Mouse Fetal Whole Intestine Culture System for Ex Vivo Manipulation of Signaling Pathways and Three-dimensional Live Imaging of Villus Development

Summary

Improved imaging technology is allowing three-dimensional imaging of organs during development. Here we describe a whole organ culture system that allows live imaging of the developing villi in the fetal mouse intestine.

Abstract

Most morphogenetic processes in the fetal intestine have been inferred from thin sections of fixed tissues, providing snapshots of changes over developmental stages. Three-dimensional information from thin serial sections can be challenging to interpret because of the difficulty of reconstructing serial sections perfectly and maintaining proper orientation of the tissue over serial sections. Recent findings by Grosse et al., 2011 highlight the importance of three- dimensional information in understanding morphogenesis of the developing villi of the intestine¹. Three-dimensional reconstruction of singly labeled intestinal cells demonstrated that the majority of the intestinal epithelial cells contact both the apical and basal surfaces. Furthermore, three-dimensional reconstruction of the actin cytoskeleton at the apical surface of the epithelium demonstrated that the intestinal lumen is continuous and that secondary lumens are an artifact of sectioning. Those two points, along with the demonstration of interkinetic nuclear migration in the intestinal epithelium, defined the developing intestinal epithelium as a pseudostratified epithelium and not stratified as previously thought¹. The ability to observe the epithelium three-dimensionally was seminal to demonstrating this point and redefining epithelial morphogenesis in the fetal intestine. With the evolution of multi-photon imaging technology and three-dimensional reconstruction software, the ability to visualize intact, developing organs is rapidly improving. Two-photon excitation allows less damaging penetration deeper into tissues with high resolution. Two-photon imaging and 3D reconstruction of the whole fetal mouse intestines in Walton et al., 2012 helped to define the pattern of villus outgrowth². Here we describe a whole organ culture system that allows ex vivo development of villi and extensions of that culture system to allow the intestines to be three-dimensionally imaged during their development.

Introduction

Each intestinal villus is composed of two main tissue compartments: an epithelial surface layer and a mesenchymal core. The mouse small intestine is formed at embryonic day 10 when a sheet of endoderm closes and seals to form a tube of epithelium surrounded by mesenchymal cells³. This flat tube of epithelium undergoes rapid proliferation, growing both in length and girth and undergoes dramatic rearrangements involving dynamic cell shape changes¹. At the same time, the surrounding mesenchyme also undergoes many developmental processes including the formation of the vascular plexus, differentiation of smooth muscle and recruitment of enteric neuron....

Protocol

NOTE: All mice were handled humanely using protocols approved by the University of Michigan Medical School Unit for Laboratory Animal Medicine and according to the guidelines of the University Committee on Use and Care of Animals.

1. Whole Organ Culture System

1. Preparation of media and culture plates
   1. In a tissue culture hood, remove 5 ml of BGJb media from the stock bottle and add 5 ml of Pen/Strep. Prepare a working stock of media in a 50 ml conical tube, by adding 1 ml of 5 mg/ml ascorbic acid to 49 ml of BGJb media (with Pen/Strep).
   2. Prepare a 6 well culture plate by adding 1 ml underneath each of the tra....

Results

Culture of whole explants of fetal intestines allows for the analyses of the location, distribution, and duration of the signaling molecules that coordinate intestinal development, as this system enables the manipulation of the signaling with pharmacological reagents or recombinant proteins. The transwell culture system (Figure 1A, reproduced from Walton et al., 2012)² provides an air-liquid interface, which makes it possible to place drug- or protein soaked agarose beads onto the tis.......

Discussion

The dynamic nature and complex tissue interactions of the developing intestine requires 3D visualization to have a full appreciation of these morphogenetic events. With evolving imaging technology, the ability to examine villus morphogenesis in detail is developing/improving and with it, the understanding of the spatial communication and interaction during organogenesis is greatly enhanced.

Alternative methods for culturing whole intestines have also been tested, but the transwell system remai.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Fine dissecting forceps	Fine Science Tools	11254-20	2 pairs
70% Ethanol
1x sterile Dulbecco's Phosphate-Buffered Saline (DPBS)	Gibco	14040-133	500 ml
6 well plates	Costar	3516
24 well plates	Costar	3524
60 x 15 mm petri dishes	Falcon	451007
Transwell plates, 24 mm inserts, 8.0 mm polycarbonate membranes	Corning Costar	3428	6 inserts per plate
BGJb media	Invitrogen	12591-038	500 ml
PenStrep (10,000U/ml Penicillin; 10,000 mg/ml Streptomycin)	Gibco	15140
Ascorbic Acid	Sigma	A0278	make 5 mg/ml stock, filter, aliquot and store at -20 °C
Mouth pipet (Drummond 1-15 inch aspirator tube assembly)	Fisher	21-180-10	remove the aspirator assembly and replace it with a 1,000 µl pipet tip which acts as an adaptor to plug in a 6 inch glass Pasteur pipet.
6 inch glass pasteur pipets
Capillary Tubes	World Precision Instruments	TW100F-4	pull to needles
4% Paraformaldehyde			made in 1 x PBS, pH to 7.3
Culture plates	Falcon	353037
Fine mesh stainless steel screen	purchase at hardware store
Polycarbonate membranes	Thomas scientific	4663H25	alternatively, cut Corning Costar 3428 membranes off of transwell supports
Instant glue	purchase at hardware store	gel based preferrably
35 x 10 mm plates	Falcon	351008
7% agarose	Sigma	A9414	prepare w/v in 1x DPBS, heating to dissolve in a waterbath
minutien pins	Fine Science Tools	26002-20
Phenol red free media (DMEM)	Gibco	21063-029
Xylazine (100 mg/ml)	AnaSed	139-236
Matrigel	BD	356231	basement membrane matrix, growth factor reduced, phenol red-free
3-4% agarose	Sigma	A9414	prepare w/v in 1x DPBS, heating to dissolve in a waterbath
Imaging of fixed intestines
Name of Material/Equipment	Company	Catalog Number	Comments/Description
vaseline	purchase at pharmacy		used to make VALAP: equal parts vaseline, lanolin, paraffin
lanolin	Sigma	L7387	used to make VALAP: equal parts vaseline, lanolin, paraffin
paraffin	Surgipath	39601006	used to make VALAP: equal parts vaseline, lanolin, paraffin
70% glycerol in 1 x PBS
Focus clear and Mount Clear	CelExplorer Labs Co.	F101-KIT
Modeling clay	purchase at art supply store
double stick tape
cotton applicator swabs
plastic molds, 10mm x 10mm x 5 mm)	Tissue Tek	4565
slides
coverslips
lab wipe	Kimberly Clark	34155	lint free delicate task wipe
Theiler staging chart			http://www.emouseatlas.org/emap/ema/theiler_stages/ downloads/theiler2.pdf
Leica SP5X confocal microscope	Leica		Used to conduct the live imaging
Leica DMI 6000 stand	Leica		Used to conduct the live imaging
Aqueous mounting medium (Prolong Gold)	Molecular Probes	P36930
Name of Material/Equipment	Company	Catalog Number	Comments/Description
24 well plate	Costar	3524
Triton X-100	Sigma	T-8787	used to make Permeabilization solution: 0.5% Triton X-100 in 1 x PBS
Goat serum			used to make Blocking Solution: 4% Goat serum, 0.1% Tween20 in 1x PBS
Tween20	Sigma	P9416