Is Subchondral Bone Plate Innervation And Vascularisation Associated With Knee Oa

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During Osteoarthritis (OA) development the joint is under abnormal stress conditions leading to cartilage degeneration and subchondral bone modifications. Pain is a main symptom in OA, while the cartilage is not innervated nor vascularised the source and mechanisms generating pain are poorly understood. Vascularisation and innervation are causes of alterations in the articular joint causing anatomic and radiological changes enhancing the evolution of OA. Also the articular instability can lead to modifications in the neurovascular physiology of the joint. PURPOSE: To investigate both innervation and vascularisation in human tibial plateaux in different grades of OA progression. METHODS: An experimental model, 5 human osteoarthritic tibial plateaux were obtained during total knee replacement surgery, with all specimens stored immediately in liquid nitrogen. The samples were macroscopically classified in different grades (0-4) based on cartilage damage status and representative samples of each grade were taken from the tibial plateaux using a hole saw. We obtained samples 6mm diameter and 5 to 8mm length. Samples used for qRT-PCR were stored in RNAlater (Qiagen) -80°C and those for histology in acetic formaldehyde 4%. Gene expression of Neuronal Growth Factor (NGF) and Vascular Endothelial Growth Factor (VEGF) was determined by qRT-PCR after RNA isolation and reverse transcription. Samples were fixed in acetic formaldehyde 4% for 2 days and decalcified in 6% HCl for 1 week. After decalcification the samples were embedded in paraffin and 3μm sections were prepared, then deparafinized and stained with Hematoxylin Erythrosine Saffron (HES). RESULTS: NGF and VEGF expression increased with the severity of OA. While an increased VEGF expression was detected in the early stages of OA (grade 1 and 2), NGF expression appeared later (grade 3). Histological slides showed varied cartilage, subchondral and bone pathology depending on the severity of OA. HES staining showed structural modifications of cartilage, subchondral bone, calcified cartilage and trabecular bone. CONCLUSION: A modulation of VEGF and NGF was detected in OA progression. VEGF seems to be involved in the early stages of OA when NGF expression is detected later. Histological slides showed many modifications and a progressive vascular invasion.