Use of extracorporeal membrane oxygenation and cerebral oximetry in a stage 1 norwood repair for hypoplastic left heart syndrome

The role of extracorporeal membrane oxygenation (ECMO) and its indications in stage I Norwood palliation are controversial. The decision to initiate ECMO and its timing remains difficult with no definitive cut-off points or evidence-based guidelines. It varies on a case-to-case basis. We report a case where the use of ECMO was beneficial after stage I Norwood palliation with severe ventricular dysfunction. The systemic-to-pulmonary artery shunt was kept open to balance the systemic and pulmonary circulations. Cerebral oximetry can be useful as an additional monitoring modality to guide management, monitor cerebral perfusion, and help detect cerebral steal.

P1-02-02: Zoledronic Acid Reverses the Epithelial-Mesenchymal Transition While Inhibiting the Tumor Initiating Cell Population of Highly Tumorigenic Breast Cancer Cell Lines

Breast cancer remains the second leading cause of cancer related death amongst women in the United States. This is largely due to metastasis of cancer cells from the primary tumor to other parts of the body, and to the putative cancer stem cell population. Both are driven by the epithelial-mesenchymal transition (EMT), a cellular process whereby cancer cells of epithelial origin lose their epithelial characteristics and acquire a mesenchymal phenotype. Cells which undergo EMT tend to be motile and invasive, and therefore can metastasize to other parts of the body. EMT has also been implicated in the generation of cells expressing the cancer stem cell phenotype. As metastatic disease and the cancer stem cell are difficult to eliminate, more effective therapy is required. Zoledronic acid, originally indicated for use in the treatment of osteoporosis, has been reported to inhibit the growth of breast cancer cells. The mechanism of this effect however has yet to be determined. In preliminary data studies, treatment with zoledronic acid was found to reduce activation of nuclear factor kappa-b, an established regulator of EMT. These findings suggest that treatment with zoledronic acid may reverse EMT in breast cancer cells, driving them to express a more epithelial phenotype. To test this hypothesis, the highly metastatic, triple negative breast cancer cell lines MDA-MB-231 and Hs578t, which largely express mesenchymal proteins, were used to measure cell viability and changes in protein and mRNA expression following treatment with zoledronic acid. Dose response analysis for inhibition of cell viability showed an IC50 of approximately 2μM in the Hs578t and 6 μM in the MDA-MB-231 cell line. Zoledronic acid treated cells displayed a decreased mesenchymal phenotype, as evidenced by reduced expression of mesenchymal markers N-cadherin (75% reduction, p<0.076; 65% reduction, p<0.005) and TWIST (67% reduction, p<0.08; 64% reduction, p<0.009) in MDA-MB-231 and Hs578t cells, respectively. This was accompanied by a subsequent increase in epithelial phenotype as evidenced by increased expression of epithelial marker E-cadherin (223% increase, p<0.006) in MDA-MB-231 cells. To further elucidate the effects on the mesenchymal and epithelial phenotypes of these cells, surface expression of CD24 and CD44 was measured by flow cytometry. While vehicle treated samples of both cell lines stained positive for CD44 and negative for CD24, zoledronic acid treatment decreased CD44 expression. As both increased the ratio of surface expression of CD44high/CD24low and mammosphere formation are characteristics of the breast cancer stem cell, effects of zoledronic acid on this subpopulation in Hs578t cells were determined. Cells pretreated with zoledronic acid were seeded under mammosphere conditions and allowed to propagate for 7 days. Zoledronic acid treated cells formed significantly fewer mammospheres (86% reduction, p<0.041), while the ones that formed were smaller in size. These findings suggest that zoledronic acid is able to reverse the epithelial mesenchymal transition, which may reduce the tumor initiating capacity of highly metastatic cells.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-02-02.

[Retinal toxicity of intravitreal doxycycline. A pilot study]

OBJECTIVE

To assess the retinal toxicity of varying concentrations of intravitreally administered doxycycline, a member of tetracycline family.

METHODS

Fourteen New Zealand albino rabbits, divided into 5 groups, were used for this study. The initial concentration of doxycycline (100 mg) was titrated using 5% dextrose solution to the following concentrations in a volume of 0.1 ml: 2000 microg, 1000 microg, 500 microg, 250 microg, 125 microg, and 62.5 microg. Each concentration was injected into 2 rabbit eyes. Two control eyes received 0.1 ml of 5% dextrose solution. All animals were examined before and after injection using indirect ophthalmoscopy and slit-lamp biomicroscopy. Electroretinography (ERG) was performed on all animals prior to the intravitreal injection and 2 weeks post-injection. The animals were re-examined at this time by indirect ophthalmoscopy and slit-lamp biomicroscopy and were then subjected to euthanasia. Their eyes were enucleated and examined using light microscopy.

RESULTS

The doxycycline injected group exhibited significant decreases in ERG of the eyes injected with 2000 microg, 1000 microg, 500 microg, and 250 microg/0.1 ml. No significant changes in the ERG were observed following the injection of lesser concentration levels. There were no signs of retinal toxicity on slit-lamp examination, indirect ophthalmoscopy, or light microscopy in all the eyes injected with doxycycline concentrations of 125 microg or lower.

CONCLUSIONS

Doxycycline injected intravitreally appeared safe at concentrations of 125 microg/0.1 ml or less in albino rabbits. Intravitreal doxycycline may be beneficial, and is an inexpensive alternative drug which could be used in the treatment of bacterial endophthalmitis particularly against resistant Staphylococcus aureus organisms.

Toxicity of the photosensitizer NPe6 following intravitreal injection

BACKGROUND AND OBJECTIVE

To determine the retinal toxicity of mono-L-aspartyl chlorin e6 (NPe6) following intravitreal injection.

METHODS

Twelve Dutch-belted rabbits divided into 5 experimental groups (n=2 each) were injected intravitreally with 6.25, 12.5, 25, 50, or 100 microg of NPe6; one control group (n=2) was injected with intravitreal normal saline. One eye in each rabbit was sutured shut to test the effect of light exposure. Fundus photography and electroretinograms were performed before treatment and 2 days, 1 week, and 2 weeks after injection. Animals were euthanized and the eyes enucleated for histopathologic analysis.

RESULTS

After 1 week, 4 uncovered eyes given 50 and 100 microg had central retinal vein occlusion and varying degrees of retinal hemorrhage. RPE proliferation was seen in the covered eyes given 50 or 100 microg. Electroretinograms revealed absent retinal response at 100 microg and mild toxicity at 50 microg, but no change from normal at doses of < or = 25 microg of NPe6.

CONCLUSIONS

Intravitreal doses of < or = 25 microg NPe6 caused little or no apparent toxicity; however, toxicity was significant at doses of 50 microg and 100 microg.

Classification of diabetes mellitus

Diabetes mellitus affects almost 16 million Americans. It has become a major public health problem and the number one cause of adult blindness, end-stage renal disease, and nontraumatic amputations in the United States. It also markedly increases the risk for cardiovascular, cerebrovascular, and peripheral artery disease. The resultant increased morbidity and mortality results in a cost from diabetes of almost $100 billion annually in the United States. Studies like the UK Prospective Diabetes Study have noted that a substantial percentage of patients with newly diagnosed diabetes already have evidence of microvascular and macrovascular complications of the disease. This indicates that diabetes began in these individuals many years before it was diagnosed. By reducing the diagnostic glycemic threshold for diabetes and recommending regular screening of individuals at increased risk, the ADA hopes that patients will have diabetes diagnosed earlier, before the occurrence of complications and at a time when appropriate treatment can reduce the long-term complications, adverse clinical outcomes, and impaired quality of life that today afflict so many diabetic individuals.

Retinal toxicity of triamcinolone acetonide in silicone-filled eyes

OBJECTIVE

To determine the retinal toxicity of triamcinolone acetonide at different doses in vitrectomized, silicone-filled rabbit eyes.

MATERIALS AND METHODS

Vitrectomy with silicone oil placement was performed in 32 rabbit eyes. A dosage of 1 mg/0.025 mL, 2 mg/0.05 mL, or 4 mg/0.1 mL of triamcinolone acetonide was injected intravitreally in the study group eyes; the control group received 0.1 mL of sterile saline. Electroretinography and retinal histology were performed to evaluate toxicity.

RESULTS

No retinal toxicity was seen in the groups given 1, 2, and 4 mg of triamcinolone acetonide or in the control group. ERG and histologic sections in all groups were normal. No drug was visible in the vitreous cavity at the end of the 140-day period (average) in eyes injected with 4 mg of triamcinolone acetonide.

CONCLUSIONS

Up to 4 mg of triamcinolone acetonide can be safely injected in silicone-filled, vitrectomized eyes without any significant retinal toxicity.

VEGF, fetal liver kinase-1, and permeability increase during unilateral lung ischemia

Vascular endothelial growth factor (VEGF) is a potent mediator of increased vascular permeability and an endothelial cell mitogen. Because VEGF is upregulated during ventilated ischemia of isolated lungs and may lead to both increased vascular permeability and neovascularization, we hypothesized that VEGF and kinase insert domain-containing receptor/fetal liver kinase-1 (KDR/flk-1) expression would increase acutely after unilateral pulmonary arterial (PA) ischemia in vivo in association with evidence of endothelial cell barrier dysfunction. To test this hypothesis, VEGF and KDR/flk-1 mRNA and protein expression were measured after 4, 8, and 24 h of left PA ligation in mice. Permeability was assessed at the same time points by measurement of bronchoalveolar lavage protein concentration and lung wet-to-dry weight ratios. Results were compared with those from uninstrumented and sham-operated mice. VEGF and KDR/flk-1 protein in the left lung both increased by 4 h and then returned to baseline, whereas increased VEGF and KDR/flk-1 mRNA expression was sustained throughout 24 h of unilateral ischemia. Bronchoalveolar lavage protein concentration increased transiently during ischemia, whereas wet-to-dry weight ratio of the left lung increased more slowly and remained elevated after 24 h of left PA ligation. These results suggest that increased expression of VEGF and KDR/flk-1 during unilateral PA occlusion in mice may contribute to the development of acute lung injury in this model.

Threshold and retreatment parameters of NPe6 photodynamic therapy in retinal and choroidal vessels

BACKGROUND AND OBJECTIVE

To determine the threshold fluence for producing choroidal and retinal vascular occlusion with mono-L-aspartyl chlorin e6 (NPe6) photodynamic therapy (PDT) during primary treatment and the effect of retreatment.

METHODS

Primary treatment: Rats, rabbits, and monkeys underwent NPe6 PDT to determine the threshold fluences for choroidal and retinal vessel occlusion. The threshold was determined by analyzing fluorescein angiograms for areas of nonperfusion. Retreatment: Dutch-belted rabbits underwent NPe6 PDT followed by fluorescein angiography. Rabbits were retreated one week later at the same parameters.

RESULTS

Fluence levels and vascular damage thresholds were always higher for retinal than for choroidal vascular occlusion. Retreatment caused choroidal vessel closure at all tested fluences but retinal capillaries closed only at a fluence > 17.7 J/cm2.

CONCLUSION

NPe6 PDT has a lower threshold to occlude choroidal vessels than retinal vessels. The cumulative effect of retreatment does not damage retinal vessels unless the threshold is exceeded during a single retreatment session.

Use of perfluorocarbon liquids, silicone oil, and 5-fluorouracil in the management of experimental PVR

PURPOSE

To evaluate the toxicity and efficacy of 5-fluorouracil (5-FU) in combination with perfluoroperhydrophenanthrene (Vitreon), silicone oil, or a combination of silicone oil and Vitreon in a ratio of 3:2 in the management of experimental proliferative vitreoretinopathy (PVR).

METHODS

Toxicity study. Seventy rabbit eyes underwent vitrectomy followed by intravitreal injection of 5-FU in doses of 800, 400, or 200 microg: Group 1, 5-FU alone; Group 2, 5-FU plus 1 mL Vitreon; Group 3, 5-FU plus 1 mL silicone oil; Group 4, 5-FU plus 0.6 mL silicone oil and 0.4 mL Vitreon; Group 5, 0.6 mL silicone oil plus 0.4 mL Vitreon. Electroretinography was performed preoperatively and 8 weeks postoperatively before the animals were sacrificed. Efficacy study. Seventy-two rabbit eyes underwent vitrectomy and were injected intravitreally with 100,000-200,000 retinal pigment epithelial cells to induce PVR. Groups were injected with 200 microg 5-FU alone or with 1 mL silicone oil, 1 mL Vitreon, or a combination of 0.6 mL silicone oil and 0.4 mL Vitreon. Others were given only 1 mL Vitreon or 1 mL silicone oil. The animals were followed for 8-12 weeks; PVR was graded using Fastenberg's system.

RESULTS

Toxicity study. Eyes given 200 microg 5-FU, silicone, and Vitreon showed mild inflammation and vitritis which resolved in 1 week; the dose was nontoxic by electroretinography and histopathology. Doses of 400 and 800 microg 5-FU were toxic. Efficacy study. Clinical severity of PVR was less in the groups which received 5-FU plus vitreous substitutes when compared to the control groups at all time points. The lowest incidences were in groups given 5-FU plus Vitreon or 5-FU plus Vitreon and silicone oil: 33.33% and 11.11%, respectively.

CONCLUSIONS

A dose of 200 microg 5-FU with silicone oil and Vitreon combined was nontoxic to the rabbit retina. The combination of 5-FU, Vitreon, and silicone oil showed significant efficacy in the prevention of experimental PVR.

Threshold power levels for NPe6 photodynamic therapy

OBJECTIVE

To determine the threshold power levels for producing retinal and choroidal vascular occlusion using mono-L-aspartyl chlorin e6 (NPe6) photodynamic therapy; to evaluate its efficacy with longer intervals between photosensitizer injection and laser application; to determine the elapsed time between light application and appearance of angiographic changes.

METHODS

Pigmented and nonpigmented rabbits were injected intravenously with 2 mg/kg of NPe6 before laser irradiation of the retina-choroid. Group 1 was treated at increasing power levels; fluorescein angiograms were obtained at each fluence. Group 2 animals were exposed to laser irradiation at 5 minutes, and 1 and 3 hours postinjection to determine (by fluorescein angiography 24 hours post-treatment) if increasing the interval affected outcome. Group 3 animals underwent fluorescein angiography at 30 minutes, 1 hour, 2 hours, and 24 hours posttreatment to document the time between laser application and subsequent vessel closure.

RESULTS

Choroidal vessel occlusion was angiographically evident in all lesions at fluences of > or = 2.65 J/cm2 in pigmented rabbits and at > or = 0.88 J/cm2 in nonpigmented rabbits. Lesion diameter decreased as the time between injection and treatment increased. Vessel occlusion was documented at least 2 hours after treatment.

CONCLUSION

Choroidal vessel occlusion can occur at very low fluence.

Problems with and pitfalls of photodynamic therapy

OBJECTIVE

To delineate the various factors that may influence the outcome of photodynamic therapy of the retina and choroid.

DESIGN

Experimental animal study.

ANIMALS

Pigmented and nonpigmented rabbits; rhesus monkeys.

INTERVENTION

The hydrophilic photosensitizer, mono-L-aspartyl chlorin e6, which is maximally activated at 664 nm, was studied after intravenous injection into pigmented and nonpigmented rabbits and rhesus monkeys. Laser light was supplied by a red diode laser coupled to a modified slit-lamp biomicroscope and delivered to the ocular fundus after passing through a standard fundus contact lens. Standard photodynamic parameters were used. The effects of fundus pigmentation, intraocular pressure, spot focus and defocus, region of fundus treated, equivalent fluence, and retreatment were observed in the different animal species.

MAIN OUTCOME MEASURES

Slit-lamp biomicroscopy, fluorescein angiography, light and transmission electron microscopy.

RESULTS

Fundus pigmentation appeared to be a factor only at the lowest fluence level tested, where only 4 of 12 lesions attempted in pigmented fundi were noted on fluorescein angiography, compared with 12 of 12 lesions in albino rabbits. At normal intraocular pressures and a given fluence, 10 of 10 lesions were fully manifested on fluorescein angiography, compared with 4 of 10 at 30 mmHg and 0 of 10 at pressures sufficient to blanch the optic nerve (>60 mmHg). For laser spots either focused or defocused, there were 6 of 6 lesions that were fully manifested on fluorescein angiography for each of the parameters. Lesions treated in the fovea resulted in larger spots on fluorescein angiography. The fluence of 5 mW for 10 seconds resulted in a larger lesion on angiography than the equivalent fluence of 10 mW for 5 seconds. Areas of retreatment in rabbits demonstrated more thinning of the neurosensory retina and loss of photoreceptor outer segments and nuclei than corresponding areas receiving one treatment.

CONCLUSIONS

Photodynamic therapy results varied, depending on intraocular pressure, region of fundus treated, ocular pigmentation, and the total time of exposure to the photosensitizer. Retreatment resulted in progressive thinning of the neurosensory retina with loss of photoreceptor outer segments and nuclei in the rabbit eye.

Evaluation of toxicity of intravitreal ceftazidime, vancomycin, and ganciclovir in a silicone oil-filled eye

PURPOSE

To evaluate the toxicity of intravitreal drugs in an eye filled with silicone oil for prolonged internal retinal tamponade.

METHODS

Vitrectomy was performed in 21 rabbit eyes, and the vitreous was replaced with silicone oil. Different concentrations of various drugs (ceftazidime, vancomycin, and ganciclovir) were injected intravitreally.

RESULTS

Silicone oil increased the toxicity of these drugs, which were injected in previously determined nontoxic doses, possibly because of a reduction of the preretinal space. Injecting one quarter of the known nontoxic dose failed to show any toxicity.

CONCLUSIONS

Nontoxic concentrations of intravitreal drugs can cause toxicity in a silicone-filled eye.

Fluorescence properties of a hydrophilic sensitizer in pigmented rats, rabbits, and monkeys

BACKGROUND AND OBJECTIVE

To evaluate fluorescence properties of mono-L-aspartyl chlorin e6 (NPe6; Meija Seika Kaisha, Ltd., Tokyo, Japan) photodynamic therapy, which allows real-time simultaneous imaging of choroidal and retinal vasculature during treatment without the addition of another dye.

MATERIALS AND METHODS

Four pigmented rabbits, 4 pigmented rats, and 2 African green monkeys were administered intravenous injections of the NPe6 dye. The animals were immediately placed in front of the scanning laser ophthalmoscope and the fundus was viewed with the helium-neon laser. The resulting fluorescence was viewed and recorded on super-VHS videotape.

RESULTS

Fluorescence demonstrated clearly that NPe6 entered the retinal and choroidal circulation within seconds of intravenous injection. The concentration of NPe6 was diminished over a period of 1.5 hours in the monkey and 5 hours in the rat, as evidenced by considerable diminution of the intensity of fluorescence.

CONCLUSION

NPe6 fluorescence allows evaluation of drug availability within the retinal and choroidal circulation and visualization of pathological lesions before commencement of photodynamic therapy.