Androgen action augments ischemia-induced, bone marrow progenitor cell-mediated vasculogenesis.

Bone marrow-derived progenitor cell-mediated vasculogenesis is a key process for vascular repair and regeneration. However, the role of androgens in the mechanism of ischemia-induced vasculogenesis remains unclear. In this study, a gender-mismatch murine bone marrow transplant model was used to allow tissue tracking of transplanted cells. Bone marrow from 2-month-old male mice was transplanted into irradiated age-matched female recipients. Following the transplantation, ovariectomized female recipients were subjected to unilateral hindlimb ischemia and immediately implanted with either dihydrotestosterone (DHT) or placebo pellets. Laser Doppler perfusion imaging revealed that DHT significantly augmented blood flow recovery, with increased capillary density compared to placebo-treated female recipient controls. Flow cytometry analysis showed that DHT modulated vasculogenesis by increasing Sca1+/CXC4+ progenitor cell production in bone marrow and spleen and enhancing cell mobilization in circulating blood following hindlimb ischemia. Bone marrow cell homing was examined by detecting expression levels of male-specific SRY gene in the ischemic female tissues. DHT treatment promoted bone marrow cell homing to ischemic tissue shown by significantly higher SRY expression compared to placebo-treated females as well as reduced apoptotic features in DHT-treated females, including increased Bcl-2 expression, reduced Bax levels and decreased TUNEL staining. In conclusion, the gender-mismatched bone marrow transplant study shows that androgens directly enhance bone marrow cell-mediated vasculogenesis that contributes to ischemia-induced neovascularization.

A comparison of the pro-angiogenic potential of human induced pluripotent stem cell derived endothelial cells and induced endothelial cells in a murine model of peripheral arterial disease.

BACKGROUND: Endothelial cells derived from human induced pluripotent stem cells (iPSC-ECs) promote angiogenesis, and more recently induced endothelial cells (iECs) have been generated via fibroblast trans-differentiation. These cell types have potential as treatments for peripheral arterial disease (PAD). However, it is unknown whether different reprogramming methods produce cells that are equivalent in terms of their pro-angiogenic capabilities. OBJECTIVES: We aimed to directly compare iPSC-ECs and iECs in an animal model of PAD, in order to identify which cell type, if any, displays superior therapeutic potential. METHODS: IPSC-ECs and iECs were generated from human fibroblasts, and transduced with a reporter construct encoding GFP and firefly luciferase for bioluminescence imaging (BLI). Endothelial phenotype was confirmed using in vitro assays. NOD-SCID mice underwent hindlimb ischaemia surgery and received an intramuscular injection of either 1×106 iPSC-ECs, 1×106 iECs or control vehicle only. Perfusion recovery was measured by laser Doppler. Hindlimb muscle samples were taken for histological analyses. RESULTS: Perfusion recovery was enhanced in iPSC-EC treated mice on day 14 (Control vs. iPSC-EC; 0.35±0.04 vs. 0.54±0.08, p<0.05) and in iEC treated mice on days 7 (Control vs. iEC; 0.23±0.02 vs. 0.44±0.06, p<0.05), 10 (0.31±0.04 vs. 0.64±0.07, p<0.001) and 14 (0.35±0.04 vs. 0.68±0.07, p<0.001) post-treatment. IEC-treated mice also had greater capillary density in the ischaemic gastrocnemius muscle (Control vs. iEC; 125±10 vs. 179±11 capillaries/image; p<0.05). BLI detected iPSC-EC and iEC presence in vivo for two weeks post-treatment. CONCLUSIONS: IPSC-ECs and iECs exhibit similar, but not identical, endothelial functionality and both cell types enhance perfusion recovery after hindlimb ischaemia.

Characterization of Endothelial Progenitor Cell Interactions with Human Tropoelastin.

The deployment of endovascular implants such as stents in the treatment of cardiovascular disease damages the vascular endothelium, increasing the risk of thrombosis and promoting neointimal hyperplasia. The rapid restoration of a functional endothelium is known to reduce these complications. Circulating endothelial progenitor cells (EPCs) are increasingly recognized as important contributors to device re-endothelialization. Extracellular matrix proteins prominent in the vessel wall may enhance EPC-directed re-endothelialization. We examined attachment, spreading and proliferation on recombinant human tropoelastin (rhTE) and investigated the mechanism and site of interaction. EPCs attached and spread on rhTE in a dose dependent manner, reaching a maximal level of 56±3% and 54±3%, respectively. EPC proliferation on rhTE was comparable to vitronectin, fibronectin and collagen. EDTA, but not heparan sulfate or lactose, reduced EPC attachment by 81±3%, while full attachment was recovered after add-back of manganese, inferring a classical integrin-mediated interaction. Integrin αVß3 blocking antibodies decreased EPC adhesion and spreading on rhTE by 39±3% and 56±10% respectively, demonstrating a large contribution from this specific integrin. Attachment of EPCs on N-terminal rhTE constructs N25 and N18 accounted for most of this interaction, accompanied by comparable spreading. In contrast, attachment and spreading on N10 was negligible. αVß3 blocking antibodies reduced EPC spreading on both N25 and N18 by 45±4% and 42±14%, respectively. In conclusion, rhTE supports EPC binding via an integrin mechanism involving αVß3. N25 and N18, but not N10 constructs of rhTE contribute to EPC binding. The regulation of EPC activity by rhTE may have implications for modulation of the vascular biocompatibility of endovascular implants.

A critical role for thioredoxin-interacting protein in diabetes-related impairment of angiogenesis.

Impaired angiogenesis in ischemic tissue is a hallmark of diabetes. Thioredoxin-interacting protein (TXNIP) is an exquisitely glucose-sensitive gene that is overexpressed in diabetes. As TXNIP modulates the activity of the key angiogenic cytokine vascular endothelial growth factor (VEGF), we hypothesized that hyperglycemia-induced dysregulation of TXNIP may play a role in the pathogenesis of impaired angiogenesis in diabetes. In the current study, we report that high glucose-mediated overexpression of TXNIP induces a widespread impairment in endothelial cell (EC) function and survival by reducing VEGF production and sensitivity to VEGF action, findings that are rescued by silencing TXNIP with small interfering RNA. High glucose-induced EC dysfunction was recapitulated in normal glucose conditions by overexpressing either TXNIP or a TXNIP C247S mutant unable to bind thioredoxin, suggesting that TXNIP effects are largely independent of thioredoxin activity. In streptozotocin-induced diabetic mice, TXNIP knockdown to nondiabetic levels rescued diabetes-related impairment of angiogenesis, arteriogenesis, blood flow, and functional recovery in an ischemic hindlimb. These findings were associated with in vivo restoration of VEGF production to nondiabetic levels. These data implicate a critical role for TXNIP in diabetes-related impairment of ischemia-mediated angiogenesis and identify TXNIP as a potential therapeutic target for the vascular complications of diabetes.

Ballistic impact resistance of selected organic ophthalmic lenses.

PURPOSE: The aim was to assess the impact resistance of coated and uncoated mid-index spectacle lens materials using the ballistic impact test. METHODS: Nominally plano lenses of each material in three thicknesses were obtained. The lenses were flat edged to a 50 mm diameter. Each lens was impacted by a 6.35 mm steel ball. Impact velocities were selected using the Zippy Estimation by Sequential Testing protocol to determine the threshold fracture impact velocity. RESULTS: Threshold fracture impact velocity generally increased with thickness; however, there was a wide variation in performance among the various lens materials at each thickness. In all but two instances, the differences in impact velocity at each thickness of lens material were significant. Comparison of the data for CR39 and Hoya Phoenix with the results of earlier studies showed that the lens mounting is a significant factor. The fracture velocities found in the present study were significantly lower than the fracture velocities found when the lens edge is restrained in the mounting. A scratch resistant coating reduced the impact resistance of CR39. The effect of the antireflection coating on the fracture velocity depended on the nature of the base scratch-resistant coating. CONCLUSIONS: Mid-index lens materials of the same thickness show widely varying levels of impact resistance under the ballistic test. Impact resistance increases non-linearly with centre thickness. The lens mounting might affect the results of the ballistic impact test. The presence of 'cushion coatings' might enhance impact resistance.

Prescription compliance in ophthalmic lenses.

PURPOSE: Tolerances required for ophthalmic lenses are set down in national and international standards. It appears that the compliance of manufactured lenses has not been reported previously. Assembling a statistical quantity of lenses of a single prescription is usually an expensive process. It was, secondary to a lens impact study, possible to assemble a large number of plano lenses. In the assessment of the fracture velocity of lenses approximately 20 plano lenses of each material and thickness are required. Prior to using lenses for the impact study, they were checked for prescription. The results of the prescription measurements are reported here and the results of the impact study are reported in a separate paper. METHODS: Using an automated focimeter, 679 plano lenses in stock thickness, typical occupational eye protector thickness and up to 3.5 mm thick were measured. There were 21 combinations of material/thickness/coating from seven suppliers. The power was evaluated against Australian Standard 2228.1-1992, as the lenses were supplied in Australia. The permitted tolerances are ±0.09 D sphere and ±0.06 D cylinder. RESULTS: When assessed for material/thickness/coating combination, failure rates varied from <0.0001 per cent to 77.5 per cent (with a further 17.3 per cent classified as borderline, because they were within the uncertainty of measurement of the required limit). Grouped by supplier, the failure rates ranged from <0.0001 per cent to 7.6 per cent (with a further 12.3 per cent borderline). To improve understanding of the result, it may be easier to quote the figures without considering uncertainties. When assessed by supplier, the failure rate varies from <0.0001 per cent to 12.6 per cent. CONCLUSIONS: Compliance of plano lenses should be among the easiest of tasks for a laboratory. While we know of no defined or required acceptance rates for prescription lenses, a failure rate for a laboratory of 12.6 per cent, which includes a failure rate of 88 per cent in 2.8 mm thick refractive index = 1.53 hard coated lenses (n = 20) cannot be considered satisfactory and is a strong indication of a failure to check lenses before they leave the laboratory.

Performance of 'energy efficient' compact fluorescent lamps.

BACKGROUND: Compact fluorescent lamps (CFLs) have been heralded as highly energy efficient replacements for incandescent light globes, however, there is some public dissatisfaction with the light output and colour of CFLs. Independent examination of the claims made has not been made. Compliance with the interim Australian/New Zealand Standard has not been established by any independent authority. While the total light output (luminous flux) may meet certain standards, luminous intensity distributions of some designs do differ significantly from the incandescent sources that they are intended to replace. METHODS: Luminous intensity distribution, luminous flux and spectral energy distribution of CFLs claimed to be equivalent to 75 W incandescent globes and 75 W incandescent globes (pearl and clear) were measured. Luminous flux, luminous efficacy, colour rendering index, correlated colour temperature, wattage and power factor were then calculated and compared with claims made by manufacturers and requirements of the standards. RESULTS: The sources generally complied with the requirements for luminous flux, luminous efficacy, colour rendering index and correlated colour temperature. The claim of 75 W equivalence, which is not regulated in Australia and New Zealand, is justified less than half the time. Luminous intensity distributions of biaxial CFLs are distinctly different from the incandescent lamps they purport to replace. CONCLUSION: CFLs generally comply with the standards set. The basis on which equivalent wattages are claimed needs to be included in the Australian and New Zealand standard because this is the measure most likely to be relied on by the public. Due to the differences in luminous intensity distribution, CFLs may not necessarily be a direct replacement for incandescent sources without some consideration.