gms | German Medical Science

Objective: Cranial intraparenchymal hemorrhage (ICH) represents a potential fatal disease that imposes significant risks for patients. The pivotal role of blood coagulation factor IIa (thrombin) for the pathogenesis, as for the reconstitution in the wake of ICH, has been variously proven. Recently there has been increasing evidence for the existence of a cerebral thrombin system besides the hepatocellular thrombin formation. It is the aim of this study to clarify the influence of a putative cerebral thrombin formation in the pathogenesis and reconstitution after ICH using wild type and specific thrombin knockout mice.

Method: We established a stereotaxic ICH model in mice injecting 30 µl of either whole blood drawn from the tail vein or a volume substitute (silicone oil; coordinate: AP= +1 mm; ML= 2 mm; DV= -3 mm). The mice are either wild type (C57B/6N) or have a specific systemic thrombin knockout. Animals were euthanized after 24 hours. Paraffin sections were stained with hematoxylin and eosin to evaluate clot size and cellular damage. Immunohistochemistry was used to detect thrombin, its receptors and inactive precursor pro-thrombin. Intracranial pressure (ICP) was measured using an intraventricular catheter; cerebral blood flow (CBF) was detected using a Laser-Doppler probe.

Results: We describe a reliable intracranial hemorrhage model using either autologous blood or silicone oil as a blood replacement. We are able to demonstrate a stable and reproducible lesion formation within the striatum with either blood or silicone oil (n= 30). Both intracerebral masses induce comparable ICP elevation and CBF decrease. We detect a perilesional thrombin activation in response to blood as wells as silicon oil, i.e. in the absence of whole blood constituents.

Conclusions: The pathogenesis of ICH is still not fully understood. We present a new ICH model in mice and provide first insights into the involvement of the cerebral thrombin system in the pathogenesis of ICH. The model allows an easy and reproducible analysis of pathophysiological intracranial processes during and in the course of ICH. The establishment of an ICH model in mice provides the ability to integrate sophisticated gene knockout models. Preliminary data indicate that perilesional thrombin activation is visible in both lesion types. The activation of the intracerebral thrombin system is independent of the presence of whole blood and inducible through a mass effect caused by a volume substance.