THE ROLE OF EXTRINSIC INFROBLASTS IN THE RTEMODELING OF THE PATELLAR TENDON MATRIX

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Methods :1)Japanese White rabbits were divided into four groups.2)In Group I, the right patellar tendon underwent the in situ freeze-thaw treatment with liquid nitrogen to kill intrinsic fibroblasts of the patellar tendon and the wrapping treatment with nylon membrane filters to inhibit extrinsic cell infiltration from surrounding tissues into the patellar tendon. In Group II, the patellar tendon underwent the same wrapping treatment without the freeze-thaw treatment. In Group III, the right patellar tendon underwent the freeze-thaw treatment without the wrapping treatment.3)In each group, rabbits were sacrificed at 1,3 and 6 weeks postoperatively, and examined histologically and mechanically.Results :1)Histologically, no cells were found in the midsubstance of the patellar tendon in the Group I until 6 weeks after treatment. The patellar tendons in the Group II appeared normal until 6 weeks. In the Group III, no cells were found in the midsubstance at 1 week. Many cells were dispersed throughout the patellar tendon of the patellar tendon at 6 weeks.2)Mechanically, there were no significant differences between the Groups I and II, although the elastic modulus and the tensile strength of the Group I were slightly lower than those of the Group II at 6 weeks. In the Group III, the elastic modulus and the tensile strength of the patellar tendon were significantly lower than those of the Groups I and II.Conclusion :This study revealed that the inhibition of extrinsic cell infiltration by the wrapping treatment prohibited the reduction in mechanical properties of the patellar tendon that occurred following intrinsic cell necrosis, at least, until 6 weeks. These facts suggest that biological activities of extrinsic cells may reduce the mechanical properties of the patellar tendon matrix following intrinsic cell necrosis.