Umbilical cord blood stem cells as targets for genetic modification: new therapeutic approaches to somatic gene therapy.

Human umbilical cord blood is an abundant source of long term repopulating stem cells and therefore we investigated the utilization of these cells as targets for genetic manipulation directed towards human gene therapy. Using two different retroviral vectors, one which transfers the neomycin resistance gene and the other which transfers therapeutically relevant adenosine deaminase gene, we have demonstrated increased gene transfer efficiency into committed progenitor cells (CPCs) and long term culture-initiating cells (LTC-IC) derived from cord blood versus adult bone marrow. We further identified a chymotryptic fragment of the extracellular matrix molecule fibronectin (FN 30/35), to which primitive hematopoietic cells adhere. Gene transfer efficiency into hematopoietic cells adherent to FN 30/35 is significantly increased when compared to infection on bovine serum albumin-coated control plates. Utilization of this fragment allowed retroviral mediated gene transfer into cord blood derived CPCs and LTC-ICs with high efficiencies, similar to that observed after coculture of hematopoietic cells on virus producer cells. These data imply cord blood may be a promising source for efficient gene delivery to the human hematopoietic system, and the utilization of the FN 30/35 fibronectin molecule may provide a clinically applicable protocol to achieve this aim.