The evaluation of a biphasic osteochondral implant coupled with an electrospun membrane in a large animal model

Conventional clinical therapies are unable to resolve osteochondral defects adequately, hence tissue engineering solutions are sought to address the challenge. A biphasic implant which was seeded with Mesenchymal Stem Cells (MSC) and coupled with an electrospun membrane was evaluated as an alternative. This dual phase construct comprised of a Polycaprolactone (PCL) cartilage scaffold and a Polycaprolactone - Tri Calcium Phosphate (PCL - TCP) osseous matrix. Autologous MSC was seeded into the entire implant via fibrin and the construct was inserted into critically sized osteochondral defects located at the medial condyle and patellar groove of pigs. The defect was resurfaced with a PCL - collagen electrospun mesh that served as a substitute for periosteal flap in preventing cell leakage. Controls either without implanted MSC or resurfacing membrane were included. After 6 months, cartilaginous repair was observed with a low occurrence of fibrocartilage at the medial condyle. Osteochondral repair was promoted and host cartilage degeneration was arrested as shown by the superior Glycosaminoglycan (GAG) maintenance. This positive morphological outcome was supported by a higher relative Young's modulus which indicated functional cartilage restoration. Bone in growth and remodeling occurred in all groups with a higher degree of mineralization in the experimental group. Tissue repair was compromised in the absence of the implanted cells or the resurfacing membrane. Moreover healing was inferior at the patellar groove as compared to the medial condyle and this was attributed to the native biomechanical features.

The effect of unlocking RGD-motifs in collagen I on pre-osteoblast adhesion and differentiation

Denaturation of extracellular matrix proteins exposes cryptic binding sites. It is hypothesized that binding of cell adhesion receptors to these cryptic binding sites regulates cellular behaviour during tissue repair and regeneration. To test this hypothesis, we quantify the adhesion of pre-osteoblastic cells to native (Col) and partially-denatured (pdCol) collagen I using single-cell force spectroscopy. During early stages of cell attachment (≤180 s) pre-osteoblasts (MC3T3-E1) adhered significantly stronger to pdCol compared to Col. RGD (Arg-Gly-Asp)-containing peptides suppressed this elevated cell adhesion. We show that the RGD-binding α5β1- and αv-integrins mediated pre-osteoblast adhesion to pdCol, but not to Col. On pdCol pre-osteoblasts had a higher focal adhesion kinase tyrosine-phosphorylation level that correlated with enhanced spreading and motility. Moreover, pre-osteoblasts cultured on pdCol showed a pronounced matrix mineralization activity. Our data suggest that partially-denatured collagen exposes RGD-motifs that trigger binding of α5β1- and αv-integrins. These integrins initiate cellular processes that stimulate osteoblast adhesion, spreading, motility and differentiation. Taken together, these quantitative insights reveal an approach for the development of alternative collagen I- based surfaces for tissue engineering applications.

Online professional communities : understanding the effects of membership on teacher practice

Online communities offer teachers a forum to discuss ideas, seek support, engage in professional discussions and network with a wider peer group. The popularity of online communities for teachers is self-evident by the quantity that has emerged in recent years and they present as opportunities to engage in continued pedagogical growth. The study presented in this paper has focused on the electronic discussions of three online communities for teachers, two Australian-based communities and one UK-based community. The aim was to analyse the content of the messages, via content analysis using the Practical Inquiry Model (Garrison, Anderson & Archer, 2001) in an attempt to determine if membership had an impact pedagogy. This study will present findings that support the conclusion that membership to online communities provides genuine opportunities for continued pedagogical growth for teachers. It will also show that they are being used as a problem solving resource, provide opportunities for professional discourse and professional support.

Open content creation : the issues of voice and the challenges of listening

This paper examines the proposition that increased ability to have a voice and be listened to, through ‘open ICT4D’ and ‘open content creation’ can be an effective mechanism for development. The paper discusses empirical work that strongly indicates that this only happens when voice is appropriately valued in the development process. Having a voice in development processes are less effective when participation is limited. Open ICT allows for more and more voices to be heard, but it is open ICT4D that has the obligation to ensure voices are listened to. In the paper I first explore participatory development and the idea of open ICT4D before elaborating on issues of voice and thinking about voice as process, and voice as value. Research findings are presented from research that experimented with participatory (or open) content creation, discussed in relation to notions of openness and voice. I then consider the challenges of listening, before drawing some conclusions about opening up ICT4D research.

The distribution of the sample minimum-variance frontier

In this paper, we present a finite sample analysis of the sample minimum-variance frontier under the assumption that the returns are independent and multivariate normally distributed. We show that the sample minimum-variance frontier is a highly biased estimator of the population frontier, and we propose an improved estimator of the population frontier. In addition, we provide the exact distribution of the out-of-sample mean and variance of sample minimum-variance portfolios. This allows us to understand the impact of estimation error on the performance of in-sample optimal portfolios. Key Words: minimum-variance frontier; efficiency set constants; finite sample distribution

Why new business development projects fail : coping with the differences of technological versus market knowledge

Managing through projects has become important for generating new knowledge to cope with technological and market discontinuities. This paper examines how the fit between the creation of technological and market knowledge and important project management characteristics, i.e. project autonomy and completion criteria, influences the success of new business development (NBD) projects. In-depth longitudinal case research on NBD projects commercialised from 1993 to 2003 in the consumer electronics industry highlights that project management characteristics focusing only on the creation of technological knowledge contributed to the failure of those NBD projects that required new market knowledge as well. The findings indicate that senior management support and engaging in an alliance with partners possessing complementary market knowledge can offset this misalignment of the organisation of NBD projects.