gms | German Medical Science

Objective: Cranial intraparenchymal hemorrhage (ICH) is a potentially fatal disease that imposes significant risks for patients. A pivotal role of blood coagulation factor IIa (thrombin) is assumed for the pathogenesis, as for the reconstitution in the wake of ICH. There is increasing evidence for the existence of a cerebral thrombin system besides the hepatocellular thrombin formation. It is the aim of this study to clarify its influence on the pathogenesis and reconstitution after ICH in a mouse model.

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). Peri-procedural monitoring included intracranial pressure (ICP) via a parenchymal probe, cerebral blood flow (CBF) via a Laser-Doppler probe and blood pressure(BP) using a tail cuff monitor. The mice (C57B/6N) were euthanized 24 hours after ICH. Frozen sections were stained with hematoxylin and eosin to evaluate clot size and cellular damage. Immunohistochemistry was used to detect the precursor prothrombin and its derivative thrombin. In addition slices were stained for NeuN, GFAP and IBA-1 to evaluate parenchymal damage and inflammatory reactions.

Results: We describe a reliable intracranial hemorrhage model using either autologous blood or silicone oil as a blood replacement. The courses of ICP, CBF and BP are similar in both groups (n= 5/group). We are able to demonstrate a stable and reproducible lesion formation within the striatum with either blood or silicone oil (n= 10/ group). A marked neuronal loss is visible in both lesion types and decrease similarly in the periphery. There was no GFAP or IBA-1 alteration compared to the sham group (n=10/ group) animals after 24h. We detect a perilesional thrombin activation in response to blood as well as silicon oil, i.e. in the absence of whole blood constituents.

Conclusions: The pathogenesis of ICH is still not fully understood. We previously presented an ICH mouse model at the DGNC meeting 2015, which allows an easy and reproducible analysis of pathophysiological intracranial processes during ICH. We observe a similar neuronal loss in the absence of whole blood with no observable GFAP or IBA-1 elevation after 24h. The findings indicate that the damage after ICH probably depends on the activation of the local cerebral thrombin system rather than the influx of coagulation factors.