Purchase this article with an account.
J. D. Lindsey, C. K. Leung, M. Scadeng, D.-U. Bartsch, R. N. Weinreb; Longitudinal Confirmation of Retinal Ganglion Cell Preservation Following Manganese-Enhanced MRI Imaging of the Optic Nerve. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3290.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Observation of the central visual pathway by magnetic resonance imaging (MRI) can be enhanced following intraocular injection of manganese. In addition, expression of Thy-1 by retinal ganglion cells (RGCs) down-regulates following optic nerve injury but prior to RGC death. The present study evaluated preservation of Thy-1 expression following intraocular injection of manganese (Mn) doses sufficient for enhanced MRI imaging of the retina and optic nerve.
Fluorescent ganglion cell layer neurons of transgenic mice expressing cyan fluorescent protein under control of the Thy-1 promoter (Thy1-CFP) were imaged with a blue-light confocal scanning laser ophthalmoscope (bCSLO, modified Heidelberg HRA1 with 460 nM excitation and 490 nm detection). These animals next received 1-ul intraocular injection of 40 or 160 mM MnCl2 and subsequently were imaged under isoflurane in a 7-Tesla magnetic resonance imager. One week after the Mn injection, the fluorescent ganglion cell layer neurons were re-imaged using the bCSLO. A retinal region in which fluorescent cells were in focus in both the first and the second session images was delimited and the fluorescent cells within this region in both images were counted. The ratio of the cell count after Mn treatment to the cell count before treatment was calculated.
Retinal images obtained with thebCSLO showed bright spots corresponding to fluorescent ganglion cell layer neurons as well as bright streaks radiating from the optic nerve head corresponding to nerve fiber layer axon bundles. Enhancement of optic nerve image intensity was reproducibly detected in mice that received 160 mM manganese injections. Survival ratios comparing cell counts after Mn injection to cell counts before injection were as follows: for mice receiving 40 mM Mn, 1.06 +/- 0.09 (SD, n=3, P=0.33 2-tailed paired t-test); for mice receiving 160 mM Mn, 0.99 +/- 0.04 (n=3, P= 1.0).
There was insignificant loss of fluorescent ganglion cell layer neurons in mice that received either 40 or 160 mM Mn intraocular injection. These observations demonstrate the utility of using bCSLO examination to longitudinally assess CFP expression within Thy1-CFP mouse ganglion cell layer neurons in vivo. As prior studies indicate that Mn movement in the optic nerve is mediated by fast axonal transport, the present results also support the use of Mn-enhanced MRI to assess the integrity of the optic nerve in vivo.
This PDF is available to Subscribers Only