In Vitro Model of Coronary Angiogenesis

Summary

In vitro models of coronary angiogenesis can be utilized for the discovery of the cellular and molecular mechanisms of coronary angiogenesis. In vitro explant cultures of sinus venosus and endocardium tissues show robust growth in response to VEGF-A and display a similar pattern of COUP-TFII expression as in vivo.

Abstract

Here, we describe an in vitro culture assay to study coronary angiogenesis. Coronary vessels feed the heart muscle and are of clinical importance. Defects in these vessels represent severe health risks such as in atherosclerosis, which can lead to myocardial infarctions and heart failures in patients. Consequently, coronary artery disease is one of the leading causes of death worldwide. Despite its clinical importance, relatively little progress has been made on how to regenerate damaged coronary arteries. Nevertheless, recent progress has been made in understanding the cellular origin and differentiation pathways of coronary vessel development. The advent of tools and technologies that allow researchers to fluorescently label progenitor cells, follow their fate, and visualize progenies in vivo have been instrumental in understanding coronary vessel development. In vivo studies are valuable, but have limitations in terms of speed, accessibility, and flexibility in experimental design. Alternatively, accurate in vitro models of coronary angiogenesis can circumvent these limitations and allow researchers to interrogate important biological questions with speed and flexibility. The lack of appropriate in vitro model systems may have hindered the progress in understanding the cellular and molecular mechanisms of coronary vessel growth. Here, we describe an in vitro culture system to grow coronary vessels from the sinus venosus (SV) and endocardium (Endo), the two progenitor tissues from which many of the coronary vessels arise. We also confirmed that the cultures accurately recapitulate some of the known in vivo mechanisms. For instance, we show that the angiogenic sprouts in culture from SV downregulate COUP-TFII expression similar to what is observed in vivo. In addition, we show that VEGF-A, a well-known angiogenic factor in vivo, robustly stimulates angiogenesis from both the SV and Endo cultures. Collectively, we have devised an accurate in vitro culture model to study coronary angiogenesis.

Introduction

Blood vessels of the heart are commonly called coronary vessels. These vessels are comprised of arteries, veins, and capillaries. During development, highly branched capillaries are established first, which then remodel into coronary arteries and veins^1,2,3,4,5. These initial capillaries are built from endothelial progenitor cells found in the proepicardium, sinus venosus (SV), and endocardium (Endo) tissues^1,6,7

Protocol

Use of all the animals in this protocol followed Ball State University Institutional Animal Care and Use Committee (IACUC) guidelines.

1. Establishing Mouse Breeders and Detecting Vaginal Plugs for Timed Pregnancies

1. Set up a mouse breeding cage with wild type male and female mice. Ensure that the age of the breeding mice is between 6-8 weeks. Set up either a pair (1 male and 1 female) or as a trio (1 male and 2 female) for breeding.
2. Check for a vaginal plug the following .......

Discussion

Some of the most critical steps for successfully growing coronary vessels from the SV and Endo progenitor tissues are: 1) Correctly identifying and isolating the SV tissue for SV culture; 2) using ventricles from embryos between the ages of e11−11.5 for accurate Endo culture; 3) maintaining sterile conditions throughout the dissection period and keeping the tissues cold at all times; and 4) keeping the explants attached to the ECM coated membrane to avoid tissue floating in the medium.

F.......

Materials

Name	Company	Catalog Number	Comments
100 x 20 MM Tissue Culture Dish	Fisher Scientific	877222	Referred in the protocol as Petri dish
24-well plates	Fisher Scientific	08-772-51
8.0 uM PET membrane culture inserts	Millipore Sigma	MCEP24H48
Alexa Fluor Donkey anti-rabbit 555	Fisher Scientific	A31572	Secondary antibody
Alexa Fluor Donkey anti-rat 488	Fisher Scientific	A21206	Secondary antibody
Angled Metal Probe	Fine science tools	10088-15	Angled 45 degree, used for detecting deep plugs
Anti- ERG 1/2/3 antibody	Abcam	Ab92513	Primary antibody
Anti- VE-Cadherin antibody	Fisher Scientific	BDB550548	Primary antibody, manufacturer BD BioSciences
CO2 gas tank	Various suppliers	N/A
CO2 Incubator	Fisher Scientific	13998223	For 37 °C, 5% CO2 incubation
Dissection stereomicrosope	Leica	S9i	Leica S9i Stereomicroscope
EBM-2 basal media	Lonza	CC-3156	Endothelial cell growth basal media
ECM solution	Corning	354230	Commercially known as Matrigel
EGM-2 MV Singlequots Kit	Lonza	CC-4147	Microvascular endothelial cell supplement kit; This is mixed into the EBM-2 to make the EGM-2 complete media
Fetal Bovine Serum (FBS)	Fisher Scientific	SH3007003IR
FiJi	NIH	NA	Image processing software (https://imagej.net/Fiji/Downloads)
Fine Forceps	Fine science tools	11412-11	Used for embryo dissection
Fisherbrand Straight-Blade operating scissors	Fisher Scientific	13-808-4
Hyclone Phosphate Buffered Saline (1X)	Fisher Scientific	SH-302-5601LR
Laminar flow tissue culture hood	Fisher Scientific	various models available
Mounting Medium	Vector Laboratories	H-1200	Vectashield with DAPI
Paraformaldehyde (PFA)	Electron Microscopy/Fisher	50-980-494	This is available at 32%; needs to be diluted to 4%
Perforated spoon	Fine science tools	10370-18	Useful in removing embryo/tissues from a solution
Recombinant Murine VEGF-A 165	PeproTech	450-32
Standard forceps, Dumont #5	Fine science tools	11251-30
Sure-Seal Mouse/Rat chamber	Easysysteminc	EZ-1785	Euthanasia chamber