Angiogenesis In Intracranial Atherosclerotic Stenosis

Background and PurposeAs one of the major causes of ischemic stroke, it is really a tough issue to deal with intracranial atherosclerotic stenosis (ICAS) for its high stroke recurrence rate and poor treatment outcome. Angiogenesis is a multiple and complex process triggered by hypoxia and hypoperfusion that consists of the sprouting of new blood vessels from pre-existing vascular structures. Angiogenesis was proved to be beneficial in acute ischemic stroke by improving brain tissue recovery and functional outcome, regulated by many pro-angiogenic factors and anti-angiogenic factors. However, for those diseases causing chronic cerebral hypoperfusion like ICAS, the status of angiogensis remains unknown. Thus we aimed to investigate the angiogenesis status in ICAS by performing 68Ga-PRGD2 PET/CT imaging and measuring serum angiogenic growth factors levels.MethodsThe imaging part of our study consisted of 12 out-patients diagnosed with unilateral severe ICAS (>70%) or occlusion with magnetic resonance angiography (MRA). The patients underwent a 68Ga-PRGD2 PET/CT scan and then a 18F-FDG PET/CT scan during the later three days. The 68Ga-PRGD2 as well as the 18F-FDG PET/CT images were transferred to the MMWP workstation (Siemens Medical Solution) for comparison and analysis. The co-registered and matched images were visually analyzed by two experienced nuclear medicine physicians through consensus reading. The region-of-interest (ROI) was measured in semi-quantitative analysis, and the peak standardized uptake values (SUVmax) as well as the mean SUV (SUVavg) of the 68Ga-PRGD2 accumulation of the ROI were measured. Lesion to contralateral ratio (LCR) was defined as the ratio between the SUVmax of the lesion side and the contralateral side and was analyzed with regard to the post-ischemic event time (PIT) and other serum biomarkers. The serum test consisted of 24 patients with severe intracranial artery stenosis (>70%) or occlusion with MRA. Blood samples obtained in non-EDTA tubes were centrifuged for 10 min (3,000 rpm) and serum samples were stored at -80℃ until analysis. The Angiogenesis Array (Raybiotech, USA) was used to determine the levels of five angiogenic factors:VEGF, VEGFR2, PDGF-BB, bFGF and endostatin. Elisa was used to determine the level of αvβ3-integrin and C reactive protein was determined by immunoturbidimetry. Statistical analysis included student’s t test, non-parametric test and logistic regression analysis, while correlation analysis was performed with Pearson correlation analysis or Spearman correlation analysis.ResultsFor the imaging part,10 (83.3%) patients were found to have significant 68Ga-PRGD2 uptake in the territory of the stenotic artery in the lesion side without any obvious correlation with the focus of infarct or encephalomalacia focus. Both the the SUVmax (P< 0.001) and the SUVavg (P< 0.001) in the lesion side were significantly higher than those in the contralateral side, indicating the 68Ga-PRGD2 uptake in the lesion side was significant higer than the contralateral side. In the subgroup analysis, no significant differences were found for the Ga-PRGD2 LCR between the groups with and without focus of infart (P=0.701). Besides, no significant correlation was found between 68Ga-PRGD2 LCR and 18F-FDG LCR, PIT or any serum biomarkers. For the serum test part,24 patients with severe ICAS were tested for the serum level of VEGF, VEGFR, PDGF-BB, endostatin and avP3-integrin. Significant differences were found in serum VEGF level (P<0.001), PDGF-BB level (P=0.001) and αvβ3-integrin level (P<0.001) between the test group and the control group. No significant differences were found between the other three angiogenic growth factors. For the subgroup analysis, no significant differences were found between the symptomatic ICAS subgroup and asymptomatic ICAS subgroup, neither were the difference between the single-stenosis subgroup and the multi-stenosis subgroup. For the correlation analysis, there were no significant correlations between PIT or the stenosis counts regarding all these six serum biomarkers.ConclusionsCombining the two parts of our study, the significant difference of the 68Ga-PRGD2 uptake between the lesion side and the contralateral side as well as the significant differences of the serum levels of the angiogenic growth factors VEGF, PDGF-BB and αvβ3-integrin between test group and control group showed the existence of angiogenesis in the severe ICAS patients.