Experimental Laboratory of Translational Neuroscience and Otolaryngology, Faculty of Medicine and Health Sciences, University of Antwerp, Wilrijk, Belgium.
Bio-Imaging Lab, Faculty of Pharmaceutical, Biomedical and Veterinary Sciences, University of Antwerp, Wilrijk, Belgium.
Epilepsia. 2017 Sep;58(9):1615-1625. doi: 10.1111/epi.13845. Epub 2017 Jul 19.
Urokinase-type plasminogen activator (uPA) and kallikrein-related peptidase 8 (KLK8) are serine proteases that contribute to extracellular matrix (ECM) remodeling after brain injury. They can be labelled with the novel radiotracer [ In]MICA-401. As the first step in exploring the applicability of [ In]MICA-401 in tracing the mechanisms of postinjury ECM reorganization in vivo, we performed in vitro and ex vivo studies, assessing [ In]MICA-401 distribution in the brain in two animal models: kainic acid-induced status epilepticus (KASE) and controlled cortical impact (CCI)-induced traumatic brain injury (TBI).
In the KASE model, in vitro autoradiography with [ In]MICA-401 was performed at 7 days and 12 weeks post-SE. To assess seizure burden, rats were monitored using video-electroencephalography (EEG) for 1 month before the 12-week time point. In the CCI model, in vitro autoradiography was performed at 4 days and ex vivo autoradiography at 7 days post-TBI.
At 7 days post-SE, in vitro autoradiography revealed significantly decreased [ In]MICA-401 binding in hippocampal CA3 subfield and extrahippocampal temporal lobe (ETL). In the chronic phase, when animals had developed spontaneous seizures, specific binding was decreased in CA3 and CA1/CA2 subfields of hippocampus, dentate gyrus, ETL, and parietal cortex. Of interest, KASE rats with the highest frequency of seizures had the lowest hippocampal [ In]MICA-401 binding (r = -0.76, p ≤ 0.05). Similarly, at 4 days post-TBI, in vitro [ In]MICA-401 binding was significantly decreased in medial and lateral perilesional cortex and ipsilateral dentate gyrus. Ex vivo autoradiography at 7 days post-TBI, however, revealed increased tracer uptake in perilesional cortex and hippocampus, which was likely related to tracer leakage due to blood-brain barrier (BBB) disruption.
Strong association of reduced [ In]MICA-401 binding with seizure burden in the KASE model suggests that analysis of reduced levels of active uPA/KLK8 represents a novel biomarker candidate to be explored as a biomarker for epilepsy severity. However, limited BBB permeability of [ In]MICA-401 currently limits its application in vivo.
尿激酶型纤溶酶原激活物（uPA）和激肽释放酶相关肽 8（KLK8）是丝氨酸蛋白酶，有助于脑损伤后细胞外基质（ECM）的重塑。它们可以用新型放射性示踪剂[In]MICA-401 进行标记。作为探索[In]MICA-401 在体内追踪损伤后 ECM 重组机制的适用性的第一步，我们进行了体外和离体研究，评估了两种动物模型中的脑内[In]MICA-401 分布：海人酸诱导的癫痫持续状态（KASE）和皮质控制冲击（CCI）诱导的创伤性脑损伤（TBI）。
在 KASE 模型中，在 SE 后 7 天和 12 周进行[In]MICA-401 体外放射自显影。为了评估癫痫发作负担，在 12 周时间点之前，使用视频-脑电图（EEG）对大鼠进行了 1 个月的监测。在 CCI 模型中，在 4 天进行体外放射自显影，在 7 天进行离体放射自显影。
在 SE 后 7 天，体外放射自显影显示海马 CA3 亚区和海马外颞叶（ETL）的[In]MICA-401 结合明显减少。在慢性阶段，当动物出现自发性癫痫发作时，海马 CA3 和 CA1/CA2 亚区、齿状回、ETL 和顶叶皮质的特异性结合减少。有趣的是，癫痫发作频率最高的 KASE 大鼠具有最低的海马[In]MICA-401 结合（r=-0.76，p≤0.05）。同样，在 TBI 后 4 天，内侧和外侧旁皮质和同侧齿状回的体外[In]MICA-401 结合明显减少。然而，TBI 后 7 天的离体放射自显影显示，旁皮质和海马的示踪剂摄取增加，这可能与血脑屏障（BBB）破坏导致的示踪剂渗漏有关。
KASE 模型中[In]MICA-401 结合减少与癫痫发作负担的强烈关联表明，分析活性 uPA/KLK8 水平降低代表了一种新的生物标志物候选物，可作为癫痫严重程度的生物标志物进行探索。然而，[In]MICA-401 的 BBB 通透性有限目前限制了其在体内的应用。
