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Clearing the fog: Changes in T2 relaxation time after stroke reflect clearing processes

100%

Kranz A., Deten A., Haertig W., Boltze J., Wagner D. C.

Acta Neurobiologiae Experimentalis

2013

tom 73

nr 1

CT and MR imaging techniques are frequently used for the diagnosis and progress monitoring of ischemic stroke in clinical practice and research. After stroke, both methods are characterized by a transient pseudo-normalized imaging signal, the so-called fogging phenomenon. This study evaluates potential pathophysiological changes associated with fogging, as well as its influence on the correct determination of the ischemic lesion in a rat stroke model. Male spontaneously hypertensive rats were subjected to permanent middle cerebral artery occlusion. Ischemic lesion volume, brain edema and grey scale value spread within the ischemic lesion were determined on T2-weighted MR sequences at days 1, 4, 8, 11 and 29 after stroke onset, and compared with immunohistochemistry for astrogliosis, microglia/macrophage infiltration and angiogenesis. All animals showed MR fogging at days 4, 8 and 11 after stroke. The transient normalization of T2 signals occurred independently from the development of infarct volumes, but coincided well with the spatio-temporal occurrence of necrosis, angiogenesis and microglia/macrophage infiltration. Our results suggest that the fogging effect reflects the clearance of necrotic tissue within the ischemic lesion and is thus not relevant for the determination of the lesion volume.

Object-based analysis of astroglial reaction and astrocyte subtype morphology after ischemic brain injury

86%

Wagner D.-C., Scheibe J., Glocke I., Weise G., Deten A., Boltze J., Kranz A.

Acta Neurobiologiae Experimentalis

2013

tom 73

nr 1

The astrocytic response to ischemic brain injury is characterized by specific alterations of glial cell morphology and function. Various studies described both beneficial and detrimental aspects of activated astrocytes, suggesting the existence of different subtypes. We investigated this issue using a novel object-based approach to study characteristics of astrogliosis after stroke. Spontaneously hypertensive rats received permanent middle cerebral artery occlusion. After 96 h, brain specimens were removed, fixed and stained for GFAP, glutaminę synthetase (GS), S100P and Musashil (Mshl). Three regions of interest were defined (contralateral hemisphere, ipsilateral remote zone and infarct border zone), and confocal stacks were acquired (n=5 biological with each n=4 technical replicates). The stacks were background-corrected and colocalization between the selected markers and GFAP was determined using an automated thresholding algorithm. The fluorescence and colocalization channels were then converted into 3D-objects using both intensity and volume as filters to ultimately determine the final volumes of marker expression and colocalization, as well as the morphological changes of astrocyte process arborisation. We found that both S100P and Mshl determined the same GFAP-positive astroglial cell population albeit the cellular compartments differed. GFAP stained most of the astrocyte processes and is hence suitable for the analysis of qualitative characteristics of astrogliosis. Due to its peri-nuclear localization, Mshl is appropriate to estimate the total number of astrocytes even in regions with severe reactive astrogliosis. GS expression in GFAP-positive astrocytes was high in the remote zone and low at the infarct border, indicating the existence of astrocyte subclasses.

Ograniczanie wyników

2 Acta Neurobiologiae Experimentalis

2 Boltze J.

2 Deten A.

2 Kranz A.

1 Glocke I.

1 Haertig W.

1 Scheibe J.

1 Wagner D. C.

1 Wagner D.-C.

1 Weise G.

2 2013

Wyniki wyszukiwania

Clearing the fog: Changes in T2 relaxation time after stroke reflect clearing processes

Object-based analysis of astroglial reaction and astrocyte subtype morphology after ischemic brain injury