Although mesenchymal stem cells (MSCs) of distinct tissue origin have a large number
of similarities and differences, it has not been determined so far whether tissue-resident
MSCs are the progenies of one ancestor cell lineage or the results of parallel cell
developmental events. Here we compared the expression levels of 177 genes in murine
MSCs derived from adult and juvenile bone marrow and adult adipose tissue, as well
as juvenile spleen, thymus, and aorta wall by quantitative real-time polymerase chain
reaction and the results were partially validated at protein level. All MSC lines
uniformly expressed a large set of genes including well-known mesenchymal markers,
such as alpha-smooth muscle actin, collagen type I alpha-chain, GATA6, Mohawk, and
vimentin. In contrast, pluripotency genes and the early mesodermal marker T-gene were
not expressed. On the other hand, different MSC lines consistently expressed distinct
patterns of Hox genes determining the positional identity of a given cell population.
Moreover, MSCs of different origin expressed a few other transcription factors also
reflecting their topological identity and so the body segment or organ to which they
normally contributed in vivo: (1) thymus-derived cells specifically expressed Tbx5
and Pitx2; (2) spleen-derived MSCs were characterized with Tlx1 and Nkx2.5; (3) Pitx1
designated femoral bone marrow cells and (4) En2 appeared in aorta wall-derived MSCs.
Thus, MSCs exhibited topographic identity and memory even after long-term cultivation
in vitro. On the basis of these results, we suggest that postnatal MSCs isolated from
different anatomical sites descend from precursor cells developing in the postsegmentation
mesoderm.
