CORRELATION OF DIFFUSION MRI AND HEAT-SHOCK-PROTEIN IN A RAT EMBOLIC STROKE MODEL

The expression of 70 kDa heat shock protein (HSP-70) in focal ischemia occurs in regions that sustain sub-lethal ischemic injury, and may th erefore be considered as a biological marker of the ischemic penumbra. In a rat embolic stroke model, using fibrin-rich emboli, we correlate d the expression of HSP-70 mRNA with diffusion magnetic resonance imag ing (MRI) to determine if HSP-70 mRNA expression was associated with a lterations in the apparent diffusion coefficient (ADC) of brain tissue water, a putative early marker of cytotoxic injury that is readily me asured in vivo. Serial ADC measurements were made for 120 min followin g embolic infarction in the right carotid artery territory. HSP-70 mRN A expression was observed at the boundaries of the densely ischemic zo ne, as judged by diffusion imaging. ADC values observed in HSP-70 mRNA -positive regions were intermediate between those observed in the isch emic core or in control regions. In addition, the volume of HSP-70 mRN A-positive tissue correlated positively with the volume of tissue show ing intermediate ADC values at 120 min. These findings suggest that in termediate ADC values occur in penumbral regions. Heterogeneity of isc hemic cellular injury is suggested as the basis for the intermediate A DC values observed in these regions. (C) 1997 Elsevier Science B.V.