Background: Human adipose tissue-derived mesenchymal stromal cells (AD-MSCs) have been under focus
in regenerative medicine since their discovery as a suitable source of MSCs. AD-MSCs are heterogeneous
cells and exhibit variations in population doubling time, morphology and proliferative capacity. This study
investigated if human AD-MSCs are developing, during in vitro long-term cultivation, in an unwanted or
aberrant way.
Methods: This study monitored AD-MSCs during their in vitro culture till the tenth passage investigating
proliferation kinetics, DNA index and surface markers expression. Also, periostin gene expression was
examined.
Results: The proliferation capacity and colony forming unit were decreased after passage 6 and the
population doubling time was increased. Flow cytometric analysis revealed that newly cultivated population
strongly expressed MSCs markers, furthermore, reduction of CD105 expression appeared in passage 5
onwards, the later was associated with significant increase in expression of CD34 (a hematopoietic cell
marker). Also, reduction of CD73 and CD90 expression was observed from passage 8. Furthermore, during
the frst six passages, periostin expression was signifcantly unchanged, with signifcant upregulation in late
passages.
Conclusions: Long-term cultivation of human AD-MSCs changed their characters in an aberrant
way and the first four passages might be the most appropriate passages for therapy. More investigation
and understanding of these variations are needed to help in standardizing the expansion of MSCs-based
therapies.
Keywords: AD-MSCs; cell proliferation assay; colony forming unit (CFU); DNA index (DI); periostin gene