Cell Tracking to Assess the Efficacy of Cellbased Therapies

Relax Your Mind

Relaxation Techniques

Get Instant Access

Two factors contribute to the attractiveness of using MRI techniques for cell tracking studies: (1) the high temporospatial resolution provided by MRI and (2) the potentially high payloads of labels that can be achieved for a cell without affecting its vital functions (see Chapter 25 for more details). This overcomes in part the inherent sensitivity issues associated with MRI. Cell trafficking studies can be applied to qualitatively monitor the migration of cells within the intact organism. This has been discussed in the previous section with regard to the evaluation of stem cell therapies in stroke. Alternatively, quantitative assessments are feasible by either measuring the volume occupied by the labeled cells [82] or by estimating local cell densities via quantitative analyses of relaxation effects.

2 4 6 8 10 12 Days following permanent MCA occlusion

FIGURE 8.6 Functional recovery in cytoprotected cortex in rat permanent MCA occlusion model. Treatment with the Ca2 + antagonist isradipine spared the ipsilateral somatosensory cortex from becoming infarcted. Functional integrity was probed using electrical stimulation of the contralateral forepaw. The fMRI response in the cortical S1 area was analyzed at days 2, 5, and 12 following infarction. Signals from individual rats receiving isradipine (filled symbols) or vehicle (open symbols) are shown. The dashed line with error bars (standard deviation) represents the response measured on the contralateral intact hemisphere when stimulating the forepaw ipsilateral to the MCA occlusion site. Only a fraction of the animals displayed recovery of functionality in the cytoprotected area despite the fact that structural imaging revealed morphological integrity. (Adapted from Sauter, A. et al., Magn. Reson. Med., 47, 759, 2002.)

2 4 6 8 10 12 Days following permanent MCA occlusion

FIGURE 8.6 Functional recovery in cytoprotected cortex in rat permanent MCA occlusion model. Treatment with the Ca2 + antagonist isradipine spared the ipsilateral somatosensory cortex from becoming infarcted. Functional integrity was probed using electrical stimulation of the contralateral forepaw. The fMRI response in the cortical S1 area was analyzed at days 2, 5, and 12 following infarction. Signals from individual rats receiving isradipine (filled symbols) or vehicle (open symbols) are shown. The dashed line with error bars (standard deviation) represents the response measured on the contralateral intact hemisphere when stimulating the forepaw ipsilateral to the MCA occlusion site. Only a fraction of the animals displayed recovery of functionality in the cytoprotected area despite the fact that structural imaging revealed morphological integrity. (Adapted from Sauter, A. et al., Magn. Reson. Med., 47, 759, 2002.)

The concentration of contrast agents can be estimated based on their effects on tissue relaxation rates according to

fiTi o Ti with Tt and Tto (i = 1,2) being the tissue relaxation times measured prior to and after administration of the contrast agent, while r, is the molar relaxivity of the contrast agent. The same approach can be extended in a straightforward manner to estimate local concentration of magnetically labeled cells [83], provided the corresponding r{ value for the chosen labeling conditions is known. Even if this is not the case, accurate measurement of relaxation times would allow one to estimate relative cell concentrations, which might be sufficient for drug studies.

Was this article helpful?

0 0
Relaxation Audio Sounds Relaxation

Relaxation Audio Sounds Relaxation

This is an audio all about guiding you to relaxation. This is a Relaxation Audio Sounds with sounds called Relaxation.

Get My Free MP3 Audio


Post a comment