Rajesh Uthamanthil

Feasibility Study of Particle-Assisted Laser Ablation of Brain Tumors in Orthotopic Canine Model

We report on a pilot study showing a proof of concept for the passive delivery of nanoshells to an orthotopic tumor where they induce a local, confined therapeutic response distinct from that of normal brain resulting in the photothermal ablation of canine transmissible venereal tumor (cTVT) in a canine brain model. cTVT fragments grown in severe combined immunodeficient mice were successfully inoculated in the parietal lobe of immunosuppressed, mixed-breed hound dogs. A single dose of near-IR (NIR)-absorbing, 150-nm nanoshells was infused i.v. and allowed time to passively accumulate in the intracranial tumors, which served as a proxy for an orthotopic brain metastasis. The nanoshells accumulated within the intracranial cTVT, suggesting that its neovasculature represented an interruption of the normal blood-brain barrier. Tumors were thermally ablated by percutaneous, optical fiber-delivered, NIR radiation using a 3.5-W average, 3-minute laser dose at 808 nm that selectively elevated the temperature of tumor tissue to 65.8 +/- 4.1 degrees C. Identical laser doses applied to normal white and gray matter on the contralateral side of the brain yielded sublethal temperatures of 48.6 +/- 1.1 degrees C. The laser dose was designed to minimize thermal damage to normal brain tissue in the absence of nanoshells and compensate for variability in the accumulation of nanoshells in tumor. Postmortem histopathology of treated brain sections showed the effectiveness and selectivity of the nanoshell-assisted thermal ablation.

Novel Antiseptic Urinary Catheters for Prevention of Urinary Tract Infections: Correlation of In Vivo and In Vitro Test Results

ABSTRACT Urinary catheters are widely used for hospitalized patients and are often associated with high rates of urinary tract infection. We evaluated in vitro the antiadherence activity of a novel antiseptic Gendine-coated urinary catheter against several multidrug-resistant bacteria. Gendine-coated urinary catheters were compared to silver hydrogel-coated Foley catheters and uncoated catheters. Bacterial biofilm formation was assessed by quantitative culture and scanning electron microscopy. These data were further correlated to an in vivo rabbit model. We challenged 31 rabbits daily for 4 days by inoculating the urethral meatus with 1.0 × 109 CFU streptomycin-resistant Escherichia coli per day. In vitro, Gendine-coated urinary catheters reduced the CFU of all organisms tested for biofilm adherence compared with uncoated and silver hydrogel-coated catheters (P < 0.004). Scanning electron microscopy analysis showed that a thick biofilm overlaid the control catheter and the silver hydrogel-coated catheters but not the Gendine-coated urinary catheter. Similar results were found with the rabbit model. Bacteriuria was present in 60% of rabbits with uncoated catheters and 71% of those with silver hydrogel-coated catheters (P < 0.01) but not in those with Gendine-coated urinary catheters. No rabbits with Gendine-coated urinary catheters had invasive bladder infections. Histopathologic assessment revealed no differences in toxicity or staining. Gendine-coated urinary catheters were more efficacious in preventing catheter-associated colonization and urinary tract infections than were silver hydrogel-coated Foley catheters and uncoated catheters.

Imaging Epigenetic Regulation by Histone Deacetylases in the Brain using PET/MRI with 18F-FAHA

Epigenetic modifications mediated by histone deacetylases (HDACs) play important roles in the mechanisms of different neurologic diseases and HDAC inhibitors (HDACIs) have shown promise in therapy. However, pharmacodynamic profiles of many HDACIs in the brain remain largely unknown due to the lack of validated methods for noninvasive imaging of HDAC expression-activity. In this study, dynamic PET/CT imaging was performed in 4 rhesus macaques using [(18)F]FAHA, a novel HDAC substrate, and [(18)F]fluoroacetate, the major radio-metabolite of [(18)F]FAHA, and fused with corresponding MR images of the brain. Quantification of [(18)F]FAHA accumulation in the brain was performed using a customized dual-tracer pharmacokinetic model. Immunohistochemical analyses of brain tissue revealed the heterogeneity of expression of individual HDACs in different brain structures and cell types and confirmed that PET/CT/MRI with [(18)F]FAHA reflects the level of expression-activity of HDAC class IIa enzymes. Furthermore, PET/CT/MRI with [(18)F]FAHA enabled non-invasive, quantitative assessment of pharmacodynamics of HDAC inhibitor SAHA in the brain.

Animal models for adipose tissue engineering.

There is a critical need for adequate reconstruction of soft tissue defects resulting from tumor resection, trauma, and congenital abnormalities. To be sure, adipose tissue engineering strategies offer promising solutions. However, before clinical translation can occur, efficacy must be proven in animal studies. The aim of this review is to provide an overview of animal models currently employed for adipose tissue engineering.

Hormone suppression with GnRH antagonist promotes spermatogenic recovery from transplanted spermatogonial stem cells in irradiated cynomolgus monkeys

Hormone suppression given before or after cytotoxic treatment stimulates the recovery of spermatogenesis from endogenous and transplanted spermatogonial stem cells (SSC) and restores fertility in rodents. To test whether the combination of hormone suppression and transplantation could enhance the recovery of spermatogenesis in primates, we irradiated (7 Gy) the testes of 12 adult cynomolgus monkeys and treated six of them with gonadotropin‐releasing hormone antagonist (GnRH‐ant) for 8 weeks. At the end of this treatment, we transfected cryopreserved testicular cells with green fluorescent protein‐lentivirus and autologously transplanted them back into one of the testes. The only significant effect of GnRH‐ant treatment on endogenous spermatogenesis was an increase in the percentage of tubules containing differentiated germ cells (tubule differentiation index; TDI) in the sham‐transplanted testes of GnRH‐ant–treated monkeys compared with radiation‐only monkeys at 24 weeks after irradiation. Although transplantation alone after irradiation did not significantly increase the TDI, detection of lentiviral DNA in the spermatozoa of one radiation‐only monkey indicated that some transplanted cells colonized the testis. However, the combination of transplantation and GnRH‐ant clearly stimulated spermatogenic recovery as evidenced by several observations in the GnRH‐ant–treated monkeys receiving transplantation: (i) significant increases (~20%) in the volume and weight of the testes compared with the contralateral sham‐transplanted testes and/or to the transplanted testes of the radiation‐only monkeys; (ii) increases in TDI compared to the transplanted testes of radiation‐only monkeys at 24 weeks (9.6% vs. 2.9%; p = 0.05) and 44 weeks (16.5% vs. 6.1%, p = 0.055); (iii) detection of lentiviral sequences in the spermatozoa or testes of five of the GnRH‐ant–treated monkeys and (iv) significantly higher sperm counts than in the radiation‐only monkeys. Thus hormone suppression enhances spermatogenic recovery from transplanted SSC in primates and may be a useful tool in conjunction with spermatogonial transplantation to restore fertility in men after cancer treatment.

Whole-Body Biodistribution Kinetics, Metabolism, and Radiation Dosimetry Estimates of 18F-PEG6-IPQA in Nonhuman Primates

We recently developed the radiotracer 4-[(3-iodophenyl)amino]-7-(2-[2-{2-(2-[2-{2-(18F-fluoroethoxy)-ethoxy}-ethoxy]-ethoxy)-ethoxy}-ethoxy]-quinazoline-6-yl-acrylamide) (18F-PEG6-IPQA) for noninvasive detection of active mutant epidermal growth factor receptor kinase-expressing non–small cell lung cancer xenografts in rodents. In this study, we determined the pharmacokinetics, biodistribution, metabolism, and radiation dosimetry of 18F-PEG6-IPQA in nonhuman primates. Methods: Six rhesus macaques were injected intravenously with 141 ± 59.2 MBq of 18F-PEG6-IPQA, and dynamic PET/CT images covering the thoracoabdominal area were acquired for 30 min, followed by whole-body static images at 60, 90, 120, and 180 min. Blood samples were obtained from each animal at several time points after radiotracer administration. Radiolabeled metabolites in blood and urine were analyzed using high-performance liquid chromatography. The 18F-PEG6-IPQA pharmacokinetic and radiation dosimetry estimates were determined using volume-of-interest analysis of PET/CT image datasets and blood and urine time–activity data. Results: 18F-PEG6-IPQA exhibited rapid redistribution and was excreted via the hepatobiliary and urinary systems. 18F-PEG6 was the major radioactive metabolite. The critical organ was the gallbladder, with an average radiation-absorbed dose of 0.394 mSv/MBq. The other key organs with high radiation doses were the kidneys (0.0830 mSv/MBq), upper large intestine wall (0.0267 mSv/MBq), small intestine (0.0816 mSv/MBq), and liver (0.0429 mSv/MBq). Lung tissue exhibited low uptake of 18F-PEG6-IPQA due to the low affinity of this radiotracer to wild-type epidermal growth factor receptor kinase. The effective dose was 0.0165 mSv/MBq. No evidence of acute cardiotoxicity or of acute or delayed systemic toxicity was observed. On the basis of our estimates, diagnostic dosages of 18F-PEG6-IPQA up to 128 MBq (3.47 mCi) per injection should be safe for administration in the initial cohort of human patients in phase I clinical PET studies. Conclusion: The whole-body and individual organ radiation dosimetry characteristics and pharmacologic safety of diagnostic dosages of 18F-PEG6-IPQA in nonhuman primates indicate that this radiotracer should be acceptable for PET/CT studies in human patients.

Development of a large animal model of cirrhosis and portal hypertension using hepatic transarterial embolization: A study in swine

PURPOSE To develop a clinically relevant porcine model of liver cirrhosis with portal hypertension by means of hepatic transarterial embolization. MATERIALS AND METHODS Institutional animal care and use committee approval was obtained for all experiments. Pigs received transcatheter arterial infusion of a 3:1 mixture of iodized oil and ethanol into the hepatic artery in volumes of 16 mL in group 1 (n = 4), 28 mL in group 2 (n = 4), and 40 mL in group 3 (n = 4) with intent of bilobar distribution. Hepatic venous pressure gradient (HVPG) measurement, liver function tests, and volumetry were performed at baseline, at 2 weeks, and before necropsy. RESULTS Cirrhosis was successfully induced in three animals that received 16 mL of the embolic mixture and in all four animals that received 28 mL. The animals in the 40-mL group did not recover from the procedure and were euthanized within 48 h. Increases in HVPG after 6-8 weeks versus baseline reached statistical significance (P < .05). Correlation between degree of fibrosis and volume of embolic agent did not reach statistical significance, but there was a trend toward increased fibrosis in the 28-mL group compared with the 16-mL group. CONCLUSIONS Transcatheter hepatic arterial embolization can be used to create a reliable and reproducible porcine model of liver cirrhosis and portal hypertension.

Pharmacokinetics and magnetic resonance imaging of biodegradable macromolecular blood-pool contrast agent PG-Gd in non-human primates: a pilot study.

The purpose of this study was to evaluate poly(L-glutamic acid)-benzyl-DTPA-Gd (PG-Gd), a new biodegradable macromolecular magnetic resonance imaging contrast agent, for its pharmacokinetics and MRI enhancement in nonhuman primates. Studies were performed in rhesus monkeys at intravenous doses of 0.01, 0.02 and 0.08 mmol Gd/kg. T(1)-weighted MR images were acquired at 1.5 T using fast spoiled gradient recalled echo and fast spin echo imaging protocols. The small-molecule contrast agent Magnevist was used as a control. PG-Gd in the monkey showed a bi-exponential disposition. The initial blood concentrations within 2 h of PG-Gd administration were much higher than those for Magnevist. The high blood concentration of PG-Gd was consistent with the MR imaging data, which showed prolonged circulation of PG-Gd in the blood pool. Enhancement of blood vessels and organs with a high blood perfusion (heart, liver, and kidney) was clearly visualized at 2 h after contrast injection at the three doses used. A greater than proportional increase of the area under the blood concentration-time curve was observed when the administered single dose was increased from 0.01 to 0.08 mmol/kg. By 2 days after PG-Gd injection, the contrast agent was mostly cleared from all major organs, including kidney. The mean residence time was 15 h at the 0.08 mmol/kg dose. A similar pharmacokinetic profile was observed in mice, with a mean residence time of 5.4 h and a volume of distribution at steady-state of 85.5 ml/kg, indicating that the drug was mainly distributed in the blood compartment. Based on this pilot study, further investigations on the potential systemic toxicity of PG-Gd in both rodents and large animals are warranted before testing this agent in humans.

Validation of a Preclinical Model of Diethylnitrosamine-Induced Hepatic Neoplasia in Yucatan Miniature Pigs

Objective: The purpose of this study was to reduce the time to tumor onset in a diethylnitrosamine (DEN)-induced hepatocellular carcinoma (HCC) swine model via partial liver embolization (PLE) and to characterize the model for use in translational research. Methods: Eight Yucatan miniature pigs were injected intraperitoneally with either saline (n = 2) or DEN (n = 6) solution weekly for 12 weeks. Three of the DEN-treated pigs underwent PLE. The animals underwent periodic radiological evaluation, liver biopsy, and blood sampling, and full necropsy was performed at study termination (∼29 months). Results: All DEN-treated pigs developed hepatic adenoma and HCC. PLE accelerated the time to adenoma development but not to HCC development. Biomarker analysis results showed that IGF1 levels decreased in all DEN-treated pigs as functional liver capacity decreased with progression of HCC. VEGF and IL-6 levels were positively correlated with disease progression. Immunohistochemical probing of HCC tissues demonstrated the expression of several important survival-promoting proteins. Conclusion: To our knowledge, we are the first to demonstrate an accelerated development of hepatic neoplasia in Yucatan miniature pigs. Our HCC swine model closely mimics the human condition (i.e., progressive disease stages and expression of relevant molecular markers) and is a viable translational model.

Novel endoscopic application of a new flexible-fiber CO2 laser for esophageal mucosal ablation in a porcine model

BACKGROUND AND STUDY AIMS The CO (2) laser is a surgical tool that is widely used because of its predictable penetration depth and minimal collateral damage due to efficient absorption of CO (2) laser energy by tissue water. Until recently, endoscopic use was limited by lack of an efficient, flexible delivery system. The aim of the current study was to evaluate the performance, efficacy, and safety of a novel, photonic band-gap CO (2) laser configured for esophageal mucosal ablation. MATERIALS AND METHODS This was an endoscopic experimental study in a porcine survival model. Initial evaluation was done on ex vivo tissue followed by endoscopic studies at 7-, 10-, 15-, and 20-W power and at 0-, 1-, 2-, 5-, and 10-mm distances, using continuous and pulsed currents, to determine optimal performance settings. In an IACUC-approved protocol, six pigs underwent circumferential ablation of the distal 6 cm of the esophagus at 10W continuous current. The animals were monitored for 2 or 4 weeks to evaluate delayed effects. Prior to euthanasia, the proximal esophagus was ablated to evaluate the homogeneity of ablation and depth of injury immediately after single and repeat ablation. RESULTS The animals resumed normal diets within 24 hours and experienced no dysphagia or weight loss. Pathology at 2 and 4 weeks revealed complete re-epithelialization with minimal histologic injury. A single application of the laser produced complete transepithelial ablation of a mean of 83.3 % of the surface area (range 55 % - 100 %); depth of injury was to the muscularis mucosa in five pigs and to the superficial submucosa in one pig. With ablation, sloughing, and re-ablation, a mean of 95 % transepithelial ablation was achieved (range 80 % -100 %) with similar depth of injury. CONCLUSIONS Using a novel, flexible CO (2) laser, homogeneous ablation was achieved with predictable penetration and minimal deep tissue injury. These results warrant further evaluation of the laser in Barretts esophagus, as it may overcome the limitations of current technologies including perforation, stricture, and inhomogeneity.