Biology subjects

Samvelyan, H. J.

Publications and source records attributed to Samvelyan, H. J..

3 recordsLinked to original sources

bioRxiv2021

The role of accelerated growth plate fusion in the absence of SOCS2 on osteoarthritis vulnerability

Osteoarthritis is the most prevalent systemic musculoskeletal disorder characterised by articular cartilage degeneration and subchondral bone (SCB) sclerosis. Here we sought to examine the contribution of accelerated growth to osteoarthritis development using a murine model of excessive longitudinal growth. Suppressor of cytokine signalling 2 (SOCS2) is a negative regulator of growth hormone (GH) signalling, thus mice deficient in SOCS2 (Socs2-/-) display accelerated bone growth. We examined vulnerability of Socs2-/- mice to osteoarthritis following surgical induction of disease (destabilisation of the medial meniscus (DMM)), and with ageing, by histology and micro-CT. We observed significant increase in number (WT DMM: 532{+/-}56; WT sham: 495{+/-}45; KO DMM: 169{+/-}49; KO sham: 187{+/-}56; P<0.01) and density (WT DMM: 2.2{+/-}0.9; WT sham: 1.2{+/-}0.5; KO DMM: 13.0{+/-}0.5; KO sham: 14.4{+/-}0.7) of growth plate bridges in Socs2-/- in comparison to wild-type (WT). Histological examination of WT and Socs2-/- knees revealed articular cartilage damage with DMM in comparison to sham (WT DMM: 3.4{+/-}0.4; WT sham: 0.3{+/-}0.05 (P<0.05); KO DMM: 3.2{+/-}0.8; KO sham: 0.8{+/-}0.3). Articular cartilage lesion severity scores (mean and maximum) were similar in WT and Socs2-/- mice with either DMM, or with ageing. Micro-CT analysis revealed significant decreases in SCB thickness, epiphyseal trabecular number and thickness in the medial compartment of Socs2-/-, in comparison to WT (P<0.001). DMM had no effect on the SCB thickness in comparison to sham in either genotype. Together these data suggest that enhanced GH signalling through SOCS2 deletion accelerates growth plate fusion, however this has no effect on osteoarthritis vulnerability in this model. Summary statementDeletion of SOCS2 results in accelerated growth plate fusion, however this has no effect on osteoarthritis vulnerability.

pathology↗

bioRxiv2020

Feeding intervention potentiates the effect of mechanical loading to induce new bone formation in mice

The benefits of increased human lifespan depend upon duration of healthy, independent living; the healthspan. Bone-wasting disorders contribute significantly to loss of independence, frailty and morbidity in older people. Therefore, there is an unmet need globally for lifestyle interventions to reduce the likelihood of bone fractures with age. Although many mechanisms are involved in disorders of bone loss, there is no single regulatory pathway and, therefore, there is no single treatment available to prevent their occurrence. Our aim in these studies was to determine whether fasting/feeding interventions alter the effect of mechanical loading on bone anabolic activities and increase bone mass. In young 17-week-old mice, 16-hour fasting period followed by reintroduction of food for 2 hours increased markedly the potency of mechanical loading, that mimics the effect of exercise, to induce new cortical bone formation. Consistent with this finding, fasting and re-feeding increased the response of bone to a loading stimulus that, alone, does not stimulate new bone formation in ad-lib fed mice. Older mice (20-months) experienced no potentiation of loading-induced bone formation with the same timing of feeding interventions. Interestingly, the pre-, prandial and postprandial endocrine responses in older mice were different from those in young animals. The hormones that change in response to timing of feeding have osteogenic effects that interact with loading-mediated effects. Our findings indicate associations between timing of food ingestion and bone adaptation to loading. If translated to humans, such non-pharmacological lifestyle interventions may benefit skeletal health of humans throughout life-course and in older age.

physiology↗

bioRxiv2020

Characterisation of growth plate dynamics in murine models of osteoarthritis

BackgroundThe purpose of this study was to investigate growth plate dynamics in surgical and loading murine models of osteoarthritis, to understand whether abnormalities in these dynamics predict osteoarthritis vulnerability. Methods8-week-old C57BL/6 male mice underwent destabilisation of medial meniscus (DMM) (n = 8) surgery in right knee joints. Contralateral left knee joints had no intervention (controls). In 16-week-old C57BL/6 male mice (n = 6), osteoarthritis was induced using non-invasive mechanical loading of right knee joints with peak force of 11N. Non-loaded left knee joints were internal controls. Chondrocyte transiency in tibial articular cartilage and growth plate was confirmed by histology and immunohistochemistry. Tibial subchondral bone parameters were measured using microCT and correlated to 3D GP bridging analysis. ResultsHigher expression of chondrocyte hypertrophy markers; Col10a1 and MMP13 were observed in tibial articular cartilage chondrocytes of DMM and loaded mice. In tibial growth plate, Col10a1 and MMP13 expressions were widely dispersed in a significantly enlarged zones of proliferative and hypertrophic chondrocytes in DMM (p=0.002 and p<0.0001, respectively) and loaded (both p<0.0001) tibiae of mice compared to their controls. 3D quantification revealed enriched growth plate bridging and higher bridge densities in medial compared to lateral tibiae of DMM and loaded knee joints of the mice. Growth plate dynamics were associated with higher subchondral bone volume fraction (BV/TV; %) in medial tibiae of DMM and loaded knee joints and epiphyseal trabecular bone volume fraction in medial tibiae of loaded knee joints. ConclusionsThe results confirm articular cartilage chondrocyte transiency in a surgical and loaded murine model of osteoarthritis. Herein, we reveal for the first time spatial variation of growth plate bridging in surgical and loaded osteoarthritis models and how these may contribute to anatomical variation in vulnerability of osteoarthritis development.

physiology↗