Prevention of Idiopathic Pneumonia Syndrome by Intra-Bone Marrow Injection of Donor Cells

Abstract 1902

Several clinical and experimental studies have reported that a recently developed intra-bone marrow (IBM) stem cell transplantation (SCT) technique gives high rates of engraftment and is associated with a low incidence of acute graft-versus-host disease (GVHD). Idiopathic pneumonia syndrome (IPS) is a significant cause of mortality and remains a major obstacle after allogeneic SCT. In the present study, the extent of IPS after IBM-SCT was compared with that after conventional intravenous SCT (IV-SCT) using a lethally irradiated B6(H-2b) into F1 (H-2b/d) mouse IPS model.

Compared with IV-SCT, IBM-SCT significantly improved the clinical GVHD score and reduced total and CD3+ T cell numbers in bronchoalveolar lavage fluid (9.6± 3.5 vs. 21.3 ± 0.5 x10⁴/ml; p < 0.05). Histopathological examination of lung tissue at 6 weeks post-SCT showed significantly reduced IPS pathology in mice that underwent IBM-SCT. To explore the mechanisms of the reduction in IPS pathology in mice that underwent IBM-SCT, we monitored the in vivo distributions of infused donor cells and compared them between mice that underwent IBM-SCT versus IV-SCT. Recipient mice were imaged at different time points (1, 2, 3, and 6 h, and 1, 2, 3, and 5 days), using a lethally irradiated luciferase-expressing transgenic FVB/N (FVB/N luc+)(H-2q) into BALB/c (H-2d) mouse model. In vivo bioluminescence imaging (BLI) analysis revealed that the majority of injected donor cells were trapped in the lung 1 h after IV-SCT. In contrast, almost all donor cells were localized in the injected limbs 1 h after IBM-SCT, and significantly fewer cells had reached the lung (3.1± 0.7 vs. 16.7± 1.1 x10⁵ photons/sec/animal, IBM-SCT vs. IV-SCT, p < 0.01; Figure). After syngeneic (FVB/N luc+ into FVB/N) SCT, the majority of the injected cells were also trapped in the lung 1 h after IV-SCT, and a similar difference was observed in donor cell distribution in the lung after IV-SCT versus IBM-SCT (2.4± 0.6 vs. 11.6± 1.3 x10⁵ photons/sec/animal; p < 0.01). These results suggest that initial cell localization to the lung is dependent on the SCT method. At 2 days post-SCT, we examined the profiles of chemokines produced locally in the lung (CCL2, CCL3, CXCL1, CCL5, and CCL8). The mRNA expression of CC chemokines, especially CCL2, was more strongly induced in the lung after allogeneic IV-SCT than after allogeneic IBM-SCT (0.098 ± 0.020 vs. 0.020 ± 0.003 units/GAPDH mRNA; p < 0.05). A similar difference was observed between mice that underwent syngeneic IV-SCT and syngeneic IBM-SCT, suggesting that increases in chemokine levels in the lung early post-SCT are also dependent on the SCT method. At 5 days post-syngeneic SCT, BLI analysis revealed that no difference was observed in donor cell distribution in the lung after IV-SCT versus IBM-SCT (4.8± 1.1 vs. 4.6± 2.5 x10⁷ photons/sec/animal; p =0.94). On the other hand, the BLI signals dramatically increased in the lungs of mice that had undergone allogeneic IV-SCT after day 2 post-SCT and there was a significant difference in the BLI signals between IV-SCT and IBM-SCT mice at 5 days post-SCT (50.9± 6.6 vs. 16.0± 6.2×10⁷ photons/sec/animal; p < 0.05). These results suggest that increases in chemokine levels in the lung at day 2 post-SCT lead to increases in the allogeneic response in the lung.

In summary, we have shown that the initial localization of donor cells to the lung and increases in lung chemokine levels are dependent on the SCT method. The targeting of donor cell trafficking to the lung may be a promising strategy for preventing IPS, and IBM-SCT may reduce IPS after allogeneic SCT.

View largeDownload slide

View largeDownload slide

Close modal