglia when exposed to plasma proteins like vitronectin and fibronectin, especially during oxygen-glucose deprivation.
Area of Science:
- Neuroscience
- Biochemistry
- Cell Biology
Background:
- Hemorrhage and edema are common in ischemic stroke, linked to metalloproteinase-9 (MMP-9) in patient plasma.
- The cellular origins and triggers of MMP-9 in this context remain unclear.
Purpose of the Study:
- To investigate the cellular sources and regulation of MMP-9 and MMP-2 during ischemic stroke.
- To elucidate the role of plasma proteins and glial cells in MMP generation post-ischemia.
Main Methods:
- Immunocytochemistry, zymography, and real-time RT-PCR were used on nonhuman primate tissue and primary murine microglia and astrocytes.
- Cells were exposed to plasma proteins (vitronectin, fibronectin) and subjected to oxygen-glucose deprivation (OGD) to model ischemia.
Main Results:
- Microglia, but not astrocytes, produced pro-MMP-9 when exposed to vitronectin and fibronectin.
- Ischemia (OGD) enhanced microglial pro-MMP-9 secretion.
- Microglia-astrocyte co-culture increased pro-MMP-9 generation in a cell-density-dependent manner.
- Astrocytes primarily produced pro-MMP-2, with levels decreasing during OGD.
Conclusions:
- Microglia are the primary source of MMP-9 in response to plasma extravasation into ischemic brain tissue.
- Plasma proteins and cellular interactions significantly influence MMP-9 production during ischemic events.
- These findings explain MMP-9's presence during ischemia-induced cerebral hemorrhage and edema.
