Orthotopic location has limited benefit from allogeneic or autologous multipotent stromal cells seeded on ceramic...

Improvement of tissue-engineered grafts is still a challenge in the field of regenerative medicine. Using multipotent stromal cells (MSCs), which have immunosuppressive qualities in an allogeneic situation, off-the-shelf implants can be created. This study compared allogeneic and autologous MSCs at an orthotopic (L1 transverse process model) and ectopic (intramuscular) implantation location in 2-year-old goats. Further, the possible additional effect of platelet-leukocyte gel (PLG) as a source of growth factors on bone formation was investigated. For the orthotopic implantation, cassettes were implanted in nine goats bilaterally on the lumbar transverse processes, either with PLG-seeded or with plasma-seeded constructs. To assess the onset of bone formation, fluorochromes were administered at weeks 3, 5, and 9. Their incorporation in newly formed bone indicated that seeded cells enhanced bone formation in the first weeks. Nevertheless, after 16 weeks no beneficial effects of cells were found in the cassettes in contrast to the ectopic location. No effect of PLG on bone formation was shown at either location. Finally, we show no significant difference in bone formation between autologous and allogeneic MSCs, an important finding when considering the use of allogeneic cells as an off-the-shelf component in tissue-engineered bone in goats.