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Water ADC, extracellular space volume, and tortuosity in the rat cortex after traumatic injury.
Vorisek I, Hajek M, Tintera J, Nicolay K, Sykova E.
Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague, Czech Republic.
The diffusion parameters in rat cortex were studied 3-35 days following
a cortical stab wound, using diffusion-weighted MR to determine the apparent
diffusion coefficient of water (ADC(W)) in the tissue, and the real-time
iontophoretic tetramethylammonium (TMA) method to measure the extracellular
space (ECS) diffusion parameters: ECS volume fraction alpha and the ADC
of TMA(+) (ADC(TMA)). Severe astrogliosis was found close to the wound,
and mild astrogliosis was found in the ipsilateral but not the contralateral
cortex. Chondroitin sulfate proteoglycan (CSPG) expression was increased
throughout the ipsilateral cortex. In the hemisphere contralateral to the
wound, alpha, ADC(TMA), and ADC(W) were not significantly different from
control values. ECS volume fraction was increased only in the vicinity
of the wound, in the region of cell death and severe astrogliosis, at 3
and 7 days after injury. However, both ADC(TMA) and ADC(W) were significantly
decreased after lesion in the vicinity of the wound as well as in the rest
of the ipsilateral hemisphere distant from the wound. Thus, both ADC(W)
and ADC(TMA) decreased in regions wherein alpha did not change but CSPG
increased. An increase in extracellular matrix expression may therefore
impose diffusion barriers for water as well as for TMA molecules.
