Fibroblastoid colony forming unit (CFU-f) frequency and immunophenotype.

Mononuclear cells were isolated from bone marrow and seeded in dilution series with media containing 31 different HPLs or FCS – these experiments were performed with three individual MSC preparations. CFU-f frequency was assessed after 7 days via crystal violet staining (A). CFU-f frequency varied between different MSC preparations, but there was no association with HPL-donor age within either of the MSC preparations (B). Subsequently, cell preparations were expanded for one additional passage. Flowcytometry revealed the commonly described surface marker profile for MSC (C; autofluorescence =  black line). HPLs derived from younger donors (<35 years; n = 5), or HPLs derived from older donors (>45 years; n = 5) did not have significant impact on the immunophenotype (D). *P<0.05; scale bar = 500 µm.