While infering the details of biological processes from a dataset is time-tested and valid, nothing can compete with actually watching a biological event take place or looking at the cells in question. In this regard, imaging technologies are particularly valuable to cancer biologists interested in following the cellular and morphological progression of tumors. Here, the dorsal skin-fold window chamber, which allows repeated imaging of a tumor growing in an animal model, is a critical tool.
These drawbacks prompted Arthur Gmitro of the University of Arizona, who works on breast cancer to develop a window chamber where mammary tumors could grow in their native environments, and that would allow for multiple forms of biological imaging.
“The initial design features for the window chamber included manufacturing the structure out of a non-magnetic material to support utilization in the MR magnet, minimizing size and weight to reduce annoyance or burden on the animal, compatibility with readily available coverslip sizes, and the ability to remove the coverslip to support utilization with a special high resolution nuclear imaging technique and allow for extended use of the model in the event that the coverslip might be cracked or damaged,” explained Rachel Schafer, a graduate student in Gmitro’s lab and first author of the BioTechniques paper describing the model.
With these goals in mind, Schafer and Gmitro turned to 3-D printing to construct their device. Recent advances in 3-D printers made it possible to accommodate the very small features needed for the new window that they intended to place in the mouse mammary fat pad. “The small detailed features and desire to test multiple design options would have been substantially more expensive and time-intensive if pursued through the use of conventional machining equipment,” Schafer said.
The authors demonstrated the window’s compatibility with magnetic resonance (MR) imaging, functional nuclear imaging, and optical imaging, but according to Schafer, it should work well with x-ray, CT, and ultrasound imaging as well.
“I was somewhat surprised by the different perspectives of the tumor environment the various imaging approaches provided,” noted Schafer. For example, with optical imaging, the team was able to see a projection of the tumor size, while MR allowed observation of the tumor's complete 3D extent. As another example, a tumor may not appear to change significantly in size over a particular time period based on optical imaging, but viewing the entire 3D tumor in MR may reveal that the tumor is continuing to grow below the surface or developing spatial heterogeneity.
The team now plans to put their newly optimized window chamber to use investigating various new therapeutics and their effects on breast cancer growth.
Schafer R, Leung HM, Gmitro AF. Multi-modality imaging of a murine mammary window chamber for breast cancer research. BioTechniques. 2014 Jul 1;57(1):45-50.