Tracing transduced cells in osteochondral defects.

In this study the authors explored the feasibility of using transduced cells for gene therapy to induce healing of osteochondral defects. Both a mouse mesenchymal cell line and mixed rabbit adherent stromal cells were transduced with either liposomal transfection or retroviral transduction using a traceable gene. Transduction efficiency was more than 95% with the retroviral construct and expression was maintained for over 6 months of passage. The liposomal transfection led to a transient expression with an efficiency of 50%. The expression of osteochondral genes was diminished but preserved after transduction in vitro. Transduced rabbit cells were transplanted into osteochondral defects in rabbit femoral condyles. Cells transplanted in vivo could be detected for 4 weeks in the repair tissue. The authors' data demonstrate that mesenchymal cells from bone marrow, stably transduced with a traceable gene product, retain the bone and cartilage phenotype and can be followed in vivo after transplantation into cartilage defects.