Publications by authors named "Christopher A Mitchell"

33 Publications

Mitigating SARS-CoV-2 in the Deployed Environment.

Mil Med 2021 Jun 11. Epub 2021 Jun 11.

Department of Surgery, US Army Institute of Surgical Research, Sam Houston, TX 78234, USA.

Introduction: Unlike other communal living environments (universities, boarding schools, and camps) that have been suspended during the COVID-19 pandemic, the deployed military force must continue its mission. Early challenges in the 2020 deployed environment included limited availability of living and quarantine space and limited testing capacity. This is a brief report of stringent quarantine strategies employed to newly arriving cohorts at a NATO and U.S. military base to prevent release of SARS-CoV-2 into a larger base population.

Methods: With awareness of the worldwide pandemic, beginning in late February 2020, all personnel arriving to the Hamid Karzai International Airport NATO base were quarantined for 14 days to prevent interaction with the wider base population. Testing capacity was limited. Names, locations, and dates of those within quarantine were tracked to improve contact tracing. Between February and April 2020, the first cases of SARS-CoV-2 were diagnosed on a military base in Afghanistan within quarantine.

Results: Within quarantine, 11 males became PCR positive for SARS-CoV-2 during April 2020. Five of the 11 were PCR tested for symptoms of fever, cough, or loss of taste. A sixth individual, who had been asymptomatic upon leaving the base after completion of quarantine, later developed symptoms and tested positive. Another five asymptomatic individuals were found with antibody testing just before planned release from 14 days of quarantine post-exposure and confirmed with PCR testing. All PCR-positive individuals were diagnosed before being released into the general population of the base because of strict screening, quarantine, and exit criteria.

Conclusion: Quarantine creates significant strain on resources in a deployed environment. Group quarantine facilities where social distancing is limited allow for the possibility for intra-quarantine transmission of SARS-CoV-2. Ideally, PCR testing is done upon entry into quarantine and upon exit. With the possibility of false-negative PCR or limited PCR testing, we recommend daily symptom screening, pulse oximetry, temperature checks, and small quarantine groups that must "graduate" together-all meeting exit criteria. Any introduction of new individual, even with negative testing, to a group increases risk of SARS-CoV-2 transmission.Upon exit of quarantine, testing should be performed, regardless of entry testing. If PCR is limited, serology testing should be done, followed by PCR, if positive. Serology testing can be combined with clinical judgment to conserve PCR testing for quarantine release of asymptomatic individuals.
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http://dx.doi.org/10.1093/milmed/usab189DOI Listing
June 2021

Reduction of mechanical loading in tendons induces heterotopic ossification and activation of the β-catenin signaling pathway.

J Orthop Translat 2021 Jul 18;29:42-50. Epub 2021 May 18.

Division of Orthopaedic Surgery, Department of Surgery, Guangdong Provincial People's Hospital, Guangdong Academy of Medical Sciences, Guangzhou, Guangdong, China.

Background: Tendons are the force transferring tissue that enable joint movement. Excessive mechanical loading is commonly considered as a primary factor causing tendinopathy, however, an increasing body of evidence supports the hypothesis that overloading creates microdamage of collagen fibers resulting in a localized decreased loading on the cell population within the damaged site. Heterotopic ossification is a complication of late stage tendinopathy, which can significantly affect the mechanical properties and homeostasis of the tendon. Here, we the examine the effect of mechanical underloading on tendon ossification and investigate its underlying molecular mechanism.

Method: Rabbit Achilles tendons were dissected and cultured in an underloading environment (3% cyclic tensile stain,0.25 ​Hz, 8 ​h/day) for either 10, 15 or 20 days. Using isolated tendon-derived stem cells (TDSCs) 3D constructs were generated, cultured and subjected to an underloading environment for 6 days. Histological assessments were performed to evaluate the structure of the 3D constructs; qPCR and immunohistochemistry were employed to study TDSC differentiation and the β-catenin signal pathway was investigated by Western blotting. Mechanical testing was used to determine ability of the tendon to withstand force generation.

Result: Tendons cultured for extended times in an environment of underloading showed progressive heterotopic ossification and a reduction in biomechanical strength. qPCR revealed that 3D TDSCs constructs cultured in an underloading environment exhibited increased expression of several osteogenic genes: these include RUNX2, ALP and osteocalcin in comparison to tenogenic differentiation markers (scleraxis and tenomodulin). Immunohistochemical analysis further confirmed high osteocalcin production in 3D TDSCs constructs subject to underloading. Western blotting of TDSC constructs revealed that β-catenin accumulation and translocation were associated with an increase in phosphorylation at Ser552 and decrease phosphorylation at Ser33.

Conclusion: These findings unveil a potential mechanism for heterotopic ossification in tendinopathy due to the underloading of TDSCs at the damage sites, and also that β-catenin could be a potential target for treating heterotopic ossification in tendons.

The Translational Potential: Tendon heterotopic ossification detrimentally affect quality of life especially for those who has atheletic career. This study reveals the possible mechanism of heterotpic ossification in tendon related to mechanical loading. This study provided the possible to develop a mechanical stimulation protocol for preventive and therapeutic purpose for tendon heterotopic ossification.
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http://dx.doi.org/10.1016/j.jot.2021.03.004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8142054PMC
July 2021

US Army Combat Medic Performance With Portable Ultrasound to Detect Sonographic Findings of Pneumothorax in a Cadaveric Model.

J Spec Oper Med 2020 ;20(3):71-75

Background: Ultrasound, due to recent advances in portability and versatility, has become a valuable clinical adjunct in austere, resource-limited settings and is well demonstrated to be an accurate/efficient means to detect pneumothorax. The purpose of this study was to evaluate the impact of hands-on ultrasound training on ultrasound-naive US Army combat medics' ability to detect sonographic findings of pneumothorax with portable ultrasound in a cadaver model.

Methods: Ultrasound-naive US Army combat medics assigned to conventional military units were recruited from a single US Army installation and randomized to receive either didactic training only, or "blended" (didactic and hands-on) training on ultrasound detection of pneumothorax. Blinded participants were asked to perform a thoracic ultrasound exam on ventilated human cadaver models. Primary outcome measured was sensitivity and specificity of detecting sonographic findings of pneumothorax between cohorts.

Results: Forty-three participants examined a total of 258 hemithoraces. The didactic-only cohort (n = 24) detected sonographic findings of pneumothorax with a sensitivity of 68% and specificity of 57%. The blended cohort (n = 19) detected sonographic findings of pneumothorax with an overall sensitivity of 91% and specificity of 80%. Detection sensitivities were similar between B-mode versus M-mode use.

Conclusion: US Army combat medics can use portable U/S to detect sonographic findings of pneumothorax in a human cadaver model with high sensitivity after a brief, blended (didactic and hands-on) training intervention.
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November 2020

Electrospinning 3D bioactive glasses for wound healing.

Biomed Mater 2020 02 13;15(1):015014. Epub 2020 Feb 13.

Department of Materials, Imperial College London, South Kensington Campus, London, SW7 2AZ, United Kingdom.

An electrospinning technique was used to produce three-dimensional (3D) bioactive glass fibrous scaffolds, in the SiO-CaO sol-gel system, for wound healing applications. Previously, it was thought that 3D cotton wool-like structures could only be produced from sol-gel when the sol contained calcium nitrate, implying that the Ca and its electronic charge had a significant effect on the structure produced. Here, fibres with a 3D appearance were also electrospun from compositions containing only silica. A polymer binding agent was added to inorganic sol-gel solutions, enabling electrospinning prior to bioactive glass network formation and the polymer was removed by calcination. While the addition of Ca contributes to the 3D morphology, here we show that other factors, such as relative humidity, play an important role in producing the 3D cotton-wool-like macrostructure of the fibres. A human dermal fibroblast cell line (CD-18CO) was exposed to dissolution products of the samples. Cell proliferation and metabolic activity tests were carried out and a VEGF ELISA showed a significant increase in VEGF production in cells exposed to the bioactive glass samples compared to control in DMEM. A novel SiO-CaO nanofibrous scaffold was created that showed tailorable physical and dissolution properties, the control and composition of these release products are important for directing desirable wound healing interactions.
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http://dx.doi.org/10.1088/1748-605X/ab591dDOI Listing
February 2020

Enhanced cutaneous wound healing in rats following topical delivery of insulin-loaded nanoparticles embedded in poly(vinyl alcohol)-borate hydrogels.

Drug Deliv Transl Res 2018 10;8(5):1053-1065

School of Pharmacy and Pharmaceutical Sciences, Saad Centre for Pharmacy and Diabetes, Ulster University, Cromore Road, Coleraine, Co., Londonderry, BT52 1SA, UK.

Insulin plays an important role in the wound healing process, but its method of delivery to the wound bed and subsequent effect on rate of healing is less well investigated. In this study, we evaluated the therapeutic effectiveness of topical human insulin delivery using a nanoparticulate delivery system suspended in a structured hydrogel vehicle. Poly(lactide-co-glycolide) (PLGA) nanoparticles (NP) of 202.6 nm diameter and loaded with 33.86 μg insulin per milligram of polymer were formulated using a modified double-emulsion solvent evaporation technique and dispersed in a dilatant hydrogel (poly(vinyl alcohol)-borate). Importantly, this hydrogel formulation was used to achieve ultimate contact with the wound bed. A comparison of wound healing rates following local administration of insulin in the free and nanoencapsulated forms was performed in diabetic and healthy rats. In non-diabetic rats, there was no significant difference between healing observed in control and wounds treated with free insulin (p > 0.05), whereas treatment with insulin encapsulated within PLGA NP showed a significant difference (p < 0.001). In diabetic cohorts, both free insulin and nanoencapsulated insulin induced significant improvement in wound healing when compared to controls, with better percentage wound injury indices observed with the colloidal formulation. At day 10 of the experiment, the difference between percentage wound injury indices of insulin-PLGA NP and free insulin comparing to their controls were 29.15 and 12.16%, respectively. These results support strongly the potential of insulin-loaded colloidal carriers for improved wound healing when delivered using dilatant hydrogel formulations.
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http://dx.doi.org/10.1007/s13346-018-0554-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6133079PMC
October 2018

Microvascular ultrastructural changes precede cognitive impairment in the murine APPswe/PS1dE9 model of Alzheimer's disease.

Angiogenesis 2017 Nov 25;20(4):567-580. Epub 2017 Jul 25.

School of Biomedical Sciences, University of Ulster, Coleraine, Northern Ireland, UK.

Cerebral and systemic organ microvascular pathologies coexist with human Alzheimer's disease (AD) neuropathology. In this study, we hypothesised that both cerebral and systemic microvascular pathologies exist in 4- to 5-month-old male APPswe/PS1dE9 (APP/PS1) transgenic mice prior to the onset of cognitive impairment. To assess this we examined recognition memory in both wild-type and APP/PS1 mice using the object recognition task (ORT; n = 11 per group) and counted thioflavin-S-positive plaques in brain (n = 6 per group). Vascular casts of brain, liver, spleen and kidneys were examined using scanning electron microscopy (n = 6 per group), and the urinary albumin-to-creatinine ratio (uACR; n = 5 per group) was measured as an index of glomerular permeability. Murine recognition memory was intact, as demonstrated by a significant preference for the novel object in the ORT paradigm. Brain sections of wild-type mice were devoid of thioflavin-S positivity, whereas age-matched APP/PS1 mice had an average of 0.88 ± 0.22 thioflavin-S-positive plaques in the cortex, 0.42 ± 0.17 plaques in the dentate gyrus and 0.30 ± 0.07 plaques in the cornus ammonis 1 region. The profiles of casted cerebral capillaries of wild-type mice were smooth and regular in contrast to those of APP/PS1 mice which demonstrate characteristic (0.5-4.6 μm) 'tags'. APP/PS1 mice also had a significantly reduced hepatic vessel number (p = 0.0002) and an increase in the number of splenic microvascular pillars (p = 0.0231), in the absence of changes in either splenic microvascular density (p = 0.3746) or glomerular ultrastructure. The highly significant reduction in uACR in APP/PS1 mice compared to wild-type (p = 0.0079) is consistent with glomerular microvascular dysfunction. These findings highlight early microvascular pathologies in 4- to 5-month-old APP/PS1 transgenic mice and may indicate an amenable target for pharmacological intervention in AD.
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http://dx.doi.org/10.1007/s10456-017-9568-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5660145PMC
November 2017

Antibacterial properties of sophorolipid-modified gold surfaces against Gram positive and Gram negative pathogens.

Colloids Surf B Biointerfaces 2017 Sep 2;157:325-334. Epub 2017 Jun 2.

Sorbonne Universités, UPMC Univ Paris 06, CNRS, Laboratoire de Réactivité de Surface, UMR 7197, 4 place Jussieu, 75005 Paris, France. Electronic address:

Sophorolipids are bioderived glycolipids displaying interesting antimicrobial properties. We show that they can be used to develop biocidal monolayers against Listeria ivanovii, a Gram-positive bacterium. The present work points out the dependence between the surface density and the antibacterial activity of grafted sophorolipids. It also emphasizes the broad spectrum of activity of these coatings, demonstrating their potential against both Gram-positive strains (Enteroccocus faecalis, Staphylococcus epidermidis, Streptococcus pyogenes) and Gram-negative strains (Escherichia coli, Pseudomonas aeruginosa and Salmonella typhymurium). After exposure to sophorolipids grafted onto gold, all these bacterial strains show a significant reduction in viability resulting from membrane damage as evidenced by fluorescent labelling and SEM-FEG analysis.
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http://dx.doi.org/10.1016/j.colsurfb.2017.05.072DOI Listing
September 2017

Biotransformation of Silver Released from Nanoparticle Coated Titanium Implants Revealed in Regenerating Bone.

ACS Appl Mater Interfaces 2017 Jun 16;9(25):21169-21180. Epub 2017 Jun 16.

School of Materials, The University of Manchester , Oxford Road, Manchester M13 9PL, U.K.

Antimicrobial silver nanoparticle coatings have attracted interest for reducing prosthetic joint infection. However, few studies report in vivo investigations of the biotransformation of silver nanoparticles within the regenerating tissue and its impact on bone formation. We present a longitudinal investigation of the osseointegration of silver nanoparticle-coated additive manufactured titanium implants in rat tibial defects. Correlative imaging at different time points using nanoscale secondary ion mass spectrometry, transmission electron microscopy (TEM), histomorphometry, and 3D X-ray microcomputed tomography provided quantitative insight from the nano- to macroscales. The quality and quantity of newly formed bone is comparable between the uncoated and silver coated implants. The newly formed bone demonstrates a trabecular morphology with bone being located at the implant surface, and at a distance, at two weeks. Nanoscale elemental mapping of the bone-implant interface showed that silver was present primarily in the osseous tissue and colocalized with sulfur. TEM revealed silver sulfide nanoparticles in the newly regenerated bone, presenting strong evidence that the previously in vitro observed biotransformation of silver to silver sulfide occurs in vivo.
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http://dx.doi.org/10.1021/acsami.7b05150DOI Listing
June 2017

Highly degradable porous melt-derived bioactive glass foam scaffolds for bone regeneration.

Acta Biomater 2017 07 27;57:449-461. Epub 2017 Apr 27.

Department of Materials, Imperial College London, South Kensington Campus London, SW7 2AZ, UK. Electronic address:

A challenge in using bioactive melt-derived glass in bone regeneration is to produce scaffolds with interconnected pores while maintaining the amorphous nature of the glass and its associated bioactivity. Here we introduce a method for creating porous melt-derived bioactive glass foam scaffolds with low silica content and report in vitro and preliminary in vivo data. The gel-cast foaming process was adapted, employing temperature controlled gelation of gelatin, rather than the in situ acrylic polymerisation used previously. To form a 3D construct from melt derived glasses, particles must be fused via thermal processing, termed sintering. The original Bioglass® 45S5 composition crystallises upon sintering, altering its bioactivity, due to the temperature difference between the glass transition temperature and the crystallisation onset being small. Here, we optimised and compared scaffolds from three glass compositions, ICIE16, PSrBG and 13-93, which were selected due to their widened sintering windows. Amorphous scaffolds with modal pore interconnect diameters between 100-150µm and porosities of 75% had compressive strengths of 3.4±0.3MPa, 8.4±0.8MPa and 15.3±1.8MPa, for ICIE16, PSrBG and 13-93 respectively. These porosities and compressive strength values are within the range of cancellous bone, and greater than previously reported foamed scaffolds. Dental pulp stem cells attached to the scaffold surfaces during in vitro culture and were viable. In vivo, the scaffolds were found to regenerate bone in a rabbit model according to X-ray micro tomography imaging.

Statement Of Significance: This manuscript describes a new method for making scaffolds from bioactive glasses using highly bioactive glass compositions. The glass compositions have lower silica content that those that have been previously made into amorphous scaffolds and they have been designed to have similar network connectivity to that of the original (and commercially used) 45S5 Bioglass. The aim was to match Bioglass' bioactivity. The scaffolds retain the amorphous nature of bioactive glass while having an open pore structure and compressive strength similar to porous bone (the original 45S5 Bioglass crystallises during sintering, which can cause reduced bioactivity or instability). The new scaffolds showed unexpectedly rapid bone regeneration in a rabbit model.
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http://dx.doi.org/10.1016/j.actbio.2017.04.030DOI Listing
July 2017

Atomic Layer Deposition of a Silver Nanolayer on Advanced Titanium Orthopedic Implants Inhibits Bacterial Colonization and Supports Vascularized de Novo Bone Ingrowth.

Adv Healthc Mater 2017 Jun 21;6(11). Epub 2017 Mar 21.

Centre for Molecular Biosciences (CMB), School of Biomedical Sciences, Ulster University, Coleraine, BT521SA, UK.

Joint replacement surgery is associated with significant morbidity and mortality following infection with either methicillin-resistant Staphylococcus aureus (MRSA) or Staphylococcus epidermidis. These organisms have strong biofilm-forming capability in deep wounds and on prosthetic surfaces, with 10 -10 microbes resulting in clinically significant infections. To inhibit biofilm formation, we developed 3D titanium structures using selective laser melting and then coated them with a silver nanolayer using atomic layer deposition. On bare titanium scaffolds, S. epidermidis growth was slow but on silver-coated implants there were significant further reductions in both bacterial recovery (p < 0.0001) and biofilm formation (p < 0.001). MRSA growth was similarly slow on bare titanium scaffolds and not further affected by silver coating. Ultrastructural examination and viability assays using either human bone or endothelial cells, demonstrated strong adherence and growth on titanium-only or silver-coated implants. Histological, X-ray computed microtomographic, and ultrastructural analyses revealed that silver-coated titanium scaffolds implanted into 2.5 mm defects in rat tibia promoted robust vascularization and conspicuous bone ingrowth. We conclude that nanolayer silver of titanium implants significantly reduces pathogenic biofilm formation in vitro, facilitates vascularization and osseointegration in vivo making this a promising technique for clinical orthopedic applications.
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http://dx.doi.org/10.1002/adhm.201700033DOI Listing
June 2017

Adjuvant Antibiotic Activity of Acidic Sophorolipids with Potential for Facilitating Wound Healing.

Antimicrob Agents Chemother 2017 05 24;61(5). Epub 2017 Apr 24.

School of Biomedical Sciences, Ulster University, Coleraine, Northern Ireland, United Kingdom.

The sophorolipid class of biosurfactants is finding increasing use in personal care as well as pharmaceutical products and has the potential to disrupt biofilm formation and inhibit the growth of a variety of clinically relevant organisms. In order to investigate potential biomedical applications of sophorolipids derived from nonpathogenic organisms, we fractionated and purified glycolipid biosurfactant sophorolipids produced by the yeast , which yielded nonacetylated acidic C congeners that were essentially free from other contaminants (>95% purity). These acidic sophorolipids have antimicrobial activities against the nosocomial infective agents and , with significant reductions in CFU at concentrations of as low as 5 mg ml In addition, the sophorolipid showed similar effects against the same two bacterial strains when combined with kanamycin or cefotaxime. As a potential use of these sophorolipids is as a component of topically applied creams for the treatment of wound infections, it is clear that they must have no demonstrable adverse effect on wound healing. To assess this, we evaluated mammalian cell toxicity using viability tests, which revealed no adverse effect on either endothelial or keratinocyte-derived cell lines with sophorolipid concentrations of < 0.5 mg ml In addition, experiments using a mouse skin wounding assay revealed that the time course of healing wounds was unaffected by the application of sophorolipid-containing creams, and histological examination of regenerated skin tissue confirmed that the healing process was similar to that observed for control animals, with no evidence of inflammation. These results are consistent with the suggestion that acidic sophorolipids can be used as a component of antimicrobial creams to reduce the risk of wound infection during healing.
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http://dx.doi.org/10.1128/AAC.02547-16DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5404594PMC
May 2017

Lactonic Sophorolipids Increase Tumor Burden in Apcmin+/- Mice.

PLoS One 2016 6;11(6):e0156845. Epub 2016 Jun 6.

Biomedical Sciences Research Institute, Centre for Molecular Biosciences, Ulster University, Coleraine, BT52 1SA, United Kingdom.

Sophorolipids (SL) are amphiphilic biosurfactant molecules consisting of a disaccharide sophorose with one fatty acid at the C1 position and optional acetylation at the C6'and C6" positions. They exist in a closed ring lactonic (LSL) or open acidic (ASL) structure Sophorolipids are produced in crude mixtures in economically viable amounts by the yeast Starmerella bombicola and used in a variety of consumer products. Varying levels of anti- proliferative and anti-cancer activity of crude sophorolipid mixtures are described in a number of tumor cell lines in vitro. However, significant inter-study variation exists in the composition of sophorolipid species as well as other biologically active compounds in these mixtures, which makes interpretation of in vitro and in vivo studies difficult. We produced a 96% pure C18:1 lactonic sophorolipid that dose-dependently reduces the viability of colorectal cancer, as well as normal human colonic and lung cell lines in vitro. Oral administration of vehicle-only; or lactonic sophorolipids (50 mg/kg for 70 days), to Apcmin+/- mice resulted in an increase in the number (55.5 ± 3.3 vs 70.50 ± 7.8: p < 0.05) and size (modal size 2mm vs 4mm) of intestinal polyps. Lactonic administration resulted in a systematic effect via reduced hematocrit (49.5 ± 1.0 vs 28.2 ± 2.0 vs: p<0.03) and splenomegaly (0.56 ± 0.03g vs 0.71 ± 0.04g; p<0.01) confirming exacerbation of disease progression in this model.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0156845PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4894592PMC
August 2017

A correlative imaging based methodology for accurate quantitative assessment of bone formation in additive manufactured implants.

J Mater Sci Mater Med 2016 Jun 6;27(6):112. Epub 2016 May 6.

School of Materials, The University of Manchester, Oxford Road, Manchester, M13 9PL, UK.

A correlative imaging methodology was developed to accurately quantify bone formation in the complex lattice structure of additive manufactured implants. Micro computed tomography (μCT) and histomorphometry were combined, integrating the best features from both, while demonstrating the limitations of each imaging modality. This semi-automatic methodology registered each modality using a coarse graining technique to speed the registration of 2D histology sections to high resolution 3D μCT datasets. Once registered, histomorphometric qualitative and quantitative bone descriptors were directly correlated to 3D quantitative bone descriptors, such as bone ingrowth and bone contact. The correlative imaging allowed the significant volumetric shrinkage of histology sections to be quantified for the first time (~15 %). This technique demonstrated the importance of location of the histological section, demonstrating that up to a 30 % offset can be introduced. The results were used to quantitatively demonstrate the effectiveness of 3D printed titanium lattice implants.
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http://dx.doi.org/10.1007/s10856-016-5721-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4859838PMC
June 2016

MALDI MSI analysis of lipid changes in living skin equivalents in response to emollient creams containing palmitoylethanolamide.

Methods 2016 07 2;104:93-100. Epub 2016 Feb 2.

Centre for Mass Spectrometry Imaging, Biomolecular Sciences Research Centre, Sheffield Hallam University, Howard Street, Sheffield S1 1WB, United Kingdom. Electronic address:

Mass spectrometry imaging (MSI) is a powerful tool for the study of intact tissue sections. The use of matrix-assisted laser desorption/ionisation (MALDI) MSI for the study of the distribution and effect of emollient treatment on sections of reconstructed living skin equivalents during their development and maturation is described. Living skin equivalent (LSE) samples were obtained at 14days development, re-suspended in maintenance medium and incubated for 24h after delivery. The medium was changed, the LSE treated with either Physiogel A.I.® or Oilatum Junior® emollients and then re-incubated and samples taken at 4, 6 and 24h time points. Mass spectra and mass spectral images were recorded from 12μm sections of the LSE taken at each time point for comparison using MALDI mass spectrometry (MS). It was possible to detect ions characteristic of each emollient in the LSE. In addition a number of lipid species previously reported as being significant in the maturation of the LSE were observable. At the 24h time point, the images revealed what appeared to be differences in the organisation of the skin cells observed across the Physiogel A.I.® treatment group tissue sections when directly compared to the untreated tissue group.
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http://dx.doi.org/10.1016/j.ymeth.2016.02.001DOI Listing
July 2016

Lipid changes within the epidermis of living skin equivalents observed across a time-course by MALDI-MS imaging and profiling.

Lipids Health Dis 2015 Aug 5;14:84. Epub 2015 Aug 5.

Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield, S1 1WB, UK.

Background: Mass spectrometry imaging (MSI) is a powerful tool for the study of intact tissue sections. Here, its application to the study of the distribution of lipids in sections of reconstructed living skin equivalents during their development and maturation is described.

Methods: Living skin equivalent (LSE) samples were obtained at 14 days development, re-suspended in maintenance medium and incubated for 24 h after delivery. The medium was then changed, the LSE re-incubated and samples taken at 4, 6 and 24 h time points. Mass spectra and mass spectral images were recorded from 12 μm sections of the LSE taken at each time point for comparison using matrix assisted laser desorption ionisation mass spectrometry.

Results: A large number of lipid species were identified in the LSE via accurate mass-measurement MS and MSMS experiments carried out directly on the tissue sections. MS images acquired at a spatial resolution of 50 μm × 50 μm showed the distribution of identified lipids within the developing LSE and changes in their distribution with time. In particular development of an epidermal layer was observable as a compaction of the distribution of phosphatidylcholine species.

Conclusions: MSI can be used to study changes in lipid composition in LSE. Determination of the changes in lipid distribution during the maturation of the LSE will assist in the identification of treatment responses in future investigations.
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http://dx.doi.org/10.1186/s12944-015-0089-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4525729PMC
August 2015

2014 Fort Hood, Texas, mass casualty incident: reviews and perspectives.

Curr Rev Musculoskelet Med 2015 Sep;8(3):298-303

Department of Emergency Medicine, Carl R. Darnall Army Medical Center, 36000 Darnall Loop, Fort Hood, TX, 76554, USA,

On April 2, 2014, in Fort Hood, Texas, an active shooter incident occurred where four active duty soldiers were tragically killed. Active shooter incidents are becoming alarmingly more frequent over the last decade in the USA. The authors provide a detailed account of the events that occurred within the hospital and an evaluation of the triage decisions made on that day. A detailed review of mass casualty preparedness and the general approach to triage processes are also described.
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http://dx.doi.org/10.1007/s12178-015-9287-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4596202PMC
September 2015

MALDI-MS imaging for the study of tissue pharmacodynamics and toxicodynamics.

Bioanalysis 2015 ;7(1):91-101

Biomedical Research Centre, Sheffield Hallam University, Howard Street, Sheffield, S1 1WB, UK.

Pharmacodynamics and toxicodynamics are the study of the biochemical and physiological effects of therapeutic agents and toxicants and their mechanisms of action. MALDI-MS imaging offers great potential for the study of pharmaco/toxicodynamic responses in tissue owing is its ability to study multiple biomarkers simultaneously in a label-free manner. Here, existing examples of such studies examining anticancer drugs and topically applied treatments are described. Examination of the literature shows that the use of MS imaging in pharmaco/toxicodynamic studies is in fact quite low. The reasons for this are discussed and potential developments in the methodology that might lead to its further use are described.
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http://dx.doi.org/10.4155/bio.14.280DOI Listing
September 2015

Restoration of cerebral and systemic microvascular architecture in APP/PS1 transgenic mice following treatment with Liraglutide™.

Microcirculation 2015 Feb;22(2):133-45

School of Biomedical Sciences, University of Ulster, Coleraine, UK.

Objective: Cerebral microvascular impairments occurring in AD may reduce Aβ peptide clearance and impact upon circulatory ultrastructure and function. We hypothesized that microvascular pathologies occur in organs responsible for systemic Aβ peptide clearance in a model of AD and that Liraglutide (Victoza(®)) improves vessel architecture.

Methods: Seven-month-old APP/PS1 and age-matched wild-type mice received once-daily intraperitoneal injections of either Liraglutide or saline (n = 4 per group) for eight weeks. Casts of cerebral, splenic, hepatic, and renal microanatomy were analyzed using SEM.

Results: Casts from wild-type mice showed regularly spaced microvasculature with smooth lumenal profiles, whereas APP/PS1 mice revealed evidence of microangiopathies including cerebral microanuerysms, intracerebral microvascular leakage, extravasation from renal glomerular microvessels, and significant reductions in both splenic sinus density (p = 0.0286) and intussusceptive microvascular pillars (p = 0.0412). Quantification of hepatic vascular ultrastructure in APP/PS1 mice revealed that vessel parameters (width, length, branching points, intussusceptive pillars and microaneurysms) were not significantly different from wild-type mice. Systemic administration of Liraglutide reduced the incidence of cerebral microanuerysms and leakage, restored renal microvascular architecture and significantly increased both splenic venous sinus number (p = 0.0286) and intussusceptive pillar formation (p = 0.0129).

Conclusion: Liraglutide restores cerebral, splenic, and renal architecture in APP/PS1 mice.
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http://dx.doi.org/10.1111/micc.12186DOI Listing
February 2015

Preconditioned 70S30C bioactive glass foams promote osteogenesis in vivo.

Acta Biomater 2013 Nov 25;9(11):9169-82. Epub 2013 Jul 25.

Centre for Molecular Biosciences, University of Ulster at Coleraine, Coleraine BT52 1SA, UK.

Bioactive glass scaffolds (70S30C; 70% SiO2 and 30% CaO) produced by a sol-gel foaming process are thought to be suitable matrices for bone tissue regeneration. Previous in vitro data showed bone matrix production and active remodelling in the presence of osteogenic cells. Here we report their ability to act as scaffolds for in vivo bone regeneration in a rat tibial defect model, but only when preconditioned. Pretreatment methods (dry, pre-wetted or preconditioned without blood) for the 70S30C scaffolds were compared against commercial synthetic bone grafts (NovaBone® and Actifuse®). Poor bone ingrowth was found for both dry and wetted sol-gel foams, associated with rapid increase in pH within the scaffolds. Bone ingrowth was quantified through histology and novel micro-CT image analysis. The percentage bone ingrowth into dry, wetted and preconditioned 70S30C scaffolds at 11 weeks were 10±1%, 21±2% and 39±4%, respectively. Only the preconditioned sample showed above 60% material-bone contact, which was similar to that in NovaBone and Actifuse. Unlike the commercial products, preconditioned 70S30C scaffolds degraded and were replaced with new bone. The results suggest that bioactive glass compositions should be redesigned if sol-gel scaffolds are to be used without preconditioning to avoid excess calcium release.
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http://dx.doi.org/10.1016/j.actbio.2013.07.014DOI Listing
November 2013

Bioactive glass foam scaffolds are remodelled by osteoclasts and support the formation of mineralized matrix and vascular networks in vitro.

Adv Healthc Mater 2013 Mar 22;2(3):490-9. Epub 2012 Oct 22.

Centre for Molecular Biosciences, University of Ulster at Coleraine, BT52 1SA, UK.

Remodelling of scaffolds and new bone formation is critical for effective bone regeneration. Herein is reported the first demonstration of resorption pits due to osteoclast activity on the surface of sol-gel bioactive glass foam scaffolds. Bioactive glass foam scaffolds are known to have osteogenic potential and suitable pore networks for bone regeneration. Degradation of the scaffolds is known to be initially solution mediated, but for effective bone regeneration, remodelling of the scaffold by osteoclasts and vascularisation of the scaffold is necessary. The culture of C7 macrophages on a bioactive glass scaffold induces the cells to differentiate into (TRAP(+ve) ) osteoclasts. They then form distinctive resorption pits within 3 weeks, while MC3T3-E1 pre-osteoblasts deposit mineralized osteoid on their surfaces in co-culture. The scaffolds are of the 70S30C (70 mol% SiO2 , 30 mol% CaO) composition, with modal pore and interconnect diameters of 373 μm and 172 μm respectively (quantified by X-ray micro-tomography and 3D image analysis). The release of soluble silica and calcium ions from 70S30C scaffolds induces an increase in osteoblast numbers as determined via the MTT assay. Scaffolds also support growth of endothelial cells on their surface and tube formation (characteristic of functional microvasculature) following 4 days in culture. This data supports the hypothesis that 70S30C bioactive glass scaffolds promote the differentiation of the 3 main cell types involved in vascularized bone regeneration.
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http://dx.doi.org/10.1002/adhm.201200140DOI Listing
March 2013

Androgen deprivation results in time-dependent hypoxia in LNCaP prostate tumours: informed scheduling of the bioreductive drug AQ4N improves treatment response.

Int J Cancer 2013 Mar 23;132(6):1323-32. Epub 2012 Nov 23.

Biomedical Sciences Research Institute, Centre for Molecular Biosciences, University of Ulster, Coleraine, Co-Londonderry, United Kingdom.

Androgen withdrawal induces hypoxia in androgen-sensitive tissue; this is important as in the tumour microenvironment, hypoxia is known to drive malignant progression. Our study examined the time-dependent effect of androgen deprivation therapy (ADT) on tumour oxygenation and investigated the role of ADT-induced hypoxia on malignant progression in prostate tumours. LNCaP xenografted tumours were treated with anti-androgens and tumour oxygenation measured. Dorsal skin fold (DSF) chambers were used to image tumour vasculature in vivo. Quantitative PCR (QPCR) identified differential gene expression following treatment with bicalutamide. Bicalutamide-treated and vehicle-only-treated tumours were re-established in vitro, and invasion and sensitivity to docetaxel were measured. Tumour growth delay was calculated following treatment with bicalutamide combined with the bioreductive drug AQ4N. Tumour oxygenation measurements showed a precipitate decrease following initiation of ADT. A clinically relevant dose of bicalutamide (2 mg/kg/day) decreased tumour oxygenation by 45% within 24 hr, reaching a nadir of 0.09% oxygen (0.67 ± 0.06 mmHg) by Day 7; this persisted until Day 14 when it increased up to Day 28. Using DSF chambers, LNCaP tumours treated with bicalutamide showed loss of small vessels at Days 7 and 14 with revascularisation occurring by Day 21. QPCR showed changes in gene expression consistent with the vascular changes and malignant progression. Cells from bicalutamide-treated tumours were more malignant than vehicle-treated controls. Combining bicalutamide with AQ4N (50 mg/kg, single dose) caused greater tumour growth delay than bicalutamide alone. Our study shows that bicalutamide-induced hypoxia selects for cells that show malignant progression; targeting hypoxic cells may provide greater clinical benefit.
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http://dx.doi.org/10.1002/ijc.27796DOI Listing
March 2013

Temporal changes in microvessel leakiness during wound healing discriminated by in vivo fluorescence recovery after photobleaching.

J Physiol 2011 Oct 18;589(Pt 19):4681-96. Epub 2011 Jul 18.

Centre for Molecular Biosciences, University of Ulster, Cromore Road, Coleraine, Co. Londonderry, UK.

Regeneration of injured tissue is a dynamic process, critically dependent on the formation of new blood vessels and restructuring of the nascent plexus. Endothelial barrier function, a functional correlate of vascular restructuring and maturation, was quantified via intravital microscopic analysis of 150 kDa FITC-dextran-perfused blood vessels within discrete wounds created in the panniculus carnosus (PC) muscle of dorsal skinfold chamber (DSC) preparations in mice. Time to recovery of half-peak fluorescence intensity (t(1/2)) within individual vessel segments in three functional regions of the wound (pre-existing vessels, angiogenic plexus and blind-ended vessels (BEVs)) was quantified using in vivo fluorescence recovery after photobleaching (FRAP) and linear regression analysis of recovery profiles. Plasma flux across the walls of new vessel segments, particularly BEVs, was greater than that of pre-existing vessels at days 5-7 after injury (P < 0.05). TNP-470 reduced the permeability of BEVs at the leading edge of the advancing vascular plexus as measured by the decrease in luminal t(1/2) (P < 0.05), confirming the utility of FRAP as a quantitative measure of endothelial barrier function. Furthermore, these data are suggestive of a role for TNP-470 in selection for less leaky vascular segments within healing wounds. Increased FITC-dextran leakage was observed from pre-existing vessels after treatment with TNP-470 (P < 0.05), consistent with induction of transient vascular damage, although the significance of this finding is unclear. Using in vivo FRAP this study demonstrates the relationship between temporal changes in microvascular macromolecular flux and the morphology of maturing vascular segments. This combination of techniques may be useful to assess the therapeutic potential of angiogenic agents in restoring pre-injury levels of endothelial barrier function, following the establishment of a functional vascular plexus such as in models of wounding or tumour development.
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http://dx.doi.org/10.1113/jphysiol.2011.208355DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3213416PMC
October 2011

Dynamics of angiogenesis during wound healing: a coupled in vivo and in silico study.

Microcirculation 2011 Apr;18(3):183-97

Centre for Molecular Biosciences, University of Ulster, Coleraine, UK.

Objective: The most critical determinant of restoration of tissue structure during wound healing is the re-establishment of a functional vasculature, which largely occurs via angiogenesis, specifically endothelial sprouting from the pre-existing vasculature.

Materials And Methods: We used confocal microscopy to capture sequential images of perfused vascular segments within the injured panniculus carnosus muscle in the mouse dorsal skin-fold window chamber to quantify a range of microcirculatory parameters during the first nine days of healing. This data was used to inform a mathematical model of sequential growth of the vascular plexus. The modeling framework mirrored the experimental circular wound domain and incorporated capillary sprouting and endothelial cell (EC) sensing of vascular endothelial growth factor gradients.

Results: Wound areas, vessel densities and vessel junction densities obtained from the corresponding virtual wound were in excellent agreement both temporally and spatially with data measured during the in vivo healing process. Moreover, by perturbing the proliferative ability of ECs in the mathematical model, this leads to a severe reduction in vascular growth and poor healing. Quantitative measures from this second set of simulations were found to correlate extremely well with experimental data obtained from animals treated with an agent that targets endothelial proliferation (TNP-470).

Conclusion: Our direct combination and comparison of in vivo longitudinal analysis (over time in the same animal) and mathematical modeling employed in this study establishes a useful new paradigm. The virtual wound created in this study can be used to investigate a wide range of experimental hypotheses associated with wound healing, including disorders characterized by aberrant angiogenesis (e.g., diabetic models) and the effects of vascular enhancing/disrupting agents or therapeutic interventions such as hyperbaric oxygen.
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http://dx.doi.org/10.1111/j.1549-8719.2010.00076.xDOI Listing
April 2011

Thrombophilic-type placental pathologies and skeletal growth delay following maternal administration of angiostatin4.5 in mice.

Biol Reprod 2011 Mar 27;84(3):505-13. Epub 2010 Oct 27.

School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington Campus, Leicestershire, United Kingdom.

During placentation, the concentration of fibrinous deposits on the surfaces of maternal vasculature plays a role in villous development and has been strongly implicated in the pathophysiology of human fetal growth restriction (FGR). Fibrinous deposits are conspicuous sites of platelet aggregation where there is local activation of the hemostatic cascade. During activation of the hemostatic cascade, a number of pro- and antiangiogenic agents may be generated at the cell surface, and an imbalance in these factors may contribute to the placental pathology characteristic of FGR. We tested the hypothesis that angiostatin(4.5) (AS(4.5)), a cleavage fragment of plasminogen liberated at the cell surface, is capable of causing FGR in mice. Increased maternal levels of AS(4.5) in vivo result in reproducible placental pathology, including an altered vascular compartment (both in decidual and labyrinthine layers) and increased apoptosis throughout the placenta. In addition, there is significant skeletal growth delay and conspicuous edema in fetuses from mothers that received AS(4.5). Maternally generated AS(4.5), therefore, can access maternal placental vasculature and have a severe effect on placental architecture and inhibit fetal development in vivo. These findings strongly support the hypothesis that maternal AS(4.5) levels can influence placental development, possibly by directly influencing trophoblast turnover in the placenta, and contribute to fetal growth delay in mice.
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http://dx.doi.org/10.1095/biolreprod.110.083865DOI Listing
March 2011

Mega aorta syndrome: a case of thoracic and abdominal aortic aneurysm.

Am J Emerg Med 2010 Jul 25;28(6):747.e1-3. Epub 2010 Mar 25.

Department of Emergency Medicine, Carl R. Darnall Army Medical Center, Fort Hood, TX 76544, USA.

An 83-year-old woman presented to the emergency department (ED) via emergency medical services with the chief complaint of "strokelike symptoms." Physical examination revealed altered mental status, tachycardia, hypotension, and a large nonpulsatile periumbilical mass. Bedside ultrasound revealed a 9-cm abdominal aortic aneurysm with absent central flow. Computed tomography scan demonstrated diffuse thoracic and abdominal aortic dilation with rupture into the mediastinum along with left hemothorax. Repeat beside ultrasound demonstrated abdominal aortic aneurysm rupture not seen on the computed tomography scan. Despite aggressive resuscitation, the patient developed bradycardia, which devolved into pulseless electric activity cardiac arrest. She was unable to be resuscitated. The patient's diffuse aneurysmal dilation places her into the small category of patients with a disease entity known as mega aorta syndrome (MAS). Mega aorta syndrome is defined as aneurysmal dilation of the aorta to greater than 6 cm in diameter. Although not in our case, most cases of MAS are symptomatic before catastrophic presentation. The disease progression for these patients is slow and occurs over years. When this disease is recognized early, a surgery known as the elephant trunk procedure can be performed. This operation replaces the entire aorta in multiple stages. This gives the emergency physician a critical role in the diagnosis and outcome of these patients because they may come through the ED for an unrelated complaint early in the disease process. This case report illustrates an advanced case of MAS.
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http://dx.doi.org/10.1016/j.ajem.2009.09.036DOI Listing
July 2010

Quantitation of microcomputed tomography-imaged ocular microvasculature.

Microcirculation 2010 Jan;17(1):59-68

Department of Materials, Imperial College London, London, UK.

Purpose: To quantitatively assess microvascular dimensions in the eyes of neonatal wild-type and VEGF(120)-tg mice, using a novel combination of techniques which permit three-dimensional (3D) image reconstruction.

Methods: A novel combination of techniques was developed for the accurate 3D imaging of the microvasculature and demonstrated on the hyaloid vasculature of the neonatal mouse eye. Vascular corrosion casting is used to create a stable replica of the vascular network and X-ray microcomputed tomography (muCT) to obtain the 3D images. In-house computer-aided image analysis techniques were then used to perform a quantitative morphological analysis of the images.

Results: With the use of these methods, differences in the numbers of vessel segments, their diameter, and volume of vessels in the vitreous compartment were quantitated in wild-type neonatal mice or littermates over-expressing a labile (nonheparin binding) isoform of vascular endothelial growth factor (VEGF(120)) from the developing lens. This methodology was instructive in demonstrating that hyaloid vascular networks in VEGFA(120) over-expressing mice have a 10-fold increase in blind-ended, a six-fold increase in connected vessel segments, in addition to a sixfold increase (0.0314 versus 0.0051 mm(3)) in total vitreous vessel volume compared with wild type. These parameters are not readily quantified via histological, ultrastructural, or stereological analysis.

Conclusion: The combination of techniques described here provides the first 3D quantitative characterization of vasculature in an organ system; i.e., the neonatal murine intra-ocular vasculature in both wild-type mice and a transgenic model of lens-specific over-expression of VEGF.
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http://dx.doi.org/10.1111/j.1549-8719.2009.00009.xDOI Listing
January 2010

Synchrotron X-ray microtomography for assessment of bone tissue scaffolds.

J Mater Sci Mater Med 2010 Mar 10;21(3):847-53. Epub 2009 Oct 10.

Department of Materials, Imperial College London, London, SW7 2BP, UK.

X-ray microtomography (microCT) is a popular tool for imaging scaffolds designed for tissue engineering applications. The ability of synchrotron microCT to monitor tissue response and changes in a bioactive glass scaffold ex vivo were assessed. It was possible to observe the morphology of the bone; soft tissue ingrowth and the calcium distribution within the scaffold. A second aim was to use two newly developed compression rigs, one designed for use inside a laboratory based microCT machine for continual monitoring of the pore structure and crack formation and another designed for use in the synchrotron facility. Both rigs allowed imaging of the failure mechanism while obtaining stress-strain data. Failure mechanisms of the bioactive glass scaffolds were found not to follow classical predictions for the failure of brittle foams. Compression strengths were found to be 4.5-6 MPa while maintaining an interconnected pore network suitable for tissue engineering applications.
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http://dx.doi.org/10.1007/s10856-009-3888-9DOI Listing
March 2010

Maternal administration of anti-angiogenic agents, TNP-470 and Angiostatin4.5, induces fetal microphthalmia.

Mol Vis 2009 Jun 26;15:1260-9. Epub 2009 Jun 26.

Academic Division of Obstetrics and Gynaecology, Nottingham City Hospital, University of Nottingham, Nottingham, UK.

Purpose: Agents specifically targeting the vasculature as a mode of therapy are finding increasing use in the clinic, primarily in the treatment of colon cancer (Avastin) and age-related macular degeneration (Lucentis). We have previously shown that maternal administration of angiogenic inhibitors (TNP-470 [O-[chloroacetyl-carbamoyl]fumagillol, initially called AGM-1470], the first angiogenic inhibitor to undergo clinical trials, and Angiostatin(4.5), currently in phase I-III clinical trials) cause fetal growth restriction and/or placental abnormalities. During a rapid growth phase of ocular development in the mouse (embryonic days 12 to 19 [E12-E19]), the placenta mediates the metabolic requirements of the fetus and consequently may impact upon the growth of the highly oxygen sensitive fetal eye.

Methods: We injected pregnant dams (between E10.5 - E18.5) with anti-angiogenic agents, which caused either a placental insufficiency type of IUGR (intrauterine growth restriction; i.e., TNP-470) or frank placental pathology (Angiostatin(4.5) [AS(4.5)]), and assessed changes in absolute ocular dimensions, tissue types, and vascular profiles using stereological techniques.

Results: The experiments showed that ocular volumes were significantly reduced in fetal mice where dams were treated with either TNP-470 or AS(4.5). Furthermore, TNP-470 specifically caused a reduction in hyaloid blood vessel length and volume, the only intraocular vascular circulation in fetal mice.

Conclusions: These experiments support the hypothesis that the angiogenic inhibitors (specifically TNP-470 and AS(4.5)) induce microphthalmia either indirectly by their known effects on placental morphology (and/or function) or directly via altering microvascular growth in the fetus. These results also warrant further investigation of a new experimental paradigm linking placental pathology-related fetal growth restriction and microphthalmia.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2704144PMC
June 2009

Experimental and theoretical modelling of blind-ended vessels within a developing angiogenic plexus.

Microvasc Res 2008 Nov 15;76(3):161-8. Epub 2008 Jul 15.

Centre for Molecular Biosciences, School of Biomedical Sciences, University of Ulster, Cromore Road, Coleraine, BT52 1SA, UK.

Angiogenic sprouts at the leading edge of an expanding vascular plexus are recognised as major regulators of the structure of the developing network. Early in sprout development, a vascular lumen is often evident which communicates with the parent vessel while the distal tip is blind-ended. Here we describe the temporal evolution of blind-ended vessels (BEVs) in a small wound made in the panniculus carnosus muscle of a mouse viewed in a dorsal skin-fold window-chamber model with intra-vital microscopy during the most active period of angiogenesis (days 5-8 after injury). Although these structures have been mentioned anecdotally in previous studies, we observed BEVs to be frequent, albeit transient, features of plexus formation. Plasma leakage into the surrounding extracellular matrix occurring from these immature conduits could play an important role in preparing hypoxic tissue for vascular invasion. Although sprout growth is likely to be regulated by its flow environment, the parameters regulating flow into and through BEVs have not been characterised in situ. Longitudinal data from individual animals show that the number of BEVs filled with plasma alone peaks at day 7, when they can exceed 150 microm in length. Additionally, BEVs greater than 40 microm in length are more likely to be filled with stationary erythrocytes than with plasma alone. Using a mathematical model, we show how the flux of 150 kD fluorinated (FITC-) dextran through an individual plasma-filled BEV is related to its geometry being determined primarily by its surface area; by fitting theoretical intensity values to experimental data we assess the permeability of the vessel to FITC-dextran. Plasma skimming provides a mechanistic explanation for the observation that BEVs with larger surface area are more likely to recruit erythrocytes.
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http://dx.doi.org/10.1016/j.mvr.2008.06.005DOI Listing
November 2008

Microphthalmia, persistent hyperplastic hyaloid vasculature and lens anomalies following overexpression of VEGF-A188 from the alphaA-crystallin promoter.

Mol Vis 2007 Jan 19;13:47-56. Epub 2007 Jan 19.

School of Biomedical Sciences, Medical School, University of Nottingham, Nottingham, United Kingdom.

Purpose: During growth of the embryonic eye, dose- and site-specific expression of heparin-binding growth factors is critical for the formation of an appropriate vascular supply. Overexpression of vascular endothelial growth factor-A(188) (VEGF-A(188)), a strongly heparin-binding, endothelial-specific mitogen, leads to severe disturbance of vascular and overall ocular morphology. This study aimed to evaluate the effects of VEGF-A(188) overexpression on growth of ocular tissue components.

Methods: Stereological and immunohistochemical methods were employed to identify the vascular profiles, ocular tissue proportions, and cell types in VEGF-A(188) transgenic mice and compare them with wild-type mice.

Results: In VEGF-A(188) transgenic mice, both lens tissue and total ocular volume were reduced, whereas cross-sectional areas of hyaloid blood vessels, retina, iris, and optic stalk tissues were significantly increased compared to wild-type mice. Endothelial and pericyte cell numbers in the hyaloid vasculature of transgenic mice were increased three fold, with pericytes assuming their characteristic extraluminal position.

Conclusions: Overexpression of VEGF-A(188) in the murine lens results in microphthalmia, in addition to hypertrophy and persistence of the hyaloid vasculature. This is similar to the human disorder persistent hyperplastic primary vitreous (PHPV). The murine model is a useful, experimental paradigm for investigation of this condition.
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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2503360PMC
January 2007
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