3D imaging approaches for visualization of target biomarkers in bone metastases in vivo

点击翻译按钮获取中文摘要

Bone comprises multiple cell types interacting with each other during skeletal metastatic processes. In the first funding period, we established mouse models for in vivo imaging of bone metastases giving rise to osteolytic and osteosclerotic lesions. We developed and tested new imaging methods including I) kinetic analyses of binding of a fluorescent bisphosphonate conjugate with uptake rates indicative of location-specific metabolic status, II) a registration procedure for time lapse micro-CT which improves the long-term precision of bone mineral and microstructure measurements in vivo and can identify local regions of bone apposition or loss, and III) correction procedures for the attenuation of optical signals in bone tissue. We also IV) established a transgenic mouse strain with recombination of the osterix promoter, regulating expression of the fluorescent protein Katushka which thus labels progenitor cells, osteoblasts and stromal cells, and V) show that a fluorescent conjugate of the Kiss1 peptide localizes to bone metastatic and multiple myeloma cells as well as neighboring mesenchymal stem cells (MSCs). Based on this armamentarium of imaging biomarkers for diagnostic and therapeutic targeting, and on additional methodological developments, we will test the hypothesis that hierarchical in vivo multimodal biomarker imaging, linking mesoscopic with microscopic methods, will allow for spatiotemporal characterization of metastatic disease severity and the effects of treatment. Our specific aims for the second funding period comprise: I) the use of our osterix-Katushka transgenic mouse model to mesoscopically and microscopically monitor the dynamics of tumor-associated progenitor cells (Osx+-MSCs) and osteoblasts in vivo as potential biomarkers for bone metastatic disease progression and therapy effects, II) the optimization and validation of optical bisphosphonate conjugates for selective, rapid binding at sites of active osteosclerotic metastases, and III) the development of micro-CT and second harmonic generation imaging methods as biomarkers for multimodal assessment of metastasis severity in osteolytic, osteosclerotic and mixed lesions. Successful establishment of hybrid micro-CT & multiphoton/near infrared fluorescent imaging will allow development of methods for in vivo imaging of bone metastases and multiple myeloma with biomarkers identified in SKELMET partner projects, including the Kiss1 receptor and junctional adhesion molecule 2. With the studies outlined in this proposal we aim at progress in the preclinical development of imaging agents that have translational potential to target disease and for therapy control.