Introduction of hIGF-1 Gene into Bone Marrow Stromal Cells and Its Effects on the Cell's Biological Behaviors

Autologous and gene-modified bone marrow stromal cells (MSCs) have shown a bright future in clinical applications. However, does a gene-modified MSC still maintain its stem cell-like properties? To answer this question, human IGF-1 was introduced into rat MSCs using a recombinant retroviral vector and the effects of the gene manipulation on the cells' behaviors were investigated. The MSCs transfected with hIGF-1 could secrete 6.7-fold higher IGF-1 than the native cells. These MSCs had an elevated baseline activity of ERK signaling, an enhanced proliferation, increased accumulative numbers of cell doublings, and a reduced apoptosis; they showed upregulated expressions of OCT-4, CYP51, and SM22α, and a downregulated expression of nestin. This indicates that the overexpressed IGF-1 enhances the MSCs' self-renewal, endodermal and mesodermal differentiation, but weakens their neuronal potential. Although a puromycin selection after hIGF-1 gene transfection could produce a purer transfected MSC population with stronger ability to express functional hIGF-1, it induced premature senescence of the selected cells by activating oncogene Ras, leading to a shortened replicative life span and a weakened multipotency.