Quantitative Measurement of Intrathecally Synthesized Proteins in Mice

Summary

Elevated spinal fluid protein levels can either be the result of diffusion of plasma protein across an altered blood-brain barrier or intrathecal synthesis. An optimized testing protocol is presented in this article that helps to discriminate both cases and provides quantitative measurements of intrathecally synthesized proteins.

Abstract

Cerebrospinal fluid (CSF), a fluid found in the brain and the spinal cord, is of great importance to both basic and clinical science. The analysis of the CSF protein composition delivers crucial information in basic neuroscience research as well as neurological diseases. One caveat is that proteins measured in CSF may derive from both intrathecal synthesis and transudation from serum, and protein analysis of CSF can only determine the sum of these two components. To discriminate between protein transudation from the blood and intrathecally produced proteins in animal models as well as in humans, CSF protein profiling measurements using conventional protein analysis tools must include the calculation of the albumin CSF/serum quotient (Q_albumin), a marker of the integrity of the blood-brain interface (BBI), and the protein index (Q_protein/Q_albumin), an estimate of intrathecal protein synthesis. This protocol illustrates the entire procedure, from CSF and blood collection to quotients and indices calculations, for the quantitative measurement of intrathecal protein synthesis and BBI impairment in mouse models of neurological disorders.

Introduction

Cerebrospinal fluid (CSF), a clear and colorless liquid surrounding the brain and the spinal cord, holds great clinical and basic scientific importance. The CSF preserves the electrolytic environment of the central nervous system (CNS), balances the systemic acid-base status, supplies nutrients to neuronal and glial cells, functions as a lymphatic system for the CNS, and transports hormones, neurotransmitters, cytokines and other neuropeptides throughout the CNS¹. Thus, as the CSF composition reflects the activity of the CNS, this fluid offers a valuable, though indirect, access to characterize the physiological and pathological state of the CN....

Protocol

All animal work utilizes protocols reviewed and approved by the Institutional Animal Care and Use Committee (IACUC) at Geisel School of Medicine at Dartmouth.

1. Collection of fluids

NOTE: Both serum and CSF are required. Two protocols for each fluid collection are needed for survival and necropsy.

1. Serum and CSF collection using survival procedures
   NOTE: For survival fluid collection, serum collection should precede CSF collection as it is a less invasive procedure. CSF must be obtained within one week of serum draw.
   1. Retro-orbital bleeding procedure for serum collection.
      NOTE: T....

Results

This representative experiment aimed to compare the intrathecal synthesis of IgG in two clinically relevant rodent models of multiple sclerosis (MS): the PLP_139-151-induced relapsing experimental autoimmune encephalomyelitis (R-EAE) and the chronic progressive, Theiler’s murine encephalomyelitis virus-induced demyelinating disease (TMEV-IDD). R-EAE is a useful model for understanding relapsing-remitting MS, whereas the TMEV-IDD model features chronic progressive MS¹⁹.

Discussion

Quantitative methods for the evaluation of increased CSF protein concentrations are useful tools in the characterization of the physiological and pathological state of the CNS. However, beyond reliable quantification of CSF protein levels, the detection of CSF proteins requires an expression of results that discriminates between blood- and CNS-derived fractions in the CSF. However, to date, the commonly used protein quantification assays do not allow discrimination between the two protein components, even with the aid of.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
1 mL insulin syringe	BD	329650
1 mL syringe	BD	329622
25 gauge needle	BD	305122
3 mL syringe	BD	309582
30 gauge insulin needle	BD	305106
Absorbent pads	Any suitable brand
Acepromazine	Patterson Vet Supply Inc
BioPlex Handheld Magnetic Washer	BioRad	171020100	Magnet
BioPlex MAGPIX Multiplex Reader	BioRad	171015001
BioPlex Pro Flat Bottom Plates	BioRad	171025001
Biotinilated detection antibody	Any suitable source		The antibody has to be directed against the species of the protein of interest.
Bovine Serum Albumin (BSA)	Sigma	A4503
Buprenorphine hydrochloride	PAR Pharmaceutical	NDC 42023-179-05
Capillary Tubes	Sutter Instrument	B100-75-10	OD: 1.0 mm, ID: 0.75 mm Borosilicate glass 10 cm; drawn over Bunsen to make ID smaller.
Centrifuge tube, 0.2 mL	VWR	20170-012
Centrifuge tube, 0.5 mL	VWR	87003-290
Centrifuge tube, 1.5 mL	VWR	87003-294
Chlorhexidine diacetate	Nolvasan	E004272
Disposable pipettes tips	Any suitable brand
Ear bars	KOPF Instruments	1921 or 1922
Ethanol	Kopter	V1001
Freezer	VWR	VWR32086A
Gauze	Medline	NON25212
Heating pad	Sunbeam		XL King Size SoftTouch, 4 Heat Settings with Auto-Off, Teal, 12-Inch x 24-Inch
Induction Chamber	VETEQUIP
Isoflurane	Patterson Vet Supply Inc	NDC 14043-704-06
Ketamine (KetaVed)	Patterson Vet Supply Inc
MagPlex Microspheres (antibody-coupled)	BioRad		Antibody-coupled magnetic bead
Microplate Shaker	Southwest Scientific	SBT1500
Microretractors	Carfill Quality	ACD-010	Blunt - 1 mm
Microsoft Office (Excel)	Microsoft
MilliPlex MAP Mouse Immunoglobulin Isotyping Magnetic Bead Panel	EMD Millipore	MGAMMAG-300K	Commercial kit for the quantification through Luminex of a panel of immunoglobulin isotypes and subclasses in mouse fluids.
Mouse Albumin capture ELISA kit	Novus Biological	NBP2-60484	Commercial kit for the quantification through ELISA of albumin in mouse fluids.
Multichannel pipette	Eppendorf	3125000060
Non-Sterile swabs	MediChoice	WOD1002	Need to be autoclaved for sterility
Oxygen	AIRGAS	OX USPEA
Pasteur Pippettes	Fisher	13-678-20A	5 & 3/4"
PDS suture with disposable needle, 6-0 Prolen	Patterson Vet	8695G	P-3 Reverse Cutting, 18"
PE-Streptavidin	BD Biosciences	554061
Pipetters	Eppendorf	Research seriers
Polyethylene tubing
Refrigerated Centrifuge	Beckman Coulter	ALLEGRA X-12R
Scale	Uline	H2716
Scalpel	Feather	EF7281
Shaver	Harvard Apparatus	52-5204
Standard proteins	Any suitable source		The best choice for a reference standard is a purified, known concentration of the protein of interest.
Stereotaxic instrument	KOPF Instruments	Model 900LS	Standard Accessories
Sterile 1 x PBS	Corning Cellgro	21-040-CV
Sterile saline	Baxter	0338-0048-02	0.9 % Sodium Chloride Irrigation USP
Surgical Forceps Curved, 7 (2)	Fine Science Tools	11271-30	Dumont
Surgical Scissors	Fine Science Tools	14094-11	Stainless 25x
Vaporizer + Flow meter	Moduflex Anhestesia Instruments
Vortex	Fisher	02-215-414
Warming pad	Kent Scientific Corporation	RT-JR-20
Water Sonicator	Cole Parmer	EW-08895-01
Xylazine	Patterson Vet Supply Inc