At confluence, the cells were trypsinized and the cellular expansion growth rate of both HC– and SSc–MSCs was evaluated by cell count in a Burker chamber at each passage and expressed in terms of population-doubling (PD) using the formula: log n/log 2, where n is the cell number of the confluent monolayer divided by the initial number of cells seeded. We further assessed Ki67 gene expression, which is associated strictly with cell proliferation [28]. Selleck KPT-330 A more detailed

description of this assay is discussed in the section regarding quantitative polymerase chain reaction (qPCR). To confirm the human MSC phenotype, plastic adherent cells were analysed for the expression of surface-specific antigens by flow cytometry, as established elsewhere [4]. The cells were stained with the Cobimetinib following conjugated monoclonal antibodies: fluorescein isothiocyanate (FITC)-conjugated or phycoerythrin (PE)-conjugated monoclonal antibodies, including CD14, CD34, CD45,

CD105, CD90 and CD73. FITC- and PE-conjugated isotypes were used as negative controls. Analysis was performed using Cytomics FC500 (Beckman-Coulter, Brea, CA, USA). The capacity of MSCs to differentiate along osteogenic and adipogenic lineages was assessed as described elsewhere [4]. Briefly, for osteogenic differentiation cells were plated at 104 cells/cm2 in MSC medium supplemented with 10% FBS, 10 nM dexamethasone, 100 μg/ml ascorbic acid and 10 mM β-glycerophosphate (all from Sigma, St Louis, MO, USA). After 21 days, the osteogenic differentiation was demonstrated by deposition of mineral nodules detected by alizarin red S staining. Adipogenic differentiation was induced by adding culture medium supplemented with 10% FBS, 0·5 mM isobutyl methylxanthine, 1 μM dexamethasone, 10 μg/ml insulin and 70 μM indomethacin (all from Sigma) to MSCs. After 21 days’ culture, adipogenesis was measured by the accumulation of lipid-containing vacuoles stained with Oil red

O. Cultured MSCs were collected by trypsinization, washed three times and resuspended 1 × 106/300 μl with phosphate-buffered saline (PBS; Euro Clone). Cells were fixed in 700 μl of ice-cold 100% ethanol at 4°C for a minimum of 30 min. The cell suspension was centrifuged at 1700 g for 5 min and washed twice with PBS+0·1% BSA (Kedrion, Lucca, Italy). Finally, the cell Tau-protein kinase pellets were incubated with propidium iodide (PI; Sigma) (50 μg/ml)/RNase (Sigma, St Louis, MO, USA) (250 ug/ml)/0·1% Triton X (Sigma) solution for 1 h and analysed with Cytomics FC500 (Beckman-Coulter). The senescence-associated β-Gal assay was performed as described previously using a commercial kit (senescence detection kit; Calbiochem, Merck KGaA, Darmstadt, Germany). Briefly, MSCs were detected, fixed for 10 min in the fixative solution, then washed and incubated overnight at 37°C with fresh β-Gal staining solution. Cells were washed with PBS and counted using a light microscope (Eclipse Ti-S, Nikon, Florence, Italy).