Polyethylene glycol-mediated fusion between primary mouse mesenchymal stem cells and mouse fibroblasts generates hybrid cells with increased proliferation and altered differentiation

Bone marrow-derived mesenchymal stem cells (MSCs) can differentiate into different cell lineages with the appropriate stimulation in vitro. Transplantation of MSCs in human and other animal models was found to repair tissues through the fusion of transplanted MSCs with indigenous cells. We have generated mouse-mouse hybrid cell lines in vitro by polyethylene glycol-mediated fusion of primary mouse MSCs with mouse fibroblasts to investigate the characteristics of hybrid cells, including their potentials for proliferation and differentiation. Similar to the parental MSCs, hybrid cells are positive for the cell-surface markers CD29, CD44, CD49e, and Sca-1, and negative for Gr1, CD11b, CD13, CD18, CD31, CD43, CD45, CD49d, CD90.2, CD445R/B220, and CD117 markers. The hybrid cells also produce a high level of tissue nonspecific alkaline phosphatase compared to the parental cells. Conditioned medium of hybrid cells contain biologically active factors that are capable of stimulating proliferation of other cells. Although the parental MSCs can differentiate into adipogenic and osteogenic lineages, hybrid cells held disparate differentiation capacity. Hybrid cell lines in general have increased proliferative capacity than the primary MSCs. Our study demonstrates that proliferative hybrid cell lines can be generated in vitro by induced fusion of both immortal and primary somatic cells with primary MSCs.