Aims

Dystrophic calcification (DC) is the abnormal appearance of calcified deposits in degenerating tissue, often associated with injury. Extensive DC can lead to heterotopic ossification (HO), a pathological condition of ectopic bone formation. The highest rate of HO was found in combat-related blast injuries, a polytrauma condition with severe muscle injury. It has been noted that the incidence of HO significantly increased in the residual limbs of combat-injured patients if the final amputation was performed within the zone of injury compared to that which was proximal to the zone of injury. While aggressive limb salvage strategies may maximize the function of the residual limb, they may increase the possibility of retaining non-viable muscle tissue inside the body. In this study, we hypothesized that residual dead muscle tissue at the zone of injury could promote HO formation.

The growth plates of the femoral head of Japanese white rabbits aged 5, 10, 15 and 20 weeks were stained for apoptotic and proliferating chondrocytes using the TUNEL and PCNA antibody staining techniques. Both TUNEL- and PCNA-positive chondrocytes were detected in all of the specimens. The positive ratios of both stainings were calculated for the whole plate and for the resting, proliferating and hypertrophic zones. The highest ratios in both stainings occurred in the hypertrophic zone in all age groups. With growth, the TUNEL-positive ratio increased whereas the proliferating ratio decreased. We suggest that the increase in chondrocytic death by apoptosis and the decrease in cell proliferation potential led to closure of the growth plate

Tissues from five patients who underwent revision operations for failed total hip replacements were found to contain large quantities of particulate titanium. In four cases this metal must have come from titanium alloy screws used to fix the acetabular component; in the fifth case it may also have originated from a titanium alloy femoral head. Monoclonal antibody labelling showed abundant macrophages and T-lymphocytes, in the absence of B-lymphocytes, suggesting sensitisation to titanium. Skin patch testing with dilute solutions of titanium salts gave negative results in all five patients. However, two of them had a positive skin test to a titanium-containing ointment

Aims

Vertebrates have adapted to life on Earth and its constant gravitational field, which exerts load on the body and influences the structure and function of tissues. While the effects of microgravity on muscle and bone homeostasis are well described, with sarcopenia and osteoporosis observed in astronauts returning from space, the effects of shorter exposures to increased gravitational fields are less well characterized. We aimed to test how hypergravity affects early cartilage and skeletal development in a zebrafish model.

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The aim of our study is to investigate the effect induced by alternated mechanical loading on Notch-1 in mandibular condylar cartilage (MCC) of growing rabbits.

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Local recurrence remains a challenging and common problem following curettage and joint-sparing surgery for giant cell tumour of bone (GCTB). We previously reported a 15% local recurrence rate at a median follow-up of 30 months in 20 patients with high-risk GCTB treated with neoadjuvant Denosumab. The aim of this study was to determine if this initial favourable outcome following the use of Denosumab was maintained with longer follow-up.

1. A comparative study has been made of the major transplantation antigens present on the chondrocyte isolated from articular cartilage of the sheep and lymphocytes from the cartilage donors. 2. It has been shown that the chondrocyte possesses antigens of the major histocompatibility system in common with the lymphocyte. 3. In order to demonstrate the similarity between the antigen structure of the chondrocyte and the lymphocyte it was necessary to treat cartilage cells with papain after isolation in order to remove the matrix more completely. Failure to do this led to an apparent deficit of antigens on the chondrocyte. 4. It was found that lysis of cells by antibodies was slower when chondrocytes were the target cells than when lymphocytes were used. It is concluded that this is due to a protective role of remaining cartilage matrix

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Fibrinolysis plays a key transition step from haematoma formation to angiogenesis and fracture healing. Low-magnitude high-frequency vibration (LMHFV) is a non-invasive biophysical modality proven to enhance fibrinolytic factors. This study investigates the effect of LMHFV on fibrinolysis in a clinically relevant animal model to accelerate osteoporotic fracture healing.

Aims

Osteoarthritis (OA) is prevalent among the elderly and incurable. Intra-articular parathyroid hormone (PTH) ameliorated OA in papain-induced and anterior cruciate ligament transection-induced OA models; therefore, we hypothesized that PTH improved OA in a preclinical age-related OA model.

We studied 16 club feet and 27 normal feet from spontaneously aborted human fetuses in the second trimester of gestation and measured the length of the spring ligament, and the declination angle and size of the talus. We also studied the cellular characteristics of the spring ligament and the immunohistochemical features of the medial ankle ligaments using monoclonal antibodies against type-III collagen, desmin, vimentin, and smooth muscle actin. Histomorphometric results indicated that the talar deformity was not the primary lesion. Histological and immunohistochemical findings showed that the cells and collagen fibres of the medial ankle ligaments of club feet appeared to be the site of the earliest changes, in that they had lost their spatial orientation and had contracted. In severe club feet before the third trimester of gestation, myofibroblast-like cells seemed to create a disorder of the ligaments resembling fibromatosis. This led to contraction and resulted in typical club-foot deformity

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The present study investigates the effectiveness of platelet-rich plasma (PRP) gel without adjunct to induce cartilage regeneration in large osteochondral defects in a rabbit model.

Of 935 consecutive patients referred with shoulder pain, 50 fitted the criteria for primary frozen shoulder. Twelve patients who failed to improve after conservative treatment and manipulation had excision of the coracohumeral ligament and the rotator interval of the capsule. The specimens were examined histologically, using special stains for collagen. Immunocytochemistry was performed with monoclonal antibodies against leucocyte common antigen (LCA, CD45) and a macrophage/synovial antigen (PGMI, CD68) to assess the inflammatory component, and vimentin and smooth-muscle actin to evaluate fibroblasts and myofibroblasts. Our histological and immunocytochemical findings show that the pathological process is active fibroblastic proliferation, accompanied by some transformation to a smooth muscle phenotype (myofibroblasts). The fibroblasts lay down collagen which appears as a thick nodular band or fleshy mass. These appearances are very similar to those in Dupuytren's disease of the hand, with no inflammation and no synovial involvement. The contracture acts as a check-rein against external rotation, causing loss of both active and passive movement

Bone loss around replacement prostheses may be related to the activation of mononuclear phagocytes (MNP) by prosthetic wear particles. We investigated how osteoblast-like cells were regulated by human MNP stimulated by particles of prosthetic material. Particles of titanium-6-aluminium-4-vanadium (TiAlV) stimulated MNP to release interleukin (IL)-1β, tumour necrosis factor (TNF)α, IL-6 and prostaglandin E. 2. (PGE. 2. ). All these mediators are implicated in regulating bone metabolism. Particle-activated MNP inhibited bone cell proliferation and stimulated release of IL-6 and PGE. 2. The number of cells expressing alkaline phosphatase, a marker associated with mature osteo-blastic cells, was reduced. Experiments with blocking antibodies showed that TNFα was responsible for the reduction in proliferation and the numbers of cells expressing alkaline phosphatase. By contrast, IL-1β stimulated cell proliferation and differentiation. Both IL-1β and TNFα stimulated IL-6 and PGE. 2. release from the osteoblast-like cells. Our results suggest that particle-activated mono-nuclear phagocytes can induce a change in the balance between bone formation and resorption by a number of mechanisms

Aims

Extracellular matrix (ECM) and its architecture have a vital role in articular cartilage (AC) structure and function. We hypothesized that a multi-layered chitosan-gelatin (CG) scaffold that resembles ECM, as well as native collagen architecture of AC, will achieve superior chondrogenesis and AC regeneration. We also compared its in vitro and in vivo outcomes with randomly aligned CG scaffold.

We investigated the lymphocyte-mediated immune response to polymethylmethacrylate bone cement in 26 patients who had revision surgery for aseptic loosening of cemented total hip arthroplasties, at a mean time of seven years after the first replacement. We studied eight patients with cemented total hip arthroplasties which were not loose as controls. Patch tests to polymethylmethacrylate bone cement were positive in 13 patients with loosening, and these patients had higher lymphoblast transformation values against polymethylmethacrylate bone cement patients with a negative skin reaction (p < 0.01) or those in the control group (p < 0.001). Specific monoclonal antibodies were used to assess the percentage of certain cells of the immune system according to their cluster of differentiation (CD). There was a higher number of total T and B lymphocytes (CD2 and CD22) and interleukin-2 receptor-positive lymphocytes (activated cells, CD25) in patients with loose prostheses. More CD25 lymphocytes were found in patients with positive patch tests. The activation of the lymphocyte-mediated immune response was not related to the presence or absence of aggressive granulomatous lesions at the cement-bone interface

The role of three genetically distinct collagen types in the formation of endochondral bone and in calcification and resorption of cartilage has been assessed. Using antibodies specific to types I, II and III collagen we have demonstrated in the embryonic chick tibia that endochondral bone formation began with deposition of type III collagen in lacunae of hypertropic chondrocytes by invading bone-marrow-derived cells. This was followed by the deposition of type I collagen, which is the collagenous constituent of endochondral osteoid. At later stages of development endochondral osteoid was found in the epiphysial growth plate in apparently intact lacunae of hypertrophic chondrocytes; this indicated that the latter might contribute to the synthesis of osteoid type I collagen. Immuno-histological staining for collagen types, and von Kossa staining for calcium phosphate on parallel sections, demonstrated that type I and type II collagen matrices were substrates for calcification. Endochondral bone (with type I collagen) was found on scaffolding of both uncalcified and calcified cartilage (with type II collagen), indicating that calcification of endochondral osteoid and of the underlying cartilage occurred independentyl. Spicules of endochondral cancellous bone of a four-week-old chick contained a core of calcified type II collagen

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Femoroacetabular impingement (FAI) is a potential cause of hip osteoarthritis (OA). The purpose of this study was to investigate the expression profile of matrix metalloproteinases (MMPs) in the labral tissue with FAI pathology.

We studied the cellular response to physeal distraction in the growth plates of skeletally immature rabbits. We used a new method of labelling and detection of proliferating cells with bromodeoxyuridine (BUdR) and an anti-BUdR antibody. The application of an external fixator but no distraction force produced no changes in the growth plates. After five days of distraction at a maximum force of 20 N, the growth plate became thicker, mainly because of an increase in the number of hypertrophic chondrocytes, but there was no evidence of increased cell proliferation. Recent fractures were seen at the junction of growth plate and metaphysis but the increase in bone length was insignificant. After ten days of distraction at the same maximum force, the chondrocyte columns had become disorganised and cell proliferation was significantly decreased. There was an increase in bone length due to distraction of the fracture gap. In this model, physeal distraction did not stimulate cell proliferation, but actually inhibited it. The apparent increase in growth-plate thickness produced by distraction is not due to increased cell production, but results from inhibition of endochondral ossification and the consequent accumulation of hypertrophic chondrocytes. Any growth after distraction depends on the ability of growth-plate chondrocytes to divide. The decrease in proliferative activity which we found after ten days of distraction suggests the need for caution in the use of such procedures in young children

Caveolae, specialised regions of the cell membrane which have been detected in a wide range of mammalian cells, have not been described in bone cells. They are plasmalemmal invaginations, 50 to 100 nm in size, characterised by the presence of the structural protein, caveolin, which exists as three subtypes. Caveolin-1 and caveolin-2 are expressed in a wide range of cell types whereas caveolin-3 is thought to be a muscle-specific subtype. There is little information on the precise function of caveolae, but it has been proposed that they play an important role in signal transduction. As the principal bone-producing cell, the osteoblast has been widely studied in an effort to understand the signalling pathways by which it responds to extracellular stimuli. Our aim in this study was to identify caveolae and their structural protein caveolin in normal human osteoblasts, and to determine which subtypes of caveolin were present. Confocal microscopy showed staining which was associated with the plasma membrane. Transmission electron microscopy revealed the presence of membrane invaginations of 50 to 100 nm, consistent with the appearance of caveolae. Finally, we isolated protein from these osteoblasts, and performed Western blotting using anti-caveolin primary antibodies. This revealed the presence of caveolin-1 and -2, while caveolin-3 was absent. The identification of these structures and their associated protein may provide a significant contribution to our further understanding of signal transduction pathways in osteoblasts

Aims

Platelet concentrates, like platelet-rich plasma (PRP) and platelet lysate (PL), are widely used in regenerative medicine, especially in bone regeneration. However, the lack of standard procedures and controls leads to high variability in the obtained results, limiting their regular clinical use. Here, we propose the use of platelet-derived extracellular vesicles (EVs) as an off-the-shelf alternative for PRP and PL for bone regeneration. In this article, we evaluate the effect of PL-derived EVs on the biocompatibility and differentiation of mesenchymal stromal cells (MSCs).