Expansion of multipotent and lymphoid-committed human progenitors through intracellular dimerization of Mpl

Abstract

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A hyperactive Mpl-based cell growth switch drives macrophage-associated erythropoiesis through an erythroid-megakaryocytic precursor

“…by guest www.bloodjournal.org From point to a potentially important role for macrophages in these expansion cultures. Although some CGS-based cultures have been reported to support the expansion of primitive hematopoietic cells, 15,19,21,22 the cultures described here do not support the large-scale expansion of primitive HSPCs necessary for enhancing long-term engraftment.…”

“…3 Artificial cell growth switch (CGS) receptors of this type encoding the signaling domain of the thrombopoietin (TPO) receptor (Mpl) have proven especially useful for the regulated expansion of selected hematopoietic lineages in multiple settings. [11][12][13][14][15][16][17][18][19][20][21][22][23] The 635-aa native Mpl protein, also known as CD110 and TPO-receptor, is a major regulator of megakaryocyte and platelet formation and has also been implicated in HSPC maintenance. [24][25][26] Ex vivo culture and in vivo transplantation studies with constitutively active viral vectors expressing the artificially dimerizable version of this Mpl-based CGS receptor in HSPCs from mice, [13][14][15] dogs, 16,17 and humans [18][19][20][21][22][23] demonstrated an unexpected and disproportionate effect of CIDmediated expansion on primitive erythroid cells, and to a lesser extent T and B lymphocytes, as well as megakaryocytes and platelets.…”

“…Studies with high vector doses and highly purified HSPC populations provided evidence that this CGS system was capable of expanding HSPCs from human cord blood. 21,22 However, most studies with cord blood CD34 1 cells in culture, and all transplantation studies in mice and dogs, showed no evidence for CGS-mediated expansion of primitive HSPCs. Furthermore, efforts to use this system for cell expansion from adult sources of human HSPCs have also met with limited success.…”

Optimizing autologous cell grafts to improve stem cell gene therapy

“…A derivative of the thrombopoietin receptor (mpl) incorporated into a fusion protein (F36Vmpl) has the potential to respond to a nontoxic chemical inducer of dimerization (CID) and selectively expand transduced hematopoietic cells of mostly erythroid and lymphoid lineage [100–103]. It has been reported that by targeting primitive human progenitors (CD34+CD38-Lin-CD7-), mpl dimerization induces, both in vitro and in vivo, a rapid expansion of not only differentiated but also of multipotent progenitors, in the absence of exogenous cytokines [104]. …”

Creating genetic resistance to HIV

“…Brief analytical treatment interruptions of cART may enhance in vivo selection of the protected cells and are useful in analyzing the antiviral efficacy of the gene therapy. Animal models are also proving useful to explore additional strategies for in vivo selection, such as the inclusion of chemically inducible survival factors [65, 66] or the co-expression of a chemotherapeutic resistance gene under drug selection [17, 63]. …”