Abstract
Cord blood (CB) is an attractive source of hematopoietic stem cells (HSCs) for hematopoietic cell transplantation. However, its application remains limited due to the low number of HSCs/progenitors in a single CB unit and its notoriously difficulty in expanding ex vivo. Here, we demonstrated that the human fetal liver sinusoidal endothelial cells engineered to constitutively express the adenoviral E4orf1 gene (hFLSECs-E4orf1) is capable of efficient expansion ex vivo for human CB hematopoietic stem and progenitor cells (HSPCs). Coculture of CD34+ hCB cells with hFLSECs-E4orf1 resulted in generation of substantially more total nucleated cells, CD34+CD38− and CD34+ CD38−CD90+ HSPCs in comparison with that of cytokines alone after 14 days. The multilineage differentiation potential of the expanded hematopoietic cells in coculture condition, as assessed by in vitro colony formation, was also significantly heightened. The CD34+ hCB cells amplified on hFLSECs-E4orf1 were capable of engraftment in vivo. Furthermore, hFLSECs-E4orf1 highly expressed hematopoiesis related growth factor and Notch receptors. Accordingly, the CD34+ hCB cells amplified on hFLSECs-E4orf1 exhibited Notch signaling activation. Taken together, our findings indicated that FLSECs may potentially be the crucial component of the microenvironment to support recapitulation of embryonic HSC amplification in vitro and allow identification of new growth factors responsible for collective regulation of hematopoiesis.
Highlights
Hematopoietic stem cells (HSCs) can recreate a new functional hematopoietic system in recipients with high-risk leukemias or other hematologic cancers
We found that CD34+ hCB cells cocultured with hFLSECs-E4orf1 showed a significant increase above that of cytokines alone in the numbers of hematopoietic stem and progenitor cells (HSPCs) as determined by phenotype and colony assays while the expanded cells in coculture group had in vivo repopulating capacity in NSG mice
We demonstrated for the first time that hFLSECs-E4orf1 provided proper cues that enable effective expansion of CD34+ hCB cells with multipotency in vitro and engraftment capability in NSG mice
Summary
Hematopoietic stem cells (HSCs) can recreate a new functional hematopoietic system in recipients with high-risk leukemias or other hematologic cancers. The application of CB transplants remains strongly limited owing to the low absolute numbers of functional and engraftable hematopoietic stem and progenitor cells (HSPCs) within a single CB unit, which often leads to delayed neutrophil engraftment and increased mortality. To break this severe bottleneck, multiple attempts have been made to explore optimal methods for ex vivo HSC expansion, including a combination of cytokines [2], coculture with stromal cells [3,4,5], small molecules [6,7,8,9], and some specific molecular targets [10,11,12]. It is highly necessary to make further efforts to understand the crucial elements in HSC amplification in vivo
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