Relationship of Circulating CXCR4+ EPC with Prognosis of Mild Traumatic Brain Injury Patients
Lin Yunpeng1, Luo Lan Lan2, Sun Jian1, Gao Weiwei1, Tian Ye1, Park Eugene3, Baker Andrew3, Chen Jieli4,5, Jiang Rongcai1,*, Zhang Jianning1,*
1Department of Neurosurgery, Tianjin Medical University General Hospital, Tianjin Neurological Institute, Key Laboratory of Post-neurotrauma Neuro-repair and Regeneration in Central Nervous System, Ministry of Education and Tianjin City, Tianjin 300052, China 2Department off Psychological Science, Tianjin Medical University General Hospital, Tianjin 300052, China 3Department of Traumatic Critical Care Unit, St. Michael’s Hospital, Toronto, Canada 4Department of Neurology, Henry Ford Hospital, Detroit, MI USA 5Department of Geriatrics, Tianjin Geriatrics Institute, Tianjin Medical University General Hospital, Tianjin, China
To investigate the changes of circulating endothelial progenitor cells (EPCs) and stromal cell-derived factor-1α (SDF-1α)/CXCR4 expression in patients with mild traumatic brain injury (TBI) and the correlation between EPC level and the prognosis of mild TBI. 72 TBI patients (57 mild TBI, 15 moderate TBI patients) and 25 healthy subjects (control) were included. The number of circulating EPCs, CD34+, and CD133+ cells and the percentage of CXCR4+ cells in each cell population at 1,4,7,14,21 days after TBI were counted by flow cytometer. SDF-1α levels in serum were detected by ELISA assay. The patients were divided into poor and good prognosis groups based on Extended Glasgow Outcome Scale and Activity of Daily Living Scale at 3 months after TBI. Correlation analysis between each detected index and prognosis of mild TBI was performed. Moderate TBI patients have higher levels of SDF-1α and CXCR4 expression than mild TBI patients (P < 0.05). The percentage of CXCR4+ EPCs at day 7 post-TBI was significantly higher in mild TBI patients with poor prognosis than the ones with good prognosis (P < 0.05). HAMA and HAMD scores in mild TBI patients were significantly lower than moderate TBI patients (P < 0.05) in early term. The percentage of CXCR4+ EPCs at day 7 after TBI was significantly correlated with the prognosis outcome at 3 months. The mobilization of circulating EPCs can be induced in mild TBI. The expression of CXCR4+ in EPCs at 7 days after TBI reflects the short-term prognosis of brain injury, and could be a potential biological marker for prognosis prediction of mild TBI.
Figure 1. A sample illustration of detecting the percentage of CXCR4+ cells in circulating EPCs. (A) Cells were first run on a forward and side scatter to select mononuclear cells. (B) The selected cells were then gated on FITC-CD34 and PE-CD133 to choose CD34+, CD133+ and double positive EPCs. (C) The percentages of CXCR4+ cells on each cell population (EPCs) were finally measured by APC-CXCR4 staining.
Mild TBI group (n = 57)
Moderate TBI group (n = 15)
Gender [n (%)]
Time interval between onset and hospital admission (hour)
GCS score at admission
Open/closed TBI [n (%)]
Injury causes [n (%)]
Motor vehicle accidents
Table 1 Comparison of general data of TBI patients.
Figure 2. Prognosis and mental state of TBI patients. (A) Moderate TBI significantly induces a worse prognosis after TBI compared to the mild TBI group at 3 and 6 months after TBI, identified by GOS-E, IADL and ADLS scores. (B) HAMA and HAMD scores were significantly increased in the moderate TBI group compared to mild TBI group (p < 0.05) at 3 and 6 months after TBI. There was no significant difference in HAMA and HAMD scores between 3 and 6 months after discharge in mild or moderate TBI patients, respectively.
Figure 3. Number of CD34+, CD133+ and EPCs in the peripheral blood. (A) Number of circulating EPCs in mild and moderate traumatic brain injury (TBI) patients, showing a similar tendency of “from low to high”, peaked at 7 days and then gradually decreased and was significantly higher than that in the control group at 7 and 14 days after TBI (*p < 0.05). (B) Mild TBI patients were further divided into a good prognosis group (group A) and a poor prognosis group (group B). There was no significant difference in EPC number among group A, group B and moderate TBI group (P > 0.05). (C) CD34+ cell number in the peripheral blood of mild and moderate TBI patients was very high in the early stage after TBI and began to significantly decrease at 7 days after TBI, and was significantly higher than control group at 1, 4, 7 and 14 days after TBI (*p < 0.05). There was no significant difference in CD34+ cell number between mild and moderate TBI groups (p > 0.05). (D) CD133+ cell number in the peripheral blood of all TBI patients was also very high in the early stage after TBI and began to significantly decrease at 7 days after TBI, and was significantly higher than the control group at 1, 4, 7, 14 and 21 days after TBI (*p < 0.05). There was no significant difference in CD133+ cell number between mild and moderate TBI group (p > 0.05).
Figure 4. Percentage of CXCR4+ cells on EPCs, CD34+ and CD133+ cells in TBI patients. (A, D, G) show the percentages of CXCR4+ cells in EPCs, CD34+ or CD133+ cells were significantly higher than the baseline level (control group; *p < 0.05) at early stage (within 14 days) after TBI and then gradually decreased in the following days. (B) The percentage of CXCR4+ cells in EPCs of mild TBI patients was significantly higher than that in the control group (*p < 0.05) at 1, 4, and 14 days after TBI. The percentage of CXCR4+ cells in EPCs in the mild TBI group was significantly lower than the moderate TBI group at 4, 7, 14, 21 days (#p < 0.05). (E, H) There was no significant difference between mild TBI and moderate TBI groups (P > 0.05) in circulating CD34+ and CD133+ cell expression. (C, F, I) Mild TBI patients were further divided into a good prognosis group (group A) and a poor prognosis group (group B). (C) The percentage of CXCR4+/EPC in group A was significantly lower than group B at 7 days after TBI (F = 11.375, *p = 0.002). (F) The percentage of CXCR4+/CD34+ cells in group A was significantly lower than group B at 7 days after TBI (F = 6.124, *p = 0.02). (I) The percentage of CXCR4+/CD133+ cells in group A was significantly lower than group B at 7 days after TBI (F = 7.435, *p = 0.011).
Figure 5. Changes in serum SDF-1α level after TBI. (A) Serum SDF-1α levels in mild and moderate TBI groups were significantly increased at 1,4,7,14 and 21days after TBI compared to control group (*p < 0.05). SDF-1 was significantly higher in the moderate TBI group than the mild TBI group at 1 and 4 days after TBI (#p < 0.05). (B) Mild TBI patients were further divided into a good prognosis group (group A) and a poor prognosis group (group B). There was no statistical significance in SDF-1α levels between group A and B.
Figure 6. Correlation analysis. (A) There is significant relationship between percentage of CXCR4+/EPCs (7 day after admission) in mild TBI patients (R= 0.518, p = 0.002) with the prognosis at 3 months after TBI. (B) There is significant correlation between percentage of CXCR4+/EPCs (7 day after admission) in all TBI patients (R= 0.605, p = 0.000) with the prognosis at 3rd month after TBI.
95% confidence interval
Table 2 Logistic regression analysis results of each factor that influences the prognosis of patients with mild traumatic brain injury
Figure 7. Receiver operating characteristic (ROC) curve. ROC created based on the percentage of CXCR4+/EPCs at day 7 after admission and the prognosis of patients with mild TBI. The area under the AUC was 0.807 (95% CI = 0.656-0.958, critical value = 42.35%, p = 0.003).
Area under the curve
95% confidence interval
Mild TBI (n = 57)
Table 3 Parameters of receiver operating characteristic (ROC) curve created based on the percentage of CXCR4+ cells in EPCs at 7 days after admission and the prognosis of patients with mild TBI
Figure 8. Correlation between the percentage of CXCR4+/EPCs and psychological state after TBI. (A) Figure shows significant correlation between the percentage of CXCR4+/EPCs at day 7 after TBI and the HAMA score at 3 months after discharge (R = 0.501, p = 0.003). (B) Figure shows significant relationship between the percentage of CXCR4+/EPCs at day 7 after TBI and the HAMD score at 3 months after discharge (R = 0.515, p = 0.002).
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