Biology subjects

Findlay, D. M.

Publications and source records attributed to Findlay, D. M..

4 recordsLinked to original sources

bioRxiv2025

TWEAK and Fn14 expression in osteoarthritis: evidence for TWEAK-induced RANKL release from chondrocytes

ObjectiveA role for TWEAK expression and that of its receptor Fn14 by osteoblasts and synovial tissue has been proposed in the pathogenesis of osteoarthritis (OA). Here, we examined whether the cartilage in OA was also a source and target of TWEAK. DesignArticular cartilage samples from 24 patients undergoing hip or knee replacement surgery for OA were investigated for TWEAK and Fn14 expression by both immunostaining and real-time RT-PCR. Samples were graded according to the Pritzker scale from grade 0 (normal) through increasing levels of cartilage damage (grades 1-3). Human primary chondrocytes isolated from OA cartilage were treated with combinations of recombinant TWEAK and TNF and examined for acute effects on TWEAK, FN14, RANKL and ADAM17 mRNA levels. Released soluble RANKL levels were measured by ELISA. ResultsImmunostaining indicated that the majority (21/24) of OA cartilage samples expressed low levels of TWEAK protein and high levels of Fn14, however, expression did not appear to vary with respect to OA grade. TWEAK mRNA levels were elevated in grade 2 OA cartilage compared to grade 0 (p < 0.05), while Fn14 mRNA levels appeared elevated across all damage grades, significantly in grade 2 samples. Primary chondrocytes treated with TNF, alone or in combination with TWEAK, exhibited early upregulated Fn14 mRNA expression. TWEAK induced RANKL mRNA expression. while both TWEAK and TNF induced the mRNA expression of the RANKL sheddase, ADAM17. Consistent with these findings, TWEAK and TNF both induced soluble RANKL release by chondrocytes. ConclusionsThe expression and regulation of TWEAK and Fn14 is a feature of human OA articular cartilage, suggesting a pathogenetic role. TNF may prime chondrocytes for TWEAK reactivity by upregulating Fn14 expression. The TWEAK and TNF induction of ADAM17 expression and sRANKL release by chondrocytes points to a further disease pathway in human OA.

pathology↗

bioRxiv2023

Microstructural and cellular characterisation of the subchondral trabecular bone in human knee and hip osteoarthritis using synchrotron tomography

ObjectiveIt is unclear if different factors influence osteoarthritis (OA) progression and the changes characterising OA disease in hip and knee. We investigated the difference between hip OA and knee OA at the subchondral bone tissue and cellular level, relative to the degree of cartilage degeneration. DesignBone samples were collected from 11 patients (aged 70{+/-}8 years) undergoing knee arthroplasty and 8 patients (aged 64{+/-}12 years) undergoing hip arthroplasty surgery. Bone microstructure, osteocyte-lacunar network and bone matrix vascularity were evaluated using synchrotron micro-CT imaging. Samples were additionally examined histologically to determine osteocyte density, viability, and connectivity. ResultsAfter adjustment for donor gender and age, associations between the extent of cartilage degeneration, bone volume fraction [8.7, 95% CI (3.4, 14.1)], trabecular number [1.5, 95% CI (0.8, 2.3)], osteocyte lacunar density [4714.9; 95% CI (2079.1, 7350.6)] and trabecular separation [-0.06, 95% CI (0.01, 0.1)] were found in both knee and hip OA. When compared to knee OA, hip OA was characterised by higher trabecular thickness [0.006, 95% CI (-4, 0.01)], larger but less spheric osteocyte lacunae [47.3; 95% CI (11.2, 83.4), -0.04; 95% CI (-0.6, -0.01), respectively], lower vascular canal density [-22.8; 95% CI (-35.4, -10.3)] lower osteocyte density [-84.9; 95% CI (-102.4, -67.4)], and less senescent but more apoptotic osteocytes [-2.4; 95% CI (-3.6, -1.2), 24.9; 95% CI (17.7, 32.1)], respectively. ConclusionSubchondral bone from hip OA and knee OA exhibits different characteristics at the tissue and cellular levels, suggesting different mechanisms of OA progression between the hip and knee joints.

pathology↗

bioRxiv2022

The Effects of Vitamin E Analogues α-Tocopherol and γ-Tocotrienol on the Human Osteocyte Response to Ultra-high Molecular Weight Polyethylene Wear Particles

Polyethylene (PE) liners are a common bearing surface of orthopaedic prostheses. Wear particles of ultra-high molecular weight PE (UHMWPE) contribute to periprosthetic osteolysis, a major cause of aseptic loosening. Vitamin E is added to some PE liners to prevent oxidative degradation. Osteocytes, an important cell type for controlling both bone mineralisation and bone resorption, have been shown to respond UHMWPE particles by upregulating pro-osteoclastogenic and osteocytic osteolysis. Here, we examined the effects of the vitamin E analogues -tocopherol and {gamma}-tocotrienol alone or in the context of UHMWPE particles on human osteocyte gene expression and mineralisation behaviour. Human osteoblasts differentiated to an osteocyte-like stage were exposed to UHMWPE wear particles in the presence or absence of either -Tocopherol or {gamma}-Tocotrienol. Both -Tocopherol and {gamma}-Tocotrienol induced antioxidant-related gene expression. UHMWPE particles independently upregulated antioxidant gene expression, suggesting an effect of wear particles on oxidative stress. Both vitamin E analogues strongly induced OPG mRNA expression and {gamma}-Tocotrienol also inhibited RANKL mRNA expression, resulting in a significantly reduced RANKL:OPG mRNA ratio (p < 0.01) overall. UHMWPE particles reversed the suppressive effect of -Tocopherol but not of {gamma}-Tocotrienol on this pro-osteoclastogenic index. UHMWPE particles also upregulated osteocytic-osteolysis related gene expression. Vitamin E analogues alone or in combination with UHMWPE particles also resulted in upregulation of these genes. Consistent with this, both vitamin E analogues promoted calcium release from mineralised cultures of osteocyte-like cells. Our findings suggest that while vitamin E may suppress osteocyte support of osteoclastogenesis in the presence of UHMWPE particles, the antioxidant effect may induce osteocytic osteolysis, which could promote periprosthetic osteolysis. It will be important to conduct further studies of vitamin E to determine the long-term effects of its inclusion in prosthetic materials.

cell biology↗

bioRxiv2022

Hip osteoarthritis: A novel network analysis of subchondral trabecular bone structures

Hip osteoarthritis (HOA) is a degenerative joint disease that leads to the progressive destruction of subchondral bone and cartilage at the hip joint. Development of effective treatments for HOA remains an open problem, primarily due to the lack of knowledge of its pathogenesis and a typically late-stage diagnosis. We describe a novel network analysis methodology for micro-computed tomography (micro-CT) images of human trabecular bone. We explored differences between the trabecular bone microstructure of femoral heads with and without HOA. Large-scale automated extraction of the network formed by trabecular bone revealed significant network properties not previously reported for bone. Profound differences were discovered, particularly in the proximal third of the femoral head, where HOA networks demonstrated elevated numbers of edges, vertices and graph components. When further differentiating healthy joint and HOA networks, the latter showed fewer small-world network properties, due to decreased clustering coefficient and increased characteristic path length. Furthermore, we found that HOA networks had reduced length of edges, indicating the formation of compressed trabecular structures. In order to assess our network approach, we developed a deep learning model for classifying HOA and control cases, and we fed it with two separate inputs: (i) micro-CT images of the trabecular bone, and (ii) the network extracted from them. The model with plain micro-CT images achieves 74.63% overall accuracy while the trained model with extracted networks attains 96.47% accuracy. We anticipate our findings to be a starting point for a novel description of bone microstructure in HOA, by considering the phenomenon from a graph theory viewpoint.

biophysics↗