The Effect of Omega-3 as a Dietary Supplement in a Mouse Model of Stem Cell Transplantation (SCT)

Introduction: Several studies reported the importance of nutrition on SCT outcome. Many food components have been shown to affect the immune system and to interact with a number of drugs used in conditioning and in prophylactic treatment during SCT. Omega-3 fatty acids have immuno-modulatory effects via improving endothelial function, protection against oxidative DNA damage and by suppressing CD4+ T-cell function and proliferation. In the present study we examined the effects of omega-3 on the immune system in mice undergoing SCT.

Method: Female BALB/c mice, 8 – 12 weeks, were randomised to receive either diet enriched with menhaden fish oil (omega-3) or, corn oil (rich in omega-6). Both groups were fed for two weeks prior to conditioning (Day 0 was set to be the day of transplantation). Both groups injected intra-peritoneally with 80mg/kg busulfan (Bu) for four days (day –7 to day –4) followed by 200mg/kg cyclophosphamide (Cy) for two days (days –3 & -2). At day 0, half of the mice of both groups were killed and bone marrow, spleen and thymus were harvested and analysed with FACS to evaluate the lymphoid and myeloid cell phenotype. Serum was collected for analysis of cytokines. The remaining mice in both groups were transplanted with allogeneic bone marrow from 8 – 12 weeks male C57BL/6 mice (2.0 × 10⁷ bone marrow cells and 3.0 × 10⁷ spleen cells).

Results: Mice fed an omega 3-rich diet showed significant decrease in bone marrow and spleen cellularity compared to that observed in the corn oil group. In particular, the splenic B-cell population was severely affected, showing a 50% decrease in the omega-3 group compared to that seen in corn oil group. The T-cell populations of omega-3 fed mice were also affected, with a significant decrease by 10 to 20 % in the number of CD4+ cells. In contrast, no difference was observed for CD8+ cells, compared to corn oil-fed mice. In the thymus, the number of activated T-cells was decreased by 50% in the omega-3 compared to that observed in corn oil group. NK cells were decreased by 50% in the spleens of omega-3 fed mice. In bone marrow, the myeloid cells (CD11b+) were significantly lower in omega-3 fed mice compared to corn oil-fed controls. All transplanted mice that had received an omega-3 enriched diet died within the first week. These data can be compared to our previous results where more than 60% of mice receiving standard diet survive during the first week and of which at least 20% reach day+21.

Conclusion: Omega-3 administration as a dietary supplement for two weeks prior to conditioning regimen showed significant effects on the immune system in terms of a pronounced alteration in the balance of different cells lineages in both bone marrow and spleen. Rapid death of omega-3 fed animals after allogeneic transplantation was observed. Further studies are warranted to investigate the role of omega-3 on the outcome of stem cell transplantation.