In vitro studies of horse umbilical cord matrix-derived cells: from characterization to labeling for magnetic resonance imaging

Despite the increasing use of cell-based therapies for equine orthopedic problems, many questions remain to be answered, such as what is: the optimal cell source for particular injuries, the best timing and route of treatment and the long-term safety and efficacy of the procedure? Previously, equine mesenchymal stem cells (MSCs) have most frequently been isolated from bone marrow (BM) and adipose tissue. However, these cells have limited potential in terms of in vitro proliferation ability and differentiation capacity with increasing donor age and in vitro passage number. In addition, procurement of BM-derived cells in horses requires an invasive BM aspiration procedure which has been associated with pneumopericardium. Fetal adnexa could provide a useful alternative source of MSCs avoiding these limitations. To investigate this, we isolated and characterized presumptive stem cells from the intervascular and perivascular portions of equine umbilical cord matrix using enzymatic digestion. The cells isolated from the intervascular portion showed faster doubling times than cells from the perivascular portion (which are probably more highly differentiated). Cells from both portions expressed MSC mRNA markers (CD29, CD105, CD44, CD166) and were negative for CD34 and MHC-II. Osteogenic, adipogenic, chondrogenic and neurogenic differentiation were confirmed by specific staining and gene expression. To investigate the potential of umbilical cord-derived cells for use in cell therapies, pre-clinical experiments involving labeling of cells with magnetic resonance contrast agents (superparamagnetic iron oxide particles - SPIO - and manganese chloride) and the subsequent in vitro study of these were conducted. The SPIO labeling procedure proved to be an efficient and non toxic tool that merits further investigation and the possible development of in vivo studies.