Abstract 385: Circulating Progenitor Cells: Modulation of Their Differentiation and Function by the Micro-environment
Bone marrow-derived progenitor cells are therapeutically used to enhance left ventricular function after myocardial infarction. A potential hazard of such an approach might originate from the differentiation of progenitor cells into cell types that are not committed to a cardiac lineage. Therefore, we aimed to determine whether CPCs are terminally lineage-committed.
Methods: Blood-derived mononuclear cells obtained from healthy individuals were cultured in endothelium-specific medium containing growth factors for 4 days. (At this time, adherent cell are considered to represent lineage-committed endothelial progenitor cells (EPC) and are used in clinical trials.) Adherent EPCs were now cultured for 1 week in basal endothelial medium (BEM) alone (Con), in BEM supplemented with interleukin 2 (IL2, 1200 IU/mL) to induce a lymphocytelineage commitment, BEM + epidermal growth factor (EGF, 100 ng/mL) to support a development in epithelial cells and BEM + vascular endothelial growth factor (VEGF, 200 ng/ml) to promote a differentiation in endothelial cells. After this time, adherent cells were analysed for the expression of CD34 (stem cell marker), CD3 (lymphocyte marker), E-cadherin (epithelial marker), and KDR (endothelial marker) using FACS. Functional properties of EPCs were assessed by matrigel and migration assay.
Results: Exposure of EPCs to IL2 induced a lymphocyte lineage commitment with an augmentation in the number of CD3+ cells by 156±34% (p<0.05 vs. Con). On the contrary, IL2 decreased the amount of CD34+KDR+ EPCs by 60±6%, attenuated their ability to incorporate into vascular structures by 68±10% and diminished their migratory capacity by 61±9% (p<0.05 vs. Con). Exposure of EPCs to EGF resulted in an epithelial lineage-commitment with an expansion of CD34+E-cadherin+ cells by 75±15% (p<0.05 vs. Con). Culture of EPCs in BEM + VEGF enlarged the proportion of CD34+KDR+ cells by 48±8% and improved their ability to incorporate into vascular networks by 45±6 % (p<0.05 vs. Con).
Conclusion: Bone marrow-derived circulating progenitor cells are not terminally lineage-committed. The micro-environment substantially impacts on fate and function of these cells and, therefore, might modulate their therapeutic potential in clinical settings.