Running load. A possible cause for the development of osteoarthritis. Results of animal studies in rats

We review our results with an animal model for investigations on the develo pment of osteoarthritis (OA). This model is based on running exercises of w istar rats performed in a running wheel using intracranial self-stimulation to motivate rats to excessive running. In our studies a total of 49 rats w as divided into groups with running exercises of 15 km, 20 km, and 30 km re spectively. In order to investigate the influence of altered sensible joint innervation on the development of OA, in addition to a total running load of 20 km in another group of 8 rats we performed Capsaicin (8 Methyl-N-vani llyl-6-noneamide) mediated partial sensible knee joint denervation. Complet e knee joint sections of all rats were evaluated histologically using Manki ns grading system. In addition, we performed semiquantitative assessment of the immunoreactivity of the chondrocytes to MMP-3 by immunostaining with m onoclonal MMP-3 Ige antibodies. Histological assessment and immunostaining for MMP-3 of the knee joint sections revealed a significant increase in ost eoarthritic changes with higher running load. Moreover, osteoarthritic chan ges in the knee joints of the rats with sensible joint denervation and runn ing exercises were significantly greater as compared to those with sole run ning load. In conclusion, our studies revealed a significant relationship b etween the development of knee osteoarthritis and the extent of joint load. Hereby, an alteration of the sensible joint innervation seems to have a pr omoting effect on the development of osteoarthritic changes. This model off ers a wide range of further approaches to studying different processes of t he development of OA.