CD105 Is a Surface Marker for Receptor-Targeted Gene Transfer into Human Long-Term Repopulating Hematopoietic Stem Cells

Abstract

Hematopoietic stem cells (HSCs) are an important target cell population for gene therapy since they can reconstitute the entire hematopoietic system. HSC-enriched cell populations can be recognized based on cell surface marker expression, such as CD34, which is broadly expressed on immature and partially differentiated cells. In mice, co-expression of CD34 and CD105 was previously shown to be relatively more specific for the most immature, long-term repopulating HSCs. Here, we evaluated whether CD105, which is expressed on 30%-80% of CD34(+) cells, is a marker also for human long-term repopulating HSCs. Therefore, we tracked the mature progeny of CD34(+) cells transduced with the CD105-targeted lentiviral vector CD105-LV in xenotolerant mice. Transduction was blocked with soluble CD105 protein confirming specificity. Importantly, CD105-LV transduced human CD34(+) cells engrafted in NOD-scid IL2Rγ(-/-) mice with up to 20% reporter gene-positive cells detected long term in all human hematopoietic lineages in bone marrow (BM), spleen, and blood. In addition, competitive repopulation experiments in mice showed a superior engraftment of CD105-LV transduced CD34(+) cells in BM and spleen compared with cells transduced with a conventional nontargeted lentiviral vector. Thus, human CD34(+)/CD105(+) cells are enriched for early HSCs with high repopulating capacity. Targeting this cell population with CD105-LV offers a novel gene transfer strategy to reach high engraftment rates of transduced cells and highlights the applicability of receptor-targeted vectors to trace cell subsets offering an alternative to prospective isolation by surface markers.

Endoglin: a novel target for therapeutic intervention in acute leukemias revealed in xenograft mouse models

“…26 Further subfractionation of BM and cord blood based on CD38 expression revealed that CD105 is present in both fractions, but abundantly on the CD34 1 CD38 2 subpopulation (supplemental Figure 1C-D). Before investigating the expression of this receptor on malignant CD34…”

Cellular Innate Immunity and Restriction of Viral Infection: Implications for Lentiviral Gene Therapy in Human Hematopoietic Cells

“…LVs pseudotyped with a baboon retroviral envelope glycoprotein (BaEV) [112] or Measles virus glycoprotein [113] that do not rely on LDL-R for entry have been suggested to out-perform the VSV-g pseudotyped one in T and B cells as well as in quiescent CD34 + HSPC. Targeting LVs towards more primitive subsets of HSPC by exploiting the subset-specific expression of surface markers such as CD105 and CD133 has also shown promising results regarding preferential transduction of long-term repopulation HSC [114,115]. We have discussed here how LV transduction could potentially trigger innate immune responses not only in differentiated hematopoietic target cells, such as dendritic cells or macrophages, but also in HSPC, with potential consequences both in terms of efficiency of gene transfer as well as biological integrity of the target cells.…”

Serial transplantation reveals a critical role for endoglin in hematopoietic stem cell quiescence

“…Nevertheless, we and other investigators have observed that this receptor is expressed in the HSC of every hematopoietic site, including the aorta-gonad-mesonephros, 19,20 the fetal liver, 21 and the adult BM. 22 In BM, Eng has been shown to selectively mark the LT-HSCs in mice 22,23 and humans; [24][25][26] however, it remains unknown whether this receptor is required for HSC function.…”