Effect of atrial fibrillation on human CD34+ hematopoietic progenitor cells in circulation and expression of SDF-1/CXCR4 in atrium

AIM:To investigate the effect of different kinds of atrial fibrillation (AF) on human CD34+ hematopoietic cells (HPCs) in circulation and on myocardial expression of SDF-1 and its receptor CXCR4 in canines with lasting rapid atrial pacing and to explore the role of CD34+ HPCs and SDF-1/CXCR4 in repairing atrium during AF. METHODS: Included in our study were 100 subjects (35 with paroxysmal AF, 35 with persistent AF and 30 with sinus rhythm). Percentages of CD34+ HPCs in peripheral venous blood were tested by flow cytometry. Percentages of CD34+ HPCs were tested again at 48 h after receiving successful direct current cardioversion in 24 subjects with persistent AF. Thirteen canines were randomly divided into two groups: sham-operated group (n=6) and atrial pacing group (n=7). A pacemaker (AOO) was implanted to the right atrial appendage in each of the dogs. Dogs in the atrial pacing group were paced at 400 bpm for 6 weeks, whereas those in the sham-operated group were not paced. At the end of the study, expression of CXCR4 at mRNA level in myocardium of left atrium and left auricle was analyzed by reverse transcription polymerase chain reaction. SDF-1 protein in left atrium of each group was examined using Western blot. RESULTS: Subjects with persistent AF had higher level of CD34+ HPCs than those in patients with paroxysmal AF and sinus rhythm (P<0.05), with no difference between the latter two groups. The level of CD34+ HPCs in persistent AF decreased after successful cardioversion (P<0.05). Compared with the sham-operated group, lasting rapid atrial pacing significantly increased the expression of CXCR4 at mRNA level in left atrium and left auricle (P<0.05) and the expression of SDF-1 protein also increased (P<0.01). CONCLUSION: The percentage contents of CD34+ HPCs in peripheral venous blood in persistent AF increases and lasting rapid atrial pacing significantly increases the expression of SDF-1 and CXCR4 in atrium. SDF-1/CXCR4 may be involved in the process of myocardium repair during the atrium injuries caused by persistent AF.