Ectopic Implantation of Hydroxyapatite Xenograft Scaffold Loaded with Bone Marrow Aspirate Concentrate or Osteodifferentiated Bone Marrow Mesenchymal Stem Cells: A Pilot Study in Mice

Purpose: To evaluate the influence of bone marrow cells in the bone formation in an ectopic subcutaneous model in mice. Materials and Methods: Six BALB/c mice were divided into three groups of two each. In all groups, xenograft was implanted subcutaneously. In the negative control group, the xenograft was hydrated with saline solution. In the positive control group, the xenograft was embedded with osteodifferentiated adult mesenchymal stem cells derived from the bone marrow. In the experimental group, the xenograft was embedded with bone marrow aspirate concentrate. After 4 weeks, the animals were sacrificed and prepared for histologic, histomorphometric, and immunohistochemical analysis. The following tissues were evaluated: preosteoid tissue, loose connective tissue, and remaining xenograft particles. Results: There was a statistically significant difference (P = .008) in the preosteoid tissue area between the negative control group (0 ± 0%) and the other two groups, with 42 ± 11% for the experimental group and 56 ± 5% for the positive control group. Similarly, there was a statistically significant difference (P = .006) in the loose connective tissue area between the negative control group (49 ± 18%) and the other two groups, with 3 ± 9% for the experimental group and 0 ± 0% for the positive control group. Regarding the xenograft area, there was not a statistically significant difference between the three groups (P = .143). Conclusion: The use of a mineralized scaffold loaded with either concentrated bone marrow aspirate or with osteogenically induced bone marrow mesenchymal stem cells favored the formation of osteoid tissue as opposed to the scaffold alone. Keywords: bone marrow, cell transplantation, osteogenesis, stem cells