Monitoring immune response after allogeneic transplantation of mesenchymal stem cells for osteochondral repair.

The aim of this study was to investigate the safety of using allogeneic magnetically labelled mesenchymal stem cells (m-MSCs) to ameliorate osteochondral repair, with immune surveillance using a mixed lymphocyte reaction (MLR) assay. Twenty knees of Japanese white rabbits were randomly divided into two groups: the control (autologous) group, where 2 × 105 autologous m-MSCs were transplanted into the defect site; the experimental (allogeneic) group, where 2 × 105  m-MSCs from Dutch rabbits were transplanted into the defect of Japanese white rabbits. The rabbits were then euthanized after 12 weeks. The repaired tissue was stained with toluidine blue stain in order to produce histological scoring on the Fortier scale. Splenocytes were used to evaluate anti-donor alloreactivity by a MLR assay using the carboxyfluorescein diacetate succimidyl ester (CFSE) labelling technique (CFSE-MLR). In both groups, complete repair of the subchondral bone covered by a layer of chondrogenic tissue was confirmed. Also, there was no histologically significant difference on the Fortier scale. Using the CFSE-MLR assay, CD4+ T-cells showed alloreactivity in each combination, while the stimulation index of CD4+ T-cells was not statistically different between the control and experimental groups. Allogeneic m-MSCs are a safe alternative source to autologous m-MSCs, upholding repair of an osteochondral defect for clinical application using universal donor MSCs through a one-stage surgical procedure. Copyright © 2017 John Wiley & Sons, Ltd.