Intravenous Injections in Neonatal Mice

Summary

Animal models of pediatric disease can experience early onset and aggressive disease progression. Clinically relevant therapy delivery to young mouse models can be technically difficult. This protocol describes a non-invasive intravenous injection method for newborn mice within the first two postnatal days of life.

Abstract

Intravenous injection is a clinically applicable manner to deliver therapeutics. For adult rodents and larger animals, intravenous injections are technically feasible and routine. However, some mouse models can have early onset of disease with a rapid progression that makes administration of potential therapies difficult. The temporal (or facial) vein is just anterior to the ear bud in mice and is clearly visible for the first two days after birth on either side of the head using a dissecting microscope. During this window, the temporal vein can be injected with volumes up to 50 μl. The injection is safe and well tolerated by both the pups and the dams. A typical injection procedure is completed within 1-2 min, after which the pup is returned to the home cage. By the third postnatal day the vein is difficult to visualize and the injection procedure becomes technically unreliable. This technique has been used for delivery of adeno-associated virus (AAV) vectors, which in turn can provide almost body-wide, stable transgene expression for the life of the animal depending on the viral serotype chosen.

Introduction

Delivery of therapeutics to the central nervous system (CNS) in murine models of pediatric disease remains a challenge. Mice that model newborn disease states are undersized and developmentally immature, and therefore can be difficult to directly inject in appropriate structures within the CNS. Intravascular injection of therapeutic agents is a non-invasive, well tolerated method to deliver cells, drugs, or viral vectors to the entire body including the CNS^1-5 and retina^3,5-9. Previous publications describe temporal face vein injection using a transilluminator^10,11, without a dissection microscope^11,12, or requiring two indi....

Protocol

All procedures listed in the protocol have been approved Institute for Animal Use and Care committee (IACUC) of the Ohio State University.

1. Preparation of Workspace

1. Gather wet ice to anesthetize the mouse pups, an empty cage to segregate the dam from the litter, a dissecting microscope, a light source that can be positioned at an angle to the injection (use of a light source at a 90° angle to the injection site obscures the vein), a clean surface to place the animal for the injection, cotton swabs, 3/10 cc insulin syringe with 3/8” 30 G needle (one per animal) and 1% Evans Blue Dye (made with ph....

Results

During a proper injection, the vein should momentarily turn clear, or blanch. If injecting dye the entire pup should turn blue within seconds. If an improper injection has occurred, there is often a concentrated subcutaneous bolus in the head or neck and injectant may leak out of the injection site. Improper injections may also result in the appearance of bruising around the throat. Pups that receive subcutaneous injections (i.e. the injection was not fully delivered in the vein) generally experience no ill side.......

Discussion

Intravascular delivery of agents to the CNS or throughout the body is difficult in neonatal murine models of disease. The described protocol is a quick, relatively non-invasive way to intravenously administer solutions into neonatal mice with minimal equipment requirements. Though the temporal face vein can be viewed by the naked eye, injections may have greater accuracy with the use of the microscope and fiber-optic light source, especially for an unpracticed injector. Intravascular injections in neonatal mice have a hi.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Thinpro insulin syringe	Terumo	SS30M3009	3/10 cc, 3/8" needle, 30 G, 1 per mouse
Evans blue dye	Sigma-Aldrich	E2129	Dilute to 1% with 1x Phosphate Buffered Saline
Cotton tipped applicators	Fisher Scientific	23-400-101
Fiber optic light source	Fisher Scientific	12-562-36
Dissecting microscope