Alert! Does Prolonged Temporary Support Induce an Immunological Response?

Little is known about the development of human leukocyte antigen antibodies with use of the temporary transvalvular pump 5.5 mechanical circulatory support device. This case reports a patient who developed de novo antibodies prior to his heart transplantation and remains free of any episodes of rejection post transplantation to date. (Level of Difficulty: Advanced.).

Nanoscale Strontium-Substituted Hydroxyapatite Pastes and Gels for Bone Tissue Regeneration.

Injectable nanoscale hydroxyapatite (nHA) systems are highly promising biomaterials to address clinical needs in bone tissue regeneration, due to their excellent biocompatibility, bioinspired nature, and ability to be delivered in a minimally invasive manner. Bulk strontium-substituted hydroxyapatite (SrHA) is reported to encourage bone tissue growth by stimulating bone deposition and reducing bone resorption, but there are no detailed reports describing the preparation of a systematic substitution up to 100% at the nanoscale. The aim of this work was therefore to fabricate systematic series (0-100 atomic% Sr) of SrHA pastes and gels using two different rapid-mixing methodological approaches, wet precipitation and sol-gel. The full range of nanoscale SrHA materials were successfully prepared using both methods, with a measured substitution very close to the calculated amounts. As anticipated, the SrHA samples showed increased radiopacity, a beneficial property to aid in vivo or clinical monitoring of the material in situ over time. For indirect methods, the greatest cell viabilities were observed for the 100% substituted SrHA paste and gel, while direct viability results were most likely influenced by material disaggregation in the tissue culture media. It was concluded that nanoscale SrHAs were superior biomaterials for applications in bone surgery, due to increased radiopacity and improved biocompatibility.

Electrospun Scaffolds Containing Silver-Doped Hydroxyapatite with Antimicrobial Properties for Applications in Orthopedic and Dental Bone Surgery.

Preventing the development of osteomyelitis while enhancing bone regeneration is challenging, with relatively little progress to date in translating promising technologies to the clinic. Nanoscale hydroxyapatite (nHA) has been employed as a bone graft substitute, and recent work has shown that it may be modified with silver to introduce antimicrobial activity against known pathogens. The aim of this study was to incorporate silver-doped nHA into electrospun scaffolds for applications in bone repair. Silver-doped nHA was produced using a modified, rapid mixing, wet precipitation method at 2, 5, 10 mol.% silver. The silver-doped nHA was added at 20 wt.% to a polycaprolactone solution for electrospinning. Bacteria studies demonstrated reduced bacterial presence, with Escherichia coli and Staphylococcus aureus undetectable after 96 h of exposure. Mesenchymal stem cells (MSCs) were used to study both toxicity and osteogenicity of the scaffolds using PrestoBlue® and alkaline phosphatase (ALP) assays. Innovative silver nHA scaffolds significantly reduced E. coli and S. aureus bacterial populations while maintaining cytocompatibility with mammalian cells and enhancing the differentiation of MSCs into osteoblasts. It was concluded that silver-doped nHA containing scaffolds have the potential to act as an antimicrobial device while supporting bone tissue healing for applications in orthopedic and dental bone surgery.

Executive function in XXY: Comparison of performance-based measures and rating scales.

Few studies have systematically assessed executive functioning (EF) skills in boys with XXY, and these are limited by small samples and restricted EF assessment. This study used a broader battery of performance-based measures as well as parent-rating scales of EF in 77 boys and adolescents with XXY (mean age = 12.5 years), recruited from a clinical trial and an outpatient clinic. Exploratory factor analyses were used to create EF domains from performance-based measures, and similar domains were measured using the Behavior Rating Inventory of Executive Function and Conners Parent-Rating Scales. The boys with XXY showed a distinct EF profile, with the greatest deficit in attention and more moderate deficits in working memory, switching, and planning/problem solving. Parent ratings showed similar challenges, as well as impaired inhibition. Independent sample t-tests showed no difference on performance measures between boys diagnosed or not diagnosed with attention-deficit/hyperactivity disorder (ADHD), although parents of boys diagnosed with ADHD reported more difficulties. There were no differences on performance-based tests between those diagnosed pre- and postnatally, although parents of postnatally diagnosed boys reported more metacognitive problems. Language deficits, cognition, and socio-economic status did not account for EF deficits.

Barriers and Facilitators of National Diabetes Prevention Program Engagement Among Women of Childbearing Age: A Qualitative Study.

PURPOSE: The purpose of this study was to understand barriers and facilitators to engagement in a diabetes prevention program for young women at an urban safety-net health care system. METHODS: Individual semistructured interviews (N = 29) explored motivations, challenges, and successes regarding participation and suggestions for improvement among women aged 18 to 39 years who enrolled in the National Diabetes Prevention Program in the past 2 years. Participants were classified as nonattendees (n = 10), early-withdrawers (n = 9), or completers (n = 10). Interview transcriptions were analyzed using a grounded hermeneutic editing approach. RESULTS: Qualitative analysis revealed 4 main themes (enrollment, attendance, experience, and suggestions) with multiple subthemes. Most women were motivated to enroll for health and family concerns. Early-withdrawers and nonattendees reported confusion about the program's aim and relevancy, logistical barriers, and lack of connection with fellow participants/coaches. Highly engaged women noted persistent motivation, perceived weight loss, and supportive program relationships. CONCLUSIONS: Multiple barriers/facilitators for young women appear addressable in future adaptations. Additional research is needed to confirm these findings in other settings and explore implementation and effectiveness of adaptations, with a goal of reducing risks prior to conception.

The effect of a homeopathic complex on psychophysiological onset insomnia in males: a randomized pilot study.

CONTEXT: Psychophysiological onset insomnia (PI) is defined as sleeplessness exceeding 30 min due to learned, sleep-preventing behaviors and hyperarousal at bedtime. This common condition significantly impacts sufferers' health, occupational performance, and interpersonal relationships. Conventional treatment with hypnotics has many shortcomings. Homeopathic medication may present an alternative treatment for this condition. OBJECTIVE: The study intended to determine the effect of a homeopathic complex on PI. DESIGN: The research team designed a randomized, double-blind, placebo-controlled, 4-wk pilot study, using matched pairs. SETTING: The study took place at the Homeopathy Health Clinic at the University of Johannesburg in Johannesburg, South Africa. PARTICIPANTS: Forty-six males aged between 18 and 40 y with chronic PI were recruited; 28 completed the study- placebo group (n = 14) and experimental group (n = 14). INTERVENTIONS: The homeopathic complex was made in 20% alcohol. The placebo consisted of the unmedicated vehicle only. OUTCOME MEASURES: The study used the Pre-sleep Arousal Scale (PSAS) and the Sleep Diary (SD), which assessed sleep-onset latency. RESULTS: The experimental group showed a statistically significant improvement in presleep arousal as well as sleep onset latency over the 4 wks of the study. The Wilcoxon signed-rank test revealed that the improvement occurred gradually. Intergroup analysis showed through both the PSAS and the SD that the experimental group had outperformed the placebo group by day 28 of the study. CONCLUSION: Findings suggest that daily use of the homeopathic complex does have an effect over a 4-wk period on physiological and cognitive arousal at bedtime as well as on sleep onset latency in PI sufferers. Further research on the use of this complex for PI is warranted before any definitive conclusions can be drawn.

Inhibition of keratinocyte-driven contraction of tissue-engineered skin in vitro by calcium chelation and early restraint but not submerged culture.

Skin graft contracture remains a significant cause of patient morbidity with reduction in joint mobility and cosmetic deformity. Despite recent advances, its mechanism is largely unknown. The authors have previously demonstrated the importance of the keratinocyte in the contraction of tissue-engineered skin in vitro. In this study, they investigate the effect of reducing keratinocyte differentiation on contraction by adding 0.8 mM ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetra acetic acid (EGTA) to the culture medium and by culturing tissue-engineered skin submerged in medium rather than at air-liquid interface. They also simulate the effect of early mechanical splinting in vitro to study its effect on contraction. Here the study shows that removal of the epidermis after 16 days culture at air-liquid interface results in immediate dermal relaxation with a return to the original dermal surface area. Lowering extracellular calcium concentration with EGTA reduces keratinocyte differentiation and reduces the rate of contraction. Submerged culture does not significantly reduce differentiation of tissue-engineered skin and does not reduce contraction. However, following an initial short period of mechanical constraint, the rate of contraction of tissue-engineered skin is reduced. Reducing keratinocyte differentiation by lowering extracellular calcium with EGTA, reduces contraction. However, submerged culture of tissue-engineered skin is ineffective. A short period of splinting of meshed skin grafts during the initial phase of epithelialization and keratinocyte differentiation may be most effective in the prevention of subsequent contractures in vivo but additional studies are needed to establish this.

The mechanism of skin graft contraction: an update on current research and potential future therapies.

Skin graft contraction is a common and intractable problem. The current treatments focus on mechanical opposition of contractile forces using splints and on compression of the grafted skin with pressure garments. For the patients, this causes significant morbidity with restriction of joint mobility and often requires multiple episodes of corrective surgery. Despite 50 years of research in this area, treatment and prevention of graft contraction have progressed very little and understanding of the underlying mechanism remains poor. This article reviews the clinical problem and the approaches used to prevent or treat graft contracture. It also considers to what extent we currently understand the cellular basis of graft contracture, based on in vitro models of skin contraction and in vivo observation of patients.

Enhancement of keratinocyte performance in the production of tissue-engineered skin using a low-calcium medium.

The success of laboratory-expanded autologous keratinocytes for the treatment of severe burn injuries is often compromised by their lack of dermal remnants and failure to establish a secure dermo-epidermal junction on the wound bed. We have developed a tissue-engineered skin substitute for in vivo use, based on a sterilized donor human dermis seeded with autologous keratinocytes and fibroblasts. However, culture rates are currently too slow for clinical use in acute burns. Our aim in this study was to increase the rate of production of tissue-engineered skin. Two approaches were explored: one using a commercial low-calcium media and the other supplementing well-established media for keratinocyte culture with the calcium-chelating agent ethylene glutamine tetra-acetic acid (EGTA). Using commercial low-calcium media for both the initial cell culture and subsequent culture of tissue-engineered skin did not produce tissue suitable for clinical use. However, it was possible to enhance the initial proliferation of keratinocytes and to increase their horizontal migration in tissue-engineered skin by supplementing established culture medium with 0.04 mM EGTA without sacrificing epidermal attachment and differentiation. Enhancement of keratinocyte migration with EGTA was also maximal in the absence of fibroblasts or basement membrane.

Use of an in vitro model of tissue-engineered human skin to study keratinocyte attachment and migration in the process of reepithelialization.

To produce a stable epidermis, keratinocytes need to be firmly attached to the basement membrane. However, following wounding, keratinocytes are required to develop a migratory phenotype in order to reepithelialize the wound. To investigate some of the issues underlying reepithelialization, we have developed a three-dimensional in vitro model of tissue-engineered skin, comprising sterilized human dermis seeded with human keratinocytes and dermal fibroblasts. Using this model, we have shown that the inclusion of fibroblasts within the model increases the stability of keratinocyte attachment. We have also demonstrated that keratinocyte migration occurs most effectively in the absence of a basement membrane and following the inclusion of fibroblasts in the model. In addition, subjecting the keratinocyte layer to mechanical trauma induces a migratory phenotype. We conclude that this three-dimensional in vitro wound model can be used to increase our understanding of the factors that enhance keratinocyte migration and hence wound healing in vivo.

Use of an in vitro model of tissue-engineered skin to investigate the mechanism of skin graft contraction.

Skin graft contraction leading to loss of joint mobility and cosmetic deformity remains a major clinical problem. In this study we used a tissue-engineered model of human skin, based on sterilized human adult dermis seeded with keratinocytes and fibroblasts, which contracts by up to 60% over 28 days in vitro, as a model to investigate the mechanism of skin contraction. Pharmacologic agents modifying collagen synthesis, degradation, and cross-linking were examined for their effect on contraction. Collagen synthesis and degradation were determined using immunoassay techniques. The results show that skin contraction was not dependent on inhibition of collagen synthesis or stimulation of collagen degradation, but was related to collagen remodelling. Thus, reducing dermal pliability with glutaraldehyde inhibited the ability of cells to contract the dermis. So did inhibition of matrix metalloproteinases and inhibition of lysyl oxidase-mediated collagen cross-linking, but not transglutaminase-mediated cross-linking. In summary, this in vitro model of human skin has allowed us to identify specific cross-linking pathways as possible pharmacologic targets for prevention of graft contracture in vivo.

A simple in vitro model for investigating epithelial/mesenchymal interactions: keratinocyte inhibition of fibroblast proliferation and fibronectin synthesis.

Hypertrophic scarring and graft contracture are major causes of morbidity after burn injuries. It is well established that application of a split-thickness skin graft reduces scarring and contraction, and cultured epithelial autografts have a similar effect. To investigate the influence of keratinocytes on fibroblast proliferation and fibronectin synthesis, we used an in vitro separated co-culture model in which epithelial sheets were cultured above fibroblast monolayers without physical contact. We also investigated the response of fibroblasts to keratinocyte-conditioned medium (KCM) obtained from confluent and subconfluent keratinocyte monolayers. Both cultured epithelial sheets, composed of adherent fully confluent keratinocytes, and their conditioned medium, reduced fibroblast proliferation. However, KCM from subconfluent keratinocytes stimulated fibroblast proliferation at low concentrations while inhibiting it at higher concentrations, indicating that keratinocytes can produce both mitogenic and growth-inhibiting factors for fibroblasts. KCM, but not epithelial sheet co-culture, also inhibited fibroblast fibronectin synthesis. This indicates regulation of fibroblast phenotype by soluble factors released by the keratinocyte and also suggests that there is a dialogue between keratinocytes and fibroblasts with respect to fibronectin production. We conclude that this separated co-culture model is a simple way to study epithelial/mesenchymal communication particularly with respect to the role of the fibroblast in wound healing.

Replication failure, genome instability, and increased cancer susceptibility in mice with a point mutation in the DNA ligase I gene.

DNA ligase I has a key role in DNA replication in the joining together of short replication intermediates. We used gene targeting to introduce a point mutation into the mouse DNA ligase I gene that was present in a human cancer patient with immunodeficiency and a cellular accumulation of DNA replication intermediates. Mutant mice grew more slowly and showed hematopoietic defects at critical stages at which the demands for DNA replication were highest. In the spleen and thymus of mutant mice, the accumulation of a sub-G1, but nonapoptotic, population was observed that we believe may represent cells with single-strand DNA breaks. In mutant bone marrow, occasional DNA replication failure was observed. The level of genome instability was significantly elevated in the spleens of DNA ligase I mutant mice and, because we have found no evidence for any DNA repair defect associated with DNA ligase I deficiency, we believe that this may result directly from the accumulation of replication intermediates. Mutant mice showed an increased incidence of spontaneous cancers with a diverse range of epithelial tumors, particularly cutaneous adnexal tumors that are rare in mice. The origin of the tumors from generalized genome instability, rather than the inactivation of one key control gene, should make DNA ligase I mutant mice a useful model to investigate the relationship between genome instability and cancer in humans.

DNA ligase I null mouse cells show normal DNA repair activity but altered DNA replication and reduced genome stability.

DNA ligase I is the key ligase for DNA replication in mammalian cells and has also been reported to be involved in a number of recombination and repair processes. Our previous finding that Lig1 knockout mouse embryos developed normally to mid-term before succumbing to a specific haematopoietic defect was difficult to reconcile with a report that DNA ligase I is essential for the viability of cultured mammalian cells. To address this issue, we generated a second Lig1 targeted allele and found that the phenotypes of our two Lig1 mutant mouse lines are identical. Widely different levels of Lig1 fusion transcripts were detected from the two targeted alleles, but we could not detect any DNA ligase I protein, and we believe both are effective Lig1 null alleles. Using foetal liver cells to repopulate the haematopoietic system of lethally irradiated adult mice, we demonstrate that the haematopoietic defect in DNA-ligase-I-deficient embryos is a quantitative deficiency relating to reduced proliferation rather than a qualitative block in any haematopoietic lineage. DNA ligase I null fibroblasts from Lig1 mutant embryos showed an accumulation of DNA replication intermediates and increased genome instability. In the absence of a demonstrable deficiency in DNA repair we postulate that, unusually, genome instability may result directly from the DNA replication defect. Lig1 null mouse cells performed better in the survival and replication assays than a human LIG1 point mutant, and we suggest that the complete absence of DNA ligase I may make it easier for another ligase to compensate for DNA ligase I deficiency.