Abstract
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 first six passages, periostin expression was significantly unchanged, with significant 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.