Studies have confirmed that the rate of symptomatic internal carotid artery stenosis is >50%, the rate of asymptomatic internal carotid artery stenosis is >80%, and at least one patient with high risk factors for CEA treatment, CAS efficacy is not inferior to CEA . Three large international multicenter randomized controlled trials also failed to demonstrate that CAS was less effective than CEA [11–13]. In addition, there was no significant difference in primary endpoint (perioperative stroke, myocardial infarction, and ipsilateral stroke of responsible vessels within 4 years) in both symptomatic and asymptomatic carotid stenosis (CAS group 7.2% ± 0.8) %, CEA group 6.8% ± 0.8%, P = 0.51); but in terms of health-related quality of life, due to the small injury of CAS and short postoperative hospitalization period, it will benefit more in the short term .
Astrocytes are the main glial cells in brain tissue, which interact with neuronal cells and function to regulate neurotransmitters, promote immune responses, regulate intracranial blood flow, ions and antioxidants . GFAP and S100B are the main components and signature proteins of astrocytes, and their presence ensures the maintenance and functional function of astrocyte morphological structure [16–17]. The increase of GFAP and S100B in CSF [18–19] and blood  reflects the formation of astrocyte filaments in the central nervous system. High concentrations of GFAP and S100B suggest the destruction of acute brain tissue. A moderate increase suggests the astrocytosis, the formation of scars, and delayed ischemic tolerance , which plays an important role in promoting neuronal survival and repairing after brain injury . In addition, Herrmann et al found that the release of GFAP and S100B were significantly correlated with the incidence of cerebral infarction. While for patients with lacunar or mild stroke, GFAP was found to be a more sensitive cerebral biochemical marker .
The results in this study show that the serum concentration of GFAP and S100B from the operation patients’ serum is higher than that in the control group. DSA has confirmed that the patients in the operation group have different degrees of carotid artery stenosis, which makes the brain tissue in the state of chronic ischemia and hypoxia, and chronic cerebral ischemia will inevitably lead to brain tissue damage. Meanwhile, astrocytes are very sensitive to cerebral ischemia and hypoxia, which could cause the astrocytes produce excessive GFAP and S100B into the CSF. These proteins as biomarkers can be in turn released into the peripheral blood through impaired blood-brain barrier, so that the increases of GFAP and S100B could be detected in blood serum. In addition, for patients with symptomatic carotid stenosis, the increased level of GFAP and S100B in serum is more significant. After CAS operation, GFAP and S100B in serum increased first at T2 and then decreased at T3, but they both were higher than those before CAS operation. The long-term stenosis of carotid artery can cause brain tissue to establish a certain collateral circulation. When the application of the CAS mechanically expands the blood vessels, the temporary relative balanced brain tissue perfusion established before operation can be ruined, so that the excessive release of GFAP and S100B by astrocytes may happen which could be a response of cerebral ischemia-reperfusion. However, with the release of the stenosis after CAS, the blood flow of the stenosis or occlusion vessels was reestablished, the cerebral ischemia and hypoxia injury caused by insufficient blood perfusion was gradually recovered, which was reflected in the decrease of production of both GFAP and S100B proteins locally. It has been confirmed that the moderate increase of GFAP and S100B is related to repairing after brain injury . Therefore, the level of biochemical markers within 3 days after operation is still higher than that before operation, suggesting that brain tissue is still in the process of injury repairing after CAS. In addition, it is reported that the reactive gliocytosis has dual effects . When it cannot be solved in the acute and early chronic phase after injury, the reactive gliosis can have negative impact or consequences to injury area. If the intervention measures are adjusted correctly in the best time window, new methods of treating nervous system injury may be developed. The data in our current study is consistent with the results observed by Wunderlich MT . When alteplase was used to a thrombolysis to patients with middle cerebral artery occlusion, GFAP concentration can slightly decrease comparing to those in patients without thrombolysis, but it is still higher than normal control. For patients with different degrees of carotid artery stenosis, the serum concentrations of GFAP and S100B did not change significantly before and after operation. We considered that the cause of this result may be due to the mixed analysis of the patients with symptomatic and asymptomatic stenosis.
For the evaluation of the short-term effect after CAS, the changes of GFAP and S100B in serum can be monitored to timely reflect the changes after operation; for the evaluation before operation and the long-term monitoring of the effect after operation, biochemical markers and imaging tools can be used as the evaluation means; at the same time, the detection of GFAP and S100B in serum has the advantages of simplicity, low price, repeatability and small damage. However, the critical serum values of GFAP and S100B with different degrees of stenosis, different stages of operation and normal human need further study. In addition, the correct intervention of GFAP and S100B in the best time window after carotid stent implantation may lead to the development of new methods for the treatment of nervous system injury.