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Combination of Mn 2+ ‐enhanced and diffusion tensor MR imaging gives complementary information about injury and regeneration in the adult rat optic nerve
Author(s) -
Thuen Marte,
Olsen Øystein,
Berry Martin,
Pedersen Tina Bugge,
Kristoffersen Anders,
Haraldseth Olav,
Sandvig Axel,
Brekken Christian
Publication year - 2009
Publication title -
journal of magnetic resonance imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.563
H-Index - 160
eISSN - 1522-2586
pISSN - 1053-1807
DOI - 10.1002/jmri.21606
Subject(s) - retina , diffusion mri , fractional anisotropy , optic nerve , axoplasmic transport , medicine , retinal ganglion cell , retinal , anatomy , magnetic resonance imaging , ophthalmology , chemistry , neuroscience , biology , radiology
Abstract Purpose To evaluate manganese (Mn 2+ )‐enhanced MRI (MEMRI) and diffusion tensor imaging (DTI) as tools for detection of axonal injury and regeneration after intravitreal peripheral nerve graft (PNG) implantation in the rat optic nerve (ON). Materials and Methods In adult Fischer rats, retinal ganglion cell (RGC) survival was evaluated in Flurogold (FG) back‐filled retinal whole mounts after ON crush (ONC), intravitreal PNG, and intravitreal MnCl 2 injection (150 nmol) at 0 and 20 days post lesion (dpl). MEMRI and echo‐planar DTI (DTI‐EPI) was obtained of noninjured ON one day after intravitreal MnCl 2 injection, and at 1 and 21 dpl after ONC, intravitreal PNG, and intravitreal MnCl 2 injections given at 0 and 20 dpl. GAP‐43 immunohistochemistry was performed after the last MRI. Results ONC reduced RGC density in retina by 94% at 21 dpl compared to noninjured ON without MnCl 2 injections. Both intravitreal PNG and intravitreal MnCl 2 injections improved RGC survival in retina, which was reduced by 90% (ONC+MnCl 2 ), 82% (ONC+PNG), and 74% (ONC+PNG+MnCl 2 ) compared to noninjured ON. DTI‐derived parameters (fractional anisotropy [FA], mean diffusivity, axial diffusivity λ ∥ , and radial diffusivity λ ⟂ ) were unaffected by the presence of Mn 2+ in the ON. At 1 dpl, CNR MEMRI and λ ∥ were reduced at the injury site, while at 21 dpl they were increased at the injury site compared to values measured at 1 dpl. GAP‐43 immunoreactive axons were present in the ON distal to the ONC injury site. Conclusion MEMRI and DTI enabled detection of functional and structural degradation after rat ON injury, and there was correlation between the MRI‐derived and immunohistochemical measures of axon regeneration. J. Magn. Reson. Imaging 2009;29:39–51. © 2008 Wiley‐Liss, Inc.