Abstract
BACKGROUND: Although in vitro and in vivo experiments have suggested that mesenchymal stromal cells (MSC) may have important immunomodulatory functions in allogeneic hematopoietic cell transplantation (HCT), results from clinical studies have been inconsistent. In the current study we investigate the safety of dog leukocyte antigen (DLA) identical or third party unrelated MSC in DLA-identical HCT. RESULTS: There were no differences between treatment groups in depth of granulocyte or platelet nadirs, time to granulocyte or platelet engraftment, rate of acute GVHD or rejection. All dogs tolerated the MSC infusion well, although 2 dogs treated with unrelated MSC were euthanized on day 9 due to complications unrelated to the MSC infusion. While no formation of ectopic tissue was observed, GFP positive signals in bone marrow, spleen or liver were detected at time of necropsy in 75% and 50% of dogs treated with DLA-identical or unrelated MSC, respectively. DISCUSSION: Treatment with DLA-identical or unrelated MSC in high dose DLA-identical HCT is safe, and provides a large animal HCT model in which to investigate immunological mechanisms and optimal treatment strategies for future human trials. METHODS: Fourteen dogs were treated with 920 cGy total body irradiation (TBI) followed by transplantation of marrow from DLA-identical littermates and immunosuppression with cyclosporine. Prior to infusion of marrow, dogs received infusions of DLA-identical MSC from the marrow donor (n = 4), unrelated MSC (n = 4), or culture medium (n = 6), within 1 h of TBI. MSC obtained from relevant donors were ex-vivo expanded and transduced with GFP-retrovirus before infusion.