Involution of the mouse mammary gland is associated with an immune cascade and an acute-phase response, involving LBP, CD14 and STAT3.
BACKGROUND
Involution of the mammary gland is a complex process of controlled apoptosis and tissue remodelling. The aim of the project was to identify genes that are specifically involved in this process.


METHODS
We used Affymetrix oligonucleotide microarrays to perform a detailed transcript analysis on the mechanism of controlled involution after withdrawal of the pups at day seven of lactation. Some of the results were confirmed by semi-quantitative reverse transcriptase polymerase chain reaction, Western blotting or immunohistochemistry.


RESULTS
We identified 145 genes that were specifically upregulated during the first 4 days of involution; of these, 49 encoded immunoglobulin genes. A further 12 genes, including those encoding the signal transducer and activator of transcription 3 (STAT3), the lipopolysaccharide receptor (CD14) and lipopolysaccharide-binding protein (LBP), were involved in the acute-phase response, demonstrating that the expression of acute-phase response genes can occur in the mammary gland itself and not only in the liver. Expression of LBP and CD14 was upregulated, at both the RNA and protein level, immediately after pup withdrawal; CD14 was strongly expressed in the luminal epithelial cells. Other genes identified suggested neutrophil activation early in involution, followed by macrophage activation late in the process. Immunohistochemistry and histological staining confirmed the infiltration of the involuting mammary tissue with neutrophils, plasma cells, macrophages and eosinophils.


CONCLUSIONS
Oligonucleotide microarrays are a useful tool for identifying genes that are involved in the complex developmental process of mammary gland involution. The genes identified are consistent with an immune cascade, with an early acute-phase response that occurs in the mammary gland itself and resembles a wound healing process.
Division of Cancer Sciences and Molecular Pathology, Western Infirmary, Glasgow, UK. ts33s@udcf.gla.ac.uk
Torsten
T
Stein
Joanna S
JS
Morris
Claire R
CR
Davies
Stephen J
SJ
Weber-Hall
Marie-Anne
MA
Duffy
Victoria J
VJ
Heath
Alexandra K
AK
Bell
Roderick K
RK
Ferrier
Gavin P
GP
Sandilands
Barry A
BA
Gusterson
D000209:Acute-Phase Proteins / Q000235:genetics*; D000210:Acute-Phase Reaction / Q000235:genetics*; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000235:genetics*; D004804:Eosinophils / Q000502:physiology; D004847:Epithelial Cells / Q000737:chemistry / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling / Q000379:methods; D005786:Gene Expression Regulation / Q000235:genetics* / Q000276:immunology; D007107:Immune System / Q000378:metabolism*; D007239:Infections / Q000235:genetics; D018950:Lipopolysaccharide Receptors / Q000235:genetics*; D008214:Lymphocytes / Q000502:physiology; D008262:Macrophage Activation / Q000235:genetics; D008321:Mammary Glands, Animal / Q000737:chemistry* / Q000166:cytology / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics*; D051379:Mice; D018375:Neutrophil Activation / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods; D050796:STAT3 Transcription Factor; D015534:Trans-Activators / Q000235:genetics*; D000099231:Lipopolysaccharide-Binding Protein
D000209:Acute-Phase Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D018950:Lipopolysaccharide Receptors; D008562:Membrane Glycoproteins; D050796:STAT3 Transcription Factor; D015534:Trans-Activators; D000099231:Lipopolysaccharide-Binding Protein; C494087:Stat3 protein, mouse