Magnetic resonance imaging of neural transplants in rat brain using a superparamagnetic contrast agent

Rat fetal brain tissue was incubated in vitro with superparamagnetic ferrite particles covalently coupled to the lectin wheat germ agglutinin (WGA) and transplanted into the adult rat striatum. At 6 days and at 3 weeks post-surgery the transplants were observed on T₁ weighted magnetic resonance (MR) images of the rat head as an area of relatively low signal intensity which could be clearly differentiated from the higher signal intensity produced by the host brain. Histological analysis revealed that the ferrite particles were largely restricted to the transplant in a patchy distribution. The ferrite particles were associated with cells having an apparent normal morphology. Superparamagnetic ferrite particles act as potent MR contrast agents and can be used to label transplanted cells. The labeled cells are apparently not adversely affected by the WGA-ferrite particles and can be monitored for at least three weeks in vivo using noninvasive MR imaging.