Fig. 4

Irradiated MSPC maintain their immunomodulatory potency in vitro and their differentiation capacity in vivo. a Direct comparison of the inhibition of phytohemagglutinin (PHA)-induced T-cell proliferation (green bar) by non-irradiated bone marrow (BM)-MSPCs (-Rx; blue bars) versus 30 Gy irradiated BM-MSPCs (+Rx; hatched blue bars) immediately after thawing (off-the-shelf use; dark grey area) or after a 3-day rescue culture (light grey area) showed no significant difference at the three ratios as indicated (*p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001). Grey bar shows mean ± SD of unstimulated pooled T-cell proliferation. One representative experiment out of two is shown. b Representative histologic analysis of ectopic ossicles derived from native (non-irradiated, upper pictures) and irradiated (Rx; 30 Gy, lower pictures) BM-MSPC (n = 6 per group) 6 weeks after subcutaneous transplantation into immunocompromized NSG recipient mice. Bone formation via a vascularized cartilage intermediate was evident in hematoylin and eosin (HE; left panels) as well as Movat’s pentachrome (Movat; middle panels) staining. Vimentin staining (right panels) indicating persistence of reticular stromal cells (MSPCs) within the ectopic ossicles which showed infiltration by (human (hu.) Vimentin-negative) murine hematopoiesis as described previously only for native (non-irradiated) BM-MSPCs [27]. Scale bars are 100 μm in main histophotographs and 1 mm in inserts (showing overview of a section through the entire ossicle; dotted rectangles indicate the regions from where the magnified main pictures were derived). n.s. Not significant, pPBMC Pooled peripheral mononuclear cell