Y. Toritsuka et al., EFFECT OF FREEZE-DRYING OR GAMMA-IRRADIATION ON REMODELING OF TENDON ALLOGRAFT IN A RAT MODEL, Journal of orthopaedic research, 15(2), 1997, pp. 294-300
Freezing or freeze-drying and gamma-irradiation are techniques current
ly used for processing tendon allografts. However, it is still unknown
how these processing methods affect graft remodeling. In this study,
we used a rat patellar tendon transplantation model to investigate the
effect of various processing methods on remodeling by quantifying los
s of collagen labeled with a radioactive isotope. The grafts were divi
ded into the following four groups according to the processing method:
fresh-frozen, freeze-dried, fresh-frozen and gamma-irradiated, or fre
eze-dried and gamma-irradiated. The percentage of donor collagen, calc
ulated from hydroxyproline content and radioactivity level, was used a
s an indicator of graft remodeling. At 2 weeks, the level of donor col
lagen in the fresh-frozen group was 62%; in the freeze-dried group, 59
%; in the fresh-frozen and irradiated group, 57%; and in the freeze-dr
ied and irradiated group, 44%. At 4 weeks, the percentage of donor col
lagen remaining in grafts decreased to 38% in the fresh-frozen group,
19% in the freeze-dried group, 27% in the fresh-frozen and irradiated
group, and 12% in the freeze-dried and irradiated group. Finally, at 1
2 weeks, the levels were 19% in the fresh-frozen group, 20% in the fre
eze-dried group, 15% in the fresh-frozen and irradiated group, and 6%
in the freeze-dried and irradiated group. The percentages of donor col
lagen in the freeze-dried and the fresh-frozen and irradiated groups w
ere significantly lower than that in the fresh-frozen group at 4 weeks
. The values for the freeze-dried and irradiated group were significan
tly lower than those for the fresh-frozen and irradiated group at 4 an
d 12 weeks. These data suggest that freeze-drying, freeze-drying follo
wed by gamma-irradiation, and fresh-freezing followed by gamma-irradia
tion temporarily accelerate graft remodeling.