A Cryo-pulverization Protocol for Processing Mouse Paws to Evaluate Molecular Pathways of Tissue Inflammation in a Collagen Induced Arthritis Model

Summary

A cryogenic pulverization method to process murine paws using a liquid nitrogen freezer mill was developed to improve the yield and quality of RNA or protein extracted from the tissues and enable the analysis of molecular profiles associated with inflammatory responses.

Abstract

Profiling molecular changes in local tissues is crucial to understand the mechanism(s) of action of therapeutic candidates in vivo. In the field of arthritis research, many studies are focused on inflamed joints that are composed of a complex mixture of bone, cartilage, muscle, stromal cells and immune cells. Here, we established a reliable and robust mechanical method to disrupt inflamed mouse paws into homogeneous pulverized samples in a cryogenically controlled environment. Protein and RNA lysates were processed to enable proteomic and transcriptional endpoints and molecular characterization of relevant disease pathways in local tissue.

Introduction

Rheumatoid arthritis (RA) is a chronic systemic inflammatory disease with persistent symmetric synovitis in joints and extra articular involvement of organs such as the skin, heart, lungs, and eyes¹. Although the systemic manifestations of the immune response are evident in human patients, one of the hallmarks of RA pathology is infiltration of immune cells in synovial tissue and proliferation of synovial fibroblast cells².

Similar to human RA, mouse collagen induced arthritis (CIA) model elicits strong tissue inflammation with active immune responses in synovial tissues and systemic compartme....

Protocol

All animal experiments were conducted in accordance within the policies of the Institutional Animal Care and Use Committee (IACUC) of Janssen R&D.

1. Cryogenic Freezer Mill-based Pulverization Method

1. At termination of the CIA study, sacrifice mice with 1.5% isoflurane followed by cervical dislocation.
2. On the day of tissue processing, pre-chill all instruments (spatulas, grinding vials, etc.) on dry ice for a minimum of 10 min. Wear thermal gloves to avoid freeze damage.
3. Cut hind paws with a scissor at the fur line as depicted in Figure 1A.
4. Transfer ....

Results

Here, we show a representative gel image visualization of RNA extracted from front paws of CIA mice in Figure 2A. The 28S rRNA and the 18S rRNA band indicate all samples have sufficient amount of intact RNA. Next, we show a representative scatter plot of total protein concentrations based on protein BCA analysis in Figure 2B. Total protein concentrations from naïve mice, CIA mice or CIA mice unde.......

Discussion

Although there is strong scientific rationale to evaluate molecular pathways in synovial tissues, many reports on immune profiling of murine CIA model were focused on peripheral blood, while protein and RNA analysis data of inflamed paws are rather limited. There are several possible reasons for this bias: murine ankle joints are no larger than ~2 cm; the affected areas consist of skin, bone and connective tissues which are often difficult to homogenize using traditional methods like tissue grinders, pestle and mortar, s.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
5 mm stainless steel bead	Qiagen	69989
beta-mercaptoethanol	Sigma	M6250	Sample reducing agent that inhibits RNASE enzymes
Bioanalyzer Kit	Agilent	5067-1511	RNA qualification kit
b-mercaptoethanol	Sigma	M6250
Cell Culture Grade Water	Corning	25-055-CI	Water
Cell lysis stock solution	Cell Signaling	9803
Eppendorf Tube	Eppendorf	22363204	Microfuge tubes
Eppendorf tube centrifuge box	Nalgene	5055	Box for holding eppendorf tubes in horizontal tube arrangement
Everlast 247 Variable Speed Rocker	Benchmark Scientific	BR5000
Freezer Mill	Spex Sample Prep	6875	Freezer/Mill for processing paws into pulverized powder
Grinding Vial	Spex Sample Prep	6801	Polycarbonate vial for processing paws into pulverized powder
Pierce BCA kit	Pierce	23225	Kit for Total Protein Quantification
Protease Inhibitor Cocktail set 1	Calbiochem	539131	Protease Inhibitors
Protein BCA Kit	Pierce	23225
Quantigene Kit	Thermofisher	QP1013	bDNA analysis Kit
Refrigerated microcentrifuge	Eppendorf	5417R	Centrifugation
RLT Buffer	Qiagen	79216	RNA extraction buffer
RNeasy mini kit	Qiagen	74104	including RNeasy column, RLT Buffer and RW1 Buffer
Shaker	Benchmark Scientific	BR5000	Rocker/Shaker
Spatula	VWR	10806-412	Spatula for powder transfer
Stainless Steel Bead	Qiagen	69989	Bead for mixing during protein extraction
Tube Extractor	Spex Sample Prep	6884	Extractor for removing the top of grinding vial
Vortexer	VWR	10153-838	Sample mixing