Current acute stroke trials and their potential impact on the therapeutic time window

Multimodal Optical Imaging to Investigate Spatiotemporal Changes in Cerebrovascular Function in AUDA Treatment of Acute Ischemic Stroke

Administration of 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA) has been demonstrated to alleviate infarction following ischemic stroke. Reportedly, the main effect of AUDA is exerting anti-inflammation and neovascularization via the inhibition of soluble epoxide hydrolase. However, the major contribution of this anti-inflammation and neovascularization effect in the acute phase of stroke is not completely elucidated. To investigate the neuroprotective effects of AUDA in acute ischemic stroke, we combined laser speckle contrast imaging and optical intrinsic signal imaging techniques with the implantation of a lab-designed cranial window. Forepaw stimulation was applied to assess the functional changes via measuring cerebral metabolic rate of oxygen (CMRO₂) that accompany neural activity. The rats that received AUDA in the acute phase of photothrombotic ischemia stroke showed a 30.5 ± 8.1% reduction in the ischemic core, 42.3 ± 15.1% reduction in the ischemic penumbra (p < 0.05), and 42.1 ± 4.6% increase of CMRO₂ in response to forepaw stimulation at post-stroke day 1 (p < 0.05) compared with the control group (N = 10 for each group). Moreover, at post-stroke day 3, increased functional vascular density was observed in AUDA-treated rats (35.9 ± 1.9% higher than that in the control group, p < 0.05). At post-stroke day 7, a 105.4% ± 16.4% increase of astrocytes (p < 0.01), 30.0 ± 10.9% increase of neurons (p < 0.01), and 65.5 ± 15.0% decrease of microglia (p < 0.01) were observed in the penumbra region in AUDA-treated rats (N = 5 for each group). These results suggested that AUDA affects the anti-inflammation at the beginning of ischemic injury and restores neuronal metabolic rate of O₂ and tissue viability. The neovascularization triggered by AUDA restored CBF and may contribute to ischemic infarction reduction at post-stroke day 3. Moreover, for long-term neuroprotection, astrocytes in the penumbra region may play an important role in protecting neurons from apoptotic injury.

Tissue Concentration of Dodecafluoropentane (DDFP) Following Repeated IV Administration in the New Zealand White Rabbit

IV injection of dodecafluoropentane emulsion (DDFPe) increases oxygen transportation and reduces brain infarct volume in a rabbit stroke model. Tissue distribution of the parent perfluorocarbon dodecafluoropentane (DDFP) is unknown but is critical to understanding the mechanism by which DDFPe is effective in treating ischemia and for determining safe dosing. Previous studies showed a DDFP blood half-life of <2 min yet therapeutic effects lasted >90 min after injection. We describe DDFP distribution in brain, kidney, liver, spleen, and lung following nine dosing regimens in New Zealand White (NZW) rabbits. Single and multi-dose schedules were administered to NZW rabbits (n = 27). A single DDFPe dose (0.6 ml/kg) group was sacrificed 2 min after dosing and eight multi-dose groups (4 doses of 0.3 or 0.6 ml/kg and 15 doses of 0.1, 0.3, or 0.6) were sacrificed 90 min after final injections. Tissues were flash frozen and analyzed with headspace sampling/GC-MS. DDFP brain concentration increased with increasing dose in the 15 dose groups (4.70, 8.34, and 14.3 μg/g) and indicative of linear pharmacokinetics within this dose range. The DDFP lung concentration was not reflective of increasing dose or dose frequency. The total clearance of DDFP was consistent with previous reports showing 98% of DDFP is cleared within 2 h of administration.

Therapeutic imaging window of cerebral infarction revealed by multisequence magnetic resonance imaging: An animal and clinical study

In this study, we established a Wistar rat model of right middle cerebral artery occlusion and observed pathological imaging changes (T2-weighted imaging [T₂WI], T₂FLAIR, and diffusion-weighted imaging [DWI]) following cerebral infarction. The pathological changes were divided into three phases: early cerebral infarction, middle cerebral infarction, and late cerebral infarction. In the early cerebral infarction phase (less than 2 hours post-infarction), there was evidence of intracellular edema, which improved after reperfusion. This improvement was defined as the ischemic penumbra. In this phase, a high DWI signal and a low apparent diffusion coefficient were observed in the right basal ganglia region. By contrast, there were no abnormal T₂WI and T₂FLAIR signals. For the middle cerebral infarction phase (2–4 hours post-infarction), a mixed edema was observed. After reperfusion, there was a mild improvement in cell edema, while the angioedema became more serious. A high DWI signal and a low apparent diffusion coefficient signal were observed, and some rats showed high T₂WI and T₂FLAIR signals. For the late cerebral infarction phase (4–6 hours post-infarction), significant angioedema was visible in the infarction site. After reperfusion, there was a significant increase in angioedema, while there was evidence of hemorrhage and necrosis. A mixed signal was observed on DWI, while a high apparent diffusion coefficient signal, a high T₂WI signal, and a high T₂FLAIR signal were also observed. All 86 cerebral infarction patients were subjected to T₂WI, T₂FLAIR, and DWI. MRI results of clinic data similar to the early infarction phase of animal experiments were found in 51 patients, for which 10 patients (10/51) had an onset time greater than 6 hours. A total of 35 patients had MRI results similar to the middle and late infarction phase of animal experiments, of which eight patients (8/35) had an onset time less than 6 hours. These data suggest that defining the “therapeutic time window” as the time 6 hours after infarction may not be suitable for all patients. Integrated application of MRI sequences including T₂WI, T₂FLAIR, DW-MRI, and apparent diffusion coefficient mapping should be used to examine the ischemic penumbra, which may provide valuable information for identifying the “therapeutic time window”.