were derived from αSMA+ cells. Although the exact origin of these
αSMA+ cells remains to be determined, they presumably derive
from the local periosteal vasculature, since it has been shown that
the periosteum supplies the vast majority of the cells in the fracture
callus [68]. In accordance with this notion, we have recently shown
that a subpopulation of culture-expanded murine periosteal cells
localize perivascularly when co-transplanted in vivowith EC, indicating
that these cells can structurally support newly formed blood vessels
[69].