A novel pathophysiological mechanism for osteoporosis suggested by an in vivo gene expression study of circulating monocytes.
Bone mineral density (BMD) is a major risk factor for osteoporosis. Circulating monocytes may serve as early progenitors of osteoclasts and produce a wide variety of factors important to bone metabolism. However, little is known about the roles of circulating monocytes in relation to the pathophysiology of osteoporosis. Using the Affymetrix HG-U133A GeneChip(R) array, we performed a comparative gene expression study of circulating monocytes in subjects with high and low BMD. We identified in total 66 differentially expressed genes including some novel as well as some already known to be relevant to bone metabolism. Three genes potentially contributing to bone metabolism, CCR3 (chemokine receptor 3), HDC (histidine decarboxylase, i.e. the histamine synthesis enzyme), and GCR (glucocorticoid receptor), were confirmed by quantitative real-time reverse transcriptase-PCR as up-regulated in subjects with lower BMD. In addition, significant negative correlation was observed between expression levels of the genes and BMD Z-scores. These three genes and/or their products mediate monocyte chemotaxis, histamine production, and/or sensitivity to glucocorticoids. Our results suggest a novel pathophysiological mechanism for osteoporosis that is characterized by increased recruitment of circulating monocyte into bone, enhanced monocyte differentiation into osteoclasts, as well as osteoclast stimulation via monocyte functional changes. This is the first in vivo microarray study of osteoporosis in humans. The results may contribute to identification of new genes and their functions for osteoporosis and suggest genetic markers to discern individuals at higher risk to osteoporosis with an aim for preventive intervention and treatment.
Liu
Yao-Zhong
YZ
Osteoporosis Research Center, Creighton University Medical Center,Creighton University, Omaha, NE 68131, USA.
Dvornyk
Volodymyr
V
Lu
Yan
Y
Shen
Hui
H
Lappe
Joan M
JM
Recker
Robert R
RR
Deng
Hong-Wen
HW
D000368:Aged; D000465:Algorithms; D015519:Bone Density; D002633:Chemotaxis; D005260:Female; D005786:Gene Expression Regulation; D005938:Glucocorticoids / Q000378:metabolism; D006640:Histidine Decarboxylase / Q000378:metabolism; D006801:Humans; D008159:Lumbar Vertebrae / Q000378:metabolism; D008875:Middle Aged; D008954:Models, Biological; D009000:Monocytes / Q000166:cytology / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010024:Osteoporosis / Q000097:blood* / Q000235:genetics / Q000473:pathology*; D054397:Receptors, CCR3; D019707:Receptors, Chemokine / Q000378:metabolism; D011965:Receptors, Glucocorticoid / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012307:Risk Factors
C515350:CCR3 protein, human; D005938:Glucocorticoids; D054397:Receptors, CCR3; D019707:Receptors, Chemokine; D011965:Receptors, Glucocorticoid; D006640:Histidine Decarboxylase