Comparison of mouse mammary gland imaging techniques and applications: reflectance confocal microscopy, GFP imaging, and ultrasound.
BACKGROUND
Genetically engineered mouse models of mammary gland cancer enable the in vivo study of molecular mechanisms and signaling during development and cancer pathophysiology. However, traditional whole mount and histological imaging modalities are only applicable to non-viable tissue.


METHODS
We evaluated three techniques that can be quickly applied to living tissue for imaging normal and cancerous mammary gland: reflectance confocal microscopy, green fluorescent protein imaging, and ultrasound imaging.


RESULTS
In the current study, reflectance confocal imaging offered the highest resolution and was used to optically section mammary ductal structures in the whole mammary gland. Glands remained viable in mammary gland whole organ culture when 1% acetic acid was used as a contrast agent. Our application of using green fluorescent protein expressing transgenic mice in our study allowed for whole mammary gland ductal structures imaging and enabled straightforward serial imaging of mammary gland ducts in whole organ culture to visualize the growth and differentiation process. Ultrasound imaging showed the lowest resolution. However, ultrasound was able to detect mammary preneoplastic lesions 0.2 mm in size and was used to follow cancer growth with serial imaging in living mice.


CONCLUSIONS
In conclusion, each technique enabled serial imaging of living mammary tissue and visualization of growth and development, quickly and with minimal tissue preparation. The use of the higher resolution reflectance confocal and green fluorescent protein imaging techniques and lower resolution ultrasound were complementary.
Tilli
Maddalena T
MT
Lombardi Comprehensive Cancer Center, Georgetown University, Washington, DC 20057, USA. mtt7@georgetown.edu
Parrish
Angela R
AR
Cotarla
Ion
I
Jones
Laundette P
LP
Johnson
Michael D
MD
Furth
Priscilla A
PA
D000230:Adenocarcinoma / Q000175:diagnosis / Q000000981:diagnostic imaging; D000818:Animals; D005260:Female; D049452:Green Fluorescent Proteins / Q000235:genetics; D008321:Mammary Glands, Animal / Q000033:anatomy & histology* / Q000637:transplantation; D008325:Mammary Neoplasms, Experimental / Q000175:diagnosis* / Q000000981:diagnostic imaging; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence / Q000379:methods*; D008857:Microscopy, Interference; D009924:Organ Culture Techniques; D014184:Transplantation, Homologous; D014463:Ultrasonography
D049452:Green Fluorescent Proteins