FRI0040 Transitional zones displacement of the subchondral bone layers in a model of osteoporosis and osteoarthritis in rabbits

Background Subchondral bone (SB) plays a crucial role in osteoarthritis (OA) pathogenesis. Nevertheless, there is little information available about the microarchitectural characteristics of the different layers and transitional zones (TZ) comprising the SB. In previous experiments in animals, we have confirmed that an increased SB remodeling may account for the aggravation of cartilage damage in OA rabbits with previous osteoporosis (OP) that was reversed improving SB quality. Objectives To analyze, through micro-CT, the microstructural characteristics of the different SB layers in our OP and OA model to determine the effect of the microarchitecture of SB in the OA severity. Methods Experimental OA was induced in 12 female NZ white rabbits (8 months old; weight 3.5-5 kg) by ACLT and partial medial meniscectomy (OA) in the left knees. In 6 of them, OP was previously induced by bilateral oophorectomy and subsequent prednisolone administration, 1 mg sc/kg/d for 5 wks (OPOA knees). Right knees of OPOA were used as OP knee controls, while right knees of OA group were used as healthy knees. After sacrifice, knees of both groups were carefully dissected for later analysis. With this objective, cylindrical samples of SB (4 mm in diameter by 9 mm in length) were extracted from femoral condyles. The microarchitectural characteristics of the samples were studied using micro-CT with a SkyScan 1172 (Bruker micro-CT NV). Morphometric parameters were calculated “slice-by-slice” on all individual cross-sections in order to visualize the profile of each variable along the length of the sample. Furthermore, the thickness of the first layer of bone (SB plate, SBP) was determined assuming for this layer a porosity