Isolation and Time-Lapse Imaging of Primary Mouse Embryonic Palatal Mesenchyme Cells to Analyze Collective Movement Attributes

Summary

We present a protocol for isolation and culture of primary mouse embryonic palatal mesenchymal cells for time-lapse imaging of two-dimensional (2D) growth and wound-repair assays. We also provide the methodology for analysis of the time-lapse imaging data to determine cell-stream formation and directional motility.

Abstract

Development of the palate is a dynamic process, which involves vertical growth of bilateral palatal shelves next to the tongue followed by elevation and fusion above the tongue. Defects in this process lead to cleft palate, a common birth defect. Recent studies have shown that palatal shelf elevation involves a remodeling process that transforms the orientation of the shelf from a vertical to a horizontal one. The role of the palatal shelf mesenchymal cells in this dynamic remodeling has been difficult to study. Time-lapse-imaging-based quantitative analysis has been recently used to show that primary mouse embryonic palatal mesenchymal (MEPM) cells can self-organize into a collective movement. Quantitative analyses could identify differences in mutant MEPM cells from a mouse model with palate elevation defects. This paper describes methods to isolate and culture MEPM cells from E13.5 embryos-specifically for time-lapse imaging-and to determine various cellular attributes of collective movement, including measures for stream formation, shape alignment, and persistence of direction. It posits that MEPM cells can serve as a proxy model for studying the role of palatal shelf mesenchyme during the dynamic process of elevation. These quantitative methods will allow investigators in the craniofacial field to assess and compare collective movement attributes in control and mutant cells, which will augment the understanding of mesenchymal remodeling during palatal shelf elevation. Furthermore, MEPM cells provide a rare mesenchymal cell model for investigation of collective cell movement in general.

Introduction

Palate development has been studied extensively as defects in palatogenesis lead to cleft palate-a common birth defect that occurs in isolated cases or as part of hundreds of syndromes^1,2. The development of the embryonic palate is a dynamic process that involves movement and fusion of embryonic tissue. This process can be divided into four major steps: 1) induction of palatal shelves, 2) vertical growth of the palatal shelves next to the tongue, 3) elevation of the palatal shelves above the tongue, and 4) fusion of the palatal shelves at the midline^1,3

Protocol

All experiments involving animals were carried out with a protocol approved by the KUMC Institutional Animal Care and Use Committee, in accordance with their guidelines and regulations (Protocol Number: 2018-2447).

1. Harvest E13.5 embryos

1. Euthanize pregnant female mice using a CO₂ inhalation chamber or by a procedure approved by the Institutional Animal Care and Use Committee. Immediately proceed to dissection.
2. Expose the inferior half of the abdominal cavity by removing the skin and peritoneum. Excise both horns of the uterus, which contain the E13.5 embryos.
3. Briefly place the uterus in prewarmed....

Results

The dissection of palatal shelves is illustrated in Figure 1. The sequence of incisions is designed to minimize slippage of the tissue. Following the removal of the head (Figure 1A,B), the lower jaw is removed (Figure 1B,C). The incision of the upper part of the head (Figure 1C,D) is done to stabilize the tissue when placed upside down (

Discussion

Palatal shelf elevation constitutes a vertical to horizontal remodeling event^1,3,4,9,11. It is postulated that this remodeling process requires palatal shelf mesenchymal cells to behave coordinately. The analyses with wildtype MEPM cells show that this cell behavior is intrinsic and can be quantitated²¹. Thus, these assays can be used t.......

Materials

Name	Company	Catalog Number	Comments
Beaker, 250 mL (x2)	Fisher Scientific	FB-100-250
CO2	Matheson Gas	UN1013
Conical tubes, 15 mL (x1)	Midwest Scientific	C15B
Debian operating system			computational analysis of time-lapse images
Dulbecco's Modified Eagles Medium/High Glucose with 4 mM L-Glutamine and Sodium Pyruvate	Cytiva Life Sciences	SH30243.01
EtOH, 100%	Decon Laboratories	2701
EVOS FL Auto	ThermoFisher Scientific	AMAFD1000
EVOS Onstage Incubator	ThermoFisher Scientific	AMC1000
EVOS Onstage Vessel Holder, Multi-Well Plates	ThermoFisher Scientific	AMEPVH028
Fetal Bovine Serum	Corning	35-010-CV
Fine point #5 Stainless Steel Forceps (x2)	Fine Science Tools	11295-10	Dissection
Instrument sterilizer bead bath	Fine Science Tools	18000-45
Microcetrifuge tubes, 1.5mL	Avant	2925
Micro-Dissecting Stainless Steel Scissors, Straight	Roboz	RS-5910	Dissection
NucBlue (Hoechst) Live Ready Probes	ThermoFisher Scientific	R37605
Penicillin Streptomycin Solution, 100x	Corning	30-002-CI
Silicone Insert, 2-well	Ibidi	80209
Small Perforated Stainless Steel Spoon	Fine Science Tools	MC17C	Dissection
Spring Scissors, 4 mm	Fine Science Tools	15018-10
Sterile 10 cm dishe(s)	Corning	430293
Sterile 12-well plate(s)	PR1MA	667512
Sterile 6-well plate(s)	Thermo Fisher Scientific	140675
Sterile PBS	Corning	21-031-CV
Sterile plastic bulb transfer pipette	ThermoFisher Scientific	202-1S
Trypsin, 0.25%	ThermoFisher Scientific	25200056