Subchondral bone lesions in knee osteoarthritis and its link with vascular pathology

Abstract

Osteoarthritis of the knee (knee OA) is a whole joint degenerative disease. Multiple epidemiological studies demonstrated links between essential hypertension and OA, but the mechanism behind is unknown. Subchondral bone cyst (SBC), a cardinal radiographical feature of OA, is believed to be the result of chronic bone marrow oedema, which was previously hypothesised to be the link between hypertension but the aetiology and biological impacts of SBC are largely unknown. In this study, we have looked into the links between SBC, hypertension and OA from the in the Queen Mary Hospital OA cohort and a spontaneously hypertensive rat (SHR) model. Micro-Computer Tomography (micro-CT), immunohistochemistry & histomorphometry were employed to study the overall structural changes of the bone and cartilage. Tissue culture and subsequent reverse transcription quantitative polymerase chain reaction (RT-qPCR) were employed for characterisation of SBC cells in order to better understand the aetiology of SBCs. Presence of SBC was correlated with bone loss and marrow fibrosis in subchondral bone. Hypertension was a predictor of SBC occurrence. SBCs and pre-OA subchondral bone and meniscal changes were present in the SHRs. SBC cells have lower pericyte and osteogenic marker expression, indicating subchondral insufficiency could be the culprit behind SBC formation in OA.