Association of porous hydroxyapatite and bone marrow cells for bone regeneration

The preparation of hybrid material with osteoinductive capacity may be achieved by association of cultured autologous bone cells with a porous ceramic vehicle. We optimized culture conditions for rabbit marrow stromal stem cells (MSCs), notably by selection from batches of fetal calf serum. Rabbit MSCs formed colony-forming unit-fibroblastic (CFU-Fs) in vitro. Their alkaline phosphatase (ALP) activity was doubled in the presence of dexamethasone. Autologous rabbit serum allowed the formation of ALP-positive CFU-Fs, but results were highly variable depending on the rabbit. We tested the osteogenic potential of autologous cultured (with or without dexamethasone addition in the culture medium) and noncultured rabbit MSCs associated with a porous hydroxyapatite ceramic after a dorsal intramuscular implantation. Nucleated cells (107 or 108/mL) were used for the preparation of autologous hybrid material. A significantly higher number of implants containing bone was obtained with a suspension of 107 cells/mL cultured in the presence of 10−8 M dexamethasone. Some positive implants were also obtained with a suspension of 108 noncultured cells/mL. We demonstrated the feasibility of preparing rabbit autologous hybrid materials following a process for controlling culture conditions, cell characterization and cell/material association.