Allogeneic hematopoietic cell transplantation (HCT) is increasingly utilized in the treatment of hematologic malignant and non-malignant diseases. Therapy-related toxicity and graft versus host disease (GVHD) remain major challenges, with acute lung injury being associated with significant morbidity and mortality. Prolyl hydroxylase inhibitors (PHI) interfere with signaling cascades of inflammation and cell death. Their beneficial use in experimental models of ulcerative colitis and lung allograft rejection resulted in the hypothesis, that the PHI DMOG (Dimethyl oxalyl glycine) may reduce lung injury evolving after murine allogeneic HCT.
14 week old BALB/c were conditioned with 750 cGy single dose TBI, followed by transplantation of 5×10E6 bone marrow cells and 4×10E6 splenocytes from either syngeneic BALB/c or allogeneic C57BL/6 donors. DMOG in PBS was given to both syngeneic and allogeneic recipients at 8mg per mice ip on alternate days for the first two weeks post-transplant and then twice a week till day 50, while syngeneic and allogeneic controls received PBS only. Animals were monitored for clinical GVHD and survival. At day 50 post HCT, gut, liver and lung pathology as well as BAL fluid T cell numbers were assessed by using a scoring system quantifying severity and extent of parenchymal and peribronchial/perivascular infiltrates and flow cytometry, respectively. In addition, T cell expansion was analyzed both in vivo in the spleen on day +7 and in vitro by mixed lymphocyte reaction (MLR).
Allogeneic HCT resulted in severe lung pathology in PBS treated animals (mean 118.8±47.19), but was significantly reduced when DMOG was given (36.0±17.99; p < 0.05), and absent in both PBS and DMOG treated syngeneic controls. Consistently, BAL CD4+ and CD8+ T cells in DMOG recipients were decreased by 53.7% and 68.4%, respectively, when compared to PBS controls. Decreased pulmonary injury was associated with a trend towards better overall survival by day 50 (allogeneic DMOG: 59.2% vs allogeneic PBS 40.7%) and all syngeneic recipients survived. GVHD related injury to liver and GI tract at time of analysis was not different between allogeneic groups. Alloreactive proliferative T cell responses in vitro were suppressed in the presence of DMOG at a concentration of 1mM (cpm after 96h: mean 29316±875.9 vs 41735±3085; p < 0.01). In vivo, splenic T cell expansion of CD4+ but not CD8+ T cells was reduced at day +7 as well (p < 0.05). Interestingly, when compared to PBS treated controls reduced mortality of DMOG treated allogeneic HCT recipients could already be seen soon after HCT (day +10: 26.0% vs 11.1%) in association with decreased CD4+ T cell proliferation, while lung injury in this model this early is rather marginal.
DMOG treatment decreases the severity of acute noninfectious lung injury and improves overall survival after allogeneic HCT. While impaired early T cell responses likely contribute to improvement of both endpoints, altered recruitment of CD8+ T cells to the lung seems to uniquely affect the development of pulmonary but not gastrointestinal and hepatic injury at later time points. Current studies are ongoing to delineate the effects of DMOG on T cell proliferation and recruitment to different target organs, and to define the role of this novel approach in the prevention and treatment of HCT related complications.
No relevant conflicts of interest to declare.
Asterisk with author names denotes non-ASH members.