title: Investigating the Safety and Efficacy of Regenerative Medicine Therapies in Mouse Models of Kidney Disease
Creators: name: Scarfe, LN
Publisher: name: University of Liverpool Repository
Year: 2018

description: Acute kidney injury (AKI) and chronic kidney disease (CKD) are serious health problems with high morbidity and mortality. There are currently no specific treatments available to patients with AKI or CKD, and many patients require renal replacement therapy to survive. Cell-based regenerative medicine therapies have shown potential for treating AKI and CKD in preclinical models, however conventional methods of measuring kidney function and tracking exogenously administered cells are not ideal. Novel imaging-based methods provide an alternative approach, allowing kidney function and cell biodistribution to be monitored longitudinally, without sacrificing many animals at multiple time points. The work in this thesis aimed to evaluate the use of two novel methods for assessing kidney function in mice, and apply them in the assessment of cell therapy efficacy in two preclinical models of kidney disease. Furthermore, preclinical imaging approaches were used to track cell biodistribution in vivo, in order to gain insights into the mechanism of action of cell therapy, and long-term safety. Two novel methods of measuring kidney function were assessed: 1) transcutaneous measurement of FITC-sinistrin clearance, and 2) photoacoustic imaging of IRDye clearance kinetics. The transcutaneous measurement of FITC-sinistrin clearance was found to be a superior method of measuring kidney function in mice, correlating more strongly with histological assessment of structural damage compared with traditional biochemical techniques in the adriamycin model of CKD, and the ischemia-reperfusion model of AKI. Photoacoustic imaging of IRDye clearance kinetics was also found to correlate better with histology in the adriamycin model, however the transcutaneous method was preferred for subsequent studies due to practical considerations including shorter anaesthesia time, higher throughput data collection, and ease of data handling. The efficacy of human kidney-derived cells (hKCs) was assessed following early and late administration in the adriamycin model. It was found that the hKCs induced a trend towards improved kidney function when administered on day one, but there was no effect when treatment was delayed until day 15, after overt proteinuria was established. Furthermore, bioluminescence imaging of luciferase+ hKCs demonstrated that intravenously administered hKCs remained trapped in the lungs, where they promptly died and did not migrate to the kidneys. These results support a paracrine/endocrine mechanism of action of cell therapy, and suggest that efficacy may be absent or diminished when treatment is administered later in the course of the disease. The efficacy of hKCs was also assessed in the ischemia-reperfusion model, and was compared with human mesenchymal stromal cells derived from either bone marrow or the umbilical cord. These results were unexpected, as it was found that none of the cell types tested had any effect on kidney structure or function, and furthermore, the cells did not die in the lungs within 24h of administration. These results may allude to a potential role of cell death in the mechanism of action of cell therapy, however this requires a great deal of further investigation. Finally, preclinical imaging techniques were used to optimise an intracardiac method of cell administration, and to compare the short- and long-term biodistribution of cells following intravenous and intracardiac administration. Intracardiac administration was shown to deliver cells to all organs of the body, including the kidney, and a multi-modal imaging approach enabled whole-body imaging of live cells by bioluminescence imaging, in conjunction with detailed organ-specific imaging of intra-organ biodistribution with magnetic resonance imaging. Longitudinal bioluminescence imaging demonstrated the effect of route of administration on tumour development, with intracardiac administration leading to more aggressive tumour development compared with intravenous administration. These results highlight the value of preclinical imaging in the assessment of regenerative medicine therapies, and show the importance of longitudinal monitoring of the safety of a cell therapy. Overall, the results of this thesis demonstrate the use of novel imaging-based methods of assessing kidney function and cell biodistribution in preclinical assessment of the safety and efficacy of cell-based regenerative medicine therapies. These minimally-invasive methods are more reliable than traditional analyses, and allow individual animals’ responses to be monitored over time, thus reducing the number of animals required for such experiments.