Significance of CD271 in bone marrow mesenchymal stem cells--changes by cryopreservation

In investigating the biological activities of bone marrow mesenchymal stem cells (BMMSCs), an important task is cell sorting of effective BMMSCs. In the present study, we examined the usefulness of CD271 as a cell surface marker of BMMSCs. Specifically, we investigated (1) CD271 expression before and after freezing, (2) difference between the CD271(+) and CD271(-) fractions regarding calcium formation level after bone differentiation, and (3) method of harvesting effective BMMSCs from marrow tissue. CD271 was partially expressed in cryopreserved BMMSCs (CBMMSCs). We used CD271 in separating CBMMSCs into different cell groups and compared the calcium formation levels between the CD271-expressed and CD271-nonexpressed groups. A significant amount of BMMSCs existed even in the CD271(-) fraction, and the calcium formation level was high in 4 of 5 CD271(-) fraction specimens. The same investigation was conducted on nonfrozen BMMSCs. No major difference was found in CD271 expression compared with CBMMSCs. However, the calcium formation level of the CD271(+) fraction was higher in 3 of 5 specimens. We presumed that CD271 expression might have been substantially changed during culture and cryopreservation. We compared the method of directly culturing bone marrow tissue and that of washing the sample before culture and confirmed that the calcium formation level of BMMSCs was higher when the marrow tissue was washed before culture.