Cytokine Selection of MSC Clones with Different Functionality

Abstract

Summary: Mesenchymal stromal cells (MSCs) are used in many clinical applications. However, ex vivo expansion is required to reach clinically relevant cell numbers, which might lead to selection of clones with different characteristics. To follow clonal selection, we transduced MSC progenitors in umbilical cord pieces (UCPs) with vectors encoding fluorescent proteins and genetic barcodes. After marked MSC cultures grew out from UCPs, we investigated the influence of cytokines on MSC functionality. Specific cytokine conditions selected for clones from common progenitors. MSC secretome analyses revealed differences dependent on the culture conditions used. Clones expanded in human serum containing culture medium secreted a plethora of growth factors. When expanded in the same medium containing TGF-β, MSCs secreted negligible amounts of cytokines but at the same time led to an increased human chimerism after hematopoietic stem cell transplantation into immunodeficient mice. Our results suggest a major influence of cytokine additives on MSC functionality. : Rothe and colleagues transduced mesenchymal stromal cell initiating cells (MSC-I) in the umbilical cord pieces with lentiviral barcode vectors and observed a cytokine-dependent selection of MSC clones with common MSC-I. TGFB1 drastically decreased the cytokine production of selected MSCs, whereas the conditioned medium from these cultures enhanced the engraftment of human hematopoietic stem cells. Keywords: MSC, cytokines, expansion media, secretome, umbilical cord, genetic barcodes, clonal tracking, HSC, hematopoietic stem cells, engraftment, TGFB1