Development and Optimization of 19F-MRI for Tracking Cellular Therapeutics

Introduction: This thesis aims to advance magnetic resonance imaging (MRI) for imaging cellular therapeutics. Traditional, proton-based, MRI provides detailed anatomical images, particularly of soft tissue. However, in order to obtain information at a cellular level specialized imaging agents are required to detect the cells of interest. Perfluorocarbons containing non-radioactive fluorine-19 (19F) are both biologically safe and MR sensitive. Methods: Pre-clinical 19F-MRI was implemented on a Varian 9.4T MRI scanner, using a dual 19F/1H-tuned birdcage volume coil. Mesenchymal stromal cells (MSC) were pre-labeled with a commercial, FDA approved 19F-perfluorocarbon emulsion, then implanted intramuscularly into the mouse hindlimb. To track the inflammation resulting from transplantation, a dual-agent cellular MRI technique was developed. This technique utilizes 19F to track MSC and superparamagnetic iron oxide nanoparticles (SPIO) to image macrophages, through the presence of signal quenching. A clinical imaging protocol was developed to translate 19F-MRI on a 3T GE MR750 scanner with a dual 19F/1H-tuned surface coil. Peripheral blood mononuclear cells (PBMC) were labeled with a FDA-approved 19F-agent and injected into a ham shank phantom for protocol optimization. Results: The balanced steady-state free precession pulse sequence was chosen for all studies due to the high signal-to-noise per unit time. Image acquisition was optimized for 19F detection sensitivity, accuracy of quantification, and compatibility with isoflurane. In vivo quantification of MSC on the day of implantation was in strong agreement with the expected number of cells. The change in 19F-signal was quantified over time and compared between two murine transplantation models. When iron oxide was administered i.v., the migration of immune cells could be tracked to the injection site. The presence of SPIO decreased both the 1H and 19F signal, indicating that transplant rejection was occurring. On a clinical system, as few as 4x106 PBMC could be imaged following both surface and subcutaneous injection. The minimum number of detectable cells was strongly influenced by intracellular 19F uptake. Conclusions: 19F-MRI is a promising tool for imaging cellular therapeutics. By pre-labeling cells of interest, they can be localized and the change in signal can be quantified over time. The technique shows promise for both pre-clinical and clinical applications

Tracking the fate of stem cell implants with fluorine-19 MRI.

BACKGROUND: In this study we used cellular magnetic resonance imaging (MRI) to detect mesenchymal stem cells (MSC) labeled with a Fluorine-19 (19F) agent. 19F-MRI offers unambiguous detection and in vivo quantification of labeled cells. METHODS: We investigated two common stem cell transplant mouse models: an immune competent, syngeneic transplant model and an immune compromised, xenograft transplant model. 19F labelled stem cells were implanted intramuscularly into the hindlimb of healthy mice. The transplant was then monitored for up to 17 days using 19F-MRI, after which the tissue was excised for fluorescence microscopy and immunohistochemisty. RESULTS: Immediately following transplantation, 19F-MRI quantification correlated very well with the expected cell number in both models. The 19F signal decreased over time in both models, with a more rapid decrease in the syngeneic model. By endpoint, only 2/7 syngeneic mice had any detectable 19F signal. In the xenograft model, all mice had detectable signal at endpoint. Fluorescence microscopy and immunohistochemistry were used to show that the 19F signal was related to the presence of bystander labeled macrophages, and not original MSC. CONCLUSIONS: Our results show that 19F-MRI is an excellent tool for verifying the delivery of therapeutic cells early after transplantation. However, in certain circumstances the transfer of cellular label to other bystander cells may confuse interpretation of the long-term fate of the transplanted cells

Size-dependent rheology of type-I collagen networks

We investigate the system size dependent rheological response of branched type I collagen gels. When subjected to a shear strain, the highly interconnected mesh dynamically reorients, resulting in overall stiffening of the network. When a continuous shear strain is applied to a collagen network, we observe that the local apparent modulus, in the strain-stiffening regime, is strongly dependent on the gel thickness. In addition, we demonstrate that the overall network failure is determined by the ratio of the gel thickness to the mesh size. These findings have broad implications for cell-matrix interactions, the interpretation of rheological tissue data, and the engineering of biomimetic scaffolds.Comment: 3 pages, 4 figures, to appear in Biophysical Journal Letters, September 201

Modifiable Disease Risk, Readiness to Change, and Psychosocial Functioning Improve With Integrative Medicine Immersion Model

Background—Stroke, diabetes, and coronary heart disease (CHD) remain leading causes of death in the United States and are largely attributable to lifestyle behaviors. Integrative medicine can provide a supportive partnership that focuses on improving health by identifying and implementing lifestyle changes based upon personal values and goals. Objective—This prospective observational study was designed to assess the effectiveness of an integrative medicine intervention on modifiable disease risk, patient activation, and psychosocial risk factors for stroke, diabetes, and CHD. Design—Sixty-three adults participated in a 3-day comprehensive, multimodal health immersion program at Duke Integrative Medicine, Duke University Medical Center, Durham, North Carolina. Participants received follow-up education, physician support, and telephonic health coaching between the immersion program and the endpoint 7 to 9 months later. Primary Outcome Measures—Psychosocial functioning, readiness to change health behaviors, and risk of developing diabetes, stroke, and CHD were assessed at baseline and endpoint. Results—Although cardiac risk remained unchanged (P = .19) during the study period, risk of diabetes (P = .02) and stroke (P \u3c .01) decreased significantly. Perceived stress remained unchanged, but improvements were seen in mood (P \u3c .05) and relationship satisfaction (P \u3c . 004). Patients became more activated towards self-management of health (PPPP= .006) following the intervention. Conclusion—An integrative health model can help patients become more engaged in self management of health and support them in making and maintaining healthy lifestyle changes. These findings provide support for use of an integrative health model in adult disease risk reduction

Investigating the autonomic nervous system and cognitive functions as potential mediators of an association between cardiovascular disease and driving performance

Abstract: Cardiovascular disease (CVD) impacts the autonomic nervous system and cognitive functions related to activities of daily living, including driving an automobile. Although CVD has been linked to unsafe driving, mechanisms underlying this relationship remain elusive. The aim of this study was to examine the role of cognitive functions and the autonomic nervous system as potential mediators of driving performance. Nineteen individuals having recently suffered a cardiac event and sixteen individuals with no history of CVD completed a simulated drive using a STISIM simulator to assess driving performance. Heart rate was recorded throughout testing using a Polar RS800CX heart rate monitor and measures of executive, orienting and alerting functions were obtained through the Attention Network Test. We used the Baron and Kenny analysis method to assess potential mediating effects of the relationship between CVD and driving performance. Executive function was the only potential mediator investigated to be associated with driving (p < 0.01) and CVD (p < 0.05), however, it did not appear to play a mediating role (p = 0.28). These results suggest that individuals with CVD exhibit decrements in complex cognitive tasks such as driving and that further research is needed to better understand the mechanisms underlying this relationship

Relationship Between Sexual Activity, Contraceptive Utilization and Biopsychosocial Characteristics Among Homeless Shelter Adolescents.

Objective: To determine whether biopsychosocial factors are associated with sexual activity and contraceptive utilization among homeless shelter adolescents. Methods: A retrospective study of 440 adolescents at a shelter in Pennsylvania between February 2015 and September 2019 was conducted. The cohort was evaluated to determine what relationship age, gender identity, substance use, and trauma history have with sexual activity and contraceptive utilization. Results: Sexual activity was significantly related to age (mean 15.8+1.4 years in sexually active vs. 14.7+1.6 years in abstinent youth, p\u3c0.001); remote history of self-harm behavior (relative risk ratio (RR) 1.23 [95% CI 1.03-1.46]; p=0.02), history of aggressive behavior (RR 1.21 [95% CI 1.01-1.46]; p=0.04), history of trauma (RR 1.24 [95% CI 1.04-1.48]; p=0.03), and substance use (RR 2.27 [95%CI 1.86-2.77]; p\u3c0.001). There were 55.7% sexually active females vs. 42.50% males reporting contraception use (p=0.01). After adjustment, older age and substance use remained significantly associated with sexual activity (adjusted odds ratio (AOR) 1.58 [95% CI 1.36-1.83]; p\u3c0.001 and AOR 5.18 [95% CI 3.28-8.18]; p\u3c0.001, respectively). Conclusions: Females self-reported sexual activity using contraception more than males. After adjustment, older age and substance use were associated with sexual activity. By better understanding the impact these factors can have on contraceptive utilization, informed policy and practice interventions can be developed and implemented to help increase safe sex practices in spaces where homeless adolescents access healthcare

Anomalous metamagnetism in the low carrier density Kondo lattice YbRh3Si7

We report complex metamagnetic transitions in single crystals of the new low carrier Kondo antiferromagnet YbRh3Si7. Electrical transport, magnetization, and specific heat measurements reveal antiferromagnetic order at T_N = 7.5 K. Neutron diffraction measurements show that the magnetic ground state of YbRh3Si7 is a collinear antiferromagnet where the moments are aligned in the ab plane. With such an ordered state, no metamagnetic transitions are expected when a magnetic field is applied along the c axis. It is therefore surprising that high field magnetization, torque, and resistivity measurements with H||c reveal two metamagnetic transitions at mu_0H_1 = 6.7 T and mu_0H_2 = 21 T. When the field is tilted away from the c axis, towards the ab plane, both metamagnetic transitions are shifted to higher fields. The first metamagnetic transition leads to an abrupt increase in the electrical resistivity, while the second transition is accompanied by a dramatic reduction in the electrical resistivity. Thus, the magnetic and electronic degrees of freedom in YbRh3Si7 are strongly coupled. We discuss the origin of the anomalous metamagnetism and conclude that it is related to competition between crystal electric field anisotropy and anisotropic exchange interactions.Comment: 23 pages and 4 figures in the main text. 7 pages and 5 figures in the supplementary materia