Figure 4.
The constituents of progressive stem cell differentiation model are (A) Symmetric non-conserved cell division. The division of a stem cell with ALP activity a results in two daughter stem cells, each with ALP activity a. (B) Osteogenic differentiation. The osteogenic differentiation in Model 1 proceeds via gradual loss of ALP activity. Such a process gives rise to temporary states of intermediate pre-osteoblasts.