Mouse Bmi1 Lentivirus (CMV, Puro)

Responsible for transporting oxygen and exchanging carbon dioxide, red blood cells (RBCs) are essential for our health. As the population ages, the need for RBC transfusions is expected to increase, necessitating the need for alternative RBC sources to meet this demand. Previous studies have shown that RBCs derived from early mouse embryos can undergo extensive self-renewal in vitro for up to several months. To better understand the mechanisms regulating extensive RBC self-renewal, researchers analyzed global gene expression datasets of self-renewing and differentiating RBCs and revealed differential expression of Bmi-1. Bmi-1 overexpression confers extensive self-renewal capacity to adult bone marrow-derived self-renewing RBCs, which normally have limited proliferative potential. Importantly, Bmi-1 transduction did not interfere with the ability of extensively self-renewing erythrocytes (ESREs) to terminally mature in vitro or in vivo. Bmi-1-induced ESREs can be used to generate in vitro models of intrinsic erythrocyte diseases and ultimately serve as a source of cultured RBCs for transfusion therapy.

Adult SREs transduced with an empty lentiviral vector ceased to proliferate within 2 weeks, consistent with their limited in vitro self-renewal capacity. In contrast, erythroid cells transduced with mouse Bmi1 lentivirus proliferated for at least 25 days in 10 of 11 bone marrow-derived SRE cultures (Figure 1A), and 3 cultures of Bmi-1-induced ESRE (iESRE) were maintained for more than 100 days (Figure 1B). Because the Bmi-1 expression vector contains GFP, the researchers analyzed the percentage of erythroid cells that were transduced with Bmi-1 during culture. Although 20%–30% of erythroid cells were initially GFP+ after transduction, nearly all erythroid cells in the extensive proliferation phase were GFP+ (Figure 1C), consistent with the notion that Bmi-1 expression promotes erythroid self-renewal. In fact, BMI-1 was overexpressed in these transduced iESREs compared with fetal-derived ESREs.

Figure 1. Bmi-1 is sufficient to induce the extensive ex vivo self-renewal of adult erythroblasts. (A) Lentiviral transduction of mouse Bmi-1 resulted in prolonged proliferation of bone marrow-derived SREs grown in erythroid expansion medium. (B) Bmi-1-induced ESRE (iESRE) was maintained for 100 days with more than 1030-fold expansion of total erythroid cells. (C) The percentage of erythroid cells transduced with Bmi-1 (GFP+ cells) was analyzed at 3 and 18 days post-infection. (Kim A R, et al. 2015)