IntroductionMesenchymal stromal cells (MSCs) are multipotent stem cells able to differentiate into mesoderm-derived cells, 1 and exhibit immunoregulatory properties. 2 MSCs have been used in the context of allogeneic hematopoietic stem cell transplantation to improve hematopoietic engraftment, to prevent graft failure, and to reduce the incidence or severity of acute graft-versus-host disease (GVHD). [3][4][5] MSCs obtained from bone marrow (BM) can undergo in vitro expansion in medium containing either fetal calf serum (FCS), with or without fibroblast growth factor (FGF-2), or platelet lysate (PL). 6 However, little is known about the effect of donor selection or culture conditions on the functional properties and therapeutic potential of clinical-grade MSCs.Recent studies have suggested that MSCs can contribute to tumor growth and metastasis. 7 A related concern is the capacity of MSCs for oncogenic transformation. Mouse MSCs show chromosomal abnormalities and are highly susceptible to transformation associated with an increased telomerase activity and myc expression, and a loss of p53 and p16. [8][9][10] In contrast, human MSCs are more resistant to transformation in vitro with no genomic instability detected and no tumor induced after long-term in vivo transfer. [11][12][13][14][15] After 20 to 50 population doublings (PDs), human MSCs undergo replicative senescence, with telomere shortening and increased p16 expression. 16 They require the same steps to achieve transformation as for differentiated cells, suggesting that they are not prone to spontaneous transformation. 17 Nevertheless, one recent study described the transformation of human adipose tissue-derived MSCs with up-regulation of myc, repression of p16, acquisition of telomerase activity, 18 and generation of carcinoma in mice. 19 We investigated the immune properties and resistance to transformation of MSCs produced in 4 cell therapy facilities during 2 multicenter clinical trials designed to evaluate the capacity of BM-MSCs to prevent acute GVHD or to treat irradiationinduced lesions. MethodsDetails regarding methods are provided in the supplemental data (available on the Blood website; see the Supplemental Materials link at the top of the online article). For personal use only. on March 28, 2019. by guest www.bloodjournal.org From (1A to 11A) were done for the GVHD prevention clinical trial, and 4 (12A, 13A2) to treat accidentally irradiated patients. For irradiated patients, 5 supplemental MSC productions (12B to 16B) were done using human PL. 6 MSC production Growth kinetics and MSC characterizationGrowth kinetics was assessed by studying total fold increase, total number of PDs, and colony-forming unit-fibroblast. MSCs were screened for the expression of CD45, CD73, CD105, CD90, and human leukocyte antigen-DR (HLA-DR) and were also checked for their capacity to stimulate the growth of allogeneic peripheral blood mononuclear cells (PBMCs) and to inhibit alloantigen-driven proliferation of PBMCs. Cytogenetic analysisAt the end of the first (P ...

Mesenchymal stem cells (MSCs) have been shown to migrate to various tissues. There is little information on the fate and potential therapeutic efficacy of the reinfusion of MSCs following total body irradiation (TBI). We addressed this question using human MSC (hMSCs) infused to nonobese diabetic/ severe combined immunodeficient (NOD/SCID) mice submitted to TBI. Further, we tested the impact of additional local irradiation (ALI) superimposed to TBI, as a model of accidental irradiation. NOD/SCID mice were transplanted with hMSCs. Group 1 was not irradiated before receiving hMSC infusion. Group 2 received only TBI at a dose of 3.5 Gy, group 3 received local irradiation to the abdomen at a dose of 4.5 Gy in addition to TBI, and group 4 received local irradiation to the leg at 26.5 Gy in addition to TBI. Fifteen days after irradiation, quantitative and spatial distribution of the hMSCs were studied. Histological analysis of mouse tissues confirmed the presence of radio-induced lesions in the irradiated fields. Following their infusion into nonirradiated animals, hMSCs homed at a very low level to various tissues (lung, bone marrow, and muscles) and no significant engraftment was found in other organs. TBI induced an increase of engraftment levels of hMSCs in the brain, heart, bone marrow, and muscles. Abdominal irradiation (AI) as compared with leg irradiation (LI) increased hMSC engraftment in the exposed area (the gut, liver, and spleen). Hind LI as compared with AI increased hMSC engraftment in the exposed area (skin, quadriceps, and muscles). An increase of hMSC engraftment in organs outside the fields of the ALI was also observed. Conversely, following LI, hMSC engraftment was increased in the brain as compared with AI. This study shows that engraftment of hMSCs in NOD/ SCID mice with significantly increased in response to tissue injuries following TBI with or without ALI. ALI induced an increase of the level of engraftment at sites outside the local irradiation field, thus suggesting a distant (abscopal) effect of radiation damage. This work supports the use of MSCs to repair damaged normal tissues following accidental irradiation and possibly in

This is the first evidence of expanded MSCs homing in numerous tissues following a severe multi-organ injury in primates. Localization of the transduced MSCs correlated to the severity and geometry of irradiation. A repair process was observed in various tissues. The plasticity potential of the MSCs and their contribution to the repair process in vivo remains to be studied.

Objective-We hypothesized that adipose tissue may contain progenitors cells with cutaneous and angiogenic potential. Methods and Results-Adipose tissue-derived stroma cells (ADSCs) were administrated to skin punched wounds of both nonirradiated and irradiated mice (20 Gy, locally). At day14, ADSCs promoted dermal wound healing and enhanced wound closure, viscolesticity, and collagen tissue secretion in both irradiated and nonirradiated mice. Interestingly, GFP-positive ADSCs incorporated in dermal and epidermal tissue in vivo and expressed epidermal markers K5 and K14. Cultured ADSCs in keratinocyte medium have been shown to differentiate into K5-and K14-positive cells and produced high levels of KGF. At Day 7, ADSCs also improved skin blood perfusion assessed by laser Doppler imaging, capillary density, and VEGF plasma levels in both irradiated and nonirradiated animals. GFP-positive ADSCs incorporated into capillary structures in vivo and expressed the endothelial cell marker CD31. Finally, in situ interphase fluorescence hybridization showed that a small number of ADSCs have the potential to fuse with endogenous keratinocytes. Conclusion-ADSCs