Mesenchymal Stem Cell-Platelet Aggregates Increased in the Peripheral Blood of Patients with Acute Myocardial Infarction and Might Depend on the Stromal Cell-Derived Factor 1/CXCR4 Axis.

Bone marrow mesenchymal stem cells (MSCs) are a rare subset of nonhematopoietic progenitor cells and are appealing biomaterial for multiple tissue damage repairs. Transplantation of MSCs is proved to improve heart function after myocardial ischemia. However, the limitations of MSC injection approaches are equally obvious. As a multiple-function cell, platelets (PLTs) are also known playing important roles in cardiac recovery after myocardial infarction. In this study, we analyzed circulating MSC-PLT aggregate numbers in acute myocardial infarction (AMI) patients by flow cytometry. We found more MSC-PLT aggregates in patients with AMI than in healthy controls, and the patients with higher MSC-PLT aggregates had better prognosis. When stromal cell-derived factor 1 (SDF-1) binds to its receptor CXC chemokine receptor 4 (CXCR4), they play an important role in MSC migration and engraftment. We explored SDF-1 and CXCR4 expression on PLT surface by flow cytometry and found relative mean fluorescence intensity of PLT CXCR4 and the number of MSC-PLT aggregates showed a significant correlation. Meanwhile, in vitro experiments demonstrated that SDF-1/CXCR4 was crucial in MSC-PLT aggregate formation, which might suggest a novel mechanism that SDF-1/CXCR4 is involved in MSCs homing and myocardial repair after AMI. There may be another strategy to encourage myocardial repair in AMI patients by increasing the expression of SDF-1 on MSCs and promoting the formation of MSC-PLT aggregates.