Survival of human mesenchymal stromal cells from bone marrow and adipose tissue after xenogenic transplantation in immunocompetent mice

Introduction Mesenchymal stromal cells (MSC) represent an attractive cell population for tissue engineering purposes. As MSC are described as immunoprivileged, non-autologous applications seem possible. A basic requirement is the survival of MSC after transplantation in the host. The purpose of the current paper was to evaluate the survival of undifferentiated and osteogenically induced human MSC from different origins after transplantation in immunocompetent mice. Methods Human MSC were isolated from bone marrow (BMSC) and adipose tissue (ASC). After cultivation on mineralized collagen, MSC were transplanted subcutaneously into immunocompetent mice (n = 12). Undifferentiated MSC (group A) were compared with osteogenic-induced MSC (group B). Human-specific in situ hybridization and anti-vimentin staining was used to follow MSC after transplantation. Quantitative evaluation of lymphocytes and macrophages was performed as a measure of immunologic rejection. Unloaded scaffolds served as controls (group C). Specimens were harvested at 4 and 8 weeks. Results Undifferentiated BMSC and ASC were detected in the majority of cases after xenogenic transplantation (group A, a total of 22 out of 24 cases), while osteogenic-induced MSC (group B) could be detected in only three of 24 cases. Quantification of lymphocytes and macrophages revealed significantly higher cell numbers in group B compared with group A (P < 0.05). Discussion Our results suggest that undifferentiated MSC are candidates for non-autologous cell transplantation, while osteogenic-induced MSC seem to be eliminated by the host's immune system. This observation seems independent of the origin of MSC and applies to BMSC and ASC.