A Proximal Culture Method to Study Paracrine Signaling Between Cells

Summary

Paracrine and juxtacrine cellular interactions play an important role in many biological processes, including tumor progression, immune responses, angiogenesis, and development. Here, a proximal culture method is used to study paracrine signaling where the localized concentrations of the secreted factors are maintained while preventing direct cellular contact.

Abstract

Intercellular interactions play an important role in many biological processes, including tumor progression, immune responses, angiogenesis, and development. Paracrine or juxtacrine signaling mediates such interactions. The use of a conditioned medium and coculture studies are the most common methods to discriminate between these two types of interactions. However, the effect of localized high concentrations of secreted factors in the microenvironment during the paracrine interactions is not accurately recapitulated by conditioned medium and, thus, may lead to imprecise conclusions. To overcome this problem, we have devised a proximal culture method to study paracrine signaling. The two cell types are grown on either surface of a 10 µm-thick polycarbonate membrane with 0.4 µm pores. The pores allow the exchange of secreted factors and, at the same time, inhibit juxtacrine signaling. The cells can be collected and lysed at the endpoint to determine the effects of the paracrine signaling. In addition to allowing for localized concentration gradients of secreted factors, this method is amenable to experiments involving prolonged periods of culture, as well as the use of inhibitors. While we use this method to study the interactions between ovarian cancer cells and the mesothelial cells they encounter at the site of metastasis, it can be adapted to any two adherent cell types for researchers to study paracrine signaling in various fields, including tumor microenvironment, immunology, and development.

Introduction

The role of productive reciprocal interactions between cancer cells and the tumor microenvironment in tumor progression has been well established and has become a major focus of research in cancer biology¹. Similar instances of bidirectional signaling are crucial during wound healing, immune responses, angiogenesis, stem cell niches, and during development^{2,3,4,5,6,7,8}. A common theme in all these biological proces....

Protocol

The protocol follows the guidelines of the Institutional Regulatory Board of Indiana University.

1. Cell Preparation

1. Isolation and culture of human primary mesothelial cells
   1. Isolate human primary mesothelial cells (HPMCs) from human omentum as described previously^17,18 and grow them in complete growth medium [Dulbecco’s Modified Eagle’s Medium (DMEM) containing 10% fetal bovine serum, 1% penicillin-streptomycin, 1% non-essential amino acids, and 1% vitamins] at 37 °C and 5% CO₂.
      NOTE: The HPMCs are typicall....

Results

Metastasizing ovarian cancer cells encounter mesothelial cells at the site of metastasis within the peritoneal cavity¹⁹. Productive paracrine and juxtacrine interactions with the mesothelial cells help in inducing adaptive responses in the ovarian cancer cells, which enable successful metastasis^17,18,20,21. To test the effectiveness of th.......

Discussion

Understanding the mechanism of paracrine and juxtacrine signaling between cells is essential for developing a better knowledge of normal tissue homeostasis and disease conditions^7,8. Most paracrine signaling studies are conducted by collecting conditioned medium from one cell type and using it to treat the other cell type. This method has an advantage in its inherent simplicity. However, it does not accurately recapitulate the localized concentrations of the secr.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
24 mm Transwell permeable support with 0.4 µm Pore Polycarbonate Membrane Insert	Corning (Costar)	3412	• 10 µm thick translucent polycarbonate membrane • Treated for optimal cell attachment • Packaged 6 inserts in a 6 well plate, 4 plates per case • Membrane must be stained for cell visibility • Sterilized by gamma radiation
6 well plate	Corning (Falcon)	353046	Flat Bottom, TC-treated, sterile, with Lid
15 cm culture dish	Corning (Falcon)	353025	Sterile, TC-treated Cell Culture Dish
DMEM	Corning (Cellgro)	10-013-CV
Penicillin Streptomycin	Corning	30-002-CI
MEM Nonessential amino acids	Corning (Cellgro)	25-025-CI
MEM Vitamins	Corning (Cellgro)	25-020-CI
0.25% Trypsin, 2.21 mM EDTA	Corning	25-053-CI
Fetal bovine serum	Atlanta Biologicals	S11150
Pipets			Any make is fine
CO2 Incubator			Any make is fine
Biosafety level II cabinet			Any make is fine
FN1 TaqMan Gene Expression Assay	ThermoFisher Scientific	Hs01549976_m1
TGFB1 TaqMan Gene Expression Assay	ThermoFisher Scientific	Hs00998133_m1
CDH1 TaqMan Gene Expression Assay	ThermoFisher Scientific	Hs01023895_m1
GAPDH TaqMan Gene Expression Assay	ThermoFisher Scientific	Hs99999905_m1
miRNeasy mini RNA isolation Kit	Qiagen	217004
High-Capacity cDNA Reverse Transcription Kit	ThermoFisher Scientific	43-688-13
HeyA8 ovarian cancer cells	Obtained from Ernst Lengyel Lab, University of Chicago
TGFβ Neutralizing Antibody	R&D Systems	MAB1835-100