A biomaterials approach to peripheral nerve regeneration: bridging the peripheral nerve gap and enhancing functional recovery

Microsurgical techniques for the treatment of large peripheral nerve injuries (such as the gold standard autograft) and its main clinically approved alternative--hollow nerve guidance conduits (NGCs)--have a number of limitations that need to be addressed. NGCs, in particular, are limited to treating a relatively short nerve gap (4 cm in length) and are often associated with poor functional recovery. Recent advances in biomaterials and tissue engineering approaches are seeking to overcome the limitations associated with these treatment methods. This review critically discusses the advances in biomaterial-based NGCs, their limitations and where future improvements may be required. Recent developments include the incorporation of topographical guidance features and/or intraluminal structures, which attempt to guide Schwann cell (SC) migration and axonal regrowth towards their distal targets. The use of such strategies requires consideration of the size and distribution of these topographical features, as well as a suitable surface for cell-material interactions. Likewise, cellular and molecular-based therapies are being considered for the creation of a more conductive nerve microenvironment. For example, hurdles associated with the short half-lives and low stability of molecular therapies are being surmounted through the use of controlled delivery systems. Similarly, cells (SCs, stem cells and genetically modified cells) are being delivered with biomaterial matrices in attempts to control their dispersion and to facilitate their incorporation within the host regeneration process. Despite recent advances in peripheral nerve repair, there are a number of key factors that need to be considered in order for these new technologies to reach the clinic.

High-resolution mapping, cloning and molecular characterization of the Pi-k ( h ) gene of rice, which confers resistance to Magnaporthe grisea

In order to understand the molecular mechanisms involved in the gene-for-gene type of pathogen resistance, high-resolution genetic and physical mapping of resistance loci is required to facilitate map-based cloning of resistance genes. Here, we report the molecular mapping and cloning of a dominant gene (Pi-k ( h )) present in the rice line Tetep, which is associated with resistance to rice blast disease caused by Magnaporthe grisea. This gene is effective against M. grisea populations prevalent in the Northwestern Himalayan region of India. Using 178 sequence tagged microsatellite, sequence-tagged site, expressed sequence tag and simple sequence repeat (SSR) markers to genotype a population of 208 F(2) individuals, we mapped the Pi-k ( h ) gene between two SSR markers (TRS26 and TRS33) which are 0.7 and 0.5 cM away, respectively, and can be used in marker-assisted-selection for blast-resistant rice cultivars. We used the markers to identify the homologous region in the genomic sequence of Oryza sativa cv. Nipponbare, and a physical map consisting of two overlapping bacterial artificial chromosome and P1 artificial chromosome clones was assembled, spanning a region of 143,537 bp on the long arm of chromosome 11. Using bioinformatic analyses, we then identified a candidate blast-resistance gene in the region, and cloned the homologous sequence from Tetep. The putative Pi-k ( h ) gene cloned from Tetep is 1.5 kbp long with a single ORF, and belongs to the nucleotide binding site-leucine rich repeat class of disease resistance genes. Structural and expression analysis of the Pi-k ( h ) gene revealed that its expression is pathogen inducible.

Regeneration and repair of tendon and ligament tissue using collagen fibre biomaterials

Collagen fibres are ubiquitous macromolecular assemblies in nature, providing the structures that support tensile mechanical loads within the human body. Aligned type I collagen fibres are the primary structural motif for tendon and ligament, and therefore biomaterials based on these structures are considered promising candidates for mediating regeneration of these tissues. However, despite considerable investigation, there remains no collagen-fibre-based biomaterial that has undergone clinical evaluation for this application. Recent research in this area has significantly enhanced our understanding of these complex and challenging biomaterials, and is reinvigorating interest in the development of such structures to recapitulate mechanical function. In this review we describe the progress to date towards a ligament or tendon regeneration template based on collagen fibre scaffolds. We highlight reports of particular relevance to the development of the underlying biomaterials science in this area. In addition, the potential for tailoring and manipulating the interactions between collagen fibres and biological systems, as hybrid biomaterial-biological ensembles, is discussed in the context of developing novel tissue engineering strategies for tendon and ligament.

Bioreactors for Cardiovascular Cell and Tissue Growth: A Review

Heart disease is a major cause of death in the Western world. In the past three decades there has been a number of improvements in artificial devices and surgical techniques for cardiovascular disease; however, there is still a need for novel devices, especially for those individuals who cannot receive conventional therapy. The major disadvantage of current artificial devices lies in the fact that they cannot grow, remodel, or repair in vivo. Tissue engineering offers the possibility of developing a biological substitute material in vitro with the inherent mechanical, chemical, biological, and morphological properties required in vivo, on an individual patient basis. In order to develop a true biological cardiovascular device a dynamic physiological environment needs to be created. One approach that employs the use of a simulated biological environment is a bioreactor in which the in vivo biomechanical and biochemical conditions are created in vitro for functional tissue development. A review of the current state of the art bioreactors for the generation of tissue engineered cardiovascular devices is presented in this study. The effect of the simulated physiological environment of the bioreactor on tissue development is examined with respect to the materials properties of vascular grafts, heart valves, and cardiac muscles developed in these bioreactors.

Living artificial heart valve alternatives: a review

Conventional replacement therapies for heart valve disease are associated with significant drawbacks. The field of tissue engineering has emerged as an exciting alternative in the search for improved heart valve replacement structures. One of the principles behind this concept is the transplantation of living elements, embedded in a suitable scaffold material, to the diseased site where the structure becomes integrated with patients' tissue to restore natural function. Significant progress has been made in the last ten years in the development of a living artificial heart valve alternative (LAHVA), with the identification of potential replacement sources for valve cells, scaffolds to maintain the cells in a three-dimensional environment, and signals to promote tissue development. This review addresses the need for a tissue-engineered alternative to current prostheses and provides a detailed account of normal heart valve structure--the blueprint for LAHVA fabrication. The research efforts to create a viable LAHVA, including recent developments, are discussed. Particular attention is focused on the choice of cell source for LAHVA construction, the use of biodegradable natural and synthetic polymeric scaffolds as extracellular matrix derivatives, and exogenous stimulation of tissue growth. The critical challenges involved in LAHVA development and possible future areas of investigation are also discussed.

B7 costimulation is required for IL-5 and IL-13 secretion by bronchial biopsy tissue of atopic asthmatic subjects in response to allergen stimulation

Asthma is a complex disorder characterized by airway hyperreactivity and inflammation. To analyze cellular interactions required for the secretion of cytokines by the bronchial mucosa, we have evaluated the ex vivo response of tissue explants to allergen. Endobronchial mucosal biopsy tissue from mild atopic asthmatic subjects and normal control subjects were maintained in culture for 24 h. To detect reactivity to allergen, the explants were stimulated with dust mite extract Dermatophagoides pteronyssinus (Der p). Our analysis revealed that without any overt stimulation, mRNA transcripts for interleukin (IL)-5 and IL-13 were expressed by asthmatic but not normal bronchial tissue. In contrast, the expression of interferon-gamma was observed in a higher proportion of cultured bronchial biopsies from the normal control subjects than in those from asthmatic subjects. Addition of Der p allergen did not change the cytokine profile of the explants from control volunteers but augmented the expression of IL-5 mRNA and induced secretion of the protein by the asthmatic bronchial tissue. In most cases, allergen also increased the production of IL-13 by bronchial tissue from asthmatic subjects. The allergen-induced secretion of IL-5 and IL-13 was inhibited by the fusion protein CTLA-4Ig, reflecting a requirement for CD80 (B7-1) and/or CD86 (B7-2) costimulation for the expression of the Th2 cytokines. This requirement for B7/CD28 costimulation is consistent with the hypothesis that IL-5 and IL-13 are produced by allergen-specific T cells resident in the asthmatic bronchial mucosa.

Silicon gel sheeting for preventing and treating hypertrophic and keloid scars

BACKGROUND

Keloid and hypertrophic scars are common and are caused by a proliferation of dermal tissue following skin injury. They cause functional and psychological problems for patients, and their management can be difficult. The use of silicon gel sheeting to prevent and treat hypertrophic scarring is still relatively new, and started in 1981 with treatment of burn scars.

OBJECTIVES

To determine the effectiveness of silicon gel sheeting for: (1) prevention of hypertrophic or keloid scarring in people with newly healed wounds (e.g. post surgery); (2) treatment of established scarring in people with existing keloid or hypertrophic scars.

SEARCH STRATEGY

Trials were identified from searches of the Cochrane Wounds Group Specialised Register (searched September 2005), the Cochrane Central Register of Controlled Trials (The Cochrane Library Issue 3, 2005); MEDLINE (1989 to June 2002); EMBASE (1988 to May 2002); CINAHL (1982 to May 2002) and reference lists of articles and relevant reviews. The major supplier of silicon gel sheeting (Smith and Nephew) was approached for details of unpublished, ongoing and recently published trials.

SELECTION CRITERIA

Any randomised or quasi-randomised controlled trials, or controlled clinical trials comparing silicon gel sheeting for prevention or treatment of hypertrophic or keloid scars against no treatment, placebo, or any other treatment type except surgery.

DATA COLLECTION AND ANALYSIS

All relevant trials were assessed for methodological quality. Data were extracted independently by both reviewers using a standardized form, and the results cross-checked. All trials, meeting the selection criteria were assessed for methodological quality.

MAIN RESULTS

Thirteen trials, involving 559 people, ranging in age from 2 to 81 years, were included in the review. The trials compared adhesive silicon gel sheeting with control; non-silicon gel sheeting; silicon gel plates with added Vitamin E; laser therapy; triamcinolone acetonide injection, and non-adhesive silicon gel sheeting. In the prevention studies, when compared with a no treatment option; whilst silicon gel sheeting reduced the incidence of hypertrophic scarring in people prone to scarring, (RR 0.46, 95% CI 0.21 to 0.98) these studies were highly susceptible to bias. Silicon gel sheeting produced a statistically significant improvement in scar elasticity, (RR 8.60, 95% CI 2.55 to 29.02), but again these studies were highly susceptible to bias.

AUTHORS' CONCLUSIONS

Trials evaluating silicon gel sheeting as a treatment for hypertrophic and keloid scarring are of poor quality and highly susceptible to bias. There is weak evidence of a benefit of silicon gel sheeting as a prevention for abnormal scarring in high risk individuals but the poor quality of research means a great deal of uncertainty prevails.

Biaxial elastic material properties of porcine coronary media and adventitia

The importance of mechanical stresses and strains has become well recognized in vascular physiology and pathology. To compute the stress and strain on the various components of the vessel wall, we must know the constitutive equations for the different layers of the vessel wall. The objective of the present study is to determine the constitutive equation of the coronary artery treated as a two-layer composite: intima-media and adventitial layers. Twelve hearts were obtained from a local slaughterhouse, and the right coronary artery and left anterior descending artery were dissected free from the myocardium. The vessel wall was initially mechanically tested biaxially (inflation and axial extension) as a whole (intact wall) and subsequently as intima-media or adventitial layer. A Fung-type exponential strain energy function was used to curve fit the experimental data for the intact wall and individual layers for the right coronary artery and left anterior descending artery. Two methods were used for the determination of material constants, including the Marquardt-Levenberg nonlinear least squares method and the genetic algorithm method. Our results show that there were no statistically significant differences in the material constants obtained from the two methods and that either set of elastic constants results in good fit of the data. Furthermore, at an in vivo value of axial stretch ratio, we find that the stiffness is as follows: intima-media > intact > adventitia. These results underscore the composite nature of coronary arteries with different material properties in each layer. The present results are necessary for analysis of coronary artery mechanics and to provide a fundamental understanding of vessel physiology.

The effect of TGF-beta delivered through a collagen scaffold on wound healing

In this preliminary study, the wound healing response of full-thickness skin defects to transforming growth factor beta (TGF-beta) incorporated in a collagen scaffold was evaluated. The objectives of this study were (1) to compare the effects of TGF-beta on the cellular and tissue response and mechanical properties and (2) to determine the effects of a collagen scaffold on wound healing when compared to control. Three 3 x 3 cm, full-thickness defects were created on the dorsi of 15 New Zealand White rabbits. Each rabbit had a control (no treatment), collagen scaffold, and collagen scaffold with TGF-beta (2 microg/cm2). All the wounds were covered with a transparent polyurethane dressing. There were three periods of study (1, 2, and 3 weeks) with five rabbits in each period. The volume fraction of the tissue and cells was histomorphometrically determined for each wound. A greater inflammatory response was found in the collagen scaffold-treated group, but the fastest epithelialization and contraction rates were associated with TGF-beta and collagen. No significant differences in the mechanical strength between the different treatment groups were seen. Overall, TGF-beta delivered through a collagen scaffold enhanced the healing process and showed promise for future clinical applications.

Present interpretation of the role of copper in Indian childhood cirrhosis

A common killer disease of the past, Indian childhood cirrhosis (ICC), which became preventable and treatable in the early 1990s, is now rare. ICC must be clearly distinguished in Indian children from other chronic liver disorders including Wilson disease. Grossly increased hepatic, urinary, and serum copper concentrations are characteristic of ICC. These increased concentrations are easily demonstrated histologically with orcein-rhodanine staining. Environmental ingestion of copper appears to be the most plausible explanation for ICC, as shown by feeding histories, the prevention of ICC is siblings and in the Pune district by a change in feeding vessels, and the dramatic reduction in incidence of ICC throughout India. The nature and role of a second factor in the causation of ICC remains unclear, although an inherited defect in copper metabolism is strongly suspected. ICC, however, does not appear to be a straightforward early onset of Wilson disease because ceruloplasmin is consistently normal and clinical and histologic recovery is maintained in the long term despite withdrawal of D-penicillamine therapy. Descriptions of an ICC-like illness in the West suggest that different mechanisms (environmental, genetic, or both) can lead to the same end-stage liver disease: copper-associated childhood cirrhosis. ICC probably represents a specific form of copper-associated childhood cirrhosis that requires high environmental copper ingestion for its full expression.

Biaxial incremental homeostatic elastic moduli of coronary artery: two-layer model

The detailed mechanical properties of various layers of the coronary artery are important for understanding the function of the vessel. The present article is focused on the determination of the incremental modulus in different layers and directions in the neighborhood of the in vivo state. The incremental modulus can be defined for any material subjected to a large deformation if small perturbations in strain lead to small perturbations of stresses in a linear fashion. This analysis was applied to the porcine coronary artery, which was treated as a two-layered structure consisting of an inner intima-media layer and an outer adventitia layer. We adopted a theory based on small-perturbation experiments at homeostatic conditions for determination of incremental moduli in circumferential, axial, and cross directions in the two layers. The experiments were based on inflation and axial stretch. We demonstrate that under homeostatic conditions the incremental moduli are layer- and direction dependent. The incremental modulus is highest in the circumferential direction. Furthermore, in the circumferential direction, the media is stiffer than the whole wall, which is stiffer than the adventitia. In the axial direction, the adventitia is stiffer than the intact wall, which is stiffer than the media. Hence, the coronary artery must be treated as a composite, nonisotropic body. The data acquire physiological relevance in relation to coronary artery health and disease.

Microbial biofilms in nature: unlocking their potential for agricultural applications

Soil environments are dynamic and the plant rhizosphere harbours a phenomenal diversity of micro-organisms which exchange signals and beneficial nutrients. Bipartite beneficial or symbiotic interactions with host roots, such as mycorrhizae and various bacteria, are relatively well characterized. In addition, a tripartite interaction also exists between plant roots, arbuscular mycorrhizal fungi (AMF) and associated bacteria. Bacterial biofilms exist as a sheet of bacterial cells in association with AMF structures, embedded within a self-produced exopolysaccharide matrix. Such biofilms may play important functional roles within these tripartite interactions. However, the details about such interactions in the rhizosphere and their relevant functional relationships have not been elucidated. This review explores the current understanding of naturally occurring microbial biofilms, and their interaction with biotic surfaces, especially AMF. The possible roles played by bacterial biofilms and the potential for their application for a more productive and sustainable agriculture is discussed in this review.

Exacerbations of asthma and chronic obstructive pulmonary disease (COPD): focus on virus induced exacerbations

Asthma and chronic obstructive pulmonary disease (COPD) are the 2 most prevalent chronic airway diseases. Much of the morbidity, mortality and health care costs of the diseases are associated with acute exacerbations, which are episodes of increased symptoms and airflow obstruction. Over the last decade evidence has emerged implicating virus respiratory tract infections as a major cause of exacerbations of both asthma and COPD. Current therapies are not very effective in the prevention or treatment of virus-induced exacerbations and exacerbations are therefore a major unmet medical need. The development of new and novel treatments requires a better understanding of the molecular and cellular mechanisms linking virus infection with exacerbations of asthma and COPD. This article provides an overview of current knowledge regarding the mechanisms of virus-induced exacerbations in both asthma and COPD. It will also review existing treatments and future treatments that are in advanced stages of development.

Assessment of cell viability in a three-dimensional enzymatically cross-linked collagen scaffold

Microbial transglutaminase (mTGase) is an enzyme that introduces a covalent bond between peptide bound glutamine and lysine residues. Proteins cross-linked in this manner are often more resistant to proteolytic degradation and show increased tensile strength. This study evaluates the effects of mTGase mediated cross-linking of collagen on the cellular morphology, behaviour and viability of murine 3T3 fibroblasts following their seeding into collagen scaffolds. Additionally, cell mediated scaffold contraction, porosity and level of cross-linking of the scaffold has been analysed using image analysis software, scanning electron microscopy (SEM), colorimetric assays, and Fourier transform infrared spectroscopy (FTIR). We demonstrate that the biocompatibility and cellular morphology, when comparing cultures of fibroblasts integrated in mTGase cross-linked collagen scaffolds with the native collagen counterparts, remained unaffected. It has been also elicited that the structural characteristics of collagen have been preserved while introducing enzymatically resistant covalent bonds.

Redesigning metabolism based on orthogonality principles

Modifications made during metabolic engineering for overproduction of chemicals have network-wide effects on cellular function due to ubiquitous metabolic interactions. These interactions, that make metabolic network structures robust and optimized for cell growth, act to constrain the capability of the cell factory. To overcome these challenges, we explore the idea of an orthogonal network structure that is designed to operate with minimal interaction between chemical production pathways and the components of the network that produce biomass. We show that this orthogonal pathway design approach has significant advantages over contemporary growth-coupled approaches using a case study on succinate production. We find that natural pathways, fundamentally linked to biomass synthesis, are less orthogonal in comparison to synthetic pathways. We suggest that the use of such orthogonal pathways can be highly amenable for dynamic control of metabolism and have other implications for metabolic engineering.

In Vitro Enzymatic Degradation of Tissue Grafts and Collagen Biomaterials by Matrix Metalloproteinases: Improving the Collagenase Assay

Matrix metalloproteinase-1 and -8 are active during the wound healing and remodelling processes, degrading native extracellular matrix and implantable devices. However, traditional in vitro assays utilize primarily matrix metalloproteinase-1 to mimic the in vivo degradation microenvironment. Herein, we assessed the influence of various concentrations of matrix metalloproteinase- 1 and 8 (50, 100, and 200 U/mL) as a function of pH (5.5 and 7.4) and time (3, 6, 9, 12, and 24 h) on the degradation profile of three tissue grafts (chemically cross-linked Permacol, nonchemically cross-linked Permacol and nonchemically cross-linked Strattice) and a collagen biomaterial (nonchemically cross-linked collagen sponge). Chemically cross-linked and nonchemically cross-linked Permacol samples exhibited the highest resistance to enzymatic degradation, while nonchemically cross-linked collagen sponges exhibited the least resistance to enzymatic degradation. Qualitative and quantitative degradation analysis of all samples revealed a similar degradation profile over time, independently of the matrix metalloproteinase used and its respective concentration and pH. These data indicate that matrix metalloproteinase-1 and matrix metalloproteinase-8 exhibit similar degradation profile in vitro, suggesting that matrix metalloproteinase-8 should be used for collagenase assay.

How do Jains get toxoplasma infection?

Toxoplasma infection is as prevalent among Jains as among other religious groups in the same area. Jain laws mean that exposure to Toxoplasma gondii via well known routes of infection is unlikely; drinking water may be the vehicle of infection.

Use of a fibrin-based system for enhancing angiogenesis and modulating inflammation in the treatment of hyperglycemic wounds

The complex pathophysiology of chronic ulceration in diabetic patients is poorly understood; diabetes-related lower limb amputation is a major health issue, which has limited effective treatment regimes in the clinic. This study attempted to understand the complex pathology of hyperglycemic wound healing by showing profound changes in gene expression profiles in wounded human keratinocytes in hyperglycemic conditions compared to normal glucose conditions. In the hyper-secretory wound microenvironment of hyperglycemia, Rab18, a secretory control molecule, was found to be significantly downregulated. Using a biomaterial platform for dual therapy targeting the two distinct pathways, this study aimed to resolve the major dysregulated pathways in hyperglycemic wound healing. To complement Rab18, and promote angiogenesis eNOS was also targeted, and this novel Rab18-eNOS therapy via a dynamically controlled 'fibrin-in-fibrin' delivery system, demonstrated enhanced wound closure, by increasing functional angiogenesis and reducing inflammation, in an alloxan-induced hyperglycemic preclinical ear ulcer model of compromised wound healing.

Folding and signaling share the same pathway in a photoreceptor

The photoreceptor photoactive yellow protein (PYP) was used as a model system to study receptor activation and protein folding. Refolding was studied by stopped-flow absorbance spectroscopy for PYP with either a trans or a cis chromophore. Chromophore trans to cis isomerization, the mechanism of light detection by PYP, greatly affects the protein folding process. When the cis chromophore is present, refolding from the unfolded state proceeds through the putative signaling state of PYP as an on-pathway intermediate. In addition, moderate denaturant concentrations result in the specific unfolding of the signaling state of PYP. Thus, the signaling state is common to the pathways of folding and signaling. This result provides an avenue for the study of protein folding. We demonstrate how this approach can be used to establish whether a folding intermediate is on-pathway or off-pathway. The results also reveal transient partial unfolding as a molecular mechanism for signaling.

Electromechanical properties of dried tendon and isoelectrically focused collagen hydrogels

Assembling artificial collagenous tissues with structural, functional, and mechanical properties which mimic natural tissues is of vital importance for many tissue engineering applications. While the electro-mechanical properties of collagen are thought to play a role in, for example, bone formation and remodeling, this functional property has not been adequately addressed in engineered tissues. Here the electro-mechanical properties of rat tail tendon are compared with those of dried isoelectrically focused collagen hydrogels using piezoresponse force microscopy under ambient conditions. In both the natural tissue and the engineered hydrogel D-periodic type I collagen fibrils are observed, which exhibit shear piezoelectricity. While both tissues also exhibit fibrils with parallel orientations, Fourier transform analysis has revealed that the degree of parallel alignment of the fibrils in the tendon is three times that of the dried hydrogel. The results obtained demonstrate that isoelectrically focused collagen has similar structural and electro-mechanical properties to that of tendon, which is relevant for tissue engineering applications.

Imbalance of folic acid and vitamin B12 is associated with birth outcome: an Indian pregnant women study

BACKGROUND/OBJECTIVES

Maternal nutrient supplementation in developing countries is generally restricted to provision of iron and folic acid. Along with folic acid, vitamin B12 is also an important determinant of fetal growth and development. During pregnancy, the increased requirement of folic acid is met with supplementation, while vitamin B12 remains untreated and possibly deficient. The objective of our study was to study the combined effect of maternal plasma folate and vitamin B12, and their ratio on birth anthropometrics.

SUBJECTS/METHODS

We carried out an observational study on 49 full-term pregnant women at KEM Hospital, Pune, India, during 2006-2008, and measured plasma folate, vitamin B12 and homocysteine in venous blood at 36 weeks of gestation. Neonatal anthropometrics (birth weight, length, head circumference, abdominal circumference, mid arm circumference, chest circumference, triceps skinfold and subscapular skinfold thickness) were measured within 24 h of birth.

RESULTS

Maternal plasma folate and vitamin B12 were not correlated to neonatal anthropometrics. The combined association of folate and vitamin B12 expressed as folate to vitamin B12 ratio was correlated to the neonatal anthropometrics. Imbalance in the maternal micronutrients with increasing ratio of folate to vitamin B12 was associated with an increase in plasma homocysteine (P=0.014), lowering of neonatal birth weight (P=0.009), birth length (P=0.034), head circumference (P=0.018) and chest circumference (P=0.009), while no significant association to other anthropometrics was observed.

CONCLUSIONS

Supplementation of vitamin B12 in addition to supplementation of folic acid in pregnancy may be important for improving birth weight, birth length, head circumference and chest circumference.

Investigation of acidic fibroblast growth factor delivered through a collagen scaffold for the treatment of full-thickness skin defects in a rabbit model

In this study the wound healing response of full-thickness skin defects was enhanced through the use of acidic fibroblast growth factor using a collagen scaffold. The objectives of this study were (1) to compare the facilitatory effects of acidic fibroblast growth factor on the cellular response (fibroblast, neutrophil, macrophage, epithelial), tissue response (angiogenesis, collagen) and mechanical properties in a healing wound; and (2) to determine the effect of a collagen scaffold on wound healing when compared with the control. Three 3 x 3 cm full-thickness defects were created on the dorsi of 15 New Zealand White rabbits. Each rabbit had a control (no treatment), collagen scaffold, and collagen scaffold with FGF-1 (100 microg/cm2). All the wounds were covered with a transparent polyurethane dressing. There were three periods of study (1, 2, and 3 weeks) with five rabbits in each period. The volume fraction of the tissue and cells was histomorphometrically determined for each wound. The acidic fibroblast growth factor/collagen system showed promise in enhancing the healing process. Acidic fibroblast growth factor/collagen treatment increased angiogenesis, enhanced epithelialization, and reduced contraction rate over the control. A higher inflammatory response was indicated in the collagen scaffold treated group. Hence acidic fibroblast growth factor delivered through a collagen scaffold shows promise in future clinical applications.

Endothelial cell response to biomechanical forces under simulated vascular loading conditions

In vivo, endothelial cells (EC) are constantly exposed to the haemodynamic forces (HF) of pressure, wall shear stress and hoop stress. The main aim of this study was to design, create and validate a novel perfusion bioreactor capable of delivering shear stress and intravascular pressure to EC in vitro and to characterise their morphology, orientation and gene expression. Here we report the creation and validation of such a simulator and the dual application of pressure (120/60 mmHg) and low shear stress (5 dyn/cm(2)) to a monolayer of EC established on a non-compliant silicone tube. Under these conditions, EC elongated and realigned obliquely to the direction of applied shear stress in a time-dependent manner. Furthermore, randomly distributed F-actin microfilaments reorganised into long, dense stress fibres crossing the cells in a direction perpendicular to that of flow. Finally, combinatorial biomechanical conditioning of EC induced the expression of the inflammatory-associated E-selectin gene.

HIV-1 drug resistance genotyping quality assessment: results of the ENVA7 Genotyping Proficiency Programme

BACKGROUND

Drug-resistance testing plays a critical role in selection of optimal treatment regimens for HIV infected individuals. Laboratories performing testing must implement quality control measures including external quality assessment.

OBJECTIVES

The ENVA7 Programme (2007) was organised by QCMD to assess the performance of laboratories testing for drug-resistance mutations in the HIV-1 Protease and Reverse Transcriptase genes.

STUDY DESIGN

The ENVA7 panel consisted of 5 lyophilised plasma samples (HIV-1 subtypes B, C and F). The viruses harboured wild type or resistant genotypes at various positions of the PR and RT genes. All IAS-defined resistance-associated codons were scored in comparison to the consensus sequence for each sample using a scoring system developed to allow simple and standardised comparisons between laboratories and/or technologies.

RESULTS

111 laboratories from 44 countries participated of which 95 submitted 98 datasets. 36 datasets were generated using ViroSeq (Abbott), 27 using TruGene (Siemens) and 35 using in-house assays.

CONCLUSIONS

All technologies successfully genotyped each of the panel samples, irrespective of the virus subtype. While the assays for genotypic HIV drug-resistance determination have evolved into reliable and technically capable procedures of generating high quality results, variation in the quality of results is still observed between laboratories.