Mesenchymal stem cells (MSC) are multipotent cells that are considered one of the most promising product for cellular therapy in regenerative medicine. MSC have been obtained and expanded from bone marrow and umbilical cord blood in adequate amounts for clinical applications. Under the right conditions, MSC could migrate from bone marrow into the peripheral circulation; however MSC have not been routinely isolated from peripheral blood, and studies are rare and not conclusive. The aim of the present study was to evaluate mobilised peripheral blood (MPB), obtained from patients undergoing apheresis collection of circulating hematopoietic progenitor cells, as a potential source of MSC for clinical applications. MPB samples (500–900 × 106 cells, N = 17) were separated by negative lineage-depletion immunoselection (RosetteSep). Selected cells were seeded in multi-well plates at low density in MesenCult Basal Medium without and with different combinations of growth factors (EGF, PDGF-BB, b-FGF). On reaching confluence, adherent cells were detached by 0.25% trypsin-EDTA treatment and replated for at least two passages. At each passage, surface antigen expression was analyzed by flowcytometry (CD45, CD34, CD105, CD44, CD73, CD166, CD31, HLA-DR and VE-caderine). Following immunoselection 9.5–17.1 × 106 cells were recovered from MPB samples. Cultured cells reached confluency in 3–4 weeks on first passage and in two weeks thereafter. Immunophenotyping showed negativity for CD45 antigen. The absence of growth factors in culture medium conditioned MSC growth capability, while the addition of PDGF-BB+EGF or b-FGF was able to boost the number of CD45/CD73+/CD90+ cells in culture (see figure). However expansion remains still sub-optimal, having been reached in 8/17 samples. In conclusion, we demonstrate that MSC can be obtained from MPB, but expansion requires longer time period and appears more difficult compared to bone marrow. Therefore, further studies need to be conducted to find better culture conditions and optimal growth factor combinations to support MPB-derived MSC expansion.

Author notes

Disclosure: No relevant conflicts of interest to declare.