Circulating Stromal Cell-Derived Factor 1α Levels in Heart Failure: A Matter of Proper Sampling

Background The chemokine Stromal cell-derived factor 1 alpha (SDF1 alpha, CXCL12) is currently under investigation as a biomarker for various cardiac diseases. The correct interpretation of SDF1 alpha levels is complicated by the occurrence of truncated forms that possess an altered biological activity. Methodology We studied the immunoreactivities of SDF1 alpha forms and evaluated the effect of adding a DPP4 inhibitor in sampling tubes on measured SDF1 alpha levels. Using optimized sampling, we measured DPP4 activity and SDF1 alpha levels in patients with varying degrees of heart failure. Results The immunoreactivities of SDF1 alpha and its degradation products were determined with three immunoassays. A one hour incubation of SDF1 alpha with DPP4 at 37 degrees C resulted in 2/3 loss of immunoreactivity in each of the assays. Incubation with serum gave a similar result. Using appropriate sampling, SDF1 alpha levels were found to be significantly higher in those heart failure patients with a severe loss of left ventricular function. DPP4 activity in serum was not altered in the heart failure population. However, the DPP4 activity was found to be significantly decreased in patients with high SDF1 alpha levels Conclusions We propose that all samples for SDF1 alpha analysis should be collected in the presence of at least a DPP4 inhibitor. In doing so, we found higher SDF1 alpha levels in subgroups of patients with heart failure. Our work supports the need for further research on the clinical relevance of SDF1 alpha levels in cardiac disease.