Ex vivo cell-growing technique might be a solution for treatment of bone diseases leading to the local bone defects. We assessed the effect of ex vivo-cultured cells in ectopic bone induction in animals with normally functioning connective tissue cells.

Material and methods: Bone marrow cells, harvested via puncture of tibial canal of male Wistar rats, were cultured, and differented into osteogenic lineage using chemical stimulus.

After differentiation osteoprogenitor cells were transferred into beta-tricalcium phosphate scaffolds using either centrifugation or simple diffusion. Six types of implants (beta-tricalcium phosphate matrixes) were implanted into subcutaneous pouches. In the first group saline-immersed implants were used; in the second group the ex vivo cells were transferred into the implant by diffusion and in the third group by centrifuging; in the 4th, 5th and 6th group the implants were processed as in first three groups, respectively, but 12.5 microgram of rhBMP2 was added to the each implant. After 21 days the implants were removed and dissected systematically. Histomorphometry analysis was performed following the principles of stereology.

Results and discussion: Bone formation was found only in the rhBMP2-immersed implants. Other implants consisted mostly of connective tissue and in lesser extent of the unchanged scaffold. No distinctive differences were found between the rhBMP2-implants. The osteoinduction seems to be crucial in ectopic bone formation if there is no cellular dysfunction present. The inductive effect of rhBMP2 cannot be compensated by the abundance of the pre-differentiated osteogenic cells as shown by the absence of bone induction in the groups two and three in this model.

• Supported by Estonian Government SF 0180030s07