A murine photothrombotic stroke model with an increased fibrin content and improved responses to tPA-lytic treatment

Abstract

The Rose Bengal (RB) dye-based photothrombotic stroke (PTS) model has many methodological advantages including consistent location and size of infarct, low mortality, and relatively simple surgical procedures. However, the standard PTS has the caveat of poor responses to tissue-type plasminogen activator (tPA)–mediated lytic treatment, likely as a result of the platelet-rich, fibrin-poor content of the blood clots. Here we tested whether the admixture of thrombin (80 U/kg) and RB dye (50 mg/kg) in the proximal middle cerebral artery (MCA)–targeted PTS will modify the clot composition and elevate the responsiveness to tPA-lytic treatment (Alteplase, 10 mg/kg). Indeed, intravital imaging, immunostaining, and immunoblot analyses showed less-compacted platelet aggregates with a higher fibrin content in the modified thrombin (T) plus RB photothrombotic stroke (T+RB-PTS) model compared with the standard RB-PTS-induced clots. Both RB-PTS and T+RB-PTS showed steady recovery of cerebral blood flow (CBF) in the ischemic border from 1 day after infarction, but without recanalization of the proximal MCA branch. Intravital imaging showed high potency of restoring the blood flow by tPA after single vessel-targeted T+RB-PTS. Further, although intravenous tPA failed to restore CBF or attenuate infarction in RB-PTS, it conferred 25% recovery of CBF and 55% reduction of the infarct size in T+RB-PTS (P < .05) if tPA was administered within 2 hours postphotoactivation. These results suggest that T+RB-PTS produces mixed platelet:fibrin clots closer to the clinical thrombus composition and enhanced the sensitivity to tPA-lytic treatment. As such, the modified photothrombosis may be a useful tool to develop more effective thrombolytic therapies of cerebral ischemia.

Metabolome Changes in Cerebral Ischemia

“…In the case of mouse strains, C57B1/6 mice are reported to generate relatively larger infarcts compared with Sv129 mice [ 107 ]. Animal models of cerebral ischemia include the intraluminal filament MCAo, direct MCA ligation by a subtemporal craniectomy approach, photothrombosis, endothelin-1, and the embolic stroke model [ 103 , 108 , 109 , 110 ]. Among these, the rodent intraluminal filament MCAo model is the most commonly used because of the high similarity with human cerebral ischemia, exhibits a penumbra, is highly reproducible, has a highly controllable reperfusion, and does not require craniectomy [ 103 ].…”

Nebulization of Low-Dose S-Nitrosoglutathione in Diabetic Stroke Enhances Benefits of Reperfusion and Prevents Post-Thrombolysis Hemorrhage

“…Modified PT-stroke model which produces fibrin-rich clot was adopted from elsewhere [ 18 ], but with significant modifications such as lateral-side surgical approach without craniotomy, laser-beam source, and route of injection. Briefly, mice were anesthetized with isoflurane (1.5–2% mixed with room air) using a low-flow gas anesthesia system (Somnosuite, Kent Scientific, Torrington, CT, USA).…”

Animal models of stroke

“…The modified photothrombosis is rose bengal plus thrombin, which can produce mixed platelet:fibrin clots and enhance the sensitivity to rt‐PA treatment. 157 In addition, it has been proven that some details of the procedure can be refined, such as the application route of the photosensitive dye, illumination, and stereotactic parameters. 158 Using noncoherent visible light instead of a laser beam also leads to ischemic brain damage, but at the same time, it reduces laser‐mediated thermal tissue damage and the cost of the procedure.…”