Methods: Primary human osteoblasts were cultured for 3 weeks and osteoblasts/matrix sheets were obtained. Subperiosteal pocket was created to the calvarial periosteum of F344/NJcl-rnu immuno-deficient rats (8-week old, male) and the osteoblasts/matrix sheet was transplanted. After 1, 3 and 5 days of transplantation, rats were sacrificed and paraffin embedded decalcified histology sections were prepared. Cell proliferation was analyzed by Proliferating Cell Nuclear Antigen(PCNA) and Apoptosis was detected by TUNEL staining.
Results: TUNEL positive cell ratio in transplants was 4.5, 14.5 and 4.7% at day 1, 3 and 5 days of transplantation respectively. The highest TUNEL-positive cell ratio was observed 3 days after the transplantation. On the other hand, while PCNA-positive cells were not detected at day 1 and 3, 4.6% of PCNA-positive cells become detectable at day 5. Neoangiogenesis was also detected at the center of transplants at day 5, but it was not observed at day 1 and 3.
Conclusions: In the present study, we showed that a certain number of transplanted cells cannot survive at early stage of transplantation mainly due to apoptosis. However, neoangiogenesis was initiated and cell proliferation was recovered at day 5. These results suggest that anti-apoptotic treatment for transplants may enhance the successful engraftment of transplanted cells that leads to more effective cell transplantation therapy.