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Received Mar 8, 2017; Revised Jun 28, 2017; Accepted Sep 10, 2017
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1. Introduction
Mesenchymal stem/stromal cells (MSCs) are primitive cells that give rise to bone marrow (BM) stromal cells, which are responsible for supporting hematopoiesis [1, 2]. MSCs themselves also support hematopoiesis, as they form part of the niche of hematopoietic stem cells (HSCs) and provide the necessary conditions to regulate self-renewal, proliferation, and differentiation [3–6]. Previous results from our group demonstrated the capacity to support hematopoiesis of BM-MSCs in vitro because these cells favor the expansion of hematopoietic progenitor cells (HPCs) from umbilical cord blood (UCB) [7]. HPCs obtained from UCB using ex vivo expansion systems have already been used clinically in patients undergoing hematopoietic cell transplant (HCT) [8]. Moreover, BM-MSCs have been applied in patients undergoing HCT, resulting in an increase in the graft size and faster hematopoietic recovery [6, 9–11]. Therefore, BM-MSCs are considered a serious candidate for improving HCT.
The main source of MSCs is BM; however, the use of BM has some drawbacks, as obtaining BM is an invasive procedure for the donor [12], and the number of MSCs and their capacities for proliferation and differentiation decrease with the age of the individual [13, 14]. Our research group has obtained MSCs from neonatal sources, such as umbilical cord blood (UCB) and the placenta (PL). It is noteworthy that the proportion of PL samples from which we were able to obtain MSCs was higher than that of UCB samples (100% and 11%, resp.) [15]. Moreover, for the two sources, we showed that their morphologies, immunophenotypes, and capacities for osteogenic and chondrogenic differentiation are similar to those of BM-MSCs [15] and that they have immunosuppression capacities [16, 17]. Other groups have shown that MSCs from UCB [18] and PL [19] have the capacity to support hematopoiesis in vitro but have not compared these cell types to determine which type has the best capacity for potential clinical application. In this study, we used the same coculture conditions to compare the capacities of MSCs from UCB and PL to support the in vitro...