A Dorsal Skinfold Window Chamber Tumor Mouse Model for Combined Intravital Microscopy and Magnetic Resonance Imaging in Translational Cancer Research

Summary

Translation of Intravital microscopy findings is challenged by its shallow depth penetration into tissue. Here we describe a dorsal window chamber mouse model that enables co-registration of intravital microscopy and clinically applicable imaging modalities (e.g., CT, MRI) for direct spatial correlation, potentially streamlining clinical translation of intravital microscopy findings.

Abstract

Preclinical intravital imaging such as microscopy and optical coherence tomography have proven to be valuable tools in cancer research for visualizing the tumor microenvironment and its response to therapy. These imaging modalities have micron-scale resolution but have limited use in the clinic due to their shallow penetration depth into tissue. More clinically applicable imaging modalities such as CT, MRI, and PET have much greater penetration depth but have comparatively lower spatial resolution (mm scale).

To translate preclinical intravital imaging findings into the clinic, new methods must be developed to bridge this micro-to-macro resolution gap. Here we describe a dorsal skinfold window chamber tumor mouse model designed to enable preclinical intravital and clinically applicable (CT and MR) imaging in the same animal, and the image analysis platform that links these two disparate visualization methods. Importantly, the described window chamber approach enables the different imaging modalities to be co-registered in 3D using fiducial markers on the window chamber for direct spatial concordance. This model can be used for validation of existing clinical imaging methods, as well as for the development of new ones through direct correlation with "ground truth" high-resolution intravital findings.

Finally, the tumor response to various treatments-chemotherapy, radiotherapy, photodynamic therapy-can be monitored longitudinally with this methodology using preclinical and clinically applicable imaging modalities. The dorsal skinfold window chamber tumor mouse model and imaging platforms described here can thus be used in a variety of cancer research studies, for example, in translating preclinical intravital microscopy findings to more clinically applicable imaging modalities such as CT or MRI.

Introduction

Tumor microvasculature is an important component of the tumor microenvironment that can be a target for therapy and a determinant of treatment response. In the preclinical setting, the microvasculature is typically studied using intravital microscopy in orthotopic or heterotopic window chamber animal models^1,2. This has several advantages over histological studies since the imaging is done in live tissues and the tumor can be monitored longitudinally over several weeks or even months^2,3. These studies can leverage the high-resolution imaging capabiliti....

Protocol

All animal procedures were performed in accordance with the Guide to the Care and Use of Experimental Animals which is set forth by the Canadian Council on Animal Care. Experiments were performed according to a protocol approved by the University Health Network Institutional Animal Care and Use Committee in Toronto, Canada.

1. Tumor inoculation landmarking

NOTE: "Landmarking" refers to the process of marking the skin of the mouse to indicate w.......

Discussion

In this work, we have developed a workflow to perform both intravital microscopy and clinically applicable imaging (CT, MRI, and PET) in the same animal. This was done with the goal of translating preclinical microscopy findings to the clinic by direct correlation of intravital microscopy with clinical imaging modalities such as MRI. Although conventional DSFC designs are made of metal^2,3, we have adapted the DSFC to be MR-compatible by using 3D-printed window ch.......

Materials

Name	Company	Catalog Number	Comments
Cell Culture Materials
BxPC-3 Human Pancreatic Cancer Cells	ATCC (American Type Culture Collection)	CRL-1687
Corning Matrigel Basement Membrane Matrix, LDEV-free, 10 mL	Corning	354234
Corning Stripettor Ultra Pipet Controller	Corning	07-202-350
Dulbecco Phospphate buffered saline without Calcium, Magnesium, or phenol red, 500 mL	Gibco	14190144
Fetal Bovine Serum (Canada), 500 mL	Sigma-Aldrich	F1051-500ML
Penicillin-Streptomycin 100x (liquid,stabilized, sterile-filtered, cell culture tested)	Sigma-Aldrich	P4333-100ML
RPMI Medium 1640 (1x), liquid; with L-Glutamine, 500 mL	Gibco	11875093
TrypLE Express Enzyme, 500 mL	Gibco	12605028
Window Chamber Materials
12 mm Glass Coverslip	Harvard Apparatus	CS-12R No. 1.5
Connex 500 3D Printer	Stratasys	N/A
Biocompatible clear MED610 resin	Stratasys	RGD810
Loctite AA 3105 UV curable glue	Loctite	LCT1214249
Window chamber back frame	Trimech Inc	N/A
Window chamber fiducial marker	Trimech Inc	N/A
Window Chamber front frame	Trimech Inc	N/A
Window chamber support clip	Trimech Inc	N/A
inoculation and Surgery Materials
BD SafetyGlide Insulin Syringes with Permanently Attached Needles, 0.5 mL, 29 G x 1/2"	BD	CABD305932
Betadine Solution	Betadine	AP-B002C2R98U
Cidex OPA 14 Day Solution 3.8 L	ASP	JOH20394
Disposable Surgical Underpads 23 inch x 24 inch	Kendall	7134
Eye lubricant	Optixcare	50-218-8442
Hair removal cream	Nair	‎061700222611
Halstead Hemostatic Forceps	Almedic	7742-A12-150
Heating pad	Sunbeam	B086MCN59R
Iris Scissors	Almedic	7601-A8-690
Isoflurane	Sigma	792632
Metacam	Boehringer Ingelheim Animal Health USA Inc	NDC 0010-6015-03
NOD.Cg-Rag1tm1Mom Il2rgtm1Wjl/SzJ mouse	the Jackson laboratory	7799
Peanut Clipper & Trimmer	Wahl	8655-200
SOFSILK Nonabsorbable Surgical Suture #5-0 with 3/8" Taper point needle (17 mm) (Wax Coated,Braided Black Silk, Sterile)	Syneture	VS880
Splinter Forceps	Almedic	7725-A10-634
MR Imaging
3D printed window chamber immobilization device.			custom 3D printed, refer to figure 3 for details.
Convection heating device	3M Bair Hugger	70200791401
Drug injection system	Harvard Apparatus	PY2 70-2131	PHD 22/2200 MRI compatible Syringe Pump
Gadovist 1.0	Bayer	2241089
Respiratory monitoring system	SAII	Model 1030	MR-compatible monitoring and gating system for small animals.
Tail vein catheter (27 G 0.5" )	Terumo Medical Corp	15253
Optical Imaging
3D printed imaging stage			Custom 3D printed, refer to supplementary figure 3 for details.
12 V 7 W Flexible Polyimide Heater Plate Thin Adhesive PI Heating Film 25 mm x 50 mm	BANRIA	B09X16XCVS	Heating element used for mouse body temeprature regulation.
DC power supply	BK Precission	1761	Used to power the heating element.
Leica MZ FLIII	Leica Microsystems	15209
svOCT imaging system			In-house made imaging system. Details can be found in reference 23.
Software
MATLAB Software	MathWorks	R2020A