Changes in the extracellular matrix of the autogenous patellar tendon graft after posterior cruciate ligament reconstruction: a biochemical study in sheep

Abstract

The left knee joints of female German sheep were operated, replacing the posterior cruciate ligament by the central third of the patellar tendon. After 2, 6, 16, 26 and 52 weeks the graft of the operated leg as well as the contralateral central third of the patellar tendon and the posterior cruciate ligament were dissected and used for biochemical analysis. The total glycosaminoglycan content in grafts increases within the first year up to 5 fold and is higher than that of the patellar tendon, but is lower than that of the cruciate ligament. The distribution pattern of glycosaminoglycans differ in the posterior cruciate ligament and the patellar tendon. In cruciate ligament the main components are chondroitin sulfate (76%) and hyaluronan (15%). In the patellar tendon a higher portion of dermatan sulfate (approx. 16%) was found, next to 52% chondroitin sulfate and 22% hyaluronan. During the examination time the grafts show changes in the concentration and the distribution pattern of glycosaminoglycans. The chondroitin sulfate content increases during the experimental period from 1.4 +/- 1.2 mumol/g dry weight (d.w.) to 8.7 +/- 2.9 mumol/g d.w. After 1 year the chondroitin sulfate content in the graft does not differ significantly from that of the cruciate ligament. In the grafts the concentration of chondroitin (non sulfated) increases after 6 weeks up to 1.3 +/- 0.6 mumol/g d.w. in comparison to the value after 2 weeks (0.2 +/- 0.1 mumol/g d.w.) and also in the other groups (16, 26 and 52 weeks) it remains significantly increased. After 1 year the dermatan sulfate content in the graft has increased up to the fifth-fold compared to the value after 2 weeks and is higher than in the patellar tendon and in the cruciate ligament. In graft the hyaluronan content (1.0 +/- 0.4 mumol/g d.w. does not differ significantly in the groups 2, 6, 16, 26 and 52 weeks after operation, but in all five groups it is lower than in the cruciate ligament (2.4 +/- 1.0 mumol/g d.w.). Dermatan and heparan sulfate are not or only little detected in all three tissues. The distribution pattern of glycosaminoglycans in graft shows chondroitin sulfate and dermatan sulfate being the major parts of glycosaminoglycans with a slight increase of these components in the different groups during the experimental period. Hyaluronan makes up to 24 +/- 5% of the whole content of glycosaminoglycans after 2 weeks and decrease to 8 +/- 1% after 52 weeks.(ABSTRACT TRUNCATED AT 400 WORDS)