Improved Engraftment Of Human Hematopoietic Stem Cells In NOD/SCID Mice By Antioxidant

NOD/SCID mice are a widely used human-mouse xenotransplant model in detecting engrefment of human Hematopoietic Stem Cells (HSCs). However, the efficiency of engraftment remains to be improved. A number of factors are considered to have an effect on the engraftment such as radiation dose, cell dosage, age and sex of mice, maternal and neonatal characteristics of the cord blood donor and so on. However, the effects of reactive oxygen species (ROS) on the transplantation of human HSCs after sub lethal irradiation in NOD/SCID mice have not been investigated.HSCs are defined by their ability of both self-renewal and long term multi-lineage engraftment. It is important that the HSCs bone marrow niche and its components protect stem cells from stress, such as accumulation of ROS and DNA damage. For example, total body irradiation can lead to persistent oxidative stress and ROS production in recipient bone marrow. ROS have been shown to regulate the HSC fate. A proper association between donor HSCs and their recipient microenvironment is essential for the survival and proliferation of transplanted HSCs.We hypothesized that the poor engraftment of human hematopoietic cells in NOD/SCID recipients may be partially due to increased levels of ROS in bone marrow microenvironment. To this end, we first measured the levels of ROS in NOD/SCID in comparison with other mouse strains. We found that NOD/SCID mice had a higher ROS level in bone marrow cells in comparison with age-matched B6.SJL and BALB/C mice (B6.SJL:38.49±4.829,BALB/C:55.42±7.301, NOD/SCID:638.1±136.9,p<0.0001).We transplanted human CD34+cells into NOD/SCID mice that were pre-exposed to NAC, to exame whether human hematopoietic engraftment can be improved in the NAC-treated NOD/SCID mice. Besides, Umbilical Cord Mesenchymal Stem Cells (UC-MSCs) were transfected by using pMSCV carrying GFP (pMSCV-GFP) and pMSCV carrying Catalase(pMSCV-GFP-CAT). The ROS of H2O2and·OH could be decreased by CAT, when we transplanted HSCs with UC-MSCs to NOD/SCID mice.It is concluded that the ROS levels were decreased modestly in bone marrow cells compared to control group (p< 0.0001).NAC administration significantly enhanced the engraftment of human CD34+cells in NOD/SCID mice 8-12 week post-transplantation. UC-MSCs were successfully transfected by retrovirus carrying GFP or CAT gene, the activity of catalase increased by 3.4-fold. The tansfected UC-MSCs maintain proliferation potential and ability of differentiation into osteoblasts and adipocytes. In short, our study offered an useful method to improve the human hematopoietic engraftment in the NOD/SCID model.