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Updated: Jul 26, 2025
Analysis of Cerebral Vasospasm in a Murine Model of Subarachnoid Hemorrhage with High Frequency Transcranial Duplex Ultrasound
Published on: June 3, 2021
Perivascular Macrophages Mediate Microvasospasms After Experimental Subarachnoid Hemorrhage
Xiangjiang Lin1,2, Igor Khalin1,2, Biyan Nathanael Harapan1,3,2
1Institute for Stroke and Dementia Research (ISD) (X.L., I.K., B.N.H., N.A.T., J.S., N.P.), Munich University Hospital, Germany.
Background:
Subarachnoid hemorrhage (SAH) is characterized by acute and delayed reductions of cerebral blood flow (CBF) caused, among others, by spasms of cerebral arteries and arterioles. Recently, the inactivation of perivascular macrophages (PVM) has been demonstrated to improve neurological outcomes after experimental SAH, but the underlying mechanisms of protection remain unclear. The aim of our exploratory study was, therefore, to investigate the role of PVM in the formation of acute microvasospasms after experimental SAH.
Methods:
PVMs were depleted in 8- to 10-week-old male C57BL/6 mice (n=8/group) by intracerebroventricular application of clodronate-loaded liposomes and compared with mice with vehicle liposome injections. Seven days later, SAH was induced by filament perforation under continuous monitoring of CBF and intracranial pressure. Results were compared with sham-operated animals and animals who underwent SAH induction but no liposome injection (n=4/group each). Six hours after SAH induction or sham surgery, numbers of microvasospasms per volume of interest and % of affected pial and penetrating arterioles were examined in 9 standardized regions of interest per animal by in vivo 2-photon microscopy. Depletion of PVMs was proven by quantification of PVMs/mm3 identified by immunohistochemical staining for CD206 and Collagen IV. Statistical significance was tested with t tests for parametric data and Mann-Whitney U test for nonparametric data.
Results:
PVMs were located around pial and intraparenchymal arterioles and were effectively depleted by clodronate from 671±28 to 46±14 PVMs/mm3 (P<0.001). After SAH, microvasospasms was observed in pial arteries and penetrating and precapillary arterioles and were accompanied by an increase to 1405±142 PVMs/mm3. PVM depletion significantly reduced the number of microvasospasms from 9 IQR 5 to 3 IQR 3 (P<0.001).
Conclusions:
Our results suggest that PVMs contribute to the formation of microvasospasms after experimental SAH.
Insights
Perivascular macrophages (PVMs) contribute to microvasospasms after subarachnoid hemorrhage (SAH). Depleting PVMs significantly reduced microvasospasms, suggesting a key role in SAH-induced vascular dysfunction.
Area of Science:
- Neuroscience
- Immunology
- Vascular Biology
Background:
- Subarachnoid hemorrhage (SAH) can cause reduced cerebral blood flow (CBF) due to cerebral artery spasms.
- Inactivating perivascular macrophages (PVMs) improves outcomes in experimental SAH, but mechanisms are unclear.
Purpose of the Study:
- To investigate the role of PVMs in the formation of acute microvasospasms following experimental SAH.
Main Methods:
- PVMs were depleted using clodronate liposomes in mice.
- SAH was induced, and microvasospasms were quantified using in vivo 2-photon microscopy.
- PVM depletion was confirmed via immunohistochemistry.
Main Results:
- PVMs were located around arterioles and effectively depleted by clodronate.
- SAH increased PVMs and caused microvasospasms in pial and penetrating arterioles.
- PVM depletion significantly reduced the number of microvasospasms post-SAH.
Conclusions:
- PVMs play a significant role in the development of microvasospasms after experimental SAH.
- Targeting PVMs may be a therapeutic strategy for managing SAH-induced vascular complications.
