Hyperspectral Mapping of Human Primary and Stem Cells at Cell-Matrix Interfaces

Extracellular matrices interface with cells to promote cell growth and tissue development. Given this critical role, matrix mimetics are introduced to enable biomedical materials ranging from tissue engineering scaffolds and tumor models to organoids for drug screening and implant surface coatings. Traditional microscopy methods are used to evaluate such materials in their ability to support exploitable cell responses, which are expressed in changes in cell proliferation rates and morphology. However, the physical imaging methods do not capture the chemistry of cells at cell-matrix interfaces. Herein, we report hyperspectral imaging to map the chemistry of human primary and embryonic stem cells grown on matrix materials, both native and artificial. We provide the statistical analysis of changes in lipid and protein content of the cells obtained from infrared spectral maps to conclude matrix morphologies as a major determinant of biochemical cell responses. The study demonstrates an effective methodology for evaluating bespoke matrix materials directly at cell-matrix interfaces.

Extracellular matrix type 0: From ancient collagen lineage to a versatile product pipeline - JellaGel™

Extracellular matrix type 0 is reported. The matrix is developed from a jellyfish collagen predating mammalian forms by over 0.5 billion years. With its ancient lineage, compositional simplicity, and resemblance to multiple collagen types, the matrix is referred to as the extracellular matrix type 0. Here we validate the matrix describing its physicochemical and biological properties and present it as a versatile, minimalist biomaterial underpinning a pipeline of commercialised products under the collective name of JellaGelTM. We describe an extensive body of evidence for folding and assembly of the matrix in comparison to mammalian matrices, such as bovine collagen, and its use to support cell growth and development in comparison to known tissue-derived products, such as Matrigel™. We apply the matrix to co-culture human astrocytes and cortical neurons derived from induced pluripotent stem cells and visualise neuron firing synchronicity with correlations indicative of a homogenous extracellular material in contrast to the performance of heterogenous commercial matrices. We prove the ability of the matrix to induce spheroid formation and support the 3D culture of human immortalised, primary, and mesenchymal stem cells. We conclude that the matrix offers an optimal solution for systemic evaluations of cell-matrix biology. It effectively combines the exploitable properties of mammalian tissue extracts or top-down matrices, such as biocompatibility, with the advantages of synthetic or bottom-up matrices, such as compositional control, while avoiding the drawbacks of the two types, such as biological and design heterogeneity, thereby providing a unique bridging capability of a stem extracellular matrix.

Uncovering the cytotoxic effects of air pollution with multi-modal imaging of in vitro respiratory models

Annually, an estimated seven million deaths are linked to exposure to airborne pollutants. Despite extensive epidemiological evidence supporting clear associations between poor air quality and a range of short- and long-term health effects, there are considerable gaps in our understanding of the specific mechanisms by which pollutant exposure induces adverse biological responses at the cellular and tissue levels. The development of more complex, predictive, in vitro respiratory models, including two- and three-dimensional cell cultures, spheroids, organoids and tissue cultures, along with more realistic aerosol exposure systems, offers new opportunities to investigate the cytotoxic effects of airborne particulates under controlled laboratory conditions. Parallel advances in high-resolution microscopy have resulted in a range of in vitro imaging tools capable of visualizing and analysing biological systems across unprecedented scales of length, time and complexity. This article considers state-of-the-art in vitro respiratory models and aerosol exposure systems and how they can be interrogated using high-resolution microscopy techniques to investigate cell-pollutant interactions, from the uptake and trafficking of particles to structural and functional modification of subcellular organelles and cells. These data can provide a mechanistic basis from which to advance our understanding of the health effects of airborne particulate pollution and develop improved mitigation measures.

Designer protein pseudo-capsids targeting intracellular bacteria

The emergence of multidrug-resistant bacteria stimulates the search for antimicrobial materials capable of addressing challenges conventional antibiotics fail to address. The ability to target intracellular bacteria remains one of the most fundamental tasks for contemporary antimicrobial treatments. Here we report engineered protein pseudo-capsids targeting bacteria internalised in macrophages. Using a combination of live-cell imaging and single-cell electron microscopy analysis we show that these materials effectively disrupt the bacteria without affecting the host cells. The study offers a disruptive antimicrobial strategy demonstrating potential for developing principally more challenging mechanisms for bacteria to overcome.

Ultramicrotomy Analysis of Peptide-Treated Cells

Electron microscopy offers necessary precision for the characterization of peptide materials at the nanoscale. Analysis is typically performed for acellular material specimens, whereas measurements in more complex, cellular environments prompt additional considerations for sample processing. Herein, we describe a protocol for the ultramicrotomy analysis of peptide-treated bacterial and mammalian cells. An emphasis is made on cell analysis following peptide treatment, as opposed to peptide analysis in cells, and focuses on sample processing, including fixation and staining procedures, resin embedding, sectioning, and imaging. The application of the protocol is demonstrated for intracellular measurements using antimicrobial peptide materials.

Cellular Metrology: Scoping for a Value Proposition in Extra- and Intracellular Measurements

The symptomatic irreproducibility of data in biomedicine and biotechnology prompts the need for higher order measurements of cells in their native and near-native environments. Such measurements may support the adoption of new technologies as well as the development of research programs across different sectors including healthcare and clinic, environmental control and national security. With an increasing demand for reliable cell-based products and services, cellular metrology is poised to help address current and emerging measurement challenges faced by end-users. However, metrological foundations in cell analysis remain sparse and significant advances are necessary to keep pace with the needs of modern medicine and industry. Herein we discuss a role of metrology in cell and cell-related R&D activities to underpin growing international measurement capabilities. Relevant measurands are outlined and the lack of reference methods and materials, particularly those based on functional cell responses in native environments, is highlighted. The status quo and current challenges in cellular measurements are discussed in the light of metrological traceability in cell analysis and applications (e.g., a functional cell count). An emphasis is made on the consistency of measurement results independent of the analytical platform used, high confidence in data quality vs. quantity, scale of measurements and issues of building infrastructure for end-users.

Helminth Defense Molecules as Design Templates for Membrane Active Antibiotics

A design template for membrane active antibiotics against microbial and tumor cells is described. The template is an amino acid sequence that combines the properties of helminth defense molecules, which are not cytolytic, with the properties of host-defense peptides, which disrupt microbial membranes. Like helminth defense molecules, the template folds into an amphipathic helix in both mammalian host and microbial phospholipid membranes. Unlike these molecules, the template exhibits antimicrobial and anticancer properties that are comparable to those of antimicrobial and anticancer antibiotics. The selective antibiotic activity of the template builds upon a functional synergy between three distinctive faces of the helix, which is in contrast to two faces of membrane-disrupting amphipathic structures. This synergy enables the template to adapt pore formation mechanisms according to the nature of the target membrane, inducing the lysis of microbial and tumor cells.

Author Correction: Tuneable poration: host defense peptides as sequence probes for antimicrobial mechanisms

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Tuneable poration: host defense peptides as sequence probes for antimicrobial mechanisms

The spread of antimicrobial resistance stimulates discovery strategies that place emphasis on mechanisms circumventing the drawbacks of traditional antibiotics and on agents that hit multiple targets. Host defense peptides (HDPs) are promising candidates in this regard. Here we demonstrate that a given HDP sequence intrinsically encodes for tuneable mechanisms of membrane disruption. Using an archetypal HDP (cecropin B) we show that subtle structural alterations convert antimicrobial mechanisms from native carpet-like scenarios to poration and non-porating membrane exfoliation. Such distinct mechanisms, studied using low- and high-resolution spectroscopy, nanoscale imaging and molecular dynamics simulations, all maintain strong antimicrobial effects, albeit with diminished activity against pathogens resistant to HDPs. The strategy offers an effective search paradigm for the sequence probing of discrete antimicrobial mechanisms within a single HDP.

Positional plagiocephaly reduces parental adherence to SIDS Guidelines and inundates the health system

BACKGROUND

This study sought to better understand parent, grandparent and clinician views of prevention, treatment and costs of plagiocephaly.

METHODS

A qualitative study was conducted using focus groups and semi-structured interviews. A grounded theory approach was taken to build theories from the qualitative data collected. A subjectivist epistemological orientation was taken under the paradigm of positivism.

RESULTS

Ninety-one parents, 6 grandparents and 24 clinicians were recruited from the community as well as primary and tertiary care clinics. Plagiocephaly worried most parents because it could permanently affect their child's 'looks' and some thought it would affect a child's development. Parents were 'willing to do anything' to prevent plagiocephaly including using products or sleeping positions that are contraindicated under sudden infant death syndrome guidelines. Parents found the care pathway convoluted and inconsistent messages were given from different health providers. For clinicians, the high prevalence of flat head is 'clogging up their patient pool', taking up time they used to spend with children with more severe conditions.

CONCLUSION

There is a need to re-emphasize sudden infant death syndrome guidelines for families when they present with an infant with plagiocephaly. Stronger messaging regarding the lack of safety of current pillows marketed to prevent flat head may be useful to decrease their use. Increasing education for all health professionals including general practitioners, allied health and complementary health providers and standardizing assessment and referral criteria may allow the majority of diagnosis and treatment of positional plagiocephaly to occur at points of first contact (e.g. general practitioners, community nurse) and may prevent further burden on the health care system.

Nano-mechanical single-cell sensing of cell-matrix contacts

Extracellular protein matrices provide a rigidity interface exhibiting nano-mechanical cues that guide cell growth and proliferation. Cells sense such cues using actin-rich filopodia extensions which encourage favourable cell-matrix contacts to recruit more actin-mediated local forces into forming stable focal adhesions. A challenge remains in identifying and measuring these local cellular forces and in establishing empirical relationships between them, cell adhesion and filopodia formation. Here we investigate such relationships using a micromanipulation system designed to operate at the time scale of focal contact dynamics, with the sample frequency of a force probe being 0.1 ms, and to apply and measure forces at nano-to-micro Newton ranges for individual mammalian cells. We explore correlations between cell biomechanics, cell-matrix attachment forces and the spread areas of adhered cells as well as their relative dependence on filopodia formation using synthetic protein matrices with a proven ability to induce enhanced filopodia numbers in adherent cells. This study offers a basis for engineering exploitable cell-matrix contacts in situ at the nanoscale and single-cell levels.

Engineering monolayer poration for rapid exfoliation of microbial membranes

A novel mechanism of monolayer poration leading to the rapid exfoliation and lysis of microbial membranes is reported.

The spread of bacterial resistance to traditional antibiotics continues to stimulate the search for alternative antimicrobial strategies. All forms of life, from bacteria to humans, are postulated to rely on a fundamental host defense mechanism, which exploits the formation of open pores in microbial phospholipid bilayers. Here we predict that transmembrane poration is not necessary for antimicrobial activity and reveal a distinct poration mechanism that targets the outer leaflet of phospholipid bilayers. Using a combination of molecular-scale and real-time imaging, spectroscopy and spectrometry approaches, we introduce a structural motif with a universal insertion mode in reconstituted membranes and live bacteria. We demonstrate that this motif rapidly assembles into monolayer pits that coalesce during progressive membrane exfoliation, leading to bacterial cell death within minutes. The findings offer a new physical basis for designing effective antibiotics.

Exploitable length correlations in peptide nanofibres

Sequence-prescribed biomolecular assemblies find increasing use in the development of novel nanostructured materials. Critical requirements for emerging designs remain in matching form with function. Peptide assembly diversifies form and supports function, but lacks control over both. Herein we exploit length correlations in peptide nanoscale fibres (form) using a model helical template. We establish that different assembly patterns result from a synergistic interplay between peptide length, net charge and folding and supra-molecular cooperativity, while correlating with increases in cell proliferation (function) as a function of peptide length. The revealed correlations offer an efficient rationale for the programming of longitudinally finite and biologically active nanoscale fibres.

Three-dimensional cell morphometry for the quantification of cell-substrate interactions

The initial attachment of cells to biomaterials is an important indicator of longer term cell-substrate biocompatibility. To study and quantify this interaction, we have developed a protocol for measuring temporal changes in the three-dimensional (3D) morphology of mammalian cells seeded onto different substrates using fluorescence confocal laser scanning microscopy and image processing techniques. This method has been used to investigate how morphology parameters, such as cell thickness, volume, and the footprint area, change over time for osteosarcoma cells on uncoated glass control, fibronectin-coated glass, and titanium substrates. Consistent with other studies, our results show that the presence of a fibronectin coating significantly increases the rate of cell spreading, judged by an increase in the cell footprint area and a decrease in cell thickness, indicating enhanced biocompatibility. Using similar criteria, the same cell line was observed to spread faster on titanium than on uncoated glass. We propose that 3D cell morphometry is a valuable multiparametric tool for quantifying initial cell-substrate interactions providing data which has important applications in quality control for ensuring product/batch consistency and for developing tailored surface finishes.

Trends in the management of inguinal hernia in Karachi, Pakistan: a survey of practice patterns

INTRODUCTION

The study was conducted to identify and document the various aspects of elective inguinal hernia repair performed by general surgeons working in the different university hospitals of Karachi, Pakistan.

METHODS

This questionnaire-based survey, carried out over a two-year period, involved 84 general surgeons of Karachi. The respondents were divided into groups and comparative analysis was carried out.

RESULTS

65 respondents (77.4 percent) were male and 19 (22.6 percent) were female. Mean years and standard deviation since post graduation were 7.7 and 7.3 years, respectively. 60 respondents (71.4 percent) reported the routine use of prophylactic antibiotics in all inguinal hernia repairs. 34 respondents (40.5 percent) quoted "spinal anaesthesia" as their preferred type of anaesthesia, 46 respondents (54.8 percent) chose to perform the procedure as a day case, and 49 respondents (58.3 percent) reported mesh repair as their preferred type of repair. 60 respondents (71.4 percent) did not recommend the laparoscopic approach to hernia repair. Surgeons associated with private hospitals were found more likely to choose mesh as their preferred method of inguinal hernia repair (p-value is 0.007), but less likely to use prophylactic antibiotics (p-value is 0.05) and respondents with more than ten years of postgraduate experience were found more likely to perform hernia repairs on an inpatient basis (p-value is 0.045).

CONCLUSION

Various aspects of management of inguinal hernias are still determined by the preference of the operating surgeon. Day case management of hernia repairs, routine use of prophylactic antibiotics, use of mesh and open repair of hernias were the practice of the majority of surgeons, although differences were noted in specific groups of surgeons.

Optimization of low pre-operative hemoglobin reduces transfusion requirement in patients undergoing transurethral resection of prostate

OBJECTIVE

To identify factors that influence peri-operative hemorrhage in view of reducing the need for transfusions in patients undergoing trans uretheral resection of prostate (TURP).

METHODS

All patients undergoing TURP between January 1997 and December 1999 were identified using ICD 9CM coding and indexing system. Overall 430 patients were identified, however, 384 charts were included and reviewed for demographics, pre and intra-operative data and post-operative morbidity. Patients were divided into two groups on the basis of presence of significant hemorrhage.

RESULTS

Overall 384 patients were analyzed. Nineteen patients had hemorrhage--group I whereas 365 had no significant hemorrhage--group II. Mean age and co-morbidities in the two groups were similar. However, in group I, 58% presented with urinary retention compared to 33% in group II. In group I, factors that reached statistical significance include; operative time (p<0.05), mean resected tissue weight (p<0.02), and patient presentation (urinary retention) (p<0.032). There was no significant difference in the two groups with respect to type of anesthesia (regional versus general) and histology of the resected tissue. Patients with mean pre-operative hemoglobin of 10.6 % had a 37% transfusion rate.

CONCLUSION

Operative time, weight of resected prostate tissue are inter related and are only partly controllable. Low pre-operative hemoglobin is the only reversible factor in reducing transfusion following TURP.