A Novel Type of Stem Cells Double-Positive for SSEA-3 and CD45 in Human Peripheral Blood

Abstract

Peripheral blood (PB) contains several types of stem/progenitor cells, including hematopoietic stem and endothelial progenitor cells. We identified a population positive for both the pluripotent surface marker SSEA-3 and leukocyte common antigen CD45 that comprises 0.04% ± 0.003% of the mononuclear cells in human PB. The average size of the SSEA-3(+)/CD45(+) cells was 10.1 ± 0.3 µm and ∼22% were positive for CD105, a mesenchymal marker; ∼85% were positive for CD19, a B cell marker; and ∼94% were positive for HLA-DR, a major histocompatibility complex class II molecule relevant to antigen presentation. These SSEA-3(+)/CD45(+) cells expressed the pluripotency markers Nanog, Oct3/4, and Sox2, as well as sphingosine-1-phosphate (S1P) receptor 2, and migrated toward S1P, although their adherence and proliferative activities in vitro were low. They expressed NeuN at 7 d, Pax7 and desmin at 7 d, and alpha-fetoprotein and cytokeratin-19 at 3 d when supplied to mouse damaged tissues of the brain, skeletal muscle and liver, respectively, suggesting the ability to spontaneously differentiate into triploblastic lineages compatible to the tissue microenvironment. Multilineage-differentiating stress enduring (Muse) cells, identified as SSEA-3(+) in tissues such as the bone marrow and organ connective tissues, express pluripotency markers, migrate to sites of damage via the S1P-S1P receptor 2 system, and differentiate spontaneously into tissue-compatible cells after homing to the damaged tissue where they participate in tissue repair. After the onset of acute myocardial infarction and stroke, patients are reported to have an increase in the number of SSEA-3(+) cells in the PB. The SSEA-3(+)/CD45(+) cells in the PB showed similarity to tissue-Muse cells, although with difference in surface marker expression and cellular properties. Thus, these findings suggest that human PB contains a subset of cells that are distinct from known stem/progenitor cells, and that CD45(+)-mononuclear cells in the PB comprise a novel subpopulation of cells that express pluripotency markers.

Non-Tumorigenic Pluripotent Reparative Muse Cells Provide a New Therapeutic Approach for Neurologic Diseases

“…They are constantly mobilized from the bone marrow to the peripheral blood at a rate of approximately 0.01~0.2% of the mononucleated cell fraction in the blood. Large individual differences exist, however, and the rate varies greatly even within individuals, depending on the physical condition and presence of illness or injury [ 3 , 4 ].…”

“…Peripheral blood-derived Muse cells are unique in that, while they exhibit pluripotency gene expression, triploblastic differentiation, and migration toward S1P, like Muse cells derived from other sources, they consistently express the surface marker CD45, a general white blood cell marker, along with SSEA-3, unlike other Muse cells [ 4 ]. CD45 expression has never been observed in bone marrow-, dermal fibroblast, and adipose tissue-derived Muse cells, and this is a unique feature of peripheral blood-derived Muse cells.…”

“…CD45 expression has never been observed in bone marrow-, dermal fibroblast, and adipose tissue-derived Muse cells, and this is a unique feature of peripheral blood-derived Muse cells. In addition, the gene expression levels of Oct3/4, Nanog, and Sox2 are higher than that in other Muse cells [ 4 ]. Generally, in suspension, Muse cells have substantially increased Oct3/4, Nanog, and Sox2 gene expression levels, compared with those in an adherent state [ 27 ].…”

“…In contrast to VSELs, Muse cells are found not only in the bone marrow and peripheral blood but also in organ connective tissue. Human Muse cells in the bone marrow and organs are 13~15 μm, and those in the peripheral blood are ~10 μm; thus, Muse cells are considerably larger than VSELs [ 1 , 4 ]. Marker expression also differs between Muse cells and VSELs; Muse cells from the bone marrow and organs are double-positive for SSEA-3 and CD105, an MSC marker, whereas peripheral blood-derived Muse cells are consistently double-positive for SSEA-3 and CD45, a white blood cell marker.…”

“…Muse cells, identified as pluripotent surface marker, stage-specific embryonic antigen (SSEA)-3(+), are endogenous, reparative, non-tumorigenic, pluripotent stem cells distributed throughout the body [ 1 , 2 ]. They are constantly mobilized from the bone marrow to the peripheral blood and thus supplied to every organ ( Figure 1 ) [ 3 , 4 ]. Muse cells exhibit pluripotency and are able to differentiate into ectodermal, mesodermal, and endodermal cells and self-renew from a single cell [ 1 ].…”