Aims

The anterior cruciate ligament (ACL) is known to have a poor wound healing capacity, whereas other ligaments outside of the knee joint capsule such as the medial collateral ligament (MCL) apparently heal more easily. Plasmin has been identified as a major component in the synovial fluid that varies among patients. The aim of this study was to test whether plasmin, a component of synovial fluid, could be a main factor responsible for the poor wound healing capacity of the ACL.

Energy storing tendons such as the human Achilles and equine superficial digital flexor tendon (SDFT) are prone to age-related injury. Tendons have poor healing capacity and a lack of effective treatments can lead to ongoing pain, reduced function and re-injury. It is therefore important to identify the mechanisms underpinning age-related tendinous changes in order to develop more effective treatments. Our recent single cell sequencing data has shown that tendon cell populations have extensive heterogeneity and cells housed in the tendon interfascicular matrix (IFM) are preferentially affected by ageing. There is, however, a lack of established surface markers for cell populations in tendon, limiting the capacity to isolate distinct cell populations and study their contribution to age-related tendon degeneration. Here, we investigate the presence of the cell surface proteins MET proto-oncogene (MET), integrin subunit alpha 10 (ITGA10), fibroblast activation protein alpha (FAP) and platelet derived growth factor receptor alpha (PDGFRA) in the equine SDFT cell populations and their co-localisation with known markers. Using Western blot we validated the specificity of selected antibodies in equine tissue before performing immunohistochemistry to establish the location of the respective proteins in the SDFT. We subsequently used double labelling immunofluorescence with the established mural cell marker desmin (DES) to distinguish between tenocyte and mural cell populations. In situ, MET, ITGA10, and FAP presence was found in cells throughout the tendon whereas PDGFRA was present in cells within the IFM. Double labelling immunofluorescence with the mural cell marker DES showed lack of co-localisation between PDGFRA and DES suggesting PDGFRA is labelling an IFM cell population distinct from those associated with blood vessels. PDGFRA is a promising target for the specific cell sorting of IFM-localised tenocytes, enabling their isolation and subsequent characterisation. Acknowledgments: The authors acknowledge the Biotechnology and Biological Sciences Research Council (BB/W007282/1) for funding this work

Haemophilia is a lifelong inherited bleeding disorder characterized by spontaneous bleeding resulting in painful joint deformities. Even if prosthetic surgery and the effectiveness and safety of clotting factor concentrate have improved the therapeutic options available, sometimes the orthopaedic surgeon has to treat substance losses. First, we have to distinguish: 1) sub-chondral cysts, 2) intra-osseous cysts, 3) pseudo-tumour (a chronic expanding blood cyst with the ability to displace and destroy adjacent tissues) Surgical treatment is in relation to its anatomical location and extension and is always associated with prolonged treatment with clotting factor concentrate. In our 20 years’ experience, we have used several therapeutic options. In some cases, we use filling with bone graft and fibrin seal and today platelet derived growth factor; in the others we have used amputation or custom made prosthesis

The treatment of relapsing pseudoarthrosis of ulna presents quite a lot of perplexities as regards the surgical strategy to follow which means of synthesis to solve the biomechanical problems (lack of favourable loading stimuli and, on the contrary, presence of unfavourable torsional strengths due to the movement of pronosupination of the forearm),and how to interact in order to favour the restoration of osteogenesis (homologous or autologous bone graft, vascularized or not, bone substitutes, employment of autologous growth factors, of morphogenetic proteins (BMP),and of autologous staminal cells). The authors report about 4 particular cases of relapsing pseudoarthrosis of the ulna previously treated with autologous bone grafts but with no recovery. In order to activate osteogenesis, the authors have employed a graft of autologous bone enriched with platelet derived growth factors + adult mesenchymal stem cells from drawing from the iliac wing. The osteosyntesis has been carried out in 3 cases with endomidollar locked nail and, in one case, with external fixation. All the four cases have reached prompt lasting clinical recovery (following up from 8 to 28 month) and Rx precocious evidence of osteointegration of the grafts independently from the synthesis means. The limited casuistry does not enable us to report any comparable statistical data. The authors think that association of AGF + adult mesenchymal stem cells can be determinant and encouraging and, thanks to the results, they suggest its spreading

Dupuytren’s contracture is characterised by abnormal fibroblast proliferation and extracellular matrix deposition in the palmar fascia. Fibroblast proliferation and matrix deposition in connective tissues are regulated by cytokines. A number of cytokines including transforming growth factor beta (TGFβ), basic fibroblast growth factor (bFGF), platelet derived growth factor (PDGF) and epidermal growth factor (EGF) are known to have potent anabolic effects on connective tissue. The aim of this study was to investigate the role played by anabolic cytokines in the pathogenesis of Dupuytren’s disease. Twelve specimens of Dupuytren’s contracture and six control specimens of palmar fascia obtained from patients undergoing carpal tunnel release were cultured using a serumless method under standard conditions for 72 h. Levels of TGFβ-1, bFGF, PDGF and EGF in the medium were estimated using an enzyme linked immunoabsorbent assay technique. Neither Dupuytren’s tissue nor control palmar fascia produced any EGF. The mean (±S.D.)levels of bFGF, PDGF and TGFβ-1 produced by cultured palmar fascia were: 1270 ± 832, 74 ± 24, < 7, and for Dupuytren’s tissue were 722 ± 237, 139 ± 76.6, 645 ± 332, respectively. The levels of PDGF and TGFβ-1 were significantly higher in Dupuytren’s tissue. PDGF is produced in increased amounts by Dupuytren’s tissue. This may contribute to the fibroblast proliferation and increased ECM deposition observed in this condition. TGFβ-1 is not produced by normal palmar fascia but is produced in large amounts by Dupuytren’s tissue. The major physiologic role of TGFβ-1 is to stimulate formation of fibrous tissue. It plays a major role in wound healing and also in pathological conditions where fibrosis is a prominent feature. Inappropriate production of TGFβ-1 in the palmar fascia in Dupuytren’s disease may play a central role in initiating and stimulating the abnormal fibroblast proliferation and collagen synthesis seen in this condition

Growth factors hold great promise for the treatment of various musculoskeletal conditions. Growth factors are small proteins that serve as signaling agents for cells. The discovery of these substances revolutionized the field of cell biology by revealing the mechanism of regulation of cell activities. Growth factors are present in plasma or tissues at concentrations measured in billionths of a gram yet they are the principal effector of such critical cellular functions such as cell division, matrix synthesis and tissue differentiation. Several growth promoting substances have been identified in bone matrix and at the site of healing fractures. Among these are the transforming growth factor beta’s, bone morphogenetic proteins, fibroblast growth factors, insulin like growth factors and platelet derived growth factor. These growth factors are mainly produced by osteoblasts and incorporated into the extracellular matrix during bone formation. Small amounts of the growth factors can also be trapped systemically from serum and be incorporated into matrix. The present hypothesis is that growth factors are located within the matrix until remodeling or trauma causes solubilization and release of the proteins. The discovery of growth factors and their study in in vitro cultures has allowed an understanding of the mechanism of the regulation of a broad range of cell activities. However, their presence in plasma and tissues in minute quantities limited their evaluation in vivo and precluded clinical application of the natural purified products. Advances in recombinant DNA methodology have allowed sufficient quantities of these materials to be produced and many are in various stage of in vivo pre-clinical and clinical evaluation. Extensive efforts have been made to find methods by which growth factors can be used to stimulate local bone healing and bone formation in a variety of clinical models. The growth factors TGF-α, BMP and basic FGF are the only growth factors that have been demonstrated to possess substantial in vivo bone stimulatory capacity. The growth factors BMP-2 and BMP-7, also known as osteogenic protein-1, are in the final stages of pivotal human trials. There are many challenges to the clinical application of growth factors. It is unlikely that cell signaling molecules act independently of each other or are present in isolation from each other at their sites of action. The therapeutic application of growth factors must also accommodate the fact that most factors have a widespread and varied distribution of target cells. A growth factor administered to elicit a desired response from one cell type may also influence other cell types possible in unintended or undesirable ways. Finally, in the current era of cost consciousness in health care, a growth factor treatment must demonstrate cost effectiveness along with clinical efficacy

Introduction: Acute neurological damage from spinal cord injuries is believed to be localised, however it initiates a cascade of secondary events which usually leads to extensive and permanent neurological deficit. The secondary damage begins with the disruption of the blood-spinal cord barrier which unleashes a protracted inflammatory response. This prolonged inflammatory response is the catalyst for the secondary neurodegeneration and limited repair response that occurs in the chronic phase of a spinal cord injury. In this study it was proposed that the acute delivery of the angiogenic growth factors vascular endothelial growth factor (VEGF) and platelet derived growth factor (PDGF) would mediate inflammation and restore the blood spinal cord barrier. This would minimise the formation of glial scar and reduce the extent of secondary degeneration caudal and cranial to the lesion site. Methods: Adult male Wistar rats (400g) were anesthetised. Complete laminectomies were performed at T10 and the animals were subjected to T10 hemisection. Animals were randomised to a treatment group (Lesion Control (LC), Gel Control (GC) and Angiogenic Gel (AG)) after the spinal cord was cut. Each treatment group had 6 animals sacrificed 3 months post injury. Sections were stained with antibodies to neurofilament 200, glial fibrillary acidic protein, smooth muscle actin (SMA), and fluorescent secondary antibodies and mounted with DAPI. The lesion size was measured from horizontal histological sections of the midline from 5 animals in each group using Axiovision version 4.6.1.0 (Carl Zeiss Imaging Solutions, Germany). Results: The mean lesion size for the lesion control group was 2.09mm2, 1.97mm2 for the gel control group and 0.45mm2 for the active gel group. A t-test was used to confirm that the differences between the active gel and the two control groups were statistically significant (AG vs LC p= 0.021 AG vs GC p= 0.026). Histology showed a marked improvement of the morphology of the astrocytes in the treatment group over the control groups indicating that the treatment affected the population of reactive astrocytes. SMA staining showed an increased level of revascularisation in the treated lesions. Discussion: Spinal cords do not heal because of prolonged inflammation which leads to secondary necrotic events, scar formation and the inhibition of regeneration. In this study we present a method for regulating the post lesion inflammatory signals, significantly reducing post-lesion scar formation. We propose the delivery of VEGF/PDGF significantly increases the permeability of the blood spinal cord barrier to neutrophils and macrophages and promotes angiogenesis observed in the lesion site. This may have two major effects on the progression of the spinal cord injury. Firstly, by increasing the initial influx of inflammatory cells it enables the faster removal of damaged tissue and phagocytosis of apoptotic cells thereby restoring the balance in favour of regulated inflammation and results in a finite and reduced inflammation time. Secondly, combination of VEGF and PDGF provides a robust angiogenic response and reduces ischemia, the population of reactive astrocytes and the capacity to form glial scars. These growth factors appear to moderate the secondary degenerative changes that result from the prolonged inflammation and thus promote the inherent capacity for regeneration

Large bone defects remain a tremendous clinical challenge. There is growing evidence in support of treatment strategies that direct defect repair through an endochondral route, involving a cartilage intermediate. While culture-expanded stem/progenitor cells are being evaluated for this purpose, these cells would compete with endogenous repair cells for limited oxygen and nutrients within ischaemic defects. Alternatively, it may be possible to employ extracellular vesicles (EVs) secreted by culture-expanded cells for overcoming key bottlenecks to endochondral repair, such as defect vascularization, chondrogenesis, and osseous remodelling. While mesenchymal stromal/stem cells are a promising source of therapeutic EVs, other donor cells should also be considered. The efficacy of an EV-based therapeutic will likely depend on the design of companion scaffolds for controlled delivery to specific target cells. Ultimately, the knowledge gained from studies of EVs could one day inform the long-term development of synthetic, engineered nanovesicles. In the meantime, EVs harnessed from in vitro cell culture have near-term promise for use in bone regenerative medicine. This narrative review presents a rationale for using EVs to improve the repair of large bone defects, highlights promising cell sources and likely therapeutic targets for directing repair through an endochondral pathway, and discusses current barriers to clinical translation.

Cite this article: E. Ferreira, R. M. Porter. Harnessing extracellular vesicles to direct endochondral repair of large bone defects. Bone Joint Res 2018;7:263–273. DOI: 10.1302/2046-3758.74.BJR-2018-0006.

Objectives

Rotator cuff tears are among the most frequent upper extremity injuries. Current treatment strategies do not address the poor quality of the muscle and tendon following chronic rotator cuff tears. Hypoxia-inducible factor-1 alpha (HIF-1α) is a transcription factor that activates many genes that are important in skeletal muscle regeneration. HIF-1α is inhibited under normal physiological conditions by the HIF prolyl 4-hydroxylases (PHDs). In this study, we used a pharmacological PHD inhibitor, GSK1120360A, to enhance the activity of HIF-1α following the repair of a chronic cuff tear, and measured muscle fibre contractility, fibrosis, gene expression, and enthesis mechanics.

Objectives

Rotator cuff tears are among the most common and debilitating upper extremity injuries. Chronic cuff tears result in atrophy and an infiltration of fat into the muscle, a condition commonly referred to as ‘fatty degeneration’. While stem cell therapies hold promise for the treatment of cuff tears, a suitable immunodeficient animal model that could be used to study human or other xenograft-based therapies for the treatment of rotator cuff injuries had not previously been identified.