SDF-1 Is Elevated in Trauma Patients at the Site of Injury

Abstract

Introduction: Bone marrow derived cells (BMDC) migrate to the site of injury following trauma, which animal models suggest plays a crucial role in the healing of injured tissue. Stromal cell-derived factor-1 (SDF-1) is a chemokine which is mutually exclusive with the CXCR4 receptor found on BMDC. Multiple studies have shown the involvement of an SDF-1 gradient and the SDF-1/CXCR4 axis in homing of BMDC to injured tissue. To our knowledge, this is the first study showing elevation of SDF-1 in areas of injury in trauma patients and the presence of an SDF-1 gradient from the blood towards those areas. Methods: Peripheral blood (PB) was collected from trauma patients and volunteers. Chest tube (CT) fluid samples were collected from trauma patients with chest injuries requiring tube thoracostomy. After centrifugation, the supernatant were stored at -20 °C until assayed by ELISA for SDF-1. ELISA results were reported as nanogram of SDF-1 per milligram of total protein. Samples were categorized by initial base deficit (BD), injury severity score (ISS), age, gender, time from injury, survival, and mechanism of injury. The Mann-Whitney Test was used to determine significance. Results: Trauma patients were found to have significantly elevated SDF-1 levels in their PB (n=16) as compared to normal volunteers (n=21) (4.1 vs 2.4, p=0.0014). Furthermore, SDF-1 levels were significantly higher in trauma patient CT fluid (n=30) than in trauma patient PB (9.8 vs 4.1, p=<0.001). Both initial BD and mortality were associated with higher SDF-1 levels in CT fluid (Table 1). Conclusion: As predicted by the animal models, SDF-1 was elevated in the PB of trauma patients, with even greater levels found at the area of injury, supporting the notion of an SDF-1 gradient mechanism to promote homing of BMDC to injured tissue. The degree of shock appears to correlate to SDF-1 levels, with more severe shock resulting in greater elevation of SDF-1 levels. This study suggests that SDF-1 plays a role in the homing of BMDC to sites of injury in trauma patients.