Ex-vivo expansion of nonhuman primate CD34(+) cells by stem cell factor Sall4B.

BACKGROUND: Hematopoietic CD34(+) stem cells are widely used in the clinical therapy of complicated blood diseases. Stem cell factor Sall4B is a zinc finger transcription factor that plays a vital role in hematopoietic stem cell expansion. The purpose of our current study is to further evaluate how Sall4B might affect the expansion of CD34(+) cells derived from nonhuman primates.

METHODS: Sall4B was overexpressed in nonhuman primate bone marrow-derived CD34(+) cells via a lentiviral transduction system. The granulocyte-erythrocyte-macrophage-megakaryocyte colony-forming unit (CFU) assay evaluated the differentiation potential of primate CD34(+) cells that were expanded with Sall4B. Furthermore, an in-vivo murine system was employed to evaluate the hematopoietic potential of primate Sall4B-expanded CD34(+) cells.

RESULTS: Overexpression of Sall4B promoted ex-vivo nonhuman primate CD34(+) cell expansion by 9.21 ± 1.94-fold on day 9, whereas lentiviral transduction without Sall4B expanded cells by only 2.95 ± 0.77-fold. Sall4B maintained a significant percentage of CD34(+) cells as well. The CFU assay showed that the Sall4B-expanded CD34(+) cells still possessed multilineage differentiation potential. A study using nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice in vivo revealed that Sall4B led to an increase in the number of repopulating cells and the 9-day-old Sall4B-transduced CD34(+) cells still possess self-renewal and multilineage differentiation capacity in vivo, which are similar stemness characteristics to those in freshly isolated primate bone marrow-derived CD34(+) cells.

CONCLUSIONS: We investigated the expansion of nonhuman primate bone marrow-derived CD34(+) cells using the Sall4B lentiviral overexpression approach; our findings provide a new perspective on mechanisms of rapid stem cell proliferation. The utilization of Sall4B to expand CD34(+) cells on a large scale through use of suitable model systems would prove helpful towards preclinical trials of autologous transplantation.