Visualizing murine breast and melanoma tumor microenvironment using intravital multiphoton microscopy

Minimally invasive longitudinal intravital imaging of cellular dynamics in intact long bone

Intravital two-photon microscopy enables deep-tissue imaging at high temporospatial resolution in live animals. However, the endosteal bone compartment and underlying bone marrow pose unique challenges to optical imaging as light is absorbed, scattered and dispersed by thick mineralized bone matrix and the adipose-rich bone marrow. Early bone intravital imaging methods exploited gaps in the cranial sutures to bypass the need to penetrate through cortical bone. More recently, investigators have developed invasive methods to thin the cortical bone or implant imaging windows to image cellular dynamics in weight-bearing long bones. Here, we provide a step-by-step procedure for the preparation of animals for minimally invasive, nondestructive, longitudinal intravital imaging of the murine tibia. This method involves the use of mixed bone marrow radiation chimeras to unambiguously double-label osteoclasts and osteomorphs. The tibia is exposed by a simple skin incision and an imaging chamber constructed using thermoconductive T-putty. Imaging sessions up to 12 h long can be repeated over multiple timepoints to provide a longitudinal time window into the endosteal and marrow niches. The approach can be used to investigate cellular dynamics in bone remodeling, cancer cell life cycle and hematopoiesis, as well as long-lived humoral and cellular immunity. The procedure requires an hour to complete and is suitable for users with minimal prior expertise in small animal surgery.

Volume imaging to interrogate cancer cell-tumor microenvironment interactions in space and time

Volume imaging visualizes the three-dimensional (3D) complexity of tumors to unravel the dynamic crosstalk between cancer cells and the heterogeneous landscape of the tumor microenvironment (TME). Tissue clearing and intravital microscopy (IVM) constitute rapidly progressing technologies to study the architectural context of such interactions. Tissue clearing enables high-resolution imaging of large samples, allowing for the characterization of entire tumors and even organs and organisms with tumors. With IVM, the dynamic engagement between cancer cells and the TME can be visualized in 3D over time, allowing for acquisition of 4D data. Together, tissue clearing and IVM have been critical in the examination of cancer-TME interactions and have drastically advanced our knowledge in fundamental cancer research and clinical oncology. This review provides an overview of the current technical repertoire of fluorescence volume imaging technologies to study cancer and the TME, and discusses how their recent applications have been utilized to advance our fundamental understanding of tumor architecture, stromal and immune infiltration, vascularization and innervation, and to explore avenues for immunotherapy and optimized chemotherapy delivery.

Intravital Microscopy of the Metastatic Pulmonary Environment

Real-time in vivo imaging has become an integral tool for the investigation and understanding of cellular processes in health and disease at single-cell resolution. This includes the dynamic and complex cellular interactions that occur during cancer progression and the subsequent metastatic dissemination of tumor cells to sites distant from the primary tumor. Herein we outline the methodology for the establishment and intravital imaging of the pulmonary metastatic niche, a preferred site of metastasis for many cancers, and describe the implementation of a lung window to visualize and dissect the intricate behaviour of multiple cell types within this environment. We also address the advantages and limitations of this high-resolution technology.

Insights and opportunities at the crossroads of cancer and neuroscience

The biological and pathological importance of mutual interactions between the nervous system and cancer have become increasingly evident. The emerging field of cancer neuroscience aims to decipher key signalling factors of cancer-nervous system crosstalk and to exploit these modulators as targets for improved anticancer therapies. Here we discuss the key achievements in cancer neuroscience research, inspire further interactions on a variety of related research topics, and provide a roadmap for future studies.