EVALUATION OF TARGETED CONTRAST AGENTS FOR IN VIVO IMAGING AND DETECTION OF ENDOMETRIOSIS IN MOUSE MODELS

Endometriosis is a chronic condition that affects about 10% of women during their reproductive years. Yet, no clinically approved agents are available for non-invasive endometriosis detection. This dissertation explores the application of two distinct targeted imaging contrast agents for the non-invasive detection and imaging of endometriosis using magnetic resonance imaging (MRI). Dr. Asgerally (Asgi) Fazleabas and his graduate student, Maria Ariadna Ochoa Bernal, supplied the mouse models of endometriosis and Dr. Christiane Mallett played a critical role in the MR imaging studies (Chapters 2 and 3). Chapter 1 offers a comprehensive introduction about endometriosis. Chapter 2 investigates the utility of a gadolinium-based type I collagen targeting probe (EP-3533) to non-invasively detect endometriotic lesions using MRI. Previously, this probe has been used for the detection and staging of various fibrotic conditions. Recently, endometriosis has been identified as a fibrotic disease. In this study, we evaluate the potential of EP-3533 for detecting endometriosis in two murine models and compare it with a non-binding isomer (EP-3612). For imaging we utilized two GFP-expressing murine models of endometriosis injected intravenously with EP-3533 or EP33612. Mice were imaged before and after bolus injection of the probes. The dynamic signal enhancement of MR T1 FLASH images were analyzed, and the relative location of lesions was validated through ex vivo fluorescence imaging. Next, the harvested lesions were stained for collagen and their gadolinium content was quantified by inductively coupled plasma optical emission spectrometry (ICP-OES). We showed that EP-3533 probe increased the signal intensity in T1-weighted images of endometriotic lesions in both models of endometriosis. Such enhancement was not detected in the muscles of the same groups or in endometriotic lesions of mice injected with EP-3612. Consequentially, control tissues had significantly lower gadolinium content compared to the lesions in experimental groups. This study provides evidence for targeting type I collagen in the endometriotic lesions using EP-3533 probe. In Chapter 3 we evaluated cRGD peptide-conjugated nanoparticles (RGD-Cy5.5-MN), to detect lesions using MRI in a mouse model of endometriosis. RGD peptide binds preferentially to the alpha(v)beta3 integrin which has been shown to have expression in endometriotic lesions. We utilized a luciferase-expressing murine suture model of endometriosis. Animals were imaged before, and 24 hours after intravenous injection of RGD-Cy5.5-MN or control nanoparticles (Cy5.5-MN). Next, we performed biodistribution studies and correlative fluorescence microscopy of lesions stained for CD34. Iron content in tissues was quantified using ICP-OES. Our results showed that RGD-Cy5.5MN targeting of endometriotic lesions caused significantly higher deltaT2* upon accumulation compared to Cy5.5-MN. ICP-OES showed significantly higher iron content in the lesions of the experimental group compared to the control group. Histology showed colocalization of Cy5.5 signal from RGD-Cy5.5-MN with CD34 in the lesions pointing to the targeted accumulation of the probe. This work offers initial proof-of-concept for targeting angiogenesis in the endometriotic lesions which can be useful for potential clinical diagnostic and therapeutic approaches for treating this disease. Chapter 4 summarizes the conclusions drawn from the previous chapters and outlines the future direction of the presented studies. Furthermore, motivated by the fact that endometriosis is a risk factor for ovarian cancer, preliminary results of a project evolving around ovarian cancer are presented.