Abstract
BACKGROUND: Graft versus host disease (GVHD) remains the major cause of morbidity and mortality following allogeneic hematopoietic stem cell transplantation (HSCT). Due to their immunomodulatory properties, mesenchymal stem cells (MSCs) have produced durable responses in HSCT patients with steroid resistant GVHD, but their positive effects are not seen in all patients. Sackstein et al have shown that MSCs lack an E-selectin ligand on their surface, which impairs their ability to home to the bone marrow and potentially to sites of inflammation associated with GVHD. Our in vitro results confirmed that fucosylation markedly enhanced the E-selectin ligand expression on the MSC cell surface and did not adversely affected MSCs immunomodulatory properties. Hencewe postulated that ex-vivo fucosylation of MSCs would enhance their homing to sites of inflammantion and thus their clinical efficacy in our NOD/ SCID/IL-2R null (NSG) mouse model of GVHD.
METHODS: On day -1 NSG mice were sub-lethally irradiated (300cGy) and infused with 2x106 fucosylated MSCs. Briefly, healthy bone marrow donor derived MSCs were treated for 30 minutes at room temperature with FT-VI (33ng/ml) and GDP-fucose (1mM) (Targazyme, Carlsbad, CA), and then washed prior to tail vein injection. Control mice received 2x106 unfucosylated MSCs or no MSCs. On day 0 all mice received 1x107 normal human donor peripheral blood mononuclear cells (PBMNCs), representing a MSCs:PBMNCs ratio of 1:5. Mice were then followed for weight loss, clinical GVHD score and survival.
RESULTS: We found that a single dose of FT-VI treated MSCs reduced the acute severity of GVHD compared to unfucosylated MSCs and no MSCs (PBMNCs alone) in this xenogeneic mouse model. This was shown by prevention of weight loss (Fig. 1a), and lower GVHD scores (Fig 1b) in the FT-VI treated MSCs mice. Furthermore, when short-term survival was compared among the subgroups, unfucosylated MSCs did not significantly improve short-term survival over PBMNCs group (P=0.3) (Fig. 2a). However, FT-VI treated MSCs mice showed a significantly longer short-term survival compared to PBMNCs group (P=0.002) (Fig. 2b) and untreated MSCs mice (P=0.02) (Fig. 2c).
CONCLUSION. Our data suggest that fucosylated MSCs exert a better anti-GVHD effect at a similar dose than unfucosylated MSCs. Additional data is being generated to confirm these preliminary results and optimize the dose and schedule of fucosylated MSCs.
No relevant conflicts of interest to declare.
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