Table I. The phenotypes of EP, LP, and long-time proliferating cells (MDSC) investigated by immunocytochemistry, flow cytometry, and RT-PCR.
| Markers | EPq | EPa | LP | MDSC | ||||
|---|---|---|---|---|---|---|---|---|
| Imm | Imm | Flow | RT | Imm | Imm | Flow | RT | |
| CD34 | − | +/− | +/− | + | +/− | + | +/− | + |
| Sca-1 | − | +/− | +/− | ND | +/− | + | +/− | ND |
| c-Kit | ND | ND | − | ND | − | − | − | ND |
| CD45 | ND | ND | − | ND | ND | ND | − | ND |
| Desmin | + | + | ND | ND | +/− | −/+ | ND | ND |
| Bc12 | − | − | ND | + | ND | + | ND | + |
| MNF | ND | + | ND | + | ND | + | ND | + |
| MyoD | −/+ | −/+ | ND | + | +/− | ND | ND | + |
| Myogenin | +/− | +/− | ND | + | +/− | ND | ND | ND |
| m-cadherin | +/− | + | ND | ND | −/+ | − | ND | ND |
EP and LP cells were dissociated from the hindlimb muscle of normal newborn mice and separated by their adhesion characteristics (see Materials and methods for details). Two populations of EP cells were used here: the EP cells after 3 d of culturing (EPq, relatively quiescent) and the EP cells after 5 d of culturing (EPa, activated). The LP cells took 5–7 d to attach to flasks and were cultured for an additional 4 d. MDSC were isolated from a small population of long-time proliferating cells derived from the LP cells. In immunochemistry and flow cytometry, +, >95% of the cells were positive; +/−, 40–80% of the cells were positive; −/+, 10–30% of the cells were positive; −, <5% of the cells were positive. Flow, flow cytometry; Imm, immunochemistry; RT, RT-PCR.