Three-dimensional Organotypic Cultures of Vestibular and Auditory Sensory Organs

Summary

Three-dimensional organotypic cultures of the murine utricle and cochlea in optically clear collagen I gels preserve innate tissue morphology, allow for mechanical stimulation through adjustment of matrix stiffness, and permit virus-mediated gene delivery.

Abstract

The sensory organs of the inner ear are challenging to study in mammals due to their inaccessibility to experimental manipulation and optical observation. Moreover, although existing culture techniques allow biochemical perturbations, these methods do not provide a means to study the effects of mechanical force and tissue stiffness during development of the inner ear sensory organs. Here we describe a method for three-dimensional organotypic culture of the intact murine utricle and cochlea that overcomes these limitations. The technique for adjustment of a three-dimensional matrix stiffness described here permits manipulation of the elastic force opposing tissue growth. This method can therefore be used to study the role of mechanical forces during inner ear development. Additionally, the cultures permit virus-mediated gene delivery, which can be used for gain- and loss-of-function experiments. This culture method preserves innate hair cells and supporting cells and serves as a potentially superior alternative to the traditional two-dimensional culture of vestibular and auditory sensory organs.

Introduction

The study of most aspects of mammalian organ development has been facilitated by in vitro systems. Two principal methods are now used for the culture of vestibular sensory organs: free-floating¹ and adherent² preparations. Both methods permit the investigation of hair cell vulnerabilities³ and regeneration^1,4 in vitro. In addition, the developmental roles of the Notch^5,6, Wnt^7,8, and epidermal growth ....

Protocol

All methods described here have been approved by the Animal Care and Use Committees of Rockefeller University and of the University of Southern California.

1. (Optional) Preparation of Collagen I Solution from Mouse-tail Tendons

Note: Collagen I solutions are available commercially. Follow the manufacturer's instructions for gel preparation.

1. Euthanize 5 - 10 young adult (3 - 5 weeks old) mice of any wild type strain with carbon dioxide in accordance with the protocol approved by the relevant Institutional Animal Care and Use Committee¹⁶. Collect the tails a....

Results

Vestibular and auditory sensory organs from embryonic ears, cultured in 40-Pa collagen I gels mimicking low stiffness embryonic conditions¹¹, retain relatively normal three-dimensional structures (Figure 1) and maintain hair cells and supporting cells (Figure 2 and Figure 3). Although supporting cell density decreases by over 30% (Student's t-test: n = 4, p &.......

Discussion

The molecular signals that mediate growth and differentiation in the inner ear during development have been studied extensively^5,6,7,8,9,10. However, evidence obtained from the utricular model system suggests that mechanical cues, sensed through cell junctions and the activation of Hippo signaling, also play an important role.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
#10 Surgical Blades	Miltex	4-110
#5 Forceps	Dumont	11252-20
100 mm Petri dish	Sigma	P5856-500EA
250 uL large orifice pipette tips	USA Scientific	1011-8406
30 mm glass-bottom Petri dish	Matsunami Glass USA Corporation	D35-14-1.5-U
4 well plate	Thermo Fisher Scientific	176740
4-Hydroxytamoxifen	Sigma	H7904
60 mm Petri dish	Thermo Fisher Scientific	123TS1
Acetic acid	Sigma	537020
Ad-GFP	Vector Biolabs	1060
Anti-GFP, chicken IgY fraction	Invitrogen	A10262
Anti-Myo7A	Proteus Biosciences	25-6790
Anti-Sox2 Antibody (Y-17)	Santa Cruz	sc-17320
Bicinchoninic acid assay	Thermo Fisher Scientific	23225
Click-iT EdU Alexa Fluor 647 Imaging Kit	Thermo Fisher Scientific	C10340
Collagenase I	Gibco	17100017
D-glucose	Sigma	G8270
DMEM/F12	Gibco	11320033
Epidermal growth factor	Sigma	E9644
Fetal Bovine Serum (FBS)	Thermo Fisher Scientific	16140063
Fibroblast growth factor	Sigma	F5392
Flaming/Brown Micropipette Puller	Sutter Instrument	P-97
Glutamine	Sigma	G8540
HBSS	Gibco	14025092
Hemocytometer	Daigger	EF16034F
HEPES	Sigma	H4034
Insulin	Sigma	I3536
Iridectomy scissors	Zepf Medical Instruments	08-1201-10
Microinjector	Narishige	IM-6
Nicotinamide	Sigma	N0636
PBS (10X), pH 7.4	Gibco	70011044
PBS (1X), pH 7.4	Gibco	10010023
Phenol Red pH indicator	Sigma	P4633
Pure Ethanol, 200 Proof	Decon Labs	2716
RFP antibody	ChromoTek	5F8
Sodium bicarbonate	Sigma	S5761
Sodium hydroxide	Sigma	S8045
Sodium selenite	Sigma	S5261
Tabletop vortex	VWR	97043-562
Transferrin	Sigma	T8158
Trypan blue	Sigma	T6146