Platelet-rich plasma activation in combination with biphasic osteochondral scaffolds-conditions for maximal growth factor production

PURPOSE

The combination of scaffolds and biological factors may enhance articular cartilage repair. Little is known regarding the activation and subsequent growth factor release of platelet-rich plasma (PRP) in contact with biosynthetic scaffolds. The purpose of this study was i) to identify whether the addition of thrombin was required to activate PRP in the presence of a collagen osteochondral scaffold and ii) to compare the activity of PRP when applied to both collagen- and polylactide-based osteochondral scaffolds.

METHODS

Equal combined volumes of test substances were used (n = 3): 500 μl PRP alone or on scaffolds; 375 μl PRP + 125 μl autologous thrombin on scaffolds; 455 μl PRP + 45 μl bovine thrombin on scaffolds. Scaffolds and/or PRP were cultured in vitro in DMEM/F12 medium for 10 days. TGF-β1, PDGF-AB and bFGF were measured using ELISA.

RESULTS

A similar cumulative release profile in all growth factors was found over the 10-day period i.e. a burst release and further physiological prolonged release. A significantly higher release of PDGF-AB was seen in the PRP + collagen scaffold groups at all time points, compared to scaffold + PRP + thrombins (P < 0.001). A significantly increased cumulative volume of PDGF-AB was released from the collagen scaffold compared to the polylactide scaffold (P < 0.001).

CONCLUSION

This study shows that polylactide and particularly collagen osteochondral scaffolds activate PRP in vitro. If PRP is combined with these scaffolds clinically, no exogenous activation with thrombin is required to achieve growth factor release, which may be of benefit for articular cartilage repair applications.

The effect of the addition of hydroxyapatite graft substitutes upon the hoop strain and subsequent subsidence of a femoral model during impaction bone grafting

Impaction bone grafting using morcellised allograft can successfully restore bone stock in revision surgery. However, concerns exist regarding supply of bone and transmission of infection. Bone-graft extenders, such as tricalcium phosphate (TCP) and hydroxyapatite (HA), are used to minimise the use of donor bone. However, concerns exist around a reported increased risk of femoral fracture during impaction bone grafting with a 1:1 mixture of TCP/HA and morcellised bone graft (MBG) during impaction grafting in human cadaveric femora. Using a sawbones model, it was evaluated whether there was increased femoral cortical strain with a HA:MBG mixture during impaction grafting compared to MBG impacted at the same and a greater force. Subsequently the subsidence behaviour of the different graft mixes was compared by using a loaded femoral stem in an endurance test. It was demonstrated that the femora with the MBG:HA graft had greater cortical hoop stresses but improved subsidence behaviour compared to a graft composed of pure MBG impacted at the same force.

Extruded collagen fibres for tissue engineering applications: effect of crosslinking method on mechanical and biological properties

Reconstituted collagen fibres are promising candidates for tendon and ligament tissue regeneration. The crosslinking procedure determines the fibres' mechanical properties, degradation rate, and cell-fibre interactions. We aimed to compare mechanical and biological properties of collagen fibres resulting from two different types of crosslinking chemistry based on 1-ethyl-3-(3-dimethyllaminopropyl)carbodiimide (EDC). Fibres were crosslinked with either EDC or with EDC and ethylene-glycol-diglycidyl-ether (EDC/EGDE). Single fibres were mechanically tested to failure and bundles of fibres were seeded with tendon fibroblasts (TFs) and cell attachment and proliferation were determined over 14 days in culture. Collagen type I and tenascin-C production were assessed by immunohistochemistry and dot-blotting. EDC chemistry resulted in fibres with average mechanical properties but the highest cell proliferation rate and matrix protein production. EDC/EGDE chemistry resulted in fibres with improved mechanical properties but with a lower biocompatibility profile. Both chemistries may provide useful structures for scaffolding regeneration of tendon and ligament tissue and will be evaluated for in vivo tendon regeneration in future experiments.

Much more than a ratio: multivariate selection on female bodies

Studies of the attractiveness of female bodies have focussed strongly on the waist, hips and bust, but sexual selection operates on whole phenotypes rather than the relative proportions of just two or three body parts. Here, we use body scanners to extract computer-generated images of 96 Chinese women's bodies with all traits unrelated to body shape removed. We first show that Chinese and Australian men and women rate the attractiveness of these bodies the same. We then statistically explore the roles of age, body weight and a range of length and girth measures on ratings of attractiveness. Last, we use nonlinear selection analysis, a statistical approach developed by evolutionary biologists to explore the interacting effects of suites of traits on fitness, to study how body traits interact to determine attractiveness. Established proxies of adiposity and reproductive value, including age, body mass index and waist-to-hip ratio, were all correlated with attractiveness. Nonlinear response surface methods using the original traits consistently outperform all of these indices and ratios, suggesting that indices of youth and abdominal adiposity tell only part of the story of body attractiveness. In particular, our findings draw attention to the importance of integration between abdominal measures, including the bust, and the length and girth of limbs. Our results provide the most comprehensive analysis to date of the effect of body shape and fat deposition on female attractiveness.

Osteoclastogenesis on hydroxyapatite ceramics: the effect of carbonate substitution

Human osteoclasts derived from CD14+ve precursors were cultured on discs of stoichiometric hydroxyapatite (HA) and carbonate-substituted hydroxyapatite (CHA) of varying carbonate contents. The development of osteoclasts was qualitatively different on ceramics compared to dentine, occurring in discrete, confluent subpopulations, which suggests local cell signaling may be important in the process. Resorption was quantified by scanning electron microscopy, surface profilometry, and by calcium release into the culture medium. Cells were characterised by a number of histochemical markers of the osteoclast phenotype. Resorption of the ceramic increased with increasing carbonate content up to 2.35 wt %, when resorption trails and pits characteristic of osteoclast activity were seen. Controlling carbonate content may be one way of controlling the rate of resorption of synthetic HA ceramics.

Social and trauma-related pathways leading to psychological distress and functional limitations four years after the humanitarian emergency in Timor-Leste

There is growing acknowledgment that research in the postconflict field needs to include a focus on social conditions. The authors applied structural equation modeling to epidemiologic data obtained from postconflict Timor-Leste, to examine for links involving potentially traumatic events and sociodemographic factors (age, gender, educational levels, and unemployment) with psychological symptoms and functioning. Exposure to trauma and lack of education emerged as most relevant with psychological distress impacting on education in the urban area. Age and gender exerted influences at different points in the model consistent with the known history of Timor. Although based on cross-sectional data, the model supports the relevance of past trauma, posttraumatic distress, and postconflict social conditions to functioning in societies such as Timor-Leste.

Production and characterization of HA and SiHA coatings

Plasma sprayed hydroxyapatite (HA) coatings on metallic prostheses have been used clinically in dentistry and orthopedics since the mid 1980s. The coating properties are dependent on the spraying parameters. Since silicon-substituted hydroxyapatite (SiHA) has been shown to offer improved bioactivity over phase pure HA, SiHA coatings have the potential for enhanced performance in clinical application. In this study, phase pure HA and 0.8 wt% SiHA powders were synthesized with similar particle size distribution and morphology. The powders were plasma sprayed onto Ti-6Al-4V substrates at 37 kW and 40 kW plasma gun input power respectively. Four kinds of samples were prepared, HAC 37, HAC 40, SiHAC 37 and SiHAC 40. Materials characterization showed that the coatings were of relatively high phase purity. In vitro cell culture demonstrated that human osteoblast cells grew well on all samples, with the highest cell growth observed on SiHA coatings produced under the lower plasma gun input power.

Articular cartilage tissue engineering

Articular cartilage repair remains a challenge to surgeons and basic scientists. The field of tissue engineering allows the simultaneous use of material scaffolds, cells and signalling molecules to attempt to modulate the regenerative tissue. This review summarises the research that has been undertaken to date using this approach, with a particular emphasis on those techniques that have been introduced into clinical practice, via in vitro and preclinical studies.

A Stream-Wetland-Riparian (SWR) index for assessing condition of aquatic ecosystems in small watersheds along the Atlantic slope of the eastern U.S

As part of a regional study by the Atlantic Slope Consortium (ASC) to develop ecological and socioeconomic indicators of aquatic ecosystem condition, we developed and tested a protocol for rapidly assessing condition of the stream, wetland, and riparian components of freshwater aquatic ecosystems. Aspects of hydrology, vegetation, in-stream and wetland characteristics, and on-site stressors were measured in the field. The resulting metrics were used to develop an index of overall condition, termed the Stream-Wetland-Riparian (SWR) Index. Values of this Index were compared to existing biotic indices and chemical measures, and to a Landscape Index created using satellite-based land cover data and a geographic information system (GIS). Comparisons were made at several levels of spatial aggregation and resolution, from site to small watershed. The SWR Index and associated Landscape Indices were shown to correlate highly with biological indicators of stream condition at the site level and for small contributing areas. The landscape patterns prevalent throughout the entire watershed do not necessarily match the patterns found adjacent to the stream network. We suggest a top-down approach that managers can use to sequentially apply these methods, to first prioritize watersheds based on a relative condition measure provided by the Landscape Index, and then assess condition and diagnose stressors of aquatic resources at the subwatershed and site level.

Bone formation in a carbonate-substituted hydroxyapatite implant is inhibited by zoledronate

Carbonate-substituted hydroxyapatite (CHA) is more osteoconductive and more resorbable than hydroxyapatite (HA), but the underlying mode of its action is unclear. We hypothesised that increased resorption of the ceramic by osteoclasts might subsequently upregulate osteoblasts by a coupling mechanism, and sought to test this in a large animal model.

Defects were created in both the lateral femoral condyles of 12 adult sheep. Six were implanted with CHA granules bilaterally, and six with HA. Six of the animals in each group received the bisphosphonate zoledronate (0.05 mg/kg), which inhibits the function of osteoclasts, intra-operatively.

After six weeks bony ingrowth was greater in the CHA implants than in HA, but not in the animals given zoledronate. Functional osteoclasts are necessary for the enhanced osteoconduction seen in CHA compared with HA.

Do female black field crickets Teleogryllus commodus benefit from polyandry?

Female insects that mate multiply tend to have increased lifetime fitness, apparently because of greater access to male-derived resources (e.g. sperm, nuptial gifts) that elevate fertility/fecundity. Experiments that standardize the number of matings per female also show that polyandry can improve aspects of offspring performance, most notably early embryo survival (egg hatching success). This improvement is widely attributed to genetic benefits which would arise if polyandrous females skew paternity to produce fitter offspring. In two separate experiments with field crickets (Teleogryllus commodus) polyandrous females (two, three or four mates) did not have higher egg hatching success than monandrous females (effect sizes: r = 0.03 and 0.08 for the respective experiments), which is consistent with our finding of no sire effect on hatching success. Polyandry also had no effect on post-hatching offspring survival. Polyandrous females' offspring took significantly longer to mature but their sons were not heavier and their daughters were actually significantly smaller than those of monandrous females. Finally, after controlling for relative male size, monandrous females' sons were more successful when directly competing for a mate.

Sounds different: inbreeding depression in sexually selected traits in the cricket Teleogryllus commodus

If male sexual signalling is honest because it captures genetic variation in condition then traits that are important mate choice cues should be disproportionately affected by inbreeding relative to other traits. To test this, we investigated the effect of brother-sister mating on advertisement calling by male field crickets Teleogryllus commodus. We quantified the effect of one generation of inbreeding on nightly calling effort and five finer-scale aspects of call structure that have been shown to influence attractiveness. We also quantified inbreeding depression on six life history traits and one morphological trait. Inbreeding significantly reduced hatching success, nymph survival and adult lifespan but had no detectable effect on hatching rate, developmental rate or adult body mass. The effect of inbreeding on sexually selected traits was equivocal. There was no decline in calling effort (seconds of sound production/night) by inbred males, but there were highly significant changes in three of five finer-scale call parameters. Sexually selected traits clearly vary in their susceptibility to inbreeding depression.

The effect of leg fracture level and vehicle front-end geometry on pedestrian knee injury and response

In this study a MADYMO® (mathematical dynamic modelling) model has been used to identify the influence of leg fracture on the injuries sustained by the pedestrian during front end impact with a vehicle. A factorial study of a MADYMO® pedestrian and vehicle model are used to investigate the effect of different leg fracture tolerances, geometry, and vehicle compliance on the criteria measured in the European Enhanced Vehicle-safety Committee (EEVC) pedestrian safety tests. These criteria include knee bending, knee shear response, and lower leg bone (tibia) acceleration. The main study examines the spread of typical values of lower limb tolerance based on reported literature and contrasts the response of weaker, low-strength bones, normal tolerance, and limbs which do not fracture. Results show that knee bending angles and therefore ligament strains are significantly increased when fracture does not occur, and are decreased in bones exhibiting a low-strength response. Bone fracture tolerance is shown to be a significant parameter influencing knee bending. The parameters are compared to show that knee shear is significantly influenced by vehicle bumper compliance and that both criteria are heavily influenced by bumper height. Vehicles with more aggressive geometry, higher bumpers, and larger bumper lead were considered for comparative purposes.

Ultrasonic treatment to improve anaerobic digestibility of dairy waste streams

The dairy-processing industry generates various types of organic wastes, which are utilised as stock feed, for anaerobic digestion, spread on land or alternatively land-filled at high costs. Owing to the generation of renewable energy, anaerobic digestion is an attractive option for many factories. To enhance the biological degradation process, a mechanical disintegration of various waste dairy streams was undertaken. While the successful application of ultrasonic treatment has been reported for various municipal waste streams, limited information was available for dairy industry applications. The results of this study showed that ultrasonic treatment can improve the digestibility of the more problematic dairy waste streams, such as sludges, by breaking down micro-organisms' cell walls and releasing soluble cell compounds. For more soluble streams, such as dairy factory effluent, an increased gas production was observed and attributed to the reduced particle size of the fat globules.

Effect of carbonate substitution on the ultrastructural characteristics of hydroxyapatite implants

Carbonate ion substitution has been shown to be beneficial for increasing the amount of in vivo osseointegration to hydroxyapatite (HA). Nevertheless, mechanisms by which carbonate ions increase in vivo bioactivity are not fully understood. Sintered granules of HA and carbonate-substituted hydroxyapatite (CHA) were implanted for 6 and 12 weeks in an ovine model. Samples containing the bone-implant interface were prepared for transmission electron microscopy (TEM) and TEM was used to compare the in vivo reactivity of sintered granules of HA and CHA. The current findings demonstrated that CHA (1.2 and 2.05 wt.%) is more soluble than pure HA in vivo. More dissolution was observed from the CHA, at the bone-implant interface and within the implant, when compared to pure HA. A less crystalline phase was formed between the 2.05 wt.% CHA and bone at 12 weeks in vivo. Bone surrounding both the pure HA and 1.2 wt.% CHA was relatively disorganised at 12 weeks. In comparison, bone surrounding the 2.05 wt.% CHA was considerably more organised and in many regions collagen fibrils were present. Despite increased quality of bone surrounding 2.05 wt.% CHA, compared to 1.2 wt.% CHA, the amount of dissolution from both materials was similar.

Benefits of interprofessional learning: an interprofessional MSc in child health

This article addresses interprofessional education (IPE) using a case study evaluating a multidisciplinary MSc course in child health. The participants felt that the nature of the course increased their interprofessional working skills and professional confidence. They described benefits, including new insights, a balanced variety of views, development of respect and equality between professionals, improved communication and a holistic approach to child health.