Mesenchymal Stromal Cells Fail to Prevent Acute Graft-versus-Host Disease and Graft Rejection after Dog Leukocyte Antigen-Haploidentical Bone Marrow Transplantation

Clustering analysis of genes expressed by DS1-3. Three separate mRNA preparations were analyzed for each DS line. First, genes on the canine mRNA arrays (Affymetrix) with raw expression levels >100 were selected. Second, a group of 130 genes with functional annotations allowing them to be classified as “extracellular” by Gene Ontology were chosen and were found to include secreted factors, cell surface receptors, and extracellular matrix proteins. The clustering analysis by the Agilent GeneSpring GX7.3.1 program was based on average linkage, using the Pearson correlation. DS2 and DS3 differ from DS1 and from each other.

Inhibition of T cell proliferation in canine allogeneic MLC by different marrow stromal cell lines (DS1-3) under contact and noncontact conditions, and by stromal cell–conditioned medium. (A) Standard MLC was set up using PBMCs from unrelated DLA-mismatched dog pairs. Different MSC lines, designated DS1-DS3, were irradiated and added at the initiation of MLC at a 2:1 responder/MSC ratio. All 3 DS lines tested had suppressive effects on T cell proliferation. (B) Five-day DS cell CM was produced, concentrated 10-fold, and then added to allogeneic MLC in a 1:9-ratio with fresh medium. The left panel shows results for CM from individual DS lines. The right panel shows results for CM produced by coculture of the 3 DS lines (DS1/2/3 CM). (C) DS1 or DS3 cells were irradiated and cocultured with responder and irradiated stimulator PBMCs in allogeneic MLC established on 24-well plates. DS cells were either cultured in direct contact with responders/stimulators or separated by a 0.3-μm porous membrane on Transwell inserts (+ insert). “Allo Control” refers to allogeneic MLC without addition of DS cells; “Auto Control” refers to MLC without addition of DS cells using autologous responder and stimulator cells. One of 3 representative experiments is shown. Results for each experimental condition represent the mean ± standard error of the mean of 6 replicate wells. An asterisk indicates a statistically significant decrease in proliferative activity compared with Allo Controls (P < .05, 2-tailed, Mann-Whitney U test).

Canine MSC lines DS1, DS2, and DS3 inhibit alloantigen- and mitogen-induced T cell proliferation in a dose-dependent fashion. Different numbers (3.12-50.0 × 10³) of DS1, DS2, and DS3 cells, used singly or in combination (DS-Mix), were irradiated and added to 10⁵ canine PBMCs that were stimulated with 10⁵ irradiated allogeneic stimulator PBMCs in allogeneic MLC or Con A. Shown are 1 of 5 representative experiments using individual DS lines, and 1 of 2 representative experiments using the DS-Mix. Results for each experimental condition represent the mean ± standard error of the mean of 6 replicate wells. An asterisk indicates a statistically significant decrease in proliferative activity compared with controls cultured without DS cells (P <.05, 2-tailed, Mann-Whitney U test).

In vivo distribution of ¹¹¹In-labeled DS1 cells in a beagle dog (G-943). DS1 cells were labeled with ¹¹¹In in vitro and then injected into the dog immediately after 8 Gy TBI (delivered at 7 cGy/min as a single fraction). The dose of labeled and subsequently injected DS1 cells was 28 × 10⁶/kg recipient weight. Single-photon emission computed tomography images were obtained immediately after injection and at 1, 2, 4, and 9 days after injection. Shown are anterior views in craniocaudal (top to bottom) orientation.

Survival of dogs prepared with 9.2 Gy TBI followed by bone marrow transplantation from a DLA-haploidentical donor. No pharmacologic immunosuppression was administered after transplantation. MSC: MSC infusions were given after transplantation (n = 15). Control: No MSC infusions were given after transplantation (n = 11) [29]. One dog given MSCs (H-130; see Table 2) rejected the graft and, after prolonged myelosuppression, survived with autologous hematopoiesis (absolute neutrophil and platelet counts exceeding 0.5 × 10³/μL and 20 × 10³/μL on days 40 and 56 after transplantation, respectively). Survival did not differ significantly between the 2 groups (P = .18, log-rank test).