An external magnetic field produced a predominantly astrocytic response in mice, targeting the cells that support neuronal function
An external magnetic field produced a predominantly astrocytic response in mice, targeting the cells that support neuronal function
On August 19, the authors reported a mouse experiment in a preprint. They injected magnetite nanodiscs into the dentate gyrus of the hippocampus. These magnetic particles carried an antibody that binds to the astrocyte membrane. At field strengths of 25, 28 and 50 mT, the response measured by intracellular calcium was statistically greater than the response to hematite particles of the same shape and with a weak magnetic response.
Conventional stimulation affects a region of tissue containing several cell types. In this approach, the particle determines which cells are targeted. Its antibody binds to GLAST, a protein on the astrocyte surface, while an external coil generates an alternating magnetic field. The magnetite disc experiences torque. The authors propose that this torque deforms the membrane and opens mechanosensitive channels, which are proteins that allow ions to pass through the membrane when it is deformed.
The researchers monitored calcium signals using fiber photometry. An implanted optical fiber detected fluorescence from a previously introduced calcium-sensitive reporter protein. The field provided the external stimulus, while the optical fiber was used for measurement. Between the second and fifth weeks after a single injection, magnetite discs produced a greater astrocytic response than the hematite control. In mice expressing the reporter in neurons, the authors found no difference between the two materials. These comparisons support the conclusion that the response under the experimental conditions occurred predominantly in astrocytes.
This approach builds on two earlier developments. In 2022, researchers had already targeted astrocytes with antibody-functionalized magnetic particles, but they moved the particles using a strong field gradient produced at the edge of an MRI scanner or by a dedicated permanent magnet array. In 2025, a group that included Po-Han Chang, one of the authors of the current preprint, described an open coil for generating weak alternating fields. Magnetite nanodiscs connected these two lines of work because they experience torque in a uniform field of 25–28 mT.
Three studies in Science linked astrocytic calcium signals to transitions between functional states in neuronal networks. Briefly inducing such a signal in selected cells makes it possible to test whether the signal changes neuronal network activity.