80 THERAPEUTIC EFFECTS OF FIBROBLAST GROWTH FACTOR-18 IN A RAT MODEL OF ESTABLISHED OSTEOARTHRITIS

Abstract

79 – Knee cartilage morphology in various species and humans Species Number Cartilage surface area Cartilage thickness Cartilage volume Rat 16 6.2±0.9 mm2 0.14±0.12 mm 0.81±0.17 mm3 Rabbit 6 69±4.9 mm2 0.37±0.05 mm 23.5±3.9 mm3 Cat 3 85±9.1 mm2 0.67±0.05 mm 55.8±10.5 mm3 Dog 18 196±18 mm2 0.77±0.04 mm 142±15 mm3 Pig 1 1650 mm2 1.4 mm 2200 mm3 Horse 1 2390 mm2 1.4 mm 3290 mm3 Rhinoceros 1 5460 mm2 1.8 mm 9840 mm3 Human (Women) 45 1050±135 mm2 1.9±0.23 mm 1940±344 mm3 Human (Men) 72 1380±205 mm2 2.2±0.26 mm 2940±622 mm3 with those in a data base of young (18 to 35 years) healthy humans (45 women, weight 60 ± 7 kg, and 72 men, weight 77 ± 11 kg) who had been imaged at 1.5T. Sagittal spoiled gradient echo sequences with fat suppression or water excitations were acquired in all knees. The medial tibial cartilage was segmented by tracing the cartilage surface (AC) and subchondral bone area (tAB) throughout the entire medial tibia. The size of the cartilage surface areas (AC), the mean cartilage thickness (ThC) and the cartilage volume (VC) were computed using Chondrometrics software (Ainring, Germany). Results: The size of the cartilage surface areas in the rat (6.2 mm2) was approximately 200x smaller than that in humans (Table 1), whereas that in the rhinoceros was about 4.5 x larger than than in humans. The variability of cartilage thickness between the species, however, was substantially less than for cartilage surface areas. All species (including the rhinoceros: ThC = 1.8 mm) had thinner cartilage than humans (1.9 mm in women and 2.2 mm in men, respectively). The rat displayed the lowest mean cartialge thickness (0.14 mm) amongst the species investigated. Conclusions: To our knowledge these are the first quantitative data on the three-dimensional morphology of tibial cartilage in different species and humans. The data show that the interspecies differences in cartilage surface areas are much more prominent than those in cartilage thickness. This is likely due to the need to keep mechanical stresses (load/area) below a critical threshold at which the cartilage will undergo damage. These data can be used to estimate the appropriate dose of intra-articular medication with potentially beneficial structural or symptomatic effects on articular cartilage in animal models of OA.