Bone marrow concentrate and expanded mesenchymal stromal cell surnatants as cell-free approaches for the treatment of osteochondral defects in a preclinical animal model.

To evaluate the regenerative potential of surnatants (SNs) from bone marrow concentrate (SN-BMC) and expanded mesenchymal stromal cells (SN-MSCs) loaded onto a collagen scaffold (SC) in comparison with cell-based treatments (BMC and MSCs) in an osteochondral (OC) defect model in rabbits. OC defects (3 × 5 mm) were created in the rabbit femoral condyles and treated with SC alone or combined with SN-BMC, SN-MSCs, BMC, and MSCs. In control groups, the defects were left untreated. At three and six months, the quality of regenerated tissue was evaluated with macroscopic, histologic, microtomographic, and immunohistochemical assessments. The production of several immunoenzymatic markers was measured in the synovial fluid. All proposed treatments improved OC regeneration in comparison with untreated and SC-treated defects. Both BMC and MSCs showed a similar healing potential than their respective SNs, with the best performance exerted by BMC as demonstrated with macroscopic and histological scores and type I and II collagen results. SNs loaded onto SC exerted a positive effect on OC defect regeneration, underlying the biological significance of the trophic factors, thus potentially opening new opportunities for the use of cell-free-based therapies. BMC was confirmed to be the most beneficial treatment.