Abstract
The human amniotic fluid stem cell (hAFSC) population consists of two morphologically distinct subtypes, spindle-shaped and round-shaped cells (SS-hAFSCs and RS-hAFSCs). Whilst SS-hAFSCs are routinely expanded in mesenchymal-type (MT) conditions, we previously showed that they acquire broader differentiation potential when cultured under embryonic-type (ET) conditions. However, the effects of culture conditions on RS-hAFSCs have not been determined. Here, we show that culturing RS-hAFSCs under ET conditions confers faster proliferation and enhances the efficiency of osteogenic differentiation of the cells. We show that this occurs via TGFβ-induced activation of CD73 and the associated increase in the generation of extracellular adenosine. Our data demonstrate that culture conditions are decisive for the expansion of hAFSCs and that TGFβ present in ET conditions causes the phenotype of RS-hAFSCs to revert to an earlier state of stemness. Cultivating RS-hAFSCs in ET conditions with TGFβ may therefore increase their therapeutic potential for clinical applications.
Highlights
Human amniotic stem cells hold great therapeutic potential in regenerative medicine because they can be isolated from mid-trimester and term amniotic fluid samples without ethical restrictions, and are developmentally more primitive than adult stem cells[1,2,3]
We show that ET culture conditions stimulate the expansion kinetics of RS-human amniotic fluid stem cell (hAFSC) and promote the efficiency of osteogenic differentiation of the cells via transforming growth factor (TGF)β-induced activation of CD73 and the associated increase in adenosine production
RS-hAFSCs exhibited a round-shaped morphology under each culture conditions (Fig. 1B), the size of cells cultivated in ET conditions (ET and MT conditions were switched to ET conditions (MT-ET) conditions) was smaller than the size of the cells cultivated in MT conditions (Fig. 1C)
Summary
Human amniotic stem cells (hAFSCs) hold great therapeutic potential in regenerative medicine because they can be isolated from mid-trimester and term amniotic fluid samples without ethical restrictions, and are developmentally more primitive than adult stem cells[1,2,3]. The hAFSC population comprises two subpopulations of plastic-adherent multipotent cells that are morphologically distinct, i.e. fast-growing spindle-shaped cells (SS-hAFSCs) and slow-growing round-shaped cells (RS-hAFSCs)[4, 5]. Populations of plastic-adherent multipotent spindle-shaped and round-shaped ( referred to as flat-shaped) stem cells have already been described in umbilical cord tissue (UC)[6]. Like SS-hAFSCs, UC-derived spindle-shaped stem cells only constitute a minority of cells, whilst round-shaped cells are present in greater proportion[6]. SS-hAFSCs are routinely isolated and expanded under mesenchymal-type (MT) conditions, i.e. either in Dulbecco’s Modified Eagle’s Medium (DMEM), α-minimum essential medium (α-MEM) or Chang medium B and C supplemented with 5–15% fetal bovine serum (FBS), designed to sustain the phenotype of adult mesenchymal stem cells (MSCs)[3, 5, 7]. We show that ET culture conditions stimulate the expansion kinetics of RS-hAFSCs and promote the efficiency of osteogenic differentiation of the cells via transforming growth factor (TGF)β-induced activation of CD73 and the associated increase in adenosine production
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