1A). Expanded cells were characterized by FACS analysis and were negative for HLA class1, CD34 and CD45, but were positive for CD44, CD54, CD90 and CD105 (Fig. 1B). CD36 was not expressed in pMSC whereas a double population was observed in aMSC. sellectchem The expression level of CD106 varied between donors (not shown). This expression pattern remained unchanged from passages 3 to 7. CD31 and CD133 were negative in both populations (data not shown). Figure 1 Characterization of adult and pediatric multipotent mesenchymal stromal cells. Adipogenic, chondrogenic and osteogenic differentiation of adult and pediatric MSC Adult MSC and pMSC could be differentiated into adipocytes as shown by oil-red-O staining of lipid droplets (Fig. 1C), into chondrocytes as shown by Masson’s trichrome and immunohistochemistry for collagen type II (Fig.

1D) and into osteoblasts expressing alkaline phosphatase activity (Fig. 1E). For all mesodermal differentiation experiments, no difference was observed between aMSC and pMSC. Adult and pediatric MSC do not exhibit different telomerase activity Telomerase activity of MSC in culture remains controversial [16], [17], [21]. We analyzed telomerase activity of aMSC and pMSC in order to determine whether differences in expansion capacities could be related to different activity of telomerase (Fig. 2). Telomerase activity of MSC was measured and normalized to a positive control provided by the assay. IHH, cells transduced with lentivectors coding for telomerase, were used as a positive control for quality of cell extracts.

These cells displayed almost fourteen times more telomerase activity than the provided positive control. As shown in figure 2, telomerase activity in MSC extracts was low compared to positive control and not significantly different between aMSC and pMSC (p>0.4). Figure 2 Telomerase activity in adult and pediatric MSC. Pediatric MSC co-cultured with Huh-7 cells express more frequently albumin and alpha 1 anti-trypsin compared to adult MSC In order to induce hepatocyte differentiation, we cultured aMSC and pMSC at high density on Matrigel coated wells for 24 h and added hepatogenic differentiation medium as previously described [22] containing HGF, fibroblast growth factor 4 (FGF4) and oncostatin M, for 4 weeks. This medium failed to induce alpha fetoprotein (��FP) or albumin expression in both aMSC (Fig.

3A) and pMSC (data not shown). We then co-cultured aMSC or pMSC with Huh-7 cells in hepatogenic differentiation medium in a transwell system preventing direct cell-cell contacts between different cell types. In these conditions, Brefeldin_A aMSC expressed albumin and alpha 1 anti-trypsin (API) in 2 of 10 independent experiments, and this exclusively in conditions in which hepatogenic differentiation medium were present (Fig. 3B). However, aMSC expressing albumin did not express ��FP.