Phenotypic characteristics of hybrid cells produced by cell fusion of porcine adrenal chromaffin cells with human mesenchymal stem cells: a preliminary study

Abstract Background and purpose: Transplantation of adrenal chromaffin cells (CCs) that release endogenous opioid peptides and catecholamines produces significant antinociceptive effects in patients with terminal cancer pain. In clinical practice, however, obtaining a sufficient number of chromaffin cells may not be possible because of the limited availability of human adrenal tissue. Recent works have shown that fusion of bone marrow-derived cells with differentiated cells can occur spontaneously in vivo and acquire the phenotype of the recipient cells. In this study, we investigated the possibility of producing chromaffin-like cells by fusing human bone marrow-derived mesenchymal stem cells (MeSCs) with post-mitotic porcine CCs in vitro with the application of polyethylene glycol (PEG). Methods and results: Before cell-to-cell fusion was initiated, MeSCs and CCs were labeled by fluorescence dyes DiO (green) and Dil (red), respectively. The hybrid cells generated by PEG-mediated fusion expressed a DiO and Dil double-staining with estimated fusion efficiency at ∼40% of the total cell population. Further immunocytochemical examination for tyrosine hydroxylase and methionine enkephalin (markers for CCs) demonstrated positive immuno-reactivity in these hybrid cells 2 weeks post-fusion. More interestingly, some of the hybrid cells showed bromodeoxyuridine (BrdU)-positive immunostaining in the nuclei. Discussion: Our results show that these hybrid cells fused by CCs and MeSCs express some characteristics of the CC phenotype. A subpopulation of these hybrid cells are dividing cells with positive BrdU immunostaining, suggesting that a novel cellular production could be developed by a "reprogramming" mechanism through the application of targeted cell fusion strategies.