Fate changes leading to multipotency of isolated mesenchymal cells [Expression: Dense_vs_Sparse]

Mesenchymal populations include a fraction of cells exhibiting multipotency as well as others with limited differentiation range. It has been assumed that the mesenchymal cellular cascade is topped by a multipotent cell, which gives rise to progeny with diminishing differentiation potentials. Here we show that cultured mesenchymal cells, a priori exhibiting a limited differentiation potential, may gain new capacities and become multipotent following single cell isolation. These fate changes were accompanied by up-regulation of differentiation promoting genes, many of which also became H4K20me1 methylated. Early events in the process included TGFβ and Wnt modulation, and down-regulation of hypoxia signaling. Indeed, hypoxic conditions inhibited the observed cell changes. Overall, cell isolation from neighboring partners caused major molecular changes and particularly, a newly established epigenetic state. It is suggested that MSCs behave non-deterministically and non-hierarchically and should therefore be defined primarily by their capacity to undergo fate changes triggered by environmental cues. The gene expression profile of dense and sparse MSC cultures in three sequential days after seeding was compared