Gebäude 21, 1. OG
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This dissertation makes another contribution to the researchingon osteoarthritis (OA), the etiology and pathogenetic mechanisms ofwhich are not yet fully clarified. Osteoarthritis is one of the mostfrequent diseases of the human joint and is often recognized only inits later stages. Concerning the development of a method of earlydiagnosis it is assumed that in the earlier stages of osteoarthritisthere are first biochemical and later morphological changes of theaffected joints. This paper aims at a comparative description of themorphological changes of the articular cartilage and synovium of theknee joint developing in the animal model of osteoarthritis at varioustimes after the induction of osteoarthritis. At the same time theelimination rate of tritium- and fluorescence-labelled hyaluronan,ascertained by a second team of researchers shall be dealt with.The explanation of the anatomic and histological conditions of thejoint is followed by a description of the morphological structures ofthe physiological and pathologically changed joint, a definition ofosteoarthritis and a survey of both the animal models, applied in theintemational research on the induction of osteoarthritis. and thevarious scores for the morphological results of osteoarthriticalchanges.In the special part of this thesis (chapter 9) the design of theexperiments is outlined. At the left knee joint of 41 chinchilla rabbitsa part of the fibular collateral ligament, the sesamoid ligament andthe anterior lateral area of the meniscus have been removed[COLOMBO et al., 1983] and the anterior cruciate ligament of eitherthe left or right knee joint of 15 beagles has been incised in order toinduce osteoarthritis. Apart from that, one experimental group ofeach breed had to undergo a shamoperation. The respectiveopposite knee joints served as controls.In order to receive the elimination kinetics of the hyaluronancontained in he synovial fluid in dependency on the degree ofdamage, hyaluronan has been labelled with tritium (3H-HA)[LINDENHAYN et al., 1997] and fluorescence respectively[NIEDERHAUSEN, not published] and the elimination rate constant,half-life, mean residence time, clearance and volume of synovialfluid have been measured.Using 3H-HA, the induction of osteoarthritis caused an increase ofhalSlife (on average 23,5 h) four weeks after the operation of therabbits and a decrease of half-life to standard results (on average17,4 h) twelve weeks afler the operation. As to the dogs in relation toa control value of on average 18,5 h a reduction of half-life threemonth after the operation (on average 16,5 h) and five month afterthe operation (on average 13,2 h) was recognized. The eliminationrates of the differently marked HA clearly differed: the eliminationrate of 3H-HA was approximately 50 times lower than that of thefluorescence-labelled HA. The reasons for this are the changedstructure of the fluorescence-labelled HA and ist lower molecularweight, both conditioned by the production. As a consequence, inthe joint phagocytosis of the fluorescence-labelled HA is more rapidas compared to that of the 3H-HA.Histologically, four weeks after the operation the articular cartilage ofthe rabbits showed distinctive degenerative changes in relation tothe control joints. 12 and 19 weeks after the operation the damageswere less distinct. As far as the synovium is concerned, four weeksafter the operation distinctive marks of tissue alterations wererecognizable which 12 and 19 weeks after the operation were not asprominent.In the joints of the dogs 28 weeks after the ACL-incision thecartilage defects were of similar size as 35 weeks after theACL-incision. 28 weeks after the operation the synovial tissueshowed insignificant more distinctive marks of inflammation ascompared to the state of 35 weeks after the operation. The controljoints only showed slightly mild changes as compared to theoperated ones.The times of the biochemical and histological examinations of theexperiments on dogs being not identical because of the design ofthe experiment and factors as number, age, case history, genderand breed of the animals which influenced the experimental stagenegatively not being avoidable, the results could not be as definiteas those of the experiments on rabbits. With these an interpretationof the morphological results in view of the biochemical findingsshowed potential correlations between the elimination kinetics of thelabelled HA and the degree of damage of the various parts of thejoints.