Osteoblast-specific gene expression after transplantation of marrow cells: Implications for skeletal gene therapy

Abstract

Somatic gene therapies require targeted transfer of the therapeutic gene(s) into stem cells that proliferate and then differentiate and express the gene in a tissue-restricted manner. We have developed an approach for gene therapy using marrow cells that takes advantage of the osteoblast specificity of the osteocalcin promoter to confine expression of chimeric genes to bone. Adherent marrow cells, carrying a reporter gene [chloramphenicol acetyltransferase (CAT)] under the control of a 1.7-kilobase rat osteocalcin gene promoter, were expanded ex vivo. After transplantation by intravenous infusion, engrafted donor cells in recipient mice were detected by the presence of the transgene in a broad spectrum of tissues. However, expression of the transgene was restricted to osteoblasts and osteocytes, as established by biochemical analysis of CAT activity and immunohistochemical analysis of CAT expression at the single cell level. Our data indicate that donor cells achieved long-term engraftment in various tissues of the recipients and that the CAT gene under control of the osteocalcin promoter is expressed specifically in bone. Thus, transplantation of multipotential marrow cells containing the osteocalcin promoter-controlled transgene provides an efficacious approach to deliver therapeutic gene expression to osteoblasts for treatment of bone disorders or tumor metastasis to the skeleton.

Two Distinct Stem Cell Lineages in Murine Bone Marrow

“…However, in more recent studies, applying gene-tagged cells in a syngenic murine transplantation model, donor-derived MSCs were detected [39,51,52]. Therefore, it is likely that this discrepancy can be fully explained by the fact that the previous studies concerned allogeneic transplantation techniques rather than syngeneic ones.…”

Adult Stem Cell Mobilization Enhances Intramembranous Bone Regeneration: A Pilot Study

“…These endogenous progenitor cells can be mobilized to the PB [1,11,12,15,17,22,36,48,52]. Circulating MSCs, and perhaps other adult stem cells, home to sites of skeletal injury [14,23,29,35,45,54], and increasing the number of adult stem cells at sites of injury aids tissue regeneration [4,8,16,40,43,56] either directly or through trophic effects [5,8,17,53].…”

Rapid expansion of recycling stem cells in cultures of plastic-adherent cells from human bone marrow

“…The isolated cells were shown to be multipotential in that they differentiated in culture or after implantation in vivo into osteoblasts, chondrocytes, adipocytes, and myotubes. After systemic infusion of MSCs, progeny of the cells appeared in a variety of tissues, including bone (22)(23)(24)(25), cartilage (22,23), lung (22,23,26), spleen (26), and thymus (26). Also, engraftment of donor MSCs into repairing muscle was observed after either local injection or systemic injection (27).…”