Mechanical insult to articular cartilage kills chondrocytes, an event that may increase the risk of post-traumatic osteoarthritis. Recent reports indicate that antioxidants decrease impact induced chondrocyte death, but the source(s) of oxidants, the time course of oxidant release, and the identity of the oxidative species generated in response to injury are unknown. A better understanding of these processes could lead to new treatments of acute joint injuries. To that end we studied the kinetics and distribution of oxidant production in osteochondral explants subjected to a single blunt impact injury. We followed superoxide production by measuring the time-dependent accumulation of chondrocyte nuclei stained with the superoxide-sensitive probe dihydroethidium. The percentage of chondrocytes that were dihydroethidium-positive was 35% above baseline 10 minutes after impact and 65% above baseline 60 minutes after impact. Most positive cells were found within and near areas contacted directly by the impact platen. Rotenone, an electron transport chain inhibitor, was used to test the hypothesis that mitochondria contribute to superoxide release. Rotenone treatment significantly reduced dihydroethidium staining, which remained steady at 15% above baseline for up to 60 minutes post-impact. Moreover, rotenone reduced chondrocyte death in impact sites by more than 40% even when administered two hours after injury (p < 0.001). These data show that much of the acute chondrocyte mortality caused by in vitro impact injuries results from superoxide release from mitochondria and suggest that brief exposure to free radical scavengers could significantly improve chondrocyte viability following joint injury.

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SummaryReasons for performing study: Prophylactic digital hypothermia reduces the severity of acute laminitis experimentally but there is no evidence for its efficacy as a treatment once lameness has already developed. Objectives: To investigate the therapeutic effects of digital hypothermia, applied after the onset of lameness, in an experimental acute laminitis model. Study design: Randomised, controlled (within subject), blinded, experimental trial. Methods: Eight Standardbred horses underwent laminitis induction using the oligofructose model. Once lameness was detected at the walk, one forelimb was continuously cooled (CRYO), with the other forelimb maintained at ambient temperature (NON-RX). Dorsal lamellar sections (proximal, middle and distal) harvested 36 h after the onset of lameness/initiation of cryotherapy were analysed by 2 blinded observers: laminitis pathology was scored . There was complete physical separation of lamellar dermis from epidermis (score of 4) in 4 of the NON-RX feet at one or more section level(s), which was not observed in any CRYO sections. Histomorphometry was thus limited to sections that remained intact; there was a trend of increased total (TELL) and secondary (SELL) epidermal lamellar length and decreased secondary epidermal lamellar width (SELW) in NON-RX limbs compared with CRYO at all 3 levels; differences were significant (P<0.05) for SELL and SELW in the distal sections. Conclusions: Digital hypothermia reduced the severity of lamellar injury and prevented lamellar structural failure (complete dermoepidermal separation) when initiated at the detection of lameness in an acute laminitis model. This study provides the first evidence to support the use of therapeutic digital hypothermia as a treatment for acute laminitis.

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The co-administration of alfaxalone and medetomidine as an i.v. infusion after anaesthetic induction with alfaxalone was suitable for short-term field anaesthesia in the horse.

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The objective of this study was to determine how in vitro mechanical stimulation of tissue engineered constructs affects their stiffness and modulus in culture and tendon repair biomechanics 12 weeks after surgical implantation. Using six female adult New Zealand White rabbits, autogenous tissue engineered constructs were created by seeding mesenchymal stem cells (0.1 x 10(6) cells/ml) in collagen gel (2.6 mg/ml) and combining both with a collagen sponge. Employing a novel experimental design strategy, four constructs from each animal were mechanically stimulated (one 1 Hz cycle every 5 min to 2.4% peak strain for 8 h/day for 2 weeks) while the other four remained unstretched during the 2 week culture period. At the end of incubation, three of the mechanically stimulated (S) and three of the nonstimulated (NS) constructs from each animal were assigned for in vitro mechanical testing while the other two autogenous constructs were implanted into bilateral full-thickness, full-length defects created in the central third of rabbit patellar tendons (PTs). No significant differences were found in the in vitro linear stiffnesses between the S (0.15+/-0.1 N/mm) and NS constructs (0.08+/-0.02 N/mm; mean+/-SD). However, in vitro mechanical stimulation significantly increased the structural and material properties of the repair tissue, including a 14% increase in maximum force (p=0.01), a 50% increase in linear stiffness (p=0.001), and 23-41% increases in maximum stress and modulus (p=0.01). The S repairs achieved 65%, 80%, 60%, and 40% of normal central PT maximum force, linear stiffness, maximum stress, and linear modulus, respectively. The results for the S constructs exceed values obtained previously by our group using the same animal and defect model, and to our knowledge, this is the first study to show the benefits of in vitro mechanical stimulation on tendon repair biomechanics. In addition, the linear stiffnesses for the construct and repair were positively correlated (r=0.56) as were their linear moduli (r=0.68). Such in vitro predictors of in vivo outcome hold the potential to speed the development of tissue engineered products by reducing the time and costs of in vivo studies.

Objective The advent of new technologies has made it possible to explore alternative ventilator manufacturing to meet the worldwide shortfall for mechanical ventilators especially in pandemics. We describe a method using rapid prototyping technologies to create an electro-mechanical ventilator in a cost effective, timely manner and provide results of testing using an in vitro–in vivo testing model. Results Rapid prototyping technologies (3D printing and 2D cutting) were used to create a modular ventilator. The artificial manual breathing unit (AMBU) bag connected to wall oxygen source using a flow meter was used as air reservoir. Controlled variables include respiratory rate, tidal volume and inspiratory: expiratory (I:E) ratio. In vitro testing and In vivo testing in the pig model demonstrated comparable mechanical efficiency of the test ventilator to that of standard ventilator but showed the material limits of 3D printed gears. Improved gear design resulted in better ventilator durability whilst reducing manufacturing time (< 2-h). The entire cost of manufacture of ventilator was estimated at 300 Australian dollars. A cost-effective novel rapid prototyped ventilator for use in patients with respiratory failure was developed in < 2-h and was effective in anesthetized, healthy pig model.