Non-invasive detection of spatio-temporal activation of SBE and NFAT5 promoters in transgenic reporter mice following stroke.

The characterization of molecular responses following cerebral ischemia-induced changes in animal models capable of undergoing real-time analysis is an important goal for stroke research. In this study, we use transgenic mice to examine the activation of two different promoters in a firefly luciferase reporter mouse analyzable through a non-invasive bioluminescent imaging system. In the first model, we examine the middle cerebral artery occlusion (MCAO)-induced activation of Smad-binding elements (SBE), a downstream target of Smad 1/2/3 transcription factors, in which SBEs regulate the expression of the fluc reporter. We observed that MCAO induces a bilateral activation (i.e., both ipsilateral and contralateral brain hemispheres) of the SBE-luc reporter with a peak at 24 h. In the second model, we examined MCAO-induced activation of the osmolarity-sensitive promoter nuclear factor of activated T-cell 5 (NFAT5) and identified a peak reporter expression 72 h post-MCAO in the ipsilateral but not contralateral hemisphere. In each of these models, the assessment of post-MCAO fluc-expression provided both a quantitative measure (i.e., radiance in photons/sec/cm(2) /steradian) as well as qualitative localization of the molecular response following focal ischemic injury.